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VERY LARGE TELESCOPE NACO User Manual

1. Observation Number of offset positions Offset overhead NEXPO per offset position 1 time between frames without offset NEXPO per offset positionx DITxNDIT readout overhead 106 User s Manual VLT MAN ESO 14200 2761 Table 6 8 Example 3 Imaging a bright source in the L band V 11 for the VIS WES or K 7 for the IR WES with Uncorr VON NACO ne 0 2 sec 150 120 1 Uncorr Observation Number of offset positionsx Offset overhead DITXNDIT Table 6 9 Example 4 Spectroscopy of faint source with Fowler NN samp Template parameters Acquisition Template NACO_img_acq_MoveToSlit Observation Template NACO_spec_obs_AutoNodOnslit DI 300 sec NDIT Number of AB or BA cycles NEXPO per offset position Readout Mode Return to Origin Jitter Box Width a owlerNsamp Execution Time min Preset pee Guide Star Acquisition 0 75 Initial Setup AO Acquisition 100 2 3 Spectroscopic acquisition 5 Through slit J Sub Total acquisition 22 05 Observation 2x6x 27 300 2 Total min Overheads Observation 2xNumber of AB or BA cyclesx Offset overhead DIT readout overhead 107 User s Manual VLT MAN ESO 14200 2761 Table 6 10 Example 5 SW Polarimetry of bright source with the Wollaston Template parameters NACO_imeg_acq_Polarimetry NACO pol obs GenericOffset 10 sec Acquisition Template Observation Template DI NDIT Number of offset positions NEXPO per offset position
2. Sa 7 a VLT NaCo Sub field bad image I best image J band seeing 0 4 closed loop AO 04 a Lo mean image mean image NGC3603 arcsec 90 J band Strehl ratio obtained 22 J band Strehl ratio Figure 5 3 Some results of the speckle masking experiment Rengaswamy et al 2010 applied on a 0 16 separation binary star Comparison between the reconstructed intensity map bottom left and the closed loop AO image bottom right is given Seeing conditions were excellent for this test noAO mode speckle holography technique Work in progress on crowded fields by R Sch del VLT NaCo Holography S13 Field Ks band Figure 5 4 Speckle holography technique applied to the NGC3603 cluster The holography image on the right is nearly as deep as the AO corrected one on the left the 3 sigma detection limit is Ks 18 in both cases However it is advantageously more suitable for astrometry as every single star of the field appears in its true position unaffected by AO induced distortion effects The holography PSF itself is very clean diffraction limited with a K band Strehl ratio reaching 65 about 2 5 times superior to the closed loop PSF which suffers an obvious waffle mode pattern 39 User s Manual VLT MAN ESO 14200 2761 If you are interested by this mode just consider the cube mode an
3. Table 6 1 For DITs larger than 60 seconds users should consider using FowlerNsamp and not Double_RdRstRd With DITs larger than 60 seconds the number of hot pixels in Double_RdRstRd is noticeably larger Table 6 1 Recommended DIT and NDIT range DIT sec DITXNDIT sec J SW NB filters 60 300 120 300 H and Ks 20 120 60 240 Bw 0 a These recommendations do not necessarily hold for cube mode where the choice of DIT and NDIT will depend on the application 6 13 IR background Background is a function of the filter and the dichroic They are listed in Table 6 2 Users should note that the RON of the array can dominate if DIT is too small Table 6 2 IR Backgrounds The hyphens mark invalid combinations of a NAOS dichroic CONICA filter Background magnitude sq arcsec _ VIS N20C80 N90C10 JHK K J 1581158 158 58 H 1401140 140 f 140 Ks 128125 110 J gt Ip 130 q 130 j gt Mp 05 05 6 14 Recommended magnitude ranges for Standard Stars The recommended magnitude range for standard stars in imaging and spectroscopy is given in Table 6 3 Saturation with the minimum DIT can occur for targets that are about 1 magnitude brighter than the lower limit in these ranges but this limit is very sensitive to the level of correction These magnitude ranges are valid for observations with the visual dichroic Limits are similar for the JHK and K dichroics and respectively 0 2 and 3 mag
4. User s Manual VLT MAN ESO 14200 2761 Table 7 11 Parameters of NACO_img_obs_GenericOffset P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec Readout mode Double _RdRstRd Readout mode Window Size 1024 Size of the window Observation Category SCIENCE Observation Category Store Data Cube T F F Data cube flag List of NDIT s NODEFAULT List of NDIT s NEXPO per offset position 1 Number of exposutes per offset position Number of offset positions NODEFAULT Number of offset positions Observation type O or S NODEFAULT O is in closed loop S in open loop Offset coordinates NODEFAULT SKY or DETECTOR List of offsets in RA or X NODEFAULT Offsets in arcsec List of offsets in DEC or Y NODEFAULT Offsets in arcsec Filter NODEFAULT Filter name Neutral Density Filter Full Neutral density filter Full none Camera NODEFAULT Camera Name 1024 1024 N Position Angle 45 deg CONICA FOV 28 for 27 1 1 x Figure 7 4 An illustration of how the NACO img obs GenericOffset template works In this example the offsets are in DETECTOR co ordinates Exposures 1 and 5 occur at the same place The telescope will return to the origin after the eighth exposure as indicated by the dashed line connecting point 8 to 1 The parameter settings for this example were Table 7 12 parameters for the example shown in Figure 7 4 NEXPO per offset position 1 Observation Type O or S O Number of offset positions 8
5. User s Manual VLT MAN ESO 14200 2761 Table 7 17 Parameters of NACO_spec_obs_AutoNodOnS lit P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DITs Readout mode FowlerNsamp Readout mode Jitter Box Width NODEFAULT Jitter Box Width Number of AB or BA cycles NODEFAULT One cycle is one object sky pair NEXPO per offset position 1 Number of exposures per offset position Nod Throw NODEFAULT Nod Throw in arcsec Return to Origin T F T Return to Origin Slit NODEFAULT Name of slit Spectroscopic Mode NODEFAULT Spectroscopic Mode 7 6 1 NACO_app_spec_obs_AutoNodOnSlit discontinued since P93 Exactly the same as NACO spec obs AutoNodOnsSlit but allowing the APP insertion with limited setups see 1 1 1 VM only telluric standard star OBs will have to be provided by the users using this same template P87 Calibration Plan and onwards Allowed spectroscopic setups are L54 2 LP 1L542 SL 127 1 LP and 1541 IP 7 6 2 NACO spec obs GenericOffset This template is used for spectroscopy and has the flexibility of programming any sequence of telescope offsets It is essentially intended for programs requiring large offsets off the slit or slit scanning across one object Telescope offsets are defined as lists with the List of offsets in RA or X and List of offsets in DEC or Y parameters Telescope offsets are relative defined either along detector lines X and columns Y or R
6. 1 5 um imager and spectrograph which is fed by NAOS It is capable of imaging including Simultaneous Differential Imaging long slit spectroscopy coronagraphy polarimetry and Sparse Aperture Masking observations with several different plate scales This section describes the optical components of CONICA See Figure 5 1 for a drawing of the instrument As for P93 and on some modes are discontinued and appear as batred in the list hereafter The optical path includes the following components O The slider wheel which is either open or closed in calibration position or with the Half Wave Plate inserted The mask slit wheel which contains various masks for imaging SDI and polarimetry note that now only the Wollaston 00 is available since the Wollaston 45 mask had to be removed to make space for the AQPMin HandK the coronagraphic masks including the new Lp band AGPM and the slits for spectroscopy The Fabry Perot wheel which is set to open for non FPI observations The Lyot wheel which includes the ND filters and the SAM masks The grism wheel which contains the grisms the prism the SDI Wollaston the Wollaston_00 for polarimetry the J broadband filter and the new IB_4 05 filter The first filter wheel which contains all the intermediate band IB filters except the IB 4 05 filter NB 2 17 NB 2 12 and NB 4 05 The second filter wheel which contains all the broadband filters except J the remaining NB filters
7. 50 Often in Paranal the coherence time is well bellow this value and therefore despite having the requested seeing the requested Strehl ratios are difficult to obtain in reality 9 5 6 Exporting to the Exposure Time Calculator When clicking on Export to CONICA ETC at the bottom of the main panel a file browser pops up You can then give the name of an HTML file that will be created by the GUI and saved to your local disk This HTML file contains the PSF profile the CONICA filter and the magnitude and spectral type of the target 158 User s Manual VLT MAN ESO 14200 2761 To call the ETC load this file into your favourite web browser and click on the Call CONICA ETC button at the bottom of the page 9 5 7 Exporting to P2PP All NACO acquisition templates Section 7 3 require a configuration file which is produced by the Export to P2PP button It has the default extension aocfg and it is saved in the directory specified in the Preferences menu under the option set the cache folder This file contains all the information relevant to the setup of NAOS during acquisition of the target When preparing your observations with the PS and P2PP the following points should be noted o The output file is a text file and it should never be manually edited If you do the execution of your OB will be seriously compromised and the time loss will be charged to your program o There must be one configuration file per target The same conf
8. 6 6 4 SDI 4 decommissioned since P90 It is mandatory to use the NACO img acq SDIMoveToMask acquisition template for all SDI 4 OBs and also use the same setup in both the acquisition and observing templates with the possible exception of the ND_Short filter which is used during acquisition of bright stars This template provides interactive tools to centre objects behind the 4QPM_H mask 6 6 5 Polarimetry It is mandatory to use the NACO img acq Polarimetry acquisition template 6 6 6 SAM It is mandatory to use NACO img acq SAMMoveToPixel and use the same mask in both the acquisition and the science templates 6 6 7 SAMPol It is mandatory to use NACO_img_acq_SAMPol and use the same mask in both the acquisition and the science templates 6 7 Pre imaging Pre imaging is offered for programs where critical conditions need to be checked to guarantee the successful execution of the science program This mode ensures a quick delivery of the data to the user and is restricted to O programs that have already requested a separate pre imaging Run or otherwise indicated an amount of time to be used for pre imaging Examples of cases that may require pre imaging are programs needing to check either the field orientation because of possible contamination by a close by bright star or the possible binarity of potential targets for occultations or to refine the slit position in a crowded field O 2imaging templates NACO_img_obs_AutoJitt
9. A result of these tests is that we did not reach the 1 500 detection limit that was hoped for From the data we are confident we can have 50 detections with a dynamic range between 100 and 200 The second result is that the principal source of error is a bias in the closure phase signal due to some unknown artefact in the instrument and or the data reduction This bias is illustrated in Figure 5 38 which shows closure phases recorded on a given baseline triangle over 400 separate exposures when looking at a point source reference star which should give zero closure phases everywhere It is important to note that the mean red line does not converge to zero closure phase as more samples are averaged dashed envelope Even worse this bias offset from the true value zero can change as the experimental configuration is moved as illustrated in the right hand panel where the same star is observed but with the interference pattern falling on a different location on the CONICA detector What can be done about it The bias that can be observed on the phases see Figure 5 38 does change with the position of the star on the detector This is why it is difficult to calibrate with a reference star We are presently investigating the source of this bias and some possible strategies to mitigate it It may be worthwhile to attempt to put the science and calibrator star at an identical location on the detector Furthermore a strategy which consist
10. DIT Detector Integration Time DM Deformable Mirror DPR Data Product ESO European Southern Observatory ETC Exposure Time Calculator FLI Fractional Lunar Illumination FNS FowlerNsampling FoV Field of View FP Fabry Perot FS Field Selector FW Full well FWHM Full Width at Half Maximum GUI Graphical User Interface HB HighBackground HD HighDynamic HS HighSensitivity HWD HighWellDepth HW Hardware HWP Half Wave Plate IB Intermediate band ICS Instrument Control Software INS Instrumentation Software Package I O input output IR Infra red IRACE Infra red Array Control Electronics ISF Instrument Summary File 15 User s Manual VLT MAN ESO 14200 2761 LCC LCU Common Software LCU Local Control Unit LGS LGSF Laser Guide Star Laser Guide Star Facility N A Not Applicable NAOS Nasmyth Adaptive Optics System NACO NAOS CONICA NB Narrow Band ND Neutral Density NGS Natural Guide Source noAO Open loop no AO correction Observation Block A Preliminary Acceptance Europe P2PP Phase 2 Proposal Preparation PS Preparation Software PSO Paranal Science Operations PSF Point Spread Function PE Pupil Tracking Random Access Memory RON Read Out Noise RTAP Real Time Application Platform RTC Real Time Computer RTD Real Time Display SAM Sparse Aperture interferometric Mask SAMPol Sparse Aperture interferometric Mask Polarimetry O ee I T lt SDI Simultaneous Differential Imaging SDI Simultaneous Diffe
11. Readout Mode FowlerNsamp List of position angle offsets 045 Execution Time min Preset Eee Initial Setup AO Acquisition Polarimetric acquisition ANCE EET 1 Observations at 0 and 45 degrees 2x 5x 27 6x 10 2 2x8 3 16 4 Rotator offset in between angles Total min 25 95 Overheads 193 5 Observation Number of offset positionsx Offset overhead NDIT DIT readout overhead Table 6 11 Example 5b Polarimetry of bright source with the Wollaston and HWP NACO_img_acq_Polarimetry NACO_pol_obs_Retardet 0 NEXPO per offset position owletNsamp 22 5 Execution Time min Observations at 0 and 22 5 degrees 2x 5x 27 6x 10 2 2x8 3 16 4 0 25 29 6 196 Observation Number of offset positionsx Offset overhead NDIT x DIT teadout overhead Fr OT re DO OG Go Do I I UI UI 108 User s Manual VLT MAN ESO 14200 2761 Table 6 12 Example 6 SW coronagraphy of a bright source with Double_RdRstRd NACO img acq MoveToMask NACO coro obs Stare 10 sec Double RaRSRd Pea ooo O O Guide Sar Acquis 0 Tias d FAO Acquision Y O Coronagrahic acquistion oS A Observations 36 2x 10x 6x10 0 7 9x16 27 4x 5x10 0 7 27 Observation Number of AB cycles x Number of exposures OBJECT x DITxNDIT treadout overhead Number of exposures OBJECT 1 x time between frames without offset Offset ovethead Number of offset positions SKY x DITxNDIT readout overhead offse
12. The primary determinant for which mask to choose in any given situation is the brightness of the stellar target For bright targets try for a mask with many small holes 18Holes For faint targets a mask with fewer large holes and the ability to observe in the broad filter sets e g BB 9Holes is likely more optimal There can also be secondary issues motivating the choice of a mask In general to get enough Fourier coverage to do good mapping of a complex structured target one should push for a mask with more holes and short minimum baselines to extend the field of view Furthermore some 1 Hardware windowing with the CONICA array requires NY NX 2 where NX and NY are the number of pixels in X and Y respectively 67 User s Manual VLT MAN ESO 14200 2761 observations may be needed in specific narrowband filters or with special setups and so mask choice can be a complex optimization The four commissioned masks are now briefly described in turn More detailed specifications and hole layouts are given in Section 5 6 9 18Holes this mask can only be used with the narrow and intermediate NB IB filter sets Useful range is targets brighter than about 4 Mag Excellent Fourier coverage for imaging and should also serve well for faint companion detection 9Holes this mask is designed for use with the NB and IB filters although it may be marginally OK with broadband filters such as Ks Lp or Mp Useful range is from about 3 to
13. Typically closer wins over brighter but in any event the NAOS PS should be consulted It can even be the science target itself if it is sufficiently bright and point like 99 User s Manual VLT MAN ESO 14200 2761 Whenever possible several reference sources should be chosen in order to avoid acquisition problems due to binarity faintness or proper motion of the reference source The Guide Star and 2MASS catalogues can be used to find suitable references However for LGS observations to ease the operations the user is restricted to a single Tip Tilt Star per LGS OB or in the absence of a suitable Tip Tilt star to SE mode In general the visual WFS will be used for most of the observations as this ensures that the largest fraction of IR light enters the science channel The IR WFS should be used for very red sources V K Z 6 mag which could otherwise not be observed with NAOS CONICA or for which the IR WES provides a better correction LGS observations including those with SE mode are possible only with the visual WFS since the laser is a Na laser 6 10 Strehl Ratio and classification of OBs in Service mode SM To help the observatory determine whether or not an OB has been successfully executed in service mode the Strehl Ratio of the reference source can be measured with the NB 2 17 filter during acquisition or at the observed wavelength using a dedicated tool The measurement during the acquisition process is
14. frames have been acquired The lists can have any length However having lists of different lengths can become extremely confusing It is good practice to use lists of equal length or lists with only one value when one parameter remains constant 134 User s Manual Acquisition Position VLT MAN ESO 14200 2761 1024 1024 CONICA FOV S27 28 X Figure 7 8 An illustration of how the NACO_spec_obs_GenericOffset template works The AO loop is off when the sky S is observed large filled in circles and on when the object O is observed small filled in circles The dashed line connecting 4 with the acquisition position is the offset done at the end of the telescope since the Return to Origin T F was set to T In this example the parameter settings were Number of offset positions 4 NEXPO per offset position 1 Observation Type O or S OS S O Offset Coordinates DETECTOR List of offsets in RA or X 70 140 List of offsets in DEC or Y 0 707 and Return to Origin T F T This template allows slit scanning across an object by defining a list of offsets in the Y direction If the parameter Return to Origin T F is set to true T the telescope returns to the starting position If not the telescope is not moved The total integration time excluding overheads is defined in seconds by DIT x NDIT x Number of offset positions x NEXPO per offset position DIT NDIT Table 7 18 Parameters of NACO_
15. s Manual VLT MAN ESO 14200 2761 Parallactic angle from North deg TUS FUUVEUETS FUETUTVETE EVOTFEUET SS PUTETVETEN FTTETSTES FETTENESTS FSTE STONE STOSTSTETT OUTSET TST PETE 60 50 40 30 20 10 0 10 20 30 40 50 60 Hour Angle of the object from meridian deg Figure 5 43 Orientation of the pupil or spikes in field tracking FT mode angular parallactic variation as a function of time in FT mode as a function of the star declination Pupil tracking is set during acquisition of the target The users have only to specify in their template the need for pupil tracking set the flag to T and the position angle at which they wish the telescope spiders to be set Once set in the acquisition pupil tracking will be left on for the duration of the science For observations requiring a calibrator it is also possible to specify that the spiders keep the same orientation on sky as for the science In this case the PSF flag in the acquisition template for the calibrator has to be set to T The orientation of the spiders is illustrated in Figure 5 44 and Figure 5 45 90 User s Manual VLT MAN ESO 14200 2761 South dec lt 24 4deg Field Pupil N r 7 E ps o PAsky PAsky E North dec gt 24 4deg Field Pupil N E NN o V orc PAsky Figure 5 44 Pupil and Field rotations as a function of the star declination The pupil rotation is shown in black and the field rotation in red
16. very similar to observing with other IR instruments One has to deal with high and variable backgrounds and modest detector cosmetics In general the IR background particularly at longer wavelengths is higher for an IR instrument with an AO system because of the additional optics in an AO system Additionally the classical chop and nod technique which is commonly used for the LW filters in non AO systems works less well as the DM introduces background fluctuations that do not cancel perfectly This does not degrade L band observations but it may degrade M band observations Given the relatively small field of view of CONICA it is possible to observe in the L band without having to chop and nod However the overheads are relatively large typically 50 100 because the sky has to be sampled frequently at least once a minute and poor results can be obtained if one does not offset frequently ot if the time scale for fluctuations in the L band background is short We strongly recommend that users limit themselves to the autojitter template Jittered observations for the Lp NB 3 74 and NB_4 05 filters will allow a reasonably good background subtraction One of the major differences between AO and non AO systems is the pixel scale The pixel scale of CONICA can be as fine as 0 013 which is a factor 10 smaller than ISAAC Hence it will take 100 times longer to reach background limiting performance Additionally the fields of view are smaller
17. you are asked to enter its diameter in arcsec This morphology is modelled by a limb darkened disk 9 5 3 Photometry The PS also has to compute the flux coming from the reference object Since the WFS spectral bandwidths are very large a single magnitude is not sufficient to compute the detected number of photons The photometric information may be provided in different ways O Magnitude Spectral Type Well suited to main sequence stellar objects If you choose this option you will need to enter the apparent magnitude the filter in which the magnitude is measured either V J H K Lp or Mp and a spectral type The spectral type is chosen in an option button The list of available values is the same as that available in the interface of the CONICA ETC This ensures the compatibility between the two tools especially in the case when the target is also used as the reference object see also Section 9 5 6 o Magnitude Temperature The magnitude is given in the same way as above value filter but in this case the spectral energy distribution is modelled as a black body which requires a temperature Moreover the users now have the possibility to provide a visible extinction Ay value by default and if not specified this value is 0 and the PS behaves exactly as before When Ay is defined it governs by how much the brightness of the AO reference target changes as function of the wavelength which is especially important
18. 2761 Table 4 3 Summary of NACO Strehl ratios at 2 2 microns for an AO reference star at an atrmass of 1 2 Values are listed for the on axis case when the source and the reference are the same and for a source that is 30 away from the reference star The assumed seeing values are 0 8 and 1 2 at Zenith at a wavelength of 0 5 mm These values were derived with the Preparation Software PS and are also used in the CONICA Phase 1 Exposure Time Calculator to estimate signal to noise ratios Vmagnitude _ Vmagnitude _ Strehl ratios SR On axis 30 off axis On axis 30 off axis 0 8 seeing 0 8 seeing 1 2 seeing 1 2 seeing Note that a seeing of 0 8 or better can be obtained on Paranal 50 of the time while 1 2 or better can be obtained 80 of the time 4 3 Anisoplanatism Anisoplanatism is the field dependence of the PSF It corresponds to the angular decorrelation of the wavefront coming from two angularly separated stars This phenomenon affects the quality of the AO correction in the direction of the target when the reference star is not on axis 4 4 Laser Guide Star Facility LGSF 3 0 P93 LGS aided operations are no longer available with NACO Adaptive Optics Operations are strongly affected by the size of the isoplanatic angle usually 20 at 2um but only 5 in diameter at 0 6um Even for observations at 2 2um the sky coverage achievable by this technique equal to the probability of
19. 4 8 Pipeline for spectroscopy As of P82 we offer a grism spectroscopic pipeline The final product is a flat fielded wavelength calibrated combined spectrum Users can download an example dataset from the NACO spectroscopy webpage http www eso ore sci facilities paranal instruments NACO inst spectro html 5 5 Polarimetry VM only since P93 An MgF Wollaston prism is available for imaging polarimetry as well as a turnable half wave plate The latter is installed in the entrance wheel of CONICA where the calibration mirror is situated Internal calibrations with the half wave plate are thus impossible The Wollaston splits the incoming light into ordinary and extraordinary beams An image taken with the Wollaston prism will contain two images of every object To avoid sources overlapping a special mask consisting of alternating opaque and transmitting strips can be inserted at the focal plane In a single exposure at least half the field will then be missing so that three exposures with 62 User s Manual VLT MAN ESO 14200 2761 telescope offsets in between are required to image one field Sample flat fields with the special polarimetric mask in the focal plane are available from the NACO web pages To measure the Stokes parameters and hence the degree and position angle of polarisation a second set of images with the Wollaston prism rotated by 45 degrees with respect to the first pair is required This can be achiev
20. 7 Mag fainter if bandwidth smearing is not an issue Gives very good Fourier coverage and could be used for mapping relatively simple objects Good for faint companions BB 9Holes this mask was specifically optimized for broadband hence BB operation and should be used with the broad tilter set Although bandwidth smearing is unavoidable this mask is not affected because the holes are arranged so that they do not smear into each other Useful range of target brightness is about 5 to 10 Fourier coverage is not as good as 9Holes 7Holes this mask passes the most light and should operate from about 8 to 11 or maybe 12 mag Probably it is most useful for faint companion detection due to limited Fourier coverage 5 6 6 Calibrations flat fields and data cleaning Data processing entails all the normal imaging data tasks such as subtraction of any bias flat fielding and removal of bad pixels To obtain flats and bad pixel maps the standard NACO calibration plan and pipeline recipes are fine Results using the standard pipeline reduced flats were compared with flats generated by hand with the finding that there was no significant difference Normally masking data will be taken in a data cube mode which yields a large sample of the interferograms up to several hundred frames A further data cleaning strategy is based on frame selection over this data cube any frames with poor AO performance or any other strange effects are reject
21. CONICA image of the sky background through the AGPM in Lp band and L27 camera showing the clear 15 aperture and the vortex center located slightly off the intersection of CONICA s quadrants 49 Figure 15 left saturated PSF with a DIT of 0 05s Middle residual after the AGPM coronagraph DIT of 0 2s displayed at the exact same linear scale Note the attenuation of the peak brightness the diffraction pattern and the speckles pinned to the PSF including the spiders showing the threefold benefits of coronagraphy Right contrast curves showing the PSF the RAW azimuthally average intensity as well as the 5 0 final contrast after LOCI PCA type speckle subtraction on a typical but short ADI sequence 30 PA variation 200 s of total exposure time on source The purple curve shows the limit for larger PA variations The background limit reached here at 0 4 will be lower for brighter targets and or longer integration times see NACO ETC 50 11 User s Manual VLT MAN ESO 14200 2761 Figure 16 comparison between standard Full Oversized stop showing the VLT pupil and the Apo_165 stop The latter is used with the AGPM and hence requires pupil tracking mode It covers the diffraction and thermal emission from both the central obscuration M2 and the support structures spiders making the AGPM more efficient 51 Figure 17 Inner working angle AWA capabilities of the AGPM as measured in the lab left Delacroix et al 2013 in pr
22. Imaging SDI in SM VM is no longer offered since P93 Coronagraphy Since P93 only the AGPM L NB_4 05 is offered pupil tracking and cube mandatory only in VM AGPM The use of other occulting masks of various diameters 4 quadrant phase masks 4QPM_H 4QPM_K is discontinued Grism Spectroscopy Long slit spectroscopy with 4 erisms of resolving power 400 1400 over the covered spectral range Spectroscopy is now offered both in VM only since P93 17 2 1 User s Manual VLT MAN ESO 14200 2761 APP Speetroseopy Not offered since P93 erism LW Limited setups see web pages and only VM Polarimetry Imaging with a Wollaston prism works with without pupil tracking VM only since P93 SAM Sparse Aperture Masking Interferometry with 4 different masks SAM is only offered in VM Laser assisted observations with or without tip tilt star seeing enhancer mode is no longer offered since P93 and VM for any of the above modes This manual is organized as follows Section 3 a summary of AO techniques and IR observations Section 4 description of NAOS Section 5 description of CONICA Section 6 operations with NACO Section 7 acquisition and observations templates manual Section 8 filters transmission curves Section 9 the Preparation Software PS user manual Section 10 Appendix DPR keywords for NACO Additional resources NACO Web Pages NACO Online Documentation NACO News NAC
23. In the NACO_spec_obs_AutoNodOnSlht template the jitter width should be smaller than the throw the same applied for NACO app spec obs AutoNodOnsSlit Cube Mode is a feature that can be turned on for science templates not acquisition by means of the flag in the P2PP templates Note that the default window is 1024x1026 and other windows will have different sizes 512 256 128 and 64 with NY NX 2 centred on pixel 512 512 i e the user cannot set STARTX and STARTY the lower left coordinates for the detector window pP2PP Pupil tracking mode is set in the acquisition template by means of the corresponding flag in o For APP spectroscopic observations the user must supply OBs for APP standard stars Table 7 1 NACO template suite decommissioned modes are barred Action Template General to all observing modes Turn the field telescope rotator NACO all obs Rotate Acquisition Templates Preset telescope and acquite for imaging Preset telescope and acquire for imaging without gt Preset telescope and acquire for APP imaging Preset telescope and acquire for polarimetry Preset telescope and centre object s in the slit Preset telescope and centre object behind a mask Preset telescope and acquire for SAM NACO img acq MoveToPtixel NACO img acq MoveToPixelNoAO NACO app acq MoveToPixel NACO img acq Polarimetry NACO img acq MoveTosSlit NACO img acq MoveToMask NACO img acq SAMMoveT oPixel Pres
24. MAN ESO 14200 2761 Calibrations Spectroscopy Observations SAM IMAGE JITTER SAM PT As of P82 Add CUBE to existing DPR TECH JACO img obs Autolitter JACO sam obs GenericO ffset JACO img obs GenericOffset NACO img obs FixedSkyOtffset NACO sdi obe G OE SAE Od obs State JACO coro obs Astro JACO coro obs Stare JACO img cal StandardStar JACO coro cal StandardStar JACO app obs GenericOffset JACO img obs GenericOffsetNoAO NACO pol obs GenericOffset Add PT to existing DPR TECH JACO img obs Autolitter JACO sam obs GenericOffset NACO img obs GenericOffset NACO img obs FixedSkyOtffset SACO tabs Generic tet NACO sdi4 obs State NACO_coro_obs_ Astro NACO coto obs Stare NACO img cal StandardStar NACO coto cal StandardStar NACO app obs GenericOffset 164 User s Manual VLT MAN ESO 14200 2761 Calibrations Linearity Gain NACO img cal Linearity CALIB LAMP LINEARITY N ineari ACO img cal Linearity CALIB OTHER LINEARITY IMAGE NACO img cal Linearity CALIB FLAT LAMP DETCHECK I NACO img cal Linearity CALIB DARK DETCHECK I 165
25. NACO_sam_obs_GenericOffset or NACO_sampol_obs_GenericOffset Table 7 9 Parameters of NACO img acqg SAMMoveloPixel P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DITs Type of AO Observation LGS NGS NODEFAULT LGS or NGS observation type PSF Reference T F F Set to T if it is a PSF reference star Pupil Tracking Mode T F T Always set to T PT is compulsory RA offset arcsec 5 RA offset for sky image DEC offset arcsec 5 DEC offset for sky image Position angle on sky 0 Position angle Filter NODEFAULT Filter name Sparse Aperture Mask NODEFAULT SAM mask Polarizer Wheel NODEFAULT empty or Wollaston 00 Camera NODEFAULT Camera name NAOS Parameter file NODEFAULT NAOS aocfe file from JNPS 7 4 NACO imaging science templates For observations with the SW filters the readout mode of the detector should be set to either Double_RdRstRd or FowlerNsamp For observations with LW filters the readout mode should be set to Uncorr 123 User s Manual VLT MAN ESO 14200 2761 All imaging templates make use of the NEXPO per offset position parameter It is the number of exposures one exposure DIT x NDIT per offset position For very bright targets see Section 6 15 a neutral density filter can be inserted into the light path The choices are Full for no neutral density filter ND_Long for a LW neutral density filter and ND_Short for a SW neutral density filter For LW observat
26. Offset Coordinates DETECTOR Camera S27 List of offsets in RA or X 030 300 3 0 List of offsets in DEC or Y 0070 7 707 127 User s Manual VLT MAN ESO 14200 2761 1024 1024 CONICA FOY 28 for 27 1 1 x Figure 7 5 A second illustration of how the NACO img obs GenericOffset template works As with the previous example exposures 1 and 5 occur at the same place and the telescope returns to the origin after the eighth exposure indicated by the dashed line connecting point 8 with 1 5 The parameter settings for this example are given in Table 7 13 Table 7 13 parameters for the example shown in Figure 7 5 NEXPO per offset position 1 Observation Type O or S O Number of offset positions 8 Offset Coordinates SKY Camera 27 List of offsets in RA or X 0 4 0 4 0 0 4 0 List of offsets in DEC or Y 0 0 8 0 8 8 0 8 7 4 3 NACO app obs GenericOffset This is the APP template allowing cube mode pupil tracking etc Its a copy of NACO img obs GenericOffset but the APP will be allowed and only the NB 4 05 and the Lp L prime filters will be allowed The readout mode will be automatically set to Uncorr HighDynamic L27 or L54 camera are both options for this mode Note that since the APP shifts the FoV by 19 vertically the useful FoV using the L27 and associated FLM 27 field stop will be of the order of 28x9 X Y On the detector the useful FoV spans from p1 80 700 to p2 1024 1024 This is co
27. Offset from reference star arcsec RA offset arcsec 5 RA offset for sky image DEC offset arcsec 5 DEC offset for sky image Position angle on sky 0 Position angle Filter NODEFAULT Filter name e g Ks Neutral Density Filter ND_Short Full Neutral density Filter Full none DEFAULT Camera NODEFAULT Camera Name e g S27 Slit NODEFAULT Slit name 119 User s Manual VLT MAN ESO 14200 2761 NAOS parameter file NODEFAULT NAOS aoctg file from JNPS 7 3 6 NACO_app_acq_MoveToSlit This template does a telescope preset and is followed by interactive centering of the object in the slit It is essentially a copy of the NACO_img_acq_MoveToSlit 7 3 2 template however it inserts the APP at the very end and should in principle be followed by the NACO_app_spec_obs_AutoNodOnSlit template After the AO reference has been acquired the slit is placed into the beam and an image is recorded The slit position is computed the slit is removed and a drawing of the slit is superimposed on the image of the field The centering of the target is then done interactively The template also allows one to place two objects into the slit without the requirement of calculating the position angle beforehand In such cases the acquisition strategy should be adequately explained in the README file and those targets which should be placed in the slit should be clearly designated on the Finding Chart and their position on the slit clearly indicated To save t
28. RA Offset Figure 7 6 An illustration of how the NACO img obs_FixedSkyOffset template works with Jitter Box Width 9 Number of AB or BA cycles 4 Sky offset in Dec 15 Sky offset in RA 35 and Camera 13 The AO loop is off when the sky is observed large filled in circles and on when the object is observed small filled in circles The dashed line connecting 8 with 1 is the offset done at the end when the telescope returns to origin The dashed box is defined by the Jitter Box Width 7 4 6 NACO img cal StandardStar This template is used for imaging standards and is similar to the NACO img obs GenericOffset template with the difference that some DPR keywords in the FITS headers of the images are set to different values allowing pipeline processing and archiving Additionally NDIT is single valued in this template and offsets are in detector coordinates only This template should be used by all users who wish to take calibrations standard stars observation beyond the ones provided by the Calibration Plan Table 7 15 describes the parameters of this template Table 7 15 Parameters of NACO_img_cal_StandardStar P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DITs Readout mode Double _RdRstRd Readout mode Window Size 1024 Size of the window Store Data Cube T F F Data cube flag NEXPO per offset position 1 Number of exposutes per offset position Number of offset p
29. Telescope presets can only be done via acquisition templates and all observing blocks must start with one There are nine acquisition templates one for imaging one for imaging without AO and one each for SDI imaging spectroscopy coronagraphy polarimetry and APP and two for SAM one SAM one SAMPol They are listed in Table 7 1 Apart from the acquisition template for no AO observations all acquisition templates preset the telescope to the AO reference star set up NAOS and CONICA close the loop and acquire the science target NACO_img_acq_MoveToPixelNoAO presets to the science target With the same exception of the acquisition template for no AO observations all acquisition templates require a NAOS parameter file an aocfe file which contains information about the target the reference source the NAOS setup and other ancillary data Once this file is loaded the target fields in P2PP will contain the target coordinates The acquisition templates can take anywhere from one to five images during the acquisition process See the description of the individual acquisition templates for a description of what kind of images are recorded In general it is not necessary for the acquisition and the subsequent observation templates to have the same DIT and NDIT nor the same filter but it is recommended Exceptions are SAM where the mask cannot change from acquisition to science and the 4QPMs which once inserted are never re
30. a joint project in which ESO built the laser room beam relay and launch telescope while the Max Planck Institut fur extraterrestrische Physik MPE and the Max Planck Institut fur Astronomie MPIA provided the laser itself The PARSEC project is based on a 4W CW Sodium Laser 589 5 nm focused at 90 km altitude in the mesosphere The thin layer of atomic sodium present at that height backscatters the spot image and produces in best conditions a V 11 artificial star to guide the AO servo loop More typically the artificial guide star is in the range V 11 13 This artificial reference star can be created at the position specified by the target coordinates and the NAOS visible wavefront sensor is used to correct the high order wavefront aberrations on the target object The laser is hosted in a dedicated laboratory under the Nasmyth platform of UT4 Figure 4 2 custom made single mode fibre carries the high laser power to the 50 cm launch telescope situated on top of the secondary mirror assembly providing the best possible artificial source image quality As a safety measure a twin whole sky camera with specialized software is used to monitor incoming aircraft and shut down the laser beam when an airplane enters field of view of the telescope During P86 a new 14x14 lenslet array was commissioned successfully Feb 2010 giving better performance than the former 7x7 one whenever the atmospheric conditions are good to very good and the o
31. an image of the acquisition target after it has been centred If reference offsets are used an additional image either the 3rd or the 5th image recorded to disk is taken after the reference offset The APP works only in the 3 5um range but the possibility to acquire the star in Ks NB_2 17 NB 3 74 or NB 4 05 is given DEFAULT filter is L prime 120 User s Manual VLT MAN ESO 14200 2761 Table 7 6 parameters of NACO app acg MoveloS lit P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DIT s Type of AO Observation NODEFAULT LGS or NGS observation LGS NGS type PSF Reference T F F Set to T if it is a PSF reference star Alpha offset from Ref star 0 Offset from reference star arcsec Delta offset from Ref star 0 Offset from reference star arcsec RA offset arcsec 5 RA offset for sky image DEC offset arcsec S DEC offset for sky image Position angle on sky 0 Position angle Filter Ks NB_2 17 L_prime NB_3 74 NB_4 05 Filter name e g L_prime L_prime Neutral Density Filter FullND Short ND Long Full Neutral density Filter Full none Camera NODEFAULT Camera Name e g S27 Slit NODEFAULT Slit name NAOS parameter file NODEFAULT NAOS aocfg file from JNPS 7 3 7 NACO img acq_MoveToMask only with AGPM and VM since P93 7 3 8 This template does a telescope preset and is followed by interactive centering of the object behind the coronagr
32. and the order sotting filters used in spectroscopy The camera wheel which contains all the objectives 31 User s Manual VLT MAN ESO 14200 2761 Adapter Callbratlon Source i Cryogenic Shutter Fabry Perot Pupll Stop Mask Wheel Colllmator Closed Cycle Cooler Detector Mei 4 LN2 Cycllng Radlatlon Shleld Figure 5 1 CONICA Schematic overview 32 User s Manual VLT MAN ESO 14200 2761 51 CONICA detector 5 1 1 General characteristics The CONICA detector is a Santa Barbara Research Centre SBRC InSb Aladdin 3 array It was installed into CONICA during May 2004 and it replaces the Aladdin 2 detector that had been used since the instrument was first offered The main characteristics of the Aladdin 3 array are summarized in Table 5 1 Table 5 1 CONICA detector characteristics Detector Format Pixel Size Dark Current Wavelength range um ADUs pixel um Aladdin 3 1024 1026 0 05 0 15 0855 The new detector is more sensitive to heavily saturated sources The limiting magnitudes that are observable are specified in Table 6 4 Please check carefully Section 6 15 for tolerated saturated observations For bright objects a number of electronic and optical ghosts become apparent If the source is at pixel coordinates x y there will be electronic ghosts at approximately 1024 x y 1024 x 1024 y and x 1024 y and there may be an optical ghost which looks like a set o
33. annotated on the plot 82 12 User s Manual VLT MAN ESO 14200 2761 Figure 5 40 Same as Figure 5 39 but for the 9 Holes mask 83 Figure 5 41 Same as Figure 5 39 but for the BB 9 Holes mask 54 Figure 5 42 Same as Figure 5 39 but for the 7 Holes mask 89 Figure 5 43 Orientation of the pupil or spikes in field tracking FT mode angular parallactic variation as a function of time in FT mode as a function of the star declination 90 Figure 5 44 Pupil and Field rotations as a function of the star declination The pupil rotation is shown in black and the field rotation in red PAsky refers to the rotator offset that can be applied during the OB acquisition 91 Figure 5 45 Orientation of the telescope spiders for different position angles The spiders have 180 degrees symmetry i e 90 and 90 look identical Spiders rotate clockwise for positive angles 93 Figure 7 1 Orientation for imaging polarimetry and coronagraphy Left Field orientation on detector at O rotation angle on sky Right Field orientation at 45 rotation angle on sky 114 Figure 7 2 Orientation for spectroscopic observations Left Field orientation on detector at O rotation angle on sky Right Field orientation at 45 rotation angle on sky 114 Figure 7 3 An illustration of the NACO_img_obs_AutoJitter In this example the jitter box width is set to 10 NEXPO is 1 number of offset position is 7 Return to Origin is T and the camera is S27 The
34. are not reduced by the pipeline The pipeline also calculates zero points and Strehl ratios for data taken with the NACO img cal StandardStar template read out noise from detector darks and it creates master twilight flats master lamp flats and master dark frames 5 2 3 noAO speckle imaging From P86 onwards an open loop imaging mode with NAOS CONICA has been offered Associated with hardware windowing and fast readouts Cube Mode Section 5 8 it allows the user to apply various speckle interferometry techniques Some tests were carried out recently with NaCo and gave nice results using the following poor man s AO techniques simple shift and add SSA or weighted shift and add WSA methods yielding Strehl of 10 40 Ks band speckle masking image reconstruction a a Weigelt 1977 Opt Co 21 55 allowing a very high Strehl ratio but on a small field adapted to not so extended sources multiple systems etc This project is lead by Sridharan Rengaswamy srengasw eso org and gave promising results on close binaries high Strehl ratios Figure 5 3 speckle holography Petr 1998 ApJ Sch del 2013 MNRAS allowing very precise astrometry over a somewhat large field of view Figure 5 4 lead R Sch del rainer iaa es 38 User s Manual VLT MAN ESO 14200 2761 noAO mode speckle masking technique Weigelt s Bispectrum method adapted by S Rengaswamy noAO speckle masking reconstruction
35. are taken with good AO correction The causes of this jitter are not yet well understood They represent one more reason why cube mode observations and shift and add post processing of the images can result in a significant increase of Strehl and image quality 87 User s Manual VLT MAN ESO 14200 2761 Table 5 21 characteristics of cube mode Detector Setup Window Min Max NDIT Frame Loss Time Loss size DIT 050 o 0 Damb Jszs4 0109 s o o Dam zess oo o7 o o Damb s3 Joons so o o Dam ee oor m o 0 L O Noe DCR min DIT 0 35sec always loses frames 0 5 see docs nor Efficient nss oaos 175 126 J ieme o PENS HS si2xata omo 308 irme o0 PENS HS 236x258 0 14 207 rme 0 FNS HS sxo 0048 804 drame 0 PENS HS eo ood ieme 0 Nor NS one frame is lost Large overheads ucam 1024x1026 o3 pe o vamo Jasza Jo s o o ormb zess oo an o o uamo s3 0008 so o o OOOO O O OO Noe UCR HD for NB thermal imaging uamo Jomas 017s m oo PUCR HWD oaos 030 s o 0 PUcR HWD fs2xs14 oo s o o uamo Joss o an o J o PUCR HWD 128x130 oos eon o o vamo Jex oo m oo 0 5 8 1 Cube mode overheads TM a T T eee see wee eea E Overheads in cube mode depend on the readout mode and on the observing setup DIT NDIT Not all possib
36. button labelled Register Object at the bottom of the reference object form The mandatory fields are O the coordinates of the reference which sets the distance to target O the reference brightness and Oo the reference morphology If the reference object is the target one can use the Target Reference Object option from the Objects menu at the top of the panel as a shortcut For test purposes the interface can be run without knowing the precise coordinates of the target nor the reference object In this case one need only enter the separation between the two But names and coordinates must be supplied if the interface is being used for OB preparation The default morphology of the reference object is point like which does not need any additional input Other morphologies can be specified Other buttons that can be seen next to Register Object are o Reset Form this simply erases the form without confirmation o Update Object if you are modifying the characteristics of a reference object which is already recorded in the table this button will automatically turn red reminding you to click this button to record your changes o Cancel cancel any changes to the selected reference Underneath the table is another set of buttons which allows one to manipulate the list of reference objects o Up Down moves the selected object in the list by swapping it with its neighbour The order in wh
37. diffraction limited structures appearing in the masking data 72 User s Manual VLT MAN ESO 14200 2761 cannot be seen in the AO image It is possible that with deconvolution using a carefully recorded PSF frame that more real structure may be recovered from the AO but this procedure has proved to be controversial in the past and can lead to spurious structures Milliarcseconds 100 100 400 O 100 400 0 100 Milliarcseconds Milliarcseconds 200 F py d 100 Milliarcseconds O 200 200 100 0 100 200 Milliarcseconds Figure 5 30 Canis Majoris images reconstructed from 18 hole masking data top and from a set of shift and add stacked full pupil AO frames bottom Other examples of scientific results obtained with SAM on sky can be found on the NACO Web pages http www pl eso org sci facilities paranal instruments NACO inst sam html 5 6 12 Faint companion detection theory At first glance the spread out diffraction pattern generated by the mask which scatters light over a large region seems to act counter to the objective of revealing a faint companion buried in the halo Although there is no way to tell from the image plane whether a companion may be present or not the key advantage offered by a mask is that it enforces a very high degree of stability on the optical transfer function of the telescope This stability can be exploited to recover moderate to high dynamic range companions at high spa
38. field stars should be accepted prior to observation In service mode a waiver request must be submitted In most cases the waiver can be granted but depending on the level of saturation requested and the amount of persistence time will be charged to the program to wait for the persistence to clear out In visitor mode prior approval for such observation must be obtained especially if only half nights are attributed to the project The magnitude at which saturation starts depends on several parameters filters Strehl objective etc The ETC should be used to check that objects of scientific interest do not saturate the detector Moreover actual weather conditions may change this limits In particular users are warned that asking for THIN conditions is not a viable strategy given the variability of the clouds it is too risky to acquire and observe brighter targets that could saturate badly when the conditions change for the better Note also that the WFS itself cannot be allowed to saturate the penalty being the impossibility to perform AO correction Users need to restrict themselves to the magnitude limits indicated in Table 4 2 Finally it should be noted that it doesn t make sense to ask for LGS observations under THN or THK conditions since the variable conditions of the sky will significantly affect the performance of the laser LGS observations will be accepted only under PHO or CLR conditions proposals requesting otherwise w
39. finding a suitable reference star in the isoplanatic patch around the chosen target is only of the order of 0 5 to 1 The most promising way to overcome the isoplanatic angle limitation is the use of artificial reference stars or laser guide stars LGS Laser Guide Stars are artificial sources potentially replacing NGS as reference objects for Adaptive Optics AO image corrections The rationale is the much higher sky coverage offered in principle by an LGS as opposed to the standard NGS approach Due to the bright V 11 13 artificial star created near the centre of the field the probability to achieve a given minimum AO correction on an arbitrary astronomical target goes e g from a meagre 3 with an NGS to 65 with an LGS for corrected images with at least a 20 K band Strehl ratio Nevertheless there are still a number of physical limitations with an LGS The first problem is the focus anisoplanatism also called the cone effect Because the artificial star is created at a relatively low altitude back scattered light collected by the telescope forms a conical beam which does not cross exactly the same turbulence layer areas as the light coming from the distant astronomical source This leads to a phase estimation error The effect is roughly equivalent on an 8 m telescope to the phase error experienced with an NGS 10 away from the astronomical target However contrary to the case of NGS only AO LGS based corrections saturate a
40. for Lp band 0 1 7 5 360 FoV Apodizing Phase Plate for NB_4 05 0 25 1 0 180 FoV Plane Since P93 only the AGPM is only offered in PT and VM No photometric standard stars will be taken as part of the calibration plan even for CLR conditions unless provided by the users Since P91 it is allowed to use detector windowing with coronagraphy Windowed coronagraphic observations may result in overly compromised fields of view See the images linked to on http WWw eso otg sci facilities paranal instruments naco inst corono html for guidance 5 3 1 Semitransparent mask C 0 7 sep 10 The contrast between inside and outside of the 0 7 semi transparent mask has been measured to be AKs 6 3 0 1 mags and AH 6 0 0 1 mags The opaque masks are held by wires and the semi transparent mask is placed on a transparent plate Users should be aware that using the semi transparent mask with the S13 camera severely limits the availability of the field of view due to vignetting induced by mask mis alionment see Figure 5 8 This should discourage the use of this mask with the smallest scale camera except for very experienced users 43 User s Manual VLT MAN ESO 14200 2761 Figure 5 8 Semi transparent mask with the 13 camera The only useful spot is the bottom left one even this one is severely limited in the bottom left area 5 3 2 Four quadrant phase masks 4QPMs The two four quadrant phase masks 4QPM
41. is possible for the user to sample the object and the sky as desired at several rotator positions It is also possible to code the template so that the object and sky are sampled as desired for one angle only The template can be restarted with another orientation on the sky for another series of exposures The total integration time excluding overheads is defined in seconds by DIT x NDIT x NEXPO per offset position x Number of offset pos x number of rotator pos 131 User s Manual VLT MAN ESO 14200 2761 Table 7 16 Parameters of NACO_sdi_obs_GenericOffset P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec Readout mode Double _RdRstRd Readout mode Window Size 1024 Size of the window Store Data Cube T F F Data cube flag List of NDIT s NODEFAULT List of NDIT s NEXPO per offset position 1 Number of exposutes per offset position Number of offset positions NODEFAULT Number of offset positions Observation type O or S NODEFAULT O is in closed loop S in open loop List of offsets in X NODEFAULT Offsets in arcsec List of offsets in Y NODEFAULT Offsets in arcsec Return to the Original F Rotator position at the end of the template Rotator position T F List of position angle offsets NODEFAULT List of rotator offsets in degrees Neutral Density Filter Full Neutral density filter Full none 7 6 NACO spectroscopic science templates For SW observations the readout mode of the detector can b
42. of AO Observation LGS NGS NODEFAULT LGS or NGS observation type PSF Reference T F F Set to T if it is a PSF reference star Pupil Tracking Mode T F F Set to true for PT observations RA offset arcsec 5 RA offset for sky image DEC offset arcsec 5 DEC offset for sky image Position angle on sky 0 Position angle or pupil angle in degrees Filter NODEFAULT Filter name e g Ks Neutral Density Filter Full Neutral density Filter Full none Camera NODEFAULT Camera Name e g S27 NAOS parameter file NODEFAULT NAOS aocfe file from JNPS 7 3 1 NACO_ img acq_SDIMoveToPixel discontinued since P93 7 3 2 This template is very similar to NACO_img_acq_MoveToPixel 7 3 2 with the exception that the camera and the filter are not parameters of the template It should only be used to acquire targets for SDI The template does a telescope preset and is followed by interactive centering of the object It must be followed by an SDI template In service mode it is mandatory that users provide detailed information for the field centering on their Finding Charts and or in their README file In order for faint objects to be clearly seen an image of the sky is acquired in an offset position defined by the RA offset arcsec and DEC offset arcsec parameters The image is then subtracted from all images that are subsequently displayed on the RTD The integration time for these acquisition images is defined by the DIT and NDIT parameters This template
43. position 8 8 images will be stored for each position If in addition the Number of AB or BA cycles is set to 2 the template will deliver in total 32 images 8 for the first A position 16 for the B position and 8 for the second A position The total integration time excluding overheads is 64 minutes Note in the case where there are several OBs using this template on the same target for several hours of integration on the same target it is recommended to modify the Nod throw parameter by a few arcsec between each OB This is for the following reason the acquisition is always done at the same position on the array i e centre of the slit Therefore different executions of the same template will position the targets at the same positions along the slit and the spectra will fall at the same positions on the detector Therefore even if you define some non zero value for the Jitter Box Width parameter it is recommended to give the Nod throw parameter different values between OBs so as to get the spectra at different positions across the array When defining the nod throw users are requested to ensure that other objects in the slit do not cause the spectra to overlap when the throw is executed The total number of frames is Number of AB or BA cycles x NEXPO per offset position x 2 The total integration time excluding overheads is defined in seconds by DIT x NDIT x NEXPO per offset position x 2 x Number of AB or BA cycles 133
44. pre imaging the OB name must be prefixed with the string PRE_ For PSF observations which are to be done as pre imaging the OB name must begin with PRE_PSF_ The magnitude of the brightest object in all fields including standard stars must be explicitly given in the README file For LGS observations the TTS magnitude and distance from the target must be explicitly given in the README file For LGS in SE mode this must be explicitly written on the finding chart and in the README For APP please provide finding chart with the right PA with respect to the fixed orientation of the APP pattern on the detector see Figure 5 21 For OBs that need a maximum of field rotation using pupil tracking angular differential imaging users are requested to use the suffix Meridian in their OB name That way the operator will know this OB has to be observed around the meridian Beware that in Paranal the latitude is 24 35 If the declination of the object is within 4 of this value the telescope cannot cross the meridian and therefore these objects must be observed either before or after the meridian LST 10 minutes In addition explain explicitly in the ReadMe file at which LST the OB should be started taking into account the preset and acquisition overheads 6 9 Reference sources for wavefront sensing The brighter the reference source is and the closer it is to the science target the better the correction will be
45. range of masks installed in the camera is intended to span a variety of target fluxes with the 18 holes mask being tailored to give the best results for bright targets through to the 7 holes which is for use on the faintest targets Section 5 6 16 gives calibrations of the counts expected for varying mask filter combinations 5 6 11 On sky observations VY Canis Majoris VY Canis Majoris is a bright M supergiant which has produced an extensive infrared nebula several arcsec in extent At the core VY CMa exhibits a bright asymmetric plume first imaged in detail in Monnier et al 1999 ApJ 512 351 This form of strongly asymmetric structure together with the spatial structure on ideal scales of less than 200 milli arcsec all makes VY CMa an ideal test target for SAM Figure 5 30 shows images produced in narrowband filters within the H and K bands using 18Holes mask data recorded at the commissioning run in March 2008 For comparison we also show the results of contemporaneous imaging observations using the full telescope pupil and adaptive optics system We have taken an identical series of rapid exposures to the masking case and use the shift and add algorithm to stack these data into a final resultant best image This is given in the bottom panel of Figure 5 30 There is some correspondence between the AO only and masking images in that there is evidence for a similarly skewed centre of brightness in the AO image However the fine detail and
46. readout detector modes will be taken when these modes are used under CLR or PHO constraints These calibrations aim to provide a photometric accuracy of 5 Users needing higher accuracy should provide standard star OBs that will be executed either immediately before or after their observations The time spent doing user supplied observations will be charged to the user o Extinction coefficients for J H and Ks filters The observatory does not measure extinction every night Instead the observatory has calculated the average extinction from data that have been taken since operations began E Mason et al Paranal NIR Extinction Coefficients in the Proceedings of the 2007 ESO Instrument Calibration Workshop p 439 442 Springer o Internal lamp Flat Fields are taken for every setup observed during the night Weekly J H Ks S27 DCR sky flat fields are taken in Double_RdRstRd for instrument checks Long waveleneth flats Mp Lp NB_3 74 and NB_4 05 will be taken on sky but only when observations with the corresponding set up are executed during the night Twilight sky flats in any other modes are only supported in VM o Detector darks in all readout modes and DITs as required 5 2 2 Pipeline for imaging The NACO_img_obs_AutoJitter and the NACO img obs FixedSkyOftset templates are supported by the pipeline The NACO img obs GenericOffset is only partly supported Sequences of observations with offsets larger than the field of view mosaicking
47. records a flat on and a flat off image which can be used for flat fielding the subsequent science frames two optional reference images star and sky used by the operator to classify the OB and the final acquisition image with the star centred in the SDI field of view Table 7 4 Parameters of NACO_img_acq_SDIMoveT oPixel P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DITs Type of AO Observation LGS NGS NODEFAULT LGS or NGS observation type PSF Reference T F F Set to T if it is a PSF reference star Pupil Tracking Mode T F F Set to true for PT observations RA offset arcsec 5 RA offset for sky image DEC offset arcsec 5 DEC offset for sky image Position angle on sky 0 Position angle or pupil angle in degrees Neutral Density Filter Full Neutral density Filter Full none NAOS parameter file NODEFAULT NAOS aocfe file from JNPS 7 3 3 NACO app acq MoveToPixel Template very similar to the NACO img acq MoveToPtixel but created specially for the APP coronagraph pupil plane The default acquisition filter is NB 4 05 The acquisition images are taken without the APP which is placed in the optical path afterwards Allowed filters are NB 4 05 and Lp L prime 118 User s Manual VLT MAN ESO 14200 2761 7 3 4 NACO img acq_ MoveToSlit discontinued since P93 7 3 5 This template does a telescope preset and is followed by interactive centering of the object in
48. reduce the intensity of a source by splitting the focal plane into four equal areas two of which are phase shifted by amp radians As a consequence a destructive interference occurs in the relayed pupil and the on axis starlight rejected outside the geometric pupil is filtered with a diaphragm the so called Lyot stop The advantage over a classical Lyot mask is twofold there is no large opaque area at the centre enabling observations of objects that are within 0 35 of the main source and a larger achievable contrast is met cf Boccaletti et al The four quadrant phase mask coronagraph PASP 116 p 1061 2004 There are two such masks available Figure 5 9 e AQPM H optimized for a wavelength of 1 60 um circular field of view 8 diameter e AQPM K optimized for a wavelength of 2 18 um circular field of view 13 diameter These devices work best for filters that are centred at or near these wavelengths 44 User s Manual VLT MAN ESO 14200 2761 Figure 5 9 Flat field images of the 4QPM_K Ks filter left and of the 4QPM_H H filter right The many dust particles observed in the flats generate flat field variations of 10 20 locally 5 3 2 1 Radial attenuation of 4QPMs The intensity of off centred sources is also partially reduced The radial attenuation was measured to evaluate the impact of the Lyot spot on the Inner Working Angle and hence on the attenuation of an off axis point source Measurements w
49. s Manual VLT MAN ESO 14200 2761 7 8 3 NACO_coro_obs_Astto only with AGPM since P93 This template is used for coronagraphic observations It runs after a normal coronagraphic acquisition It takes NEXPO Obj only images of a target behind the coronagraphic mask without moving the telescope Then the coronagraphic mask is removed and NOFF img 1 are taken The last offset provided in the NOFF IMG list moves the telescope onto the sky position Generic offset principle There the mask is inserted again and in an auto jitter manner NOFF SKY images are taken on sky The idea is to get images of the target with and without the coronagraphic mask Since most sources are too bright for simple imaging there exists the possibility to define a different filter set up for the imaging part of the template The number of coronagraphic images to be taken on the source is defined by NEXPO CORO NOFF CORO defines the number of sky images to be taken with the coronagraphic mask The integration time DIT CORO is forced to be identical for all data taken with the coronagraphic mask but NDIT can be different for images with the target NDIT Obj and on sky NDIT Sky The Readout mode can be selected but remains the same throughout all the template For the imaging part of the template where no coronagraphic mask is used DIT IMG amp NDIT IMG can be defined independently of the rest of the template Similarly the number of exposures per
50. s Manual VLT MAN ESO 14200 2761 Table 5 9 APP Spectroscopic modes The mode name consists of the objective the grism number and the order sorting filter Mode Spectral Spatial scale Linear Dispersion R domain mas pixel nm pixel with 86 mas slit microns L54 2 LP 3 50 4 10 L54 2 SL 2 80 4 20 L27_1_LP 3 50 4 10 L54_1_LP 3 50 4 10 order overlap from 2 6 to 2 8 um order 2 visible also but does not contaminate As explained in the Calibration Plan all calibrations required for this VM only mode shared risks will have to be provided by the users standards stars using the same template as the scientific target 7 6 1 or requested to the Paranal SciOps staff i e APP imaging flats 5 4 3 Prism spectroscopy VM only Since P87 it is possible again to do prism spectroscopy in the range 1 5 microns There are three spectroscopic modes with the prism See Table 5 10 The spectral resolution varies from about 40 in the J band to 250 in the M band This is a VM only shared risk mode maintained because of its uniqueness Users should carefully prepare their observations having previously worked with similar datasets downloaded from the archive Table 5 10 Prism spectroscopic modes Mode Filter Dispersion Wavelength Fit Fit RMS Name nm pixel microns Order nm 52 P1 CaOF 2 5um 82 085250 oo To select a sub wavelength range an additional filter can be used There i
51. sampling grid on which the Fourier data is recorded permits some ambiguity when only a single snapshot is recorded Wide binaries can masquerade as much closer companions and give false sionals Taking a second or even third visit to an important target helps to eliminate these problems 5 6 8 SAM imaging tests For the imaging tests given here the 18Holes mask was used This gives the best Fourier coverage and well sampled short and long baseline data This means it is well suited to imaging of complex targets but of course this mask is the least sensitive and so only relatively bright targets are shown here Imaging using the 9Holes or other masks may be possible but the more limited Fourier coverage will limit the complexity of targets that can be mapped well One way to help circumvent this problem a little would be to observe the object over a period of several hours with visits alternating between the source and calibrator This would help build Fourier coverage by Earth rotation synthesis In general errors on the visibilities produced by masking are large The Fourier amplitude data is therefore quite poor A large fraction of the success of the images depicted in this section is due to the relatively good Closure Phase data This is an important point to keep in mind because many targets that one might wish to image do not show large closure phase signals at all Closure phases arise in situations where the source has non point symmetri
52. structures see Figure 16 50 User s Manual VLT MAN ESO 14200 2761 Figure 16 comparison between standard Full Oversized stop showing the VLT pupil and the Apo_165 stop The latter is used with the AGPM and hence requires pupil tracking mode It covers the diffraction and thermal emission from both the central obscuration M2 and the support structures spiders making the AGPM mote efficient 5 3 3 3 Inner working angle capabilities of the AGPM The AGPM has been designed to provide exquisite IWA capabilities as is demonstrated in Figure 17 The theoretical IWA of 1 A D 1 resolution element corresponding to 100 mas at Lp has been measured in the lab prior to installation Figure 17 left A representative technical test was performed on an old main sequence standard star V 7 Lp 6 under 1 2 visual seeing conditions yielding a 70 80 SR at Lp An ADI sequence was obtained with a PA range of 30 and for a total exposure time of 200 s on source The result is presented in Figure 17 right By pure chance a 1 100 off axis companion likely a late type star was discovered at 0 19 lt 2 MD demonstrating the best contrast IWA capability ever obtained by NACO L CORO PCA AGPM AP0165 DIT 0 2s HD4691B 100 0 2 Off axis throughput O Lab measurements shape preserving 1 2 3 4 Angular separation A d Figure 17 Inner working angle IWA capabilities of the AGPM as meas
53. taken The default is one This template should be used to take flats with the 4QPM and the semi transparent coronagraphic mask Only the SW filters are supported LW lamp flats are not possible For the LW filters for Lyot or AGPM coronagraphy the only alternative is to use a sky frame to flat field the data Table 7 24 describes the parameters of this template Table 7 24 Parameters of NACO_coro_cal_NightCahb P2PP Label Default Values Number of night flats 1 Description Night time flat field 7 8 5 NACO coro cal StandardStar This template is used to observe standards with the semi transparent coronagraphic mask It is similar to the NACO img obs GenericOffset template see Section 6 5 3 with the difference that some DPR keywords in the FITS headers of the images are set to values that allow pipeline 143 User s Manual VLT MAN ESO 14200 2761 processing and archiving Additionally NDIT is single valued in this template and offsets are in detector coordinates only Users should specify the offsets with some care as the purpose of this template is to allow photometry with the glass plate that holds the coronagraphic mask Images of the coronagraphic masks are available from the NACO web pages This template can also be used to observe photometric standards with the masks that are held by the wires C_0 7 and C_1 4 In this case the masks will not be inserted in the focal plane but the correct pupil mask will Ta
54. the used mask filter combinations 3 9 of pupil Flux 12 1 of pupil Flux 8 7 of pupil Flux 16 of pupil Flux L value 81 VLT MAN ESO 14200 2761 User s Manual 1000 c 3 O x O wv A 100 4 Magnitude 10000 2 1000 c 3 O AE O Q A 100 6 Magnitude Figure 5 39 Throughput for the 18 Holes mask Top panel shows throughput with three narrowband filters in J H and K bands respectively while the longer wavelengths are given to the bottom panel Various integration times are shown annotated on the plot 82 VLT MAN ESO 14200 2761 User s Manual 10000 2 1000 QO x O ov a 100 1000 Peak Counts 100 Magnitude Figure 5 40 Same as Figure 5 39 but for the 9 Holes mask VLT MAN ESO 14200 2761 User s Manual 10000 2 1000 5 OO x Ev a 100 1000 Peak Counts 100 Magnitude Figure 5 41 Same as Figure 5 39 but for the BB 9 Holes mask User s Manual 1000 3 x ov a 100 10000 1000 c 3 x Q a 100 Magnitude Figure 5 42 Same as Figure 5 39 but for the 7 Holes mask VLT MAN ESO 14200 2761 85 User s Manual VLT MAN ESO 14200 2761 5 6 17 PSF and MTF Information on PSF and MIF can be found in the NACO SAM web pages http www eso ote sci facilities paranal instruments NACO inst sam html 5 6 18 Calibration plan for SAM
55. time We are attaining 5 sigma contrasts of Delta F1 1 575 um 10 mag at 0 5 and Delta F1 1 575 um 11 mag at 1 which is comparable if not slightly better to the performance of the old SDI device on the same star shown in Figure 5 7 It is important to note that the contrast cutve provided for the old device was with a longer exposure time 28 minutes so SDI probably can attain a somewhat better contrast than SDI given the same exposure time For comparison Figure 5 7 also shows contrast curves for a variety of survey stars including AB Dor observed with the old SDI device The fact that the SDI curve seems to bottom out to a nearly constant value around 2 suggests that the contrast is read noise limited for radius gt 2 5 2 7 Pipeline for SDI The SDI mode of CONICA is not supported by either a pipeline or an ETC The term Roll Angle 1S explained in section Error Reference source not found 41 User s Manual VLT MAN ESO 14200 2761 CONICA PSF Optimized Conyentional AO SDI AF 1 50 0 0 Re 1 0 leo 2 0 arcsec from primary Figure 5 6 Contrast obtained on AB Dor with the new Wollaston SDI AB_Dor DX_leo GJ799A GJ799B GJ803 GJ862 HD 155555AB HD181321 HD48189A 4 84500 5 24200 rms 5 20100 5 20000 4 83100 5 28500 4 90700 5 05000 4 74700 ee ee ee ee ee ee AF1 50 0 0 0 5 1 0 1 9 2 0 arcsec from primary Figure 5 7 obtained on AB Dor with the old Wollasto
56. to freeze the field on the detector and let the pupil rotate with a field rotation given by the parallactic angle conventional mode called Field Tracking FT or decide to freeze the pupil and let the field rotates with the same field rotation but in the opposite direction mode called Pupil Tracking PT Both modes are available on NaCo and used for high contrast imaging observations For both modes to conduct astrometric studies one has to understand which angular offsets are applied and when to properly calibrate at the end the true north orientation in the final product of reduction and analysis The scope of this section is to clarify the field orientation issues in the case of pupil tracking observations This work was conducted by Gael Chauvin visiting scientist at ESO Chile at the end of 2010 and Julien Girard PT is a suitable option for imaging applications 4QPM coronagraphy classic Lyot coronagraphy SDI PT is imposed for AGPM coronagraphy PT was originally implemented to support SAM 5 6 but given the demand from the community it is now offered for a wider range of applications Using PT the telescope independently from NACO tracks the pupil orientation see Figure 5 43 instead of the field This new tracking mode opens the possibility to improve Angular Differential Imaging ADI a high contrast imaging technique that reduces quasi static speckle noise and facilitates the detection of nearby companions 89 User
57. with the exception only of a handful of extremely bright red late M supergiants and Miras This being the case a good calibrator is then any star which is single and without an extensive circumstellar dust shell or if binary has a relatively wide companion of at least several arcsec 68 User s Manual VLT MAN ESO 14200 2761 An attempt should be made as far as possible to preserve the same AO parameters between soutce and calibrator star If using the visible wavefront sensor this can present difficulties because often science targets will be very red or dusty to give resolved structure Finding calibrator stars for such extreme spectrum objects can be challenging If we consider an object such as WR 104 which is 14 mag in V but 2 mag in K then any normal star with similar IR fluxes will be orders of magnitude too bright for the visible WFS at the same settings For such targets it may be necessary to use the IR WFS Calibration is further enhanced by taking more rapid exposures removing the effects of seeing and irregular AO correction from the data There are compelling reasons to make multiple visits between the source and calibrator This will help to beat down the random noise and explore any systematic term in the calibration Furthermore Fourier coverage will be enhanced by the sky rotation obtained between successive visits This is helpful for imaging but even more crucial for faint companion detection The regular
58. 0 04 deg for reduced ADI observation ROT PT OFF 90 0 ADA PUPILPOS At a second order platescale and true north calibration are always mandatory to achieve an absolute astrometric precision of 0 1 deg The use of the same astrometric field is necessary for reducing the systematics 92 User s Manual VLT MAN ESO 14200 2761 Telescope spiders at PA 95 Telescope spiders at PA 90 Figure 5 45 Orientation of the telescope spiders for different position angles The spiders have 180 degrees symmetry i e 90 and 90 look identical Spiders rotate clockwise for positive angles During pupil tracking the field will rotate around the AO reference at a speed that depends on the object coordinates Targets close to zenith and passing meridian rotate the fastest Given its complexity and novelty pupil tracking was only offered in VM until P85 Starting with P86 PT is offered in SM as well only for simple imaging and APP imaging without coronagraphic or SAM masks 93 User s Manual VLT MAN ESO 14200 2761 5 10 NACO data format With the introduction of the cube mode NACO will have two different types of data formats single frames and data cubes Single frames are 2 D FITS files i e NAXIS 2 comprised of 1 image and 3 FITS extensions namely the Modal Voltage COvariance matrix MVCO the residual Modal Slope COvariance matrix MSCO and the Zernike Noise VAriance vector ZNVA The extensions store data produce
59. 14200 2761 5 6 13 On sky observations BD 21 4300 BD 21 4300 is a close unequal binary observed in March 2008 One wavelength dataset consists of 4 batches of 60 images of 1 5 sec integration time each i e a total integration time of 6 minutes It was observed with the H and K broad band filters and with the BB Yholes mask Seeing was average between 0 8 to 1 arcsec Figure 5 33 illustrates the process of fringe fitting The left panel is a single CONICA exposure the middle panel gives the best fit model image while the right pane is the residual We derived the closure phases of the object with the method mentioned in Section 5 6 12 and fitted these data with a binary star model The free parameters are the position of companion the flux ratio and a piston for each sub aperture Figure 5 33 Left CONICA image of a binary star Centre best fit artificial fringe pattern giving the Fourier amplitudes and phases Right the fitting residual shows the discrepancy between data and model The parameter space which must be searched for the position of the companion is not necessarily convex i e several minima in x2 may exist Therefore it is necessary to start with a grid search of the entire space before refining the best fit with gradient descent The resulting x2 maps are shown in Figure 5 34 RA mas Figure 5 34 xy maps showing detection of the binary BD 21 4300 Left H band data Right K band data The general minimu
60. 4 microns is due to the resin material 63 User s Manual VLT MAN ESO 14200 2761 The instrument induced polarisation as for all Nasmyth instruments is a function of the parallactic angle it is generally of the order of 2 but can be as high as 4 If users do not take care in determining the instrument induced polarisation then it is not possible to get meaningful estimates of the polarisation unless sources are more than 3 polarised In general we recommend that users come as visitors if they wish to measure the polarisation of sources that are less than 5 For more details we recommend the following reading Witzel et al 2011 A amp A 525 A130 5 5 1 Calibration plan for polarimetry For polarimetric observations a variety of calibration frames will be taken archived and updated at regular intervals The calibrations are described in detail in the NACO Calibration Plan o Twilight flats as described in Section 5 2 1 Twilight flats are done without the polarimetric mask and without the polarizer However in visitor mode twilight flats with the half wave plate can be requested Internal lamp flats are taken with the Wollaston prism as part of the Calibration Plan VM only since P93 but without the HWP since the lamp mirror needs to be inserted o Detector darks in all readout modes and DITs 5 5 2 Pipeline for polarimetry Polarimetry is not supported by the ETC or the pipeline 5 6 Sparse Aperture interferometric Ma
61. 5 Table 5 4 CONICA Broad Band Imaging filters um um 36 User s Manual VLT MAN ESO 14200 2761 Table 5 5 List of narrow and intermediate band filters um wm wass o Additionally there are two neutral density filters ND_Long which can only be used with LW setups and ND_Short which can only be used with SW setups These filters are mounted in another wheel so they can be used in parallel with other filters to reduce the flux of extremely bright soutces The intensity of sources is reduced by factors of 80 and 50 for the ND_Short and ND Long filters respectively Transmission curves are given in Section 8 2 IB 4 05 was decommissioned due to a non recoverable defocus issue and therefore it is not offered from P87 onward Please use NB_4 05 instead 37 User s Manual VLT MAN ESO 14200 2761 5 2 Imaging Imaging and SDI Simultaneous Differential Imaging use different combinations of filters and cameras 5 2 1 Calibration Plan for imaging and previously SDI For imaging observations a variety of calibration frames will be taken archived and updated at regular intervals The details are described in the NACO Calibration Plan O Nightly zero points provided it is clear in J H and Ks with the 27 objective and visual dichroic Zero points in Lp and Mp with the L27 objective and zero points in the J H and Ks filters with either the 13 S27 or S54 objectives other dichroics and
62. 5 35 Phases measurement for BD 21 4300 as a function of the baseline length The solid curve is the best fit of a model of a binary star Tuthill et al 2010 SPIE 7735 56 Right panel H band data Left panel K band data The companion position and flux ratio are reported in I able 5 17 AT Figure 5 36 Same as Figure 5 23 but using a point source reference star observed in different filters and masks Left 9 Holes NB 2 17 Middle BBY9 Holes NB 2 17 Right BBY Holes Lp All give statistically null results for the presence of a binary companion with best fit limits reported in Er Figure 5 37 Likelihood for the presence of a secondary star as a function of its position At maximum likelihood the flux ratio between the main star and its companion is 1 29 0 14 in K band left and 1 47 0 24 in H band right 78 Figure 5 38 Example of strong systematic effect on the phases Both dataset consists in 400 0 11 ms exposures The only different between these two dataset are the position of the star on the detector In red is plotted the mean phase as well as its statistical rms If the phases could be de biased potential precision on the phase would be 0 1 deg allowing detection with dynamic range of 1 000 80 Figure 5 39 Throughput for the 18 Holes mask Top panel shows throughput with three narrowband filters in J H and K bands respectively while the longer wavelengths are given to the bottom panel Various integration times are shown
63. 57 Figure 9 6 Pop up window showing the PSF profile This also gives access to the PSF FITS file The different width of the PSF in x and y direction are due to anisoplanatism The x axis is here defined as the axis that is parallel to the line connecting the reference object with the science target 158 MCC 14 User s Manual VLT MAN ESO 14200 2761 1 SCOPE This is the Naos Conica hereafter NACO User s Manual It can be used as a reference for users interested in preparing observing proposal with NACO This document has been completely revised and partly rewritten in 2009 using the latest available version of 2008 List of Abbreviations amp Acronyms This document employs several abbreviations and acronyms to refer concisely to an item after it has been introduced The following list is aimed to help the reader in recalling the extended meaning of each short expression 4QPM Four Quadrant Phase Mask 4QPM_H Four Quadrant Phase Mask optimized for H band 4QPM K Four Quadrant Phase Mask optimized for K band ADI Angular Differential Imaging AGPM Annular Groove Phase Mask Vortex coronagraph AO Adaptive Optics APP Apodizing Phase Plate pupil plane coronagraph ATP Acceptance Test Plan ATR Acceptance Test Report CCS Central Control Software CONICA High Resolution IR Camera and Spectrometer CPU Central Processing Unit DCR Double_RdRstRd DCS Detector Control Software DFS Data Flow System
64. 60 Figure 5 27 Transmission as a function of wavelength for the Wollaston prism The big absorption feature at 3 4 microns is due to the resin material 63 Figure 5 28 Mechanical drawings of the four aperture masks installed in the CONICA camera 65 Figure 5 29 Optical diagrams showing the effect of apodizing the pupil with the four 2 dimensional masks implemented in the CONICA camera 65 Figure 5 30 Canis Majoris images reconstructed from 18 hole masking data top and from a set of shift and add stacked full pupil AO frames bottom JD Figure 5 31 left image as obtained on the detector observing a calibrator star with the BB 9Holes mask right Fourier transform of this image revealing peaks corresponding to the different vector baselines passed by the mask 74 Figure 5 32 Models of fringe phase as a function of the baseline length A binary system generates phases with a sinusoidal pattern whose amplitude corresponds to the brightness ratio between the primary and the secondary while the frequency is proportional to the angular separation ZI Figure 5 33 Left CONICA image of a binary star Centre best fit artificial fringe pattern giving the Fourier amplitudes and phases Right the fitting residual shows the discrepancy between data and model 76 Figure 5 34 maps showing detection of the binary BD 21 4300 Left H band data Right K band data The general minimum is at the same position on the two maps 76 Figure
65. A and DEC and are in arcsec Offsets in X are along the slit offsets in Y are perpendicular to the slit Additionally the observation type can be defined for each image and is entered as a list in the parameter Observation Type O or S O stands for Object and assigns the DPR TYPE header keyword to OBJECT S stands for Sky and assigns the DPR TYPE header keyword to SKY The loop is closed for the former and open for the latter With large combined offsets the guide probe may not be able to follow the same guide star In such a case the guiding system will automatically find another star but not resume guiding A pop up window will instruct the operator to resume guiding If the guide star has changed during an offset the accuracy of the offset will be poorer than it would have been if the same guide star had been used This will only occur when offsetting from object to sky On the return offset the loop will close and the field selector in NAOS will make sure that the object remains centred in the slit even though the guide star has changed The total number of offset positions is defined in the parameter Number of offset positions This number can be different from the number of elements in the aforementioned lists Lists do not need to have the same length If the number of exposures is larger than the number of elements in a list the list is restarted from the beginning as many times as needed until the correct number of
66. AN ESO 14200 2761 ADA PUPILPOS specify the pupil angle Note that this value does not coincide with the position angle specified by the user ADA PUPILPOS position angle C with C 88 99x e Since the PUPILPOS is a function of the absolute rotator position and this one has a range of 270 degrees for a given position angle there can be two possible values For example if position angle 10 PUPILPOS can be either 99 9 or 260 1 99 9 360 Another important thing to remember is that the calculation of the rotator position is a function of the altitude Since the altitude changes from the moment the rotator angle is calculated to the moment the pupil is frozen in place there is an uncertainty in the value of C Let us call ROT PT OFFSET the rotator offset applied in PT mode We find the ROT PT OFF angular offset varies between 90 3 and 92 2 deg in our tests It sionificantly varies between two successive observing sequences during a same night The systematic variation seems to be reported in the ADA PUPILPOS keyword The difference ADA PUPILPOS ROT PT OFF 90 0 is stable in time and results to a 0 1 deg uncertainty If confirmed the ADA PUPILPOS keyword can then be used to calibrate the absolute position of the ROT PT OFF angular offset applied at the beginning of the PT sequence and needed for the final ADI images calibration Proposed absolute calibration using with 90 0 89 44
67. APP Apodizing Phase Plate coronagraph theory amp practice Expected gain in contrast close to the parent star o 8 Ao go Pe VLT NaCo o o 4 05 um o Bk o T o 0 0 5 1 Radius arcsec Figure 5 18 Azimuthally averaged flux of the VLT and VLT APP point spread functions simulations To determine the throughput of the APP the count rate in the inner pixels of the PSF in each individual image was computed using the IDL routine ATV pro Two different aperture sizes were used 2 pixel radius and 5 pixel radius Table 5 7 summarizes the results The count rate is the mean of the 15 individual images and the error is the corresponding standard deviation of the mean value The throughput is simply the ratio of the count rates with and without the APP It shows that for the NB 4 05 filter the throughput in the PSF core is 59 and 63 for an aperture with a radius of 2 and 5 pixels respectively This is in very good agreement with theoretical predictions that estimated a value of 56 in the innermost regions of the PSF core For the Lp filter the values are similar 55 and 61 for 2 and 5 pixel apertures respectively Table 5 7 Throughput measurements for the VLT APP as measured in April 2010 From Kenworthy et al 2010 SPIE 7735 103 pea SS pixel 53 User s Manual VLT MAN ESO 14200 2761 NB 4 05 filter 0 59 0 04 0 63 0 03 0 55 0 04 0 61 0 03 To compute the contrast curves al
68. ATES The instrument detector and telescope are controlled by OBs which are made up of templates Templates are divided into three categories acquisition observation and calibration Usually OBs consist of an acquisition template and one or more observation templates for nighttime observations and in some limited cases an additional nighttime calibration template Only one acquisition template is allowed in an OB and therefore only one preset on sky It is not possible e g to group in the same OB observation templates on the science object and calibration template on a standard star Table 7 1 provides a short summary of the templates offered for P89 These templates should cover most needs If this is not the case users must contact the User Support Department usd help eso org well before the start of observations 7 1 General remarks and reminders Only parameters specific to NACO are described The description of other parameters can be found in the P2PP User Manual http www eso org observing p2pp We strongly recommend that you consult the NACO web pages for the latest information o All imaging observations must use the NACO_img_acq_MoveToPixel template for acquisition except those using noAO mode in which case NACO_img_acq_MoveToPixelNoAO must be used o All APP imaging observations must use the NACO_app_acq_MoveToPixel template for acquisition o All polarimetric observations must use NACO img acq Polarimetry fo
69. BE MODE OVERHEADS PUPIL TRACKING PT MODE NACO DATA FORMAT 6 OBSERVING WITH CONICA AT THE VLT 6 1 6 2 6 3 6 4 6 5 6 6 6 6 1 6 6 2 6 6 3 6 6 4 6 6 5 6 6 6 6 6 7 6 7 6 8 6 9 6 10 6 11 6 12 6 13 6 14 6 15 6 16 6 17 6 18 SERVICE MODE SM CONTAINERS VISITOR MODE VM OPERATIONS ACTIVE OPTICS VERSUS ADAPTIVE OPTICS THE INFLUENCE OF THE MOON TELESCOPE CONTROL TARGET ACQUISITION IMAGING SPECTROSCOPY CORONAGRAPHY SDI 4 POLARIMETRY SAM SAMPOL PRE IMAGING FINDING CHARTS README FILES AND OB NAMING CONVENTIONS REFERENCE SOURCES FOR WAVEFRONT SENSING STREHL RATIO AND CLASSIFICATION OF OBS IN SERVICE MODE SM PSF REFERENCE STAR RECOMMENDED DIT AND NDITS IR BACKGROUND RECOMMENDED MAGNITUDE RANGES FOR STANDARD STARS MAXIMUM BRIGHTNESS OF OBSERVABLE TARGETS NIGHTTIME CALIBRATIONS INSTRUMENT AND TELESCOPE OVERHEADS OBSERVING WITH THE LGS VLT MAN ESO 14200 2761 80 86 86 86 86 86 86 87 88 89 94 95 95 95 96 96 96 97 97 98 98 98 98 98 98 98 99 99 100 100 101 101 101 102 103 103 103 User s Manual 7 NAOS CONICA TEMPLATES 7 1 TAA GENERAL REMARKS AND REMINDERS OFFSET CONVENTIONS AND DEFINITIONS 7 2 NACO GENERAL TEMPLATES Toal 7 3 Tod LL 7 3 3 7 3 4 75 5 1 56 TEGN 7 3 8 To 1 4 7 4 1 7 4 2 7 4 3 7 4 4 7 4 5 7 4 6 7 5 Tool 7 6 7 6 1 7 6 1 162 7 6 3 7 6 4 7 7 TAI Paka LTS 7 8 7 8 1 7 8 2 NACO ALL OBS ROTATE NACO ACQUISITION TEM
70. ECH for NACO has values which are linked to the various observing modes A combinations of keywords is usually necessary to give an accurate description of the technique for instance IMAGE JITTER SAM PT CUBE will describe SAM images with pupil tracking PT and CUBE mode active DIFFERENTIAL is reserved for SDI All the other names are self explanatory These keywords can be used for images selection in the archive when one uses the NACO dedicate query form available at http archive eso org wdb wdb eso naco form 161 User s Manual TPL ID NACO all cal Darks NACO img acq MoveToPixel NACO img acq MoveToPixel NACO img acq MoveToSlit NACO img acq MoveToSlit NACO img acq MoveToMask NACO img acq MoveToMask NACO img acq MoveToMask NACO img acq Polarimetry NACO img acq Polarimetry NACO ime aeq Preset NACO_img_acq_SAMMoveToPixel NACO img acq SAMMoveToPixel 1 VLT MAN ESO 14200 2761 Dark CAB bark Jima pp Acquisition PSF CALIBRATOR J IMAGE O Oo SS SKY MAGE pm PSF CALIBRATOR d mmAGE O O O SS S SKY MAGE ooo PSF CALIBRATOR imace O O O ToS SKY MAGE O Oo oo SoS CALIB FLAT LAMP CORONAGRAPHY As of P82 Only masks imaging PSF CALIBRATOR IMAGE MT SKY MAGE ooo SS PSF CALIBRATOR IMAGE IMAGE Observations Imaging NACO_img_obs_AutofJitter NACO_img_obs_AutofJitter NACO_img_obs_AutoJitterOffset SCIENCE OBJECT IMAGE PRE J SCIENCE OBJECT IMAGE JITTER LF SCI
71. ENCE OBJECT IMAGE JITTER Discontinued as of P81 162 User s Manual VLT MAN ESO 14200 2761 NACO_img_obs_AutoJitterOffset SKY Discontinued as of P81 Wee NACO_img_obs_AutofJitter TPL ID otes NACO_img_obs_FixedSkyOffset SCIENCE OBJECT IMAGE JITTER NACO_img_obs_FixedSkyOffset SCIENCE SKY IMAGE JITTER Calibration Imaging NACO_img_cal_LampFlats CAB FLAK LAMP T NACO img cal Skyrlas Cap SKY 0 NACO img cal TwFiat cam mans O a SSS NACO img cal StandardSta CALIB__ PSF CALIBRATOR imace OOOO SS Calibration SDI CALIB FLAT LAMP IMAGE DIFFERENTIAL CALIB FLAT SKY IMAGE DIFFERENTIAL SCIENCE OBJECT IMAGE DIFFERENTIAL JITTER SCIENCE SKY IMAGE DIFFERENTIAL JITTER ll Observations Coronagraphy OBJECT CORONAGRAPHY ITER NACO coro obs Sare fsm fsk GORONAGRAPHY JIMTER Calibrations Coronagraphy NACO como cal Sandardsar O Ja soo o O coronan e dT NACO coro cal NightCalib feae Aana CORONAGRAPHY O SS Observation Polarimetry Wollaston NACO_pol_obs_GenericOffset SCIENCE OBJECT POLARIMETRY WOLLASTON JITTER NACO_pol_obs_GenericOffset SCIENCE SKY POLARIMETRY WOLLASTON JITTER Calibration Polarimetry Wollaston NACO_pol_cal_LampFlats CALIB FLAT LAMP POLARIMETRY WOLLASTON DPR CATG DPR TYPE DPR TECH Notes NACO img cal StandardStar CALIB SPECTROSCOPY Ditto Observations Spectroscopy NACO_spec_obs_AutoNodOnsSlit SCIENCE OBJECT SPECTRUM NODDING PN O 163 User s Manual VLT
72. EUROPEAN SOUTHERN OBSERVATORY Organisation Europ enne pour des Recherches Astronomiques dans l H misph re Austral Europ ische Organisation fur astronomische Forschung in der s dlichen Hemisphare VERY LARGE TELESCOPE NACO User Manual Doc No VLT MAN ESO 14200 2761 Issue 93 0 Date 12 09 2013 Prepared J Girard for members of the Instrument Operations Team 01 03 2012 Name Date Signature Approved C Dumas Name Date Signature Released A Kaufer NameA Date Signature D Mawet L E Tacconi Garman E Valenti and the former Instrument Scientists E Pompei P Amico N Ageorges C Lidman User s Manual VLT MAN ESO 14200 2761 CHANGE RECORD ISSUE DATE SECTIONS REASON INITIATION AFF ENE REMARKS First issue 82 1 31 7 2001 26 2 2008 27 7 08 03 08 08 06 10 08 09 10 08 23 10 08 08 03 09 12 09 2009 26 02 2010 27 10 2010 01 03 2011 05 06 2011 30 08 2011 24 11 2011 28 02 2012 24 05 2012 06 09 2012 19 12 2012 01 03 2012 12 09 2013 revisited version Changed list of authors Porting to doc pdf Introduction of cube SAM and pupil tracking modes Corrected some errors related to the use of the Return to Origin Flag in some templates Eliminated the Add Velocity parameters Correction of typos Modified for p83 Updated added faint targets with SAM Added section on data format Updated Added DPR keywords table Improved figures refo
73. GRAPH AGPM CALIBRATION PLAN FOR CORONAGRAPHY NIGHT FLAT FIELDS FOR SW CORONAGRAPHY PIPELINE FOR MASK CORONAGRAPHY APODIZING PHASE PLATE APP CORONAGRAPHY LONG SLIT SPECTROSCOPY GRISM SPECTROSCOPY APP ENHANCED SPECTROSCOPY PRISM SPECTROSCOPY SLITLESS SPECTROSCOPY SLITS CALIBRATION PLAN NIGHTTIME ARCS AND FLAT FIELDS PIPELINE FOR SPECTROSCOPY POLARIMETRY CALIBRATION PLAN FOR POLARIMETRY PIPELINE FOR POLARIMETRY SPARSE APERTURE INTERFEROMETRIC MASKS SAM SAM WHY AND WHEN TO USE IT PUPIL TRACKING WITH SAM DETECTOR READOUT AND CUBE MODE SETUP FOR SAM SAM WITH LW FILTERS CHOOSING WHICH MASK TO USE CALIBRATIONS FLAT FIELDS AND DATA CLEANING PSF CALIBRATIONS STRATEGIES SAM IMAGING TESTS U V COVERAGE REFERENCES AND FURTHER READINGS ON SKY OBSERVATIONS VY CANIS MAJORIS FAINT COMPANION DETECTION THEORY ON SKY OBSERVATIONS BD 21 4300 ON SKY OBSERVATIONS AB DOR IN H AND K ADDITIONAL CONSIDERATIONS FOR FAINT COMPANION DETECTION VLT MAN ESO 14200 2761 41 41 43 43 44 49 52 52 53 53 57 57 58 59 61 61 62 62 62 62 64 64 64 65 66 66 67 67 68 68 69 69 72 72 73 76 78 79 User s Manual 5 6 16 CALCULATING EXPOSURE TIMES THROUGHPUT AND SENSITIVITY FOR SELECTED FILTERS 5 6 17 PSF AND MTF 5 6 18 CALIBRATION PLAN FOR SAM 5 6 19 PIPELINE FOR SAM 5 7 Doel byll 5 8 5 6 1 5 9 5 10 SAMPOL CALIBRATION PLAN FOR SAMPOL PIPELINE FOR SAMPOL CUBE MODE CU
74. Guidelines NAOSPS html Every change is automatically recorded in the jnpscf file located in the user s home directory Additionally depending on your local installation of the PS you may want to edit the file and modify the web enable resource enabling you to switch between the standard installation web enable true and the case where you access the PS server on your local machine web enable false However this latter case should normally never be encountered by the average user hence the default value is the correct one in most cases 160 User s Manual VLT MAN ESO 14200 2761 10 APPENDIX DPR KEYWORDS FOR NACO Each template that collects data with NACO being it an acquisition template or a science or calibration one writes a set of HIERARCH ESO header keywords that allows quick identification of the type of data These keywords commonly called DPR keywords are three CATG which stays for category TYPE and TECH which indicates the observing technique CATG can be of type ACQUISITION for acquisition images CALIB for CALIBRATION frames and SCIENCE There are other types such as TEST which is normally reserved for frames of no important content generated while testing TYPE can be DARK FLAT LAMP internal lamp flat WAVE LAMP internal lamp arc SKY OBJECT PSF CALIBRATOR STD for standard stars Other values are possible especially used for technical templates such that for detector s tests T
75. LT MAN ESO 14200 2761 3 6 Spectroscopy Spectroscopic observations with an AO system lead to the following effects o An increase in the Strehl ratio along the spectrum with increasing wavelengths Depending on the setting the Strehl ratio can change by 10 o A wavelength shift caused by the change in the Strehl ratio as a function of wavelength In particular at shorter wavelengths the FWHM of the PSF of the science object can be smaller than the slit width which leads to the wavelength shift that depends on the location of the object in the slit o A complex line profile The spectrum is the sum of a diffraction limited core and a halo that is limited by the external seeing The result is a combination of line profiles in the final spectrum the line core is at the highest spectral resolution while the wings have a lower spectral resolution since they are defined by the slit width Calibrating AO corrected IR spectra is therefore more complicated than calibrating IR spectra from a non AO instrument The steps are similar in both cases but the accuracy at which it can be done in AO corrected spectra is likely to be lower It will be harder to remove telluric lines that come from the Earth s Atmosphere and to do spectro photometric calibration 25 User s Manual VLT MAN ESO 14200 2761 4 NAOS 4 1 Overview NAOS provides a turbulence compensated f 15 beam and a 2 arcmin field of view FoV to CONICA Two off axis parabolas re imag
76. MoevetoPixel these templates set the instrument in coronagraphic mode andinSDI mede respectively In all cases except classic Lyot coronagraphy masks C_0 7 and C_0 14 the setup includes an optical element on glass substrate thus affected by dust which does not reposition accurately when it moves in out and again in the optical path Flat fielding used to be difficult because of repositioning problems of the mask elements unless one opted to use the NACO_coro_NightCalib template at the end of the science observations The new version of the acquisition templates now acquires one flat on off pair of images with the element in the same position as used for science For coronagraphy with classic Lyot elements users can still use the internal lamp taken during the day or obtain night calibrations by means of NACO_coro_NightCalib Note that this calibration is useless for Lp coronagraphs such as the AGPM instead a sky frame can be used 2 NACO img acq MoveToMask and NACO ims aeq SDiMoevefoMask have also been modified to allow taking a PSF image and the relative sky This is useful only when the main target i e the one which will be placed behind the mask can be used as PSF calibrator If this is the case it is not necessary to tick on the PSF keyword in the acquisition template since this process is completely hard coded within the template When the operator elects to take the PSF calibrator a pop up window will appear asking for confirmati
77. O contributed library NACO Call for Proposal NAOS Preparation Software Exposure Time Calculator Catalogues for adaptive optics reference objects Phase 2 Proposal Preparation User Support Department NACO Quality Control http www eso org instruments NACO http www eso org instruments NACO doc http www eso org instruments NACO news html http www eso org instruments NACO tools library html http www eso org sci observing ptroposals http www eso org observing p2pp OSS NAOSPS http www eso org observing etc Optical sources ESO GSC2 skycat http archive eso org skycat GSC2 at STScI http www gsss stsci edu Infrared Sources VIZIER Catalogue http vizier u strasbg fr viz bin VizieR source 2MASS http www eso otg observing p2pp NACO NACO P2PP html http www eso org sci observing phase2 USD html http www eso org obsetving dfo quality NACO qc qel1 html 18 User s Manual VLT MAN ESO 14200 2761 For any question regarding NACO Service Mode operations the point of contact is the User Support Department usd help eso org in Garching Users with approved Visitor Mode programs can contact NACO eso org 2 2 Current version of the manual This is version 93 0 of the NACO User Manual applicable for Phase 1 and Phase 2 preparation of P93 Since NACO is being constantly improved and modes are constantly refined especially the new ones it is advisable to check the NACO web page fo
78. OBs into containers for calibration or time link purposes as explained here http www eso ote sci observing phase2 P2PPSurveys html The Phase 2 OB preparation must therefore be made with P2PP version 3 P2PP3 available from the User Portal http www eso org sci php phase2 P2PP3Download html 6 2 Visitor Mode VM operations Visitors arrive on Paranal two days ahead of their observing run and receive support from Paranal Science Operations PSO Users are requested to read the P2PP and NAOS CONICA User Manuals before arriving During the night users do not have direct interaction with the instrument and the telescope The instrument operator observes the programs under the supervision of the visiting astronomer Visitors should be aware that up to 1 hour of their time can be taken by the observatory to comply with its calibration plan Typically only 15 minutes are needed The calibrations usually consist of twilight flat fields and imaging standards For spectroscopic observations the observatory automatically takes telluric standards for each setting used Visitors should think carefully about which telluric standards fundamental to remove telluric features should be observed The observatory staff will help them make the right choice Even though Paranal is an excellent site bad weather or poor and fast seeing can occur Visitors should come with backup programs particularly if the targets are in the North where on
79. PAsky refers to the rotator offset that can be applied during the OB acquisition The spiders angle can be set in the acquisition template by means of the parameter position angle the same used to set the orientation on the sky field tracking mode A positive angle rotates the spiders clockwise As of Nov 14 2008 pupil tracking is supported by the VLT software and new keywords are available to describe the pupil tracking observations TEL ROT ALTAZTRACK is set to T when PT is on to F for NORMAL tracking ADA POSANG specifies the position angle PA on sky at the start of exposure very important parameter when a lot of field rotation is expected especially for the APP imaging observations We can express the PA of the source S in the world coordinate system WCS by PA S 360 ADA POSANG ADA POSANG END specifies the position angle on sky at the end of exposure Note that it is wise to recalculate the parallactic variations if important during an exposure using the coordinates of the object and the DATE or DATE OBS keywords in ADI to derotate and stack the frames because the keywords ADA POSANG and TEL PARANG are not very precise Also we have ADA POSANG TEL PARANG 180 ADA PUPILPOS gt Asa consequence all files taken before that date are missing those keywords Since the mode was officially offered as of Oct 5t the number of affected files is rather small Jl User s Manual VLT M
80. PLATES PUPIL TRACKING PT IN THE ACQUISITION TEMPLATES NACO IMG ACQ MOVETOPIXEL NACO IMG ACQ SDIMOVETOPIXEL NACO APP ACQ MOVETOPIXEL NACO IMG ACQ MOVETOSLIT NACO APP ACQ MOVETOSLIT NACO IMG ACQ MOVETOMASK NACO IMG ACQ POLARIMETRY NACO IMG ACQ SAMMOVETOPIXEL FOR SAM AND SAMPOL NACO IMAGING SCIENCE TEMPLATES NACO_IMG_OBS_AUTOJITTER NACO_IMG_OBS_GENERICOFFSET NACO APP OBS GENERICOFFSET NACO IMG OBS GENERICOFFSETNOAO NACO IMG OBS FIXEDSKYOFFSET NACO IMG CAL STANDARDSTAR SIMULTANEOUS DIFFERENTIAL IMAGING SDI TEMPLATE NACO SDI OBS GENERICOFFSET NACO SPECTROSCOPIC SCIENCE TEMPLATES NACO SPEC OBS AUTONODONSLIT NACO APP SPEC OBS AUTONODONSLIT NACO SPEC OBS GENERICOFFSET NACO SPEC CAL STANDARDSTAR NACO SPEC CAL NIGHTCALIB NACO POLARIMETRY SCIENCE TEMPLATES NACO POL OBS GENERICOFFSET NACO POL OBS RETARDER NACO POL CAL STANDARDSTAR NACO CORONAGRAPHIC SCIENCE TEMPLATES NACO CORO OBS STARE NACO CORO OBS ASTRO VLT MAN ESO 14200 2761 111 111 114 115 115 115 117 117 118 118 119 120 121 122 123 123 124 126 128 128 129 130 131 131 132 132 134 134 136 136 136 136 138 140 140 140 142 User s Manual VLT MAN ESO 14200 2761 7 8 3 NACO_CORO_CAL_NIGHTCALIB 143 7 8 4 NACO CORO CAL STANDARDSTAR 143 7 9 NACO SAM AND SAMPOL SCIENCE TEMPLATES 144 7 9 1 NACO SAM OBS GENERICOFFSET 144 7 9 2 NACO SAMPOL OBS GENERICOFFSET 145 8 FILTER TRANSMI
81. RE This section describes the Preparation Software PS which is a key tool in the preparation of OBs in both Visitor and Service Mode The purpose of the PS is to find the optimal NAOS configuration for a given set of conditions to compute the associated performance and to provide input to P2PP and the ETC Input to the PS is done through a Graphical User Interface GUI and includes atmospheric conditions such as seeing and airmass target parameters such as the observing wavelength and the dichroic and reference source parameters such as brightness morphology and the distance between reference and target Output consists of a configuration file for P2PP Sec 9 5 7 an estimate of the performance in terms of Strehl a 2 dimensional PSF and an HTML formatted file Sec 9 5 6 for the ETC The ETC can be accessed via the web based interface at http www eso org observing etc or via the HTML file produced by PS Finally in the course of the execution of the observations at the telescope the PS is able to take into account the current external conditions and actual reference instead of expected source characteristics to optimize the observations still respecting the astronomer s requirements for observing wavelength transmission and so on The FITS headers of NACO data contain all the necessary information on the setup used Users can select the WFS directly This will allow users to use the N90C10 dichroic as neu
82. SSION CURVES 147 8 1 CONICA BROAD BAND IMAGING AND ORDER SORTING FILTERS 147 8 2 CONICA NEUTRAL DENSITY FILTERS 148 9 PREPARATION SOFTWARE 149 9 1 STARTING THE PS 149 9 2 GRAPHICAL USER INTERFACE OVERVIEW 149 9 3 TARGET AND INSTRUMENT SETUP 150 9 4 Sky CONDITIONS 151 9 5 REFERENCE OBJECTS 151 9 5 1 HANDLING SEVERAL REFERENCE OBJECTS 151 9 5 2 MORPHOLOGY 152 9 5 3 PHOTOMETRY 153 9 5 4 TRACKING TABLE 154 9 5 5 OPTIMIZING NAOS AND GETTING A PERFORMANCE ESTIMATION 155 9 5 6 EXPORTING TO THE EXPOSURE TIME CALCULATOR 158 9 5 7 EXPORTING TO P2PP 159 9 5 8 EXPORTING OBS FROM P2PP 159 9 5 9 SAVING RESTORING A PS SESSION 159 9 5 10 GIVING NAMES TO SESSION P2PP AND PSF FILES 159 9 5 11 USER S PREFERENCES 159 10 APPENDIX DPR KEYWORDS FOR NACO 161 LIST OF TABLES Table 2 1 Main modes and parameters of NACO Please check NACO public web overview for updates rrrrerrrrorvrrnrvrrvrvrrvrvrrnevene 17 ENN 26 Ve VIN jr 27 Table 4 4 Summary of NACO Strehl ratios at 2 2 microns for an AO reference star at an atrmass of 1 2 Values are listed for the on axis case when the source and the reference are the same and for a source that is 30 away from the reference star The assumed seeing values are 0 8 and 1 2 at Zenith at a wavelength of 0 5 mm These values were derived with the Preparation Software PS and are also used in the CONICA Phase 1 Exposure Time Calculator to estimate stonal to noise VATION a sensccanssssossdsussnsanssnoviisasssdvec
83. Tracking PT in the acquisition templates Pupil tracking is started in the acquisition template and it can be set to true only for the templates that support this feature NACO_img_acq_SAMMoveToPixel T by default angle is fixed NACO ime aeq_sDiMovefoPixel usualy Hs optional NTA CQO tag 9 3 4 NACO img acq MoveToPixel usually F T is optional NACO img acq MoveToPixelNoAO usually F T is optional NACO img acq MoveToMask usually F T is optional NACO app acq MoveToPixel usually F T is optional NACO img acq Polarimetry usually F T is optional In these templates the rotator angle assumes a different meaning since the pupil tracking flag has been set to T it is the angle to which the telescope spiders should be set Rotator angle offsets work the same way as in normal rotator mode A positive angle moves the spiders clockwise See Figure 5 45 for an illustration Notes for Pupil Tracking OB preparation it is encouraged for the users who wish to maximize their parallactic angle variations field rotation for ADI to stipulate in the readme at which LST their OB is supposed to be started on best effort basis It is also important for operations that users use the suffix _Meridian in their OB names when the OB has to be started close to the meridian For objects with dec 24 35 4 the meridian cannot be crossed the telescope would rotate too fast and 10 to 20 minutes have to be accounted for unless th
84. You can then attach your file to the selected reference object and the tracking table can also be seen via the View button which is enabled as soon as the file is attached Please note that the data of the tracking table are then copied into the interface which means that you do not need to keep the original file on your disk except of course if you want to edit your data You would then have to re attach the table to the reference object If you 154 User s Manual VLT MAN ESO 14200 2761 changed your mind and do not want the tracking table anymore just deselect the Tracking Table check button The Table 9 1 below shows the various cases of AO mode and tracking options Table 9 1 Various AO modes and tracking and differential tracking cases Diff Tracking table Diff Motion mao y ds ao y ds aooi y us o ooo o AO on R2 S Science target R1 Fixed NGS R2 Moving NGS 9 5 5 Optimizing NAOS and Getting a Performance Estimation The optimal configuration i e the one giving the highest Strehl and the resulting PSF are determined when the Optimize button located in the bottom left corner of the graphical user interface is selected The typical response time from the server is 10 seconds and should not exceed 60 seconds When more than one reference object has been defined the optimization is done for the selected highlighted one For complete preparation the Optimize command should
85. a full frame cube at minDIT needs 8 minutes observations for 03 45 minutes total exposure time i e 130 overheads As a general rule the smaller the window the higher the overheads which are 170 for 512 and for 256 230 for 128 170 for 64 To that one has to add the overheads for data cube writing to disk and controller TRACE overheads which are approximately 15 seconds per cube When one does not use the minimum DIT DIT gt 1 3 secs the overheads are much lower in the case of FNS the typical overhead is 1 8xNDIT seconds 5 9 Pupil Tracking PT mode IMPORTANT NOTE since October 15 2011 the PSF drift previously observed when tracking the pupil through meridian especially strong close to zenith has been fixed Pupil tracking can now be used efficiently with coronagraphic masks in the image plane Lyot 4QPM and the new AGPM as of P91 As of P90 all coronagraphs are offered in service mode with or without pupil tracking the AGPM is only offered with pupil tracking The residual drift of 1 pix hour up to 60 times smaller than before can be attributed to an imperfect flexure compensation model As for P93 however only the AGPM remains offered among the focal plane masks and only in VM because it requires a centering accuracy of 0 3 pixel Mawet 2013 A amp A When observing with an alt az telescope at the Nasmyth focus it is the case for NaCo FoV and telescope pupil are both rotating Since P82 you can either decide
86. aging a bright source V 11 with the VIS WES or K 7 with the IR WES with Double R RstRd EEE EE EE ERE niles lath oa dats EE ET dust EE 106 Table 6 12 Example 3 Imaging a bright source in the L band V 11 for the VIS WES or K 7 for the IR WES with Uncorr 107 Tabe6 15 SPEND Of Jamii JONE FO AN GAP asked ATA Aki 107 Table 6 14 Example 5 SW Polarimetry Of bright source with the Wollaston 108 Table 6 15 Example 5b Polarimetry of bright source with the Wollaston and HVD 108 Table 6 16 Example 6 SW coronagraphy of a bright source with Double RRSI RIG 109 LAOH BEN NTT ee keen 109 TAGA Ep LAE EL EE EEE EE 110 LAO IEE DENG RGT DN RER RE EE EN 110 TN PT isd titira E EATR AA ETE E 112 labe IS ROWOTAS ton bnatons USCA JOT 100 TOD CUDIA ON fI AS danseren needed 116 TARSA AT RTTE OF IAG ET ACG NOE OP ET EEEREN EEO E TOTOE E 118 LA Je TE oF IN AG Oa cg S V oe vred 118 NN NACO IE i ANNE S Ip 119 Fe Parameters Of NEO ACG Move LOSU add 121 Table fe Oe T aramada NACO Imi mg M T MG osiris thw tbe EEEE daa eet TAEAO ETE 122 De Of NACO IE AG L OUVIU EE EEEE O OOT O TOOR OOOO 122 TIDEND Parameters of a NACO JE GS TIME PR de EEEE NOE E OAE ETEN 123 Tabe St EL OUAS G NACO GE OOE AUTO TCI stata ei ett cate O OOT OT TO OONO EEEE 126 Table l Az LF araman o NACO GE OOS GUO riera 127 Tabe FT DS EA OIE NAPE SOW TIT EL RENEE EN 127 F DE Pa JO DE HODE SOW NTE FO thew Bac bate O Sa cicada delta AEAT 128 Lahes AG Pat NEO NTK 129 PN NNN 130 ve PN ee
87. al dichroic can only be used with the visual WFS and the other dichroics can only be used with the IR WES The conditions under which the dichroics can be used are listed in Table 4 1 Users are invited to study this table carefully The N90C10 can be used with the visible WFS and serves as a neutral density filter for CONICA A field selector FS is placed just after the WFS input focus in order to select the reference object for WF sensing The FS also allows object tracking pre calibrated flexure compensation and counter chopping currently this is not functional It is made up of two parallel tip tilt mirrors working in closed loop to achieve a very high angular stability Two WE sensors are implemented in NAOS one operating in the visible and one in the near IR An off axis NGS can be selected anywhere within a 110 arcsec diameter FoV facilitating a target to reference distance of up to 55 arcsec NAOS allows WF sensing with faint NGS and extended objects but with lower performance Observations of very bright objects are possible with the visible WES using neutral density filters Note that these neutral density filters are distinct from the neutral density filters of CONICA and are not selectable within the NAOS PS software or within P2PP They are linked to the first three available AO modes 1 1 1 2 and 1 3 The two WF sensors are of the Shack Hartmann type For the visible WFS two configurations are available a 14x14 lenslet
88. aocfg file from JNPS This template does a telescope preset and is followed by interactive centering of the object It is very similar to the NACO img acq MoveToPixel template however it must be followed by a polarimetric template that uses the Wollaston prism A drawing of the polarimetric mask is displayed on the RTD and is superimposed on the image of the field The centering of the target is then done interactively Acquisition must be done with the L27 objective for LW filters or the S27 objective for SW filters The subsequent polarimetric science templates allow one to set the angle before each template starts This template records an image of the field after the acquisition has been completed If three images are recorded then the first two are images of the reference and they are used by the operator to classify the OB Table 7 8 Parameters of NACO_img_acq_Polarimetry P2PP Label Default Values DIT NODEFAULT NDIT NODEFAULT Type of AO Observation NODEFAULT LGS NGS PSF Reference T F F Pupil Tracking Mode T F F Description Detector Integration Time sec Number of DIT s LGS or NGS observation type Set to T if it is a PSF reference star DEFAULT F PT supported since P88 122 User s Manual VLT MAN ESO 14200 2761 RA offset arcsec 5 RA offset for sky image DEC offset arcsec 5 DEC offset for sky image Position angle on sky 0 Position angle Filter NODEFAULT Filter name all filters theore
89. aphic mask It is very similar to the NACO_img_acq_MoveToPixel template however it must be followed by a coronagraphic template A drawing of the selected mask is displayed on the RTD and is superimposed on the image of the field The centering of the target is then done interactively Acquisition must be done with the L27 objective for LW filters and can be done with either the S13 or S27 objectives for SW filters However for precise centering with the 4QPM mask we recommend that users use the 13 objective even if LW observations are planned Note that when 4QPM masks are used the mask itself is not taken out of the optical path as was the case in the past to avoid repositioning problems This template records either two or four images If two images are recorded then the first image is an image of the approximately centred target without the mask and the second image is an image of the target accurately centred behind the mask If four images are recorded then these images become respectively the 3rd and 4th images and the first two are images of the reference and they are used by the operator to classify the OB In the case of the 4QPM masks and the semi transparent mask C_0 7_sep_10 the recorded images are o One flat on halogen lamp is on and one flat off image these images can be used for flat fielding the subsequent science frames o An image of the star off the mask 2 off with the ND filter inserted if spe
90. ar extended objects By construction there is no telescope offset before the first exposure If the parameter Return to Origin T F is set to true T the telescope moves back to its original position at the end of the template If not the telescope is not moved 124 User s Manual VLT MAN ESO 14200 2761 The total integration time excluding overheads is defined in seconds by DIT x NDIT x NEXPO per offset position x Number of offset positions 125 User s Manual VLT MAN ESO 14200 2761 Table 7 10 Parameters of NACO_img_obs_AutoJitter P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DIT s Readout mode Double _RdRstRd Readout mode Window Size 1024 Size of the window Observation Category SCIENCE Observation Category Store Data Cube T F F Data cube flag Jitter Box width NODEFAULT Jitter box width NEXPO per offset position 1 Number of exposures per offset position Number of offset positions NODEFAULT Number of offset positions Retutn to Origin T F T Return to origin at the end of the template Filter NODEFAULT Filter name Neutral Density Filter Full Neutral density filter Full none Camera NODEFAULT Camera Name 7 4 2 NACO img obs GenericOffset This template is used for imaging and has the flexibility to do any sequence of telescope offsets either in detector or sky coordinates Telescope offsets are defined as lists with the parameters List of off
91. are coded via templates Section 7 and two or more templates make up an OB OBs contain all the information necessary for the execution of an observing sequence Specific to NAOS CONICA the Preparation Software PS See Appendix B is a key tool since it allows one to optimize the adaptive optics configuration and to estimate performance Both the ETC and P2PP use the output from PS to determine feasibility and to prepare observations For Phase 2 preparation the PS must be used The ETC can be accessed via the regular web based interface http www eso org observing etc or via the HTML file produced by the PS For the former the ETC now calls the NAOS PS server itself to retrieve the performance estimate For Phase 1 preparation users can use either access route although we strongly recommend the use of the PS for Phase 1 preparation as well At the telescope OBs are executed by the instrument operator night astronomer or TIO Both NAOS and CONICA are setup according to the contents of the OB Note that the NAOS configuration might be further optimized at this time in order to provide better performance A Real Time Display is used to view the output of CONICA and to perform acquisitions while the wavefront pupil is also displayed Daytime calibrations are executed the following morning by observatory staff 6 1 Service Mode SM containers Since P90 and thanks to p2pp v3 the users are able to group Observation Blocks
92. array with 144 valid sub apertures and a 7X7 lenslet array with 36 valid sub apertures For the IR WFS three configurations are available a 14x14 lenslet array with 144 valid sub apertures and two 7X7 lenslet arrays with 36 valid sub apertures with different FoVs Independent of which Shack Hartmann sensor is being used all 185 actuators on the DM are used The FoV the temporal sampling frequency and the pixel scale of the WFS can also be optimized providing a good performance over a large magnitude range Characteristics of both WFS are given in Table 4 2 Table 4 2 Wavefront sensors characteristics Visible WFS Infrared WFS N20C80 Infrared WFS N90C10 Waveleneth range 0 45 1 0 um 0 8 2 5 um 0 8 2 5 um FoV per lenslet 14x14 2 32 515 5 15 7x7 4 64 4 8 VO and 5 5 V1 4 8 VO and 5 5 V1 Magnitude range 14x14 0 12 4 9 5 5 10 5 7x7 12 16 7 9 12 10 5 13 5 128x128 EEV CCD 1024x1024 Rockwell Hawaii 10241024 Rockwell Hawaii 4 2 NAOS Performance The level of the AO correction depends on a large number of factors such as seeing the speed of the turbulence the airmass the brightness and morphology of the reference object the distance between the reference object and target and instrument performance The performance of NAOS is summarised in Table 4 3 The preparation software should be used for more detailed predictions and simulated PSFs 2 User s Manual VLT MAN ESO 14200
93. asedasssnaaodedesneveraayonsedecsinaness 28 User s Manual VLT MAN ESO 14200 2761 Table 4 6 Summary of NACO Strehl ratios at 2 2 microns for LGS without tip tilt correction at two distinct airmass values These values were derived with the Preparation Software PS and are also used in the CONICA Phase 1 Exposure Time Calculator to estimate TNT rea dd tass de alah ade hse at gehen T 29 Table 5 2 CONICA detector readout modes for each astronomical use the mode Readout Noise RON gain full well FW capacity na ME TILT INN 34 Table 5 4 List of available Cameras with plate scales fields of view and wavelength ranges 35 Table 5 7 CONICA s masks and phase plates for coronagraphy Barred iterm are the discontinued masks since PIB snose 43 Table 5 11 Spectroscopic modes The mode name consists of the objective the grism number and the order sorting filler sss 57 Table 5 9 APP Spectroscopic modes The mode name consists of the objective the grism number and the order sorting filte 59 TIP Je 59 Te R n DE GANDI A E E AEAN A ahead T T tiny sive 101 Table 6 3 IR Backgrounds The hyphens mark invalid combinations of a NAOS dichroic CONICA filter sssr 101 Table 6 5 Recommended magnitude range of standard stars for observations with the visual dichroic 101 FSM TT ed 102 Table 6 10 Example 1 Imaging a faint source V 15 for visual WFS or K 10 for IR WES with Fowler Nsamp s ornvrnrvnrvnrnrrn 106 Table 6 11 Example 2 Im
94. automatic Users do not have to worry about it Depending on the morphology and brightness of the target the service observer will measure the Strehl ratio on the reference source and a preliminary classification will be made If the reference source is extended too faint or too bright the measurement will not be made and the OB classification will be based on the performance that is computed by the RTC If the RTC cannot give a valid estimate which is the case for slow IR WFS AO modes and no other measurement is possible the operator will report the seeing as seen by the guide probe which is more indicative of the actual observing conditions than the DIMM seeing measurement and indicate the values for other parameters of interest such as the coherence time If we believe that we have achieved a Strehl Ratio which is greater than 50 of that requested by the user we will consider that the OB has been successfully completed in the event that all other constraints are met satisfactorily For LGS operations the classification scheme is nearly the same as for NGS operations except that when there is no possibility to measure the Strehl ratio the coherence time is used instead of the seeing If the coherence time is above 2 5 ms the OB is considered completed 6 11 PSF reference star Observations of PSF stars are frequently used in the analysis of AO data Generally speaking the instrument set up should not change between t
95. be repeated for each potentially viable reference object Once you have made a request for optimization and if it has been successfully processed the GUI will be updated with the optimal AO configuration Figure 9 4 and an estimation of the resulting PSF The Strehl ratio is always computed for the reference object on axis at the observing wavelength and at 2 166 um For the science target off axis the Strehl ratio is given at the observing wavelength only 155 User s Manual VLT MAN ESO 14200 2761 Tracking Table Data UTG RA kt DEG 221010 10 0 10 0 1230000 12 0 12 0 231000 13 0 13 0 1234533 15 0 5 0 090000 12 0 12 0 1001000 13 0 13 0 Figure 9 3 An example of tracking table window acquisition and observation of moving objects Offsets in RA and DEC are given in arcsec Figure 9 4 Performance subpanel the AO optimal configuration and the PSF is available from buttons in this panel The optimal Adaptive Optics configuration can be displayed by clicking on the AO Config button in the subpanel depicted in Figure 9 4 An example is shown in Figure 9 5 156 User s Manual VLT MAN ESO 14200 2761 VIS Figure 9 5 Pop up window showing an optimal configuration of the AO system You do not have to worry about these parameters but they may give you some insight into the way NAOS works From the perspective of the astronomer the most significant result of the opti
96. bed in detail in the NACO Calibration Plan o Twilight flats and daytime lamp flats as described in Section 5 2 These calibrations are done without the focal plane masks no lamp flats for LW For additional details see also Section 5 3 5 o Detector darks in all readout modes and DITs o No photometric standard stars will be observed unless the OBs are provided by the users 5 3 5 Night flat fields for SW coronagraphy no longer offered since P93 Imperfections on the plates that hold the semi transparent Lyot mask and the 4QPMs together with instrument flexure means that flat fields depend on the rotator angle The template NACO_coro_cal_NightCalib allows one to take nighttime flat fields immediately after coronagraphic data have been taken We strongly recommend that these calibrations be taken for the said masks if one wants more than the one pair of on off images taken during acquisition Nighttime flat fields with the fully opaque masks are not needed These flats are taken without the mask Given the low transmission of the semi transparent spot it is practically impossible to normalise the response of the spot relative to the response outside it i e absolute flat fielding inside the spot is very difficult One can remove the pixel to pixel sensitivity variations by using a flat that is taken without the coronagraphic mask but this kind of flat does not remove dust features that are on the plate As of P82 a new version of the co
97. ble 7 25 describes the parameters of this template Table 7 25 Parameters of NACO_coro_cal_StandardS tar P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DIT s Readout mode Double _RdRstRd Readout mode Window Size 1024 Size of the window Store Data Cube T F F Data cube flag NEXPO per offset position 1 Number of exposutes per offset position Number of offset positions NODEFAULT Number of offset positions List of offsets in X NODEFAULT Offsets in arcsec List of offsets in Y NODEFAULT Offsets in arcsec Filter NODEFAULT Filter name Mask position C_0 7_sep_10 Coronagraphic mask Camera NODEFAULT Camera Name 7 9 NACO SAM and SAMPol science templates Starting in P83 there are two SAM based science templates one for SAM observations and the other for SAMPol 7 9 1 NACO sam obs GenericOffset The science template is similar to NACO img obs GenericOfftset Note that however not compulsory SAM will use cube mode for data storage as a default This and the handling of the offsets in pupil tracking mode account for most of the differences with the NACO img obs GenericOffset Cube mode is highly recommended with the Double_RdRstRd setup FowlerNsampling has very large overheads and users should weight the loss of time carefully against the advantage of lower noise In the most basic mode i e recommended setup SAM will typically require a 512x514 sub frame and observations wi
98. btained on AB Dor with the new Wollaston SDI 42 Figure 5 7 obtained on AB Dor with the old Wollaston SDI from Biller et al Ap J S S 173 143 2007 42 Figure 5 8 Semi transparent mask with the S13 camera The only useful spot is the bottom left one even this one is severely limited in the bottom left area 44 Figure 5 9 Flat field images of the 40PM K Ks filter left and of the 40PM H H filter right The many dust particles observed in the flats generate flat field variations of 10 20 locally 45 Figure 5 10 Radial attenuation of an off axis point source moved outwards of the mask centre in H left and Ks right The data are shown as symbols and the lines are from simulations Error bars correspond to the uncertainty in the intensity normalization with respect to the simulations The upper abscissa gives the angular separation in units of l D 45 Figure 5 11 Radial profiles of the PSF compared to that of the coronagraphic image obtained with the 4OPM_K left and the 40PM H right 46 Figure 5 12 Chromaticity of the LOPM K measured on the 2004 mask with a fibre i e no seeing effects 47 Figure 5 13 Radial profile for the PSF the 4OPM and the 0 7 Lyot obtained with a natural star in 2004 48 Figure 14 left scanning electron microscope SEM image of the AGPM center and corresponding cross cut It shows the fine microstructure patterned at the subwavelength scale Delacroix et al 2012 Appl Opt 51 5897 Right raw
99. c structure and so objects such as a spherical shell and elliptical ring or an equal binary star will all give closure phase signals which may be weak or zero everywhere and thus lead to difficulties in producing a good image 5 6 9 U V coverage This section contains information on the physical dimensions of the sparse aperture masks placed in the CONICA camera These values are necessary to compute the u v coverage of the instrument Assumptions o The pupil diameter in the camera is 10 mm o The clear aperture of the telescope is assumed 8 00m o The central obscuration assumed 1 116 m o Telescope mirror area 49 29 m Masks manufactured to fit within slots in the pupil wheel 20 mm outer diameter Each mask is pup embossed with an identifier and in addition has orientation marks at the centre and towards the edge Material 02 mm steel sheet 1 Mask 18Holes Hole size 0 465 mm diameter 69 User s Manual VLT MAN ESO 14200 2761 Table 5 13 X and Y location of the holes as measured in mm from the centre of the mask 18 Holes Y 0 203155 3 87061 0 203155 4 57435 1 42208 1 75937 3 25047 0 703745 3 85992 1 05562 2 46311 2 11124 0 351874 2 23470 2 46311 1 01577 3 87061 4 06308 2 11124 3 25047 2 11124 3 85992 2 46311 1 01577 3 16686 2 Mask 9Holes Hole size 1 156 mm diameter Table 5 14 X and Y location of the holes as measured in mm from the centre of the mask 9Hole
100. chniques during post processing of the data Please refer to Section 5 6 for information on the available setups Table 7 26 Parameters of NACO_sam_obs_GenericOffset P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec Readout mode Double _RdRstRd Readout mode Window Size 1024 Size of the window Store Data Cube T F T Data cube flag List of NDIT s NODEFAULT List of NDIT s NEXPO per offset position 1 Number of exposures per offset position Number of offset positions NODEFAULT Number of offset positions Observation type O or S NODEFAULT O is in closed loop S in open loop Offset coordinates NODEFAULT Choose DETECTOR List of offsets in RA or X NODEFAULT Offsets in arcsec List of offsets in DEC or Y NODEFAULT Offsets in arcsec Filter NODEFAULT Filter name SAM Mask Full Name of SAM mask Camera NODEFAULT Camera Name Return T F Return to origin after last offset Since P88 it is possible to set Return F default was T so that the telescope stays at the position of the last offset of the template instead of coming back to the initial position This is for users who wish to perform quick star hopping cycles between their science and their calibrators at their own risks only VM taking into account the offset sizes with the night astronomer and telescope operator 7 9 2 NACO sampol obs GenericOffset The science template is similar to NACO sam obs GenericOffset From an operational poin
101. cified in the initial setup and an image of the sky these images can be used as PSF calibrator Then the following steps are performed 121 User s Manual VLT MAN ESO 14200 2761 o Rough offset to position the star behind the mask o Removal of the ND Short ND Long filter if used For 4QPM the Full Uszd mask is used For the AGPM the Apo 165 is inserted and the rotator offset by 15 to align the pupil stop to the telescope spiders All other masks use Full o Adjustment of DIT if needed o Fine centering behind the mask o Record the final acquisition image of the star finely centred behind the mask without the ND filter Table 7 7 Parameters of NACO img acg MoveloMask P2PP Label DIT NDIT Type of AO Observation LGS NGS PSF Reference T F Pupil Tracking Mode T F RA offset arcsec DEC offset arcsec Position angle on sky Filter Mask Neutral Density Filter Camera NAOS Parameter file Default Values NODEFAULT NODEFAULT NODEFAULT F F 5 5 0 NODEFAULT NODEFAULT Full NODEFAULT NODEFAULT 7 3 9 NACO img acq Polarimetry Description Detector Integration Time sec Number of DIT s LGS or NGS observation type Set to T if it is a PSF reference star Set to T for Pupil tracking observations RA offset for sky image DEC offset for sky image Position angle or pupil angle in degrees Filter name e g Ks Coronagraphic mask Neutral density Filter Full none Camera Name e g S27 NAOS
102. d by the NAOS RTC that can in principle be used for PSF reconstruction The typical image will be a 1024 square array i e NAXIS1 and NAXIS2 1024 when the array is not windowed The two covariance matrices have dimensions 159x160 or 42x43 depending whether the WES used the 14x14 or the 7x7 subapertures The variance vector has dimension 35 Datacubes are 3 D FITS files ie NAXIS 3 a cube plus the same 3 FITS extensions The size of the third axis NAXIS3 is equal to NDIT 1 NDIT is the number of saved DIT frames and the additional frame at the end of the cube is the combined image i e the frame obtained as a sum of all DIT planes divided by NDIT This last plane in the cube is the equivalent 2 D image one would obtain in single frame mode The combined image is used for sanity check and quality control at the observatory Users are cautioned to use only the first NDIT frames of each cube for their data reduction Note also that the first frame in the cube may suffer from some reset anomaly and should probably be discarded Cubes have NAXIS2 NAXIS1 2 as a rule For example if one windows the array to half its size and takes NDIT 200 the size of the cube will be NAXIS1 NAXIS2 NAXIS3 512 514 201 The FITS extensions remain unchanged 94 User s Manual VLT MAN ESO 14200 2761 6 OBSERVING WITH CONICA AT THE VLT As with other ESO instruments users prepare their observations with P2PP Acquisitions observations and calibrations
103. d completion overheads for IRACE 1 2 3 4 typical offset 2 4 time between frames without offsets 2 Sec 0 7 sec Negligible 9 sec 7 sec 2 Sec 9 sec 27 sec 16 sec 1 min 30 sec 15 sec 1 2 min Change in instrument configuration HWP in or out HWP angle setup Rotator offset for polarimetry and SDI Re centering for 4QPM AGPM and SDI 4 All observations using chopping 2 min 30 6 min Add to the exposure time Night time spectroscopic flats per on off pair Night time spectroscopic arcs 6 min Night time coronagraphic flats 6 min per on off pair 1 5 User s Manual VLT MAN ESO 14200 2761 Table 6 6 Example 1 Imaging a faint source V 15 for visual WES or K 10 for IR WES with FowlerN samp WACO Haa NACO_img_obs_AutoJitter 3 sec 20 60 1 FowlerNsamp Observation 60x 27 20x 3 2 Observation Number of offset positionsx Offset overhead NDIT x DIT treadout overhead Table 6 7 Example 2 Imaging a bright source V 11 with the VIS WES or K 7 with the IR WES with Double_RdRstRd Template parameters Acquisition Template NACO img acq MoveToPixel Observation Template NACO img obs Autolitter DIT 2 sec NDIT 30 Number of offset positions 20 NEXPO per offset position Readout Mode Double RdRstRd Preset Guide Star Acquisition Initial Setup AO Acquisition Imaging acquisition Sub Total acquisition Observation 20x 27 2x16 3x 30x2 0 7 Total min Overheads
104. d its overheads We made simpler templates for not having to close the loop NACO img acq MoveToPixelNoAO NACO img obs GenericOffsetNoAO No aocfg file has to be created via JNPS and the overheads are hence smaller To be conservative one can use the overall execution time of an AO cube OB and remove 5 minutes Overall the acquisition template takes approximately 420 seconds value used in p2pp The science template is identical to the classical NACO_img_obs_GenericOffset one in terms of timing using cube T This mode is offered in service but no pipeline is offered as experts can apply whatever techniques they like It is recommended to not observe stars fainter than J 7 if observations carried out in J for an exposure time of 40 ms typical example using a 254x256 sub array Users have to provide their own photometric standard s as the calibration plan does not take this mode into account and photometric precision is subject to the technique used This mode is offered in SM but it is more appropriate to VM to adapt the DIT NDIT and observing strategy For the speckle holography tests have been carried out using either 512x514 0 2s DIT or 1024x1026 0 35s DIT They allow one to reach K 18 see Figure 5 4 5 2 4 Fabry Perot Imager Since P80 Fabry Perot imaging is not offered 5 2 5 Simultaneous Differential Imaging SDI 3 P93 the SDI mode is no longer offered The SDI mode of CONICA obtains four images
105. depth In this case the array is completely saturated and photometry cannot be done Generally users should keep the peak count to below two thirds of the full well depth For exposures with DITs that are within a factor of a few of the minimum DIT the well depth is reduced by a factor of approximately two because of the readout overhead 5 1 4 Cameras The characteristics of the cameras of CONICA are described in Table 5 3 in terms of plate scale and field of view Each camera has a corresponding field mask that is automatically set by the instrument software The scales and relative errors for the 13 and S27 SW cameras were measured by B Sicardy using Pluto s motion against field stars using an accurate Pluto ephemeris The errors are 1 sigma i e 68 3 confidence level obtained by tests with 13 stellar trails for S13 and 31 stellar trails for S27 These numbers agree well with the previously measured values using galactic centre data R Sch del Ph D Thesis 854 C Lidman Table 5 3 List of available Cameras with plate 2 telds of view and wavelength ranges Camera Scale Spectral Range mas pixel microns 13 221 0 017 14x14 1 0 2 5 27 053 0 019 28x28 1 0 2 5 oo 54 50 0 10 56x56 1025 a 32 Be 27 19 28x28 2 5 5 0 5 1 5 Filters All but one of the CONICA filters Section 5 and Table 5 5 are mounted on two filter wheels Transmission curves of several filters are given in Section 8 1 The J band
106. dichroic can also be selected with the visible WES in order to reduce the flux transmitted to CONICA for instance with a very bright source In a similar way the wavefront sensor can be selected This is where one can indicate the wish to use the laser guide star LGS Only if the WFS has been selected as LGS will an LGS mode be proposed to the user 150 User s Manual VLT MAN ESO 14200 2761 There are borderline cases when one has to decide whether to select LGS or NGS mode The limiting magnitude is currently my 13 5 14 i e with AO reference stars which are fainter than this limit one should select LGS mode and keep the star as a tip tilt reference Brighter stars offer better performance in NGS mode When using the PS a good rule of thumb is the following if the expected Strehl ratio calculated for the NGS mode is 10 or higher stay with NGS Otherwise move to LGS No mixed configurations or dual OBs are allowed if the first choice is LGS the second cannot be NGS with VIS WFS Moreover only PIs that explicitly requested LGS in Phase I will be granted its use Starting P85 a new mode is offered i e LGS without tip tilt star the so called seeing enhancer mode Users wishing to make use of this mode should select the LGS and tick the seeing enhancer box in the jnps main panel Users applying for this mode should explicitly select it at Phase I Target information consists of a name coordinates and proper motion For t
107. dotted line defines the jitter box width 124 Figure 74 An illustration of how the NACO_img_obs_GenericOffset template works In this example the offsets are in DETECTOR co ordinates Exposures 1 and 5 occur at the same place I he telescope will return to the origin after the eighth exposure as indicated by the dashed line connecting point 8 to 1 The parameter settings for this example were 127 Figure 7 5 A second illustration of how the NACO_img_obs_GenericOffset template works As with the previous example exposures 1 and 5 occur at the same place and the telescope returns to the origin after the eighth exposure indicated by the dashed line connecting point 8 with 1 5 The parameter settings for this example are given in Table 7 13 128 Figure 7 6 An illustration of how the NACO_img_obs_FixedSkyOffset template works with Jitter Box Width 9 Number of AB or BA cycles 4 Sky offset in Dec 15 Sky offset in RA 35 and Camera 13 130 Figure 7 7 An illustration of how the NACO_spec_obs_AutoNodOnS lit template works with 133 Figure 7 8 An illustration of how the NACO spec obs GenericOffset template works The AO loop is off when the sky S is observed large filled in circles and on when the object O is observed small filled in circles The dashed line connecting 4 with the acquisition position is the offset done at the end of the telescope since the Return to Origin T F was set to T In this example the parameter settings
108. due to the broad bandwidth of the wavefront sensor detectors We adopted a standard extinction law represented in Figure 9 2 as defined by Cardelli Clayton amp Mathis AJ 345 245 1989 Section IIIb and expressed as lt A A Ay gt a x b x Ry with Ry Ay E B V 1 We set lt Ry gt to 3 1 which is an average value for the interstellar medium and is essentially independent of Ay for wavelength longer than 0 7um 155 User s Manual VLT MAN ESO 14200 2761 ae i Figure 9 2 Illustration of the extinction curve used when giving a non zero value to the extinction Av The J H K and R bands are shown for reference along with the monochromatic wavelength for V The bottom graph represents the quantum efficiency for the WFS detectors as a function of wavelength 9 5 4 Tracking table For objects with high proper motions and this usually means solar system objects the usual set of coordinates is not sufficient The user has to provide a separate tracking table giving the relative offsets between the AO reference object and the target in arcsec AO reference science target coordinates as a function of universal time UTC An example of the format of this tracking table is given in Figure 9 3 The file containing the tracking data must be edited by hand and be available on the user s local disk Checking the Tracking Table check button below the coordinates entries enables the Choose File button next to it
109. e 132 NN ENN ON esse 134 User s Manual VLT MAN ESO 14200 2761 MSN NINE 135 VPN NON 136 TVEPTN ONE jor VP NEON Re 139 VPN NNN 143 Tes PST NTE ODO INIPADE OEE TOER TOO 143 TSI PS NACO GO CA SAANTI VAT EREE EEEE EOE ETET OOOO OOOO 144 Table 2 33 Pers NACO 5am OPS AEMET AD r E EEEE EEEE ENEN OEEO A 145 lable I Patanta s of NTE ONS GT A scr i REEERE ON paar endear ante OOA 145 Table De V anons AO modes and HARE and diferentiat HACKING TAS serii EE 155 10 User s Manual VLT MAN ESO 14200 2761 LIST OF FIGURES Figure 3 1 Principle of Adaptive Optics 22 Figure 3 2 Model atmospheric transmission between 1 and 5 mm for a water vapour column density of 1 6 mm and at airmass 1 Lord 1992 NASA Tech Mem 103957 24 Figure 4 1 view of the NAOS optical train 26 Figure 4 2 Illustration of the LGSF set up at UT4 the laser clean room is installed below Nasmyth A note that NACO itself is installed at Nasmyth B The laser beam is propagated via fibre to the launch telescope installed at the back of M2 30 Figure 4 3 Improved performances of the LGS with NACO due to the new 14x14 lenslet array visible on the top left of the Figure four actuators are poked for alignment purposes The image at the bottom left corner shows a promising 35 K band Strehl ratio diffraction limited core obtained with the LGS The centre and right images illustrate the potential of wide field correction with a 1x1 arcmin field centred on the star cluster Omega Ce
110. e OB is split into two parts before Meridian and after Meridian 7 3 2 NACO img acq MoveToPixel This template does a telescope preset and is followed by interactive centering of the object It should be used for normal imaging It must be followed by an imaging template Because the objectives are not aligned with respect to each other we recommend that the acquisition template and subsequent observing templates use the same objective In service mode it is mandatory that users provide detailed information for the field centering on their Finding Charts and or in their README file In order for faint objects to be clearly seen an image of the sky is acquired in an offset position defined by the RA offset arcsec and DEC offset arcsec parameters This image is then subtracted from all images that are subsequently displayed on the RTD The integration time for these acquisition images is defined by the DIT and NDIT parameters This template records an image of the field after the acquisition has been completed On some occasions two additional Br y images of the AO reference source which are used by the operator to help in classifying the OB are also taken the so called Strehl reference images 117 User s Manual VLT MAN ESO 14200 2761 Table 7 3 Parameters of NACO_img_acq_MoveToPixel P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DITs Type
111. e Twilight flats as described in Section 5 2 and internal flats without the masks e Detector darks in all readout modes and DITs 5 6 19 Pipeline for SAM SAM is not supported by the pipeline 5 7 SAMPol The simultaneous use of the Wollaston together with the SAM masks presents a unique opportunity with CONICA to examine systems where there may be polarization signals at very high spatial resolutions Note that given the very small fields of view of SAM it will generally not be necessary to use the image plane masks with the Wollaston 00 SAMpol is offered with all filters except J and Mp In order to get all the Stokes parameters one can chose between two options using the retarder plate the same way it is done in classic polarimetry or make use of the rotation of the field induced by the pupil tracking mode Is this sky rotation enough This is not a completely simple question to answer It partly depends on where the star is located in the sky sources which transit near the Zenith will have a position angle which rotates rapidly making it easy to get a lot of sky rotation in a hurry However being too near the Zenith could make data analysis more complicated with rotation during exposure issues For most stars in the sky the way to exploit the sky rotation to help map out the polarization would be to wait some interval maybe several hours typically and observe the object a second time In terms of efficiency the use of the retarde
112. e field of view for sky measurements to avoid saturation effects The coronagraphic mask is left in the beam for the sky exposures The object positions will be observed with the AO loop closed The sky positions will be observed with the AO loop open The template provides the flexibility to adjust the number of NDIT sub integrations for the OBJECT and SKY frames NDIT for the OBJECT positions defines the number of sub integrations on the object and NDIT for the SKY positions defines the number of sub integrations on the sky The total integration time excluding overheads is defined in seconds by DIT x NDIT for the OBJECT pos x Number of Exposures Object Only NDIT for SKY positions x Number of offset positions Sky only x Number of AB cycles 140 VLT MAN ESO 14200 2761 User s Manual Table 7 22 Parameters of NACO_coro_obs_Stare P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec Readout mode Double _RdRstRd Readout mode Window Size 1024 Size of the window Store Data Cube T F F Store in data cube flag Jitter Box Width NODEFAULT Jitter box width SKY only Number of AB cycles NODEFAULT Number of AB cycles e g 2 for ABAB NDIT for OBJECT NODEFAULT Number of DITs for OBJECT positions NDIT for SKY positions NODEFAULT Number of DIT s for SKY Number of exposures NODEFAULT Number of exposures on target Object only Number of offset positions NODEFAULT Number o
113. e first offset is gero to measure the exact position of the target out of the mask The last offset of the list NOFF SKY brings you onto the sky position where the original coronagraphic mask is inserted again and on sky coronagraphic images are taken in open loop Part III right diagram In this example NOFF SKY 5 142 Figure 8 1 Filter curves for H Ks Lp and Mp and the order sorting spectroscopic filters SJ SK L The SH and L band filters are also used as order sorting filters in spectroscopy 147 Figure 8 2 Transmission curves of the CONICA neutral density filters 148 Figure 9 1 PS GUI Note The current version is v1 105 The GUI for the current version differs from the one depicted above only in the version number that appears on the top bar 150 Figure 9 2 Illustration of the extinction curve used when giving a non zero value to the extinction Ay The J H K and R bands are shown for reference along with the monochromatic wavelength for V The bottom graph represents the quantum efficiency for the WES detectors as a function of wavelength 154 13 User s Manual VLT MAN ESO 14200 2761 Figure 9 3 An example of tracking table window acquisition and observation of moving olyects Offsets in RA and DEC are given in arcsec 156 Figure 9 4 Performance subpanel the AO optimal configuration and the PSF is available from buttons in this panel 156 Figure 9 5 Pop up window showing an optimal configuration of the AO system 1
114. e set to either FowlerNsamp or Double_RdRstRd for LW observations the readout mode will be set to Double_RdRstRd The width of the slitless mask is 13 arc seconds which is half the length of the regular slits Users should keep this point in mind when programming the offsets For the NACO spec obs AutoNodOnsSlit and NACO spec cal StandardStar templates this means that the nod throw should be less than 10 7 6 1 NACO spec obs AutoNodOnsSlit This template nods the telescope between two positions A and B along the slit A cycle is a pair of AB or BA observations Cycles are repeated on ABBA sequences E g 3 cycles correspond to an ABBAAB sequence 4 cycles correspond to an ABBAABBA sequence etc The mean size of the nod is defined by the Nod throw parameter The first exposure A is taken after offsetting the object along the slit by NodThrow 2 arcsec The second exposure B is therefore NodThrow 2 from the initial position along the slit In addition to nodding random offsets can be added in the middle of a cycle A sequence of 6 cycles with jittering will result in the following sequence A B E B E J A E A B B EJB EJ A E ATEB EJB EJ A E where E are random offsets In order to avoid the possibility of overlapping spectra E should be smaller than half of the nod throw The random offsets are generated inside an interval defined by the parameter Jitter Box Width in arcseconds Offsets are randomly distr
115. e the telescope pupil on the deformable mirror and the Nasmyth focal plane on the entrance focal plane of CONICA A schematic sketch of the optical train of NAOS common path is shown in Figure 4 1 The optical trains of the wavefront sensors are not shown in this figure The tip tilt plane mirror TTM compensates for the overall WF tip and tilt which are the largest disturbances generated by the turbulence CONICA Input Focus Deformable 1 mirror rose Output Parabola input Parabola Tip tilt WFS Input Focus mirror VLT Nasmyth Focus Figure 4 1 A view of the NAOS optical train The DM which contains 185 actuators compensates for the higher order aberrations including the static aberrations of NAOS and CONICA Table 4 1 NACO dichroics beamsplitters Name WES to CONICA VIS V R I 90 J H K L M 90 Near IR observations E ossu toss paca N20C80 VALLHK 20 VALLHK 80 WES and observations eee e eee pm J 90 AJ H 0 45 2 55 um 0 45 2 55 um in the IR 0 80 2 55 um observations and near IR WFS K K 90 V R LJ H 90 J H observations and K 1 9 2 55 um 0 45 1 8 um band WFS The N90C10 dichroic can also be used with the visible WFS In this case it acts as a neutral density filter 26 User s Manual VLT MAN ESO 14200 2761 A dichroic splits the light between CONICA and the WFS channel Each dichroic is associated with one WFS with the exception of the N90C10 For example the visu
116. ectral Type v IR Background median w 113 8 H mag arcsec2 Observed Magnitude Band y Resulting Performance 9 LA al Grain reference object www User Information Sr 2 166 on ref objecv 3 Spectral Type B3V w Sr on target FWHM on reference object arcsec Transmission Reset form Register Object Update Object Cancel Reset All Figure 9 1 PS GUI Note The current version is v1 105 The GUI for the current version differs from the one depicted above only in the version number that appears on the top bar 9 3 Target and Instrument Setup The observing wavelength in um can be entered as a filter in which case the wavelength automatically appears or it can be entered directly by selecting free from the list of CONICA filters and then typing the value directly into the space provided The dichroic name can be selected or left free If left free the PS will select the dichroic which maximizes the Strehl which usually means that most of the light will be sent to NAOS If another dichroic is preferable then the dichroic can be selected here Table 4 1 gives the conditions under which the various dichroics should be used Users should familiarize themselves with the contents of this table In particular the most critical choice will be between the N90C10 and N20C80 dichroics The former will result in higher Strehl ratios but much lower sensitivity particularly in the K band The N90C10
117. ed This can be easily achieved by cutting the data according to outliers in simple statistical tests on quantities such as the counts in the peak pixel the total counts etc 5 6 7 PSF calibrations strategies As with all forms of optical interferometry it is paramount to preserve a focus on calibration To do this it is suggested to bracket observations of the science target with observations of a nearby point source reference object Ideally this reference star will be an unresolved point or if not at least a single star of well known size Good calibration is helped by observing the reference star s at similar airmass and observed with as near identical telescope AO configuration as possible To this end the SAM template will use the PSF flag to keep the AO configuration the same as the one used for the previously observed science object The pupil position is kept identical since science and calibrator are observed with the same mask and each mask has its own assigned pupil angle Finding reference stars is straightforward but does take some work and it may help to consult some local interferometrists or interferometry web resources some institutions such as the Michelson Science Centre have calibrator finding catalogue search engines available online For the case of CONICA the resolutions are relatively modest so almost all single stars of any spectral type will present photospheres that are essentially unresolved
118. ed either by rotating the entire instrument or by taking data with the half wave plate rotated by 22 5 degrees compared to previous data The beam separations for the different cameras and as a function of wavelength are given in Table 5 12 The wavelength dependence of the beam separation shows that from 1 to 2 5um the Wollaston prism can be used for broadband application without loss of spatial resolution Within the K band for example the resulting chromatic error is about 86 mas The Wollaston can also be used with the LW filters however the beam separation is less and there is slight overlap between the ordinary and extraordinary beams At larger wavelengths is best to use narrow band filters No Mp band observations are offered with polarimetry Table 5 12 Beam separation of the W ollaston prism on the sky arcsec and in pixels as a function of the camera Wavelength um Separation arcsec Camera Separation pixels 2 2 K oe 3 Since the J band filter is in the same wheel as the Wollaston prism J band polarimetric observations are not possible The transmission curve of the Wollaston is shown in Figure 5 27 Wollaston Prism Transmission e F 8 v E v c La 2 5 3 3 5 Waelength microns Figure 5 27 Transmission as a function of wavelength for the Wollaston prism The big absorption feature at 3
119. ed milli arcsecs from a bright star Although there may be ways to mosaic larger fields together these have never been successfully demonstrated 65 User s Manual VLT MAN ESO 14200 2761 Key strengths of a dilute and ideally non redundant pupil are in the mitigation of atmospheric phase noise seeing and the use of robust self calibrating observables such as the Closure Phase For brevity we refer the reader to the references Section 5 6 10 for discussion of the philosophical underpinnings that motivate masking interferometry Masking is furthermore by its nature limited to brighter classes of targets This is because it is only effective at combating atmospheric phase noise seeing and it is counterproductive in photon starved regimes where detector readout noise dominates Earlier experiments with seeing limited telescopes before the advent of AO in the near IR had a magnitude limit of about 5 mag in K band With NACO we estimate that the useful magnitude limit for some types of observations could be as faint as 10 12 mag depending on the level of correction obtained Here we limit our discussion to two basic types of observation 1 imaging and 2 faint companion detection For both of these modes masking interferometry has demonstrated levels of performance that match or exceed those obtainable by any other means Further discussion of these strengths can be found in the sections below detailing the on sky pe
120. eeing conditions being biased by small sample statistics Table 5 20 gives mask areas and peak pixel flux ratios for all mask filter combinations used in commissioning These values have been converted into expected count rates using the throughputs from the online sensitivity calculator and verified on sky Figure 5 39 Figure 5 40 Figure 5 41 and Figure 5 42 give the expected peak throughput for various mask filter and integration time combinations The information is organized by the various masks with each plot applying to a separate mask configuration The different CONICA narrowband interference filters are indicated with different coloured line types For each mask filter the expected peak counts received is given for a range of different exposure times starting with the shortest possible per subframes up to 10 second integrations The chip nonlinear regime begins with the horizontal line near the top and saturation is at the very top 80 User s Manual 18Holes Filter NB 1 75 IB 2 24 NB 3 74 NB 4 05 9Holes Filter NB 1 75 IB 2 24 NB 3 74 NB 4 05 BB 9Holes Filter 7Holes Filter Total area Peak Pixel 6 38e 4 6 10e 4 1 12e 3 1 26e 3 Total area Peak Pixel 1 53e 3 18e 3 42e 3 75e 3 Pb Total area Peak Pixel 1 53e 3 1 37e 3 2 95e 3 2 72e 3 Total area Peak Pixel 2 67e 3 2 53e 3 5 52e 3 use VLT MAN ESO 14200 2761 Table 5 20 Mask area and peak flux ratios for
121. elated operations and other miscellaneous functionalities see following sections 149 User s Manual VLT MAN ESO 14200 2761 o The main panel divided in four sub areas which respectively deal with the science target the reference object the sky conditions and resulting performance image quality o The action area gathering general actions such as requests for optimization or creation of the P2PP parameter file and the HTML file for the ETC Sans NAOS Preparation Software v 1 103 eae File Objects Adaptive Optics Preferences rlarget amp Instrument Setup rReference Objects CONICA Filter Ks lw Observing Wavelength 2 18 microns Status Name Distance Sr G8 T Dichroic FREE v Wavefront Sensor FREE v Optional Constraints Min Strehl 0 0 Min Transmission 0 0 Target Name Epoch 2000 0 Equinox 2000 0 RA Prop Mot RA arcsec year Up Down Delete Clear all Duplicate DEC 4 Prop Mot DEC arcsec year Sky Conditions Distance to Target arcsec Seeing at zenith 0 6 v Seeing on reference object 0 67 arcsec Airmass 1 2 v r0 on reference object 0 15 m GamE IER RA gt Prop Mot RA arcsec year Windspeed 12 m s G5 ThetaQ on reference object 1 49 arcsec Wr DEC JE Prop Mot DEC arcsec year ThetaO at zenith 2 0 medium w _ Tracking Table VIS Background full moon v 20 0 V mag arcsec2 Morphology IPgint like v Photometry Mag Sp
122. elescope offsets are used several arcminutes the active optics star changes Nevertheless when returning to the science target and closing the AO loop on the same reference source any offsets that might be caused by changing guide stars should be compensated by NAOS 6 6 Target acquisition Irrespective of the observing mode the acquisition sequence is composed of a telescope preset to the object the selection of the guide star from the operator unless the star has been selected previously by the user its centering the guiding camera at least one full correction of the active optics and the telescope in guiding status Once this cycle is completed control returns to NACO and the operator is asked to identify the science target on the CONICA detector and to centre it in the middle of the field of view of the wavefront sensor indicated by a white box overlaid on the CONICA detector Once the centering is done the set up specified in the aocfg file will be sent to NAOS RTC the flux from the star is measured once then the WFS will execute a slight offset to measure the sky background around the star and come back on the position A first estimate of the adaptive optics correction is calculated The process is repeated one more time in what is called the fine acquisition and once the adaptive loop is closed the control is returned to the operator to continue with the template Below we provide a list of the various templates a
123. elical ramp around the optical axis forcing the amplitude to zero at that singular location nature prevents the phase from having an infinite number of values at a single point in space which is non physical by simply nulling the light locally When centered on the diffraction pattern of a star seen by a telescope optical vortices affect the subsequent propagation to the downstream Lyot stop by redirecting the on axis starlight outside the pupil Figure 14 left scanning electron microscope SEM image of the AGPM center and corresponding cross cut It shows the fine microstructure patterned at the subwavelength scale Delacroix et al 2012 Appl Opt 51 5897 Right raw CONICA image of the sky background through the AGPM in Lp band and L27 camera showing the clear 15 aperture and the vortex center located slightly off the intersection of CONICA s quadrants The advantages of the AGPM coronagraph over classical Lyot coronagraphs or phase amplitude apodizers such as the APP are e Small inner working angle WA down to the 1 A D diffraction limit 0 1 at Lp e Clear 360 off axis FoV discovery space up to an outer working angle of 7 5 15 FoV e Achromatic over the entire Lp band hence compatible with NB_3 74 and NB 4 05 e High throughput 88 measured The other side of the coin is sensitivity to image quality Strehl ratio as all coronagraphs It is also sensitive to pointing centering errors Indeed to ma
124. ellar target by a factor ranging from 84 to 96 depending on the mask Furthermore thermal anisotropies in the sky tend to be smooth and slowly varying with little fine grained structure on scales of tens of milli arcsec where the interference fringes from the masking are formed 5 6 5 Choosing which mask to use The philosophy of aperture masking taken to the extreme would suggest a mask with many tiny holes each of which makes an almost point sample of the incoming wavefront Such a mask would pass very little light and be useless for all but extremely bright targets With only 4 throughput the 18Holes mask is the nearest approximation to this ideal in CONICA with the other masks having fewer but larger holes and passing increasingly more light up to a maximum of 16 for the 7Holes mask Masks with many closely spaced holes also suffer from a second problem that of bandwidth smearing Using a wide optical bandwidth filter the fringes formed between a pair of holes will occupy a range of spatial frequencies proportional to the bandwidth This can mean that power from neighbouring baselines can smear into one another confusing the signals In general this means that masks with many holes must also be used with the narrowest bandwidth filter sets In terms of optical throughput this therefore gives a double penalty The use of the more closely ideal masks many tiny holes is therefore restricted to quite bright targets
125. eparation and as demonstrated on sky on a standard star under median to bad seeing conditions right Mawet et al 2013 submitted to ACA 51 Figure 5 18 Azimuthally averaged flux of the VLT and VLT APP point spread functions simulations 53 Figure 5 19 APP PSF obtained with the NB 4 05 filter and under relatively good seeing conditions and the 5 0 contrast curve of the clean side 54 Figure 5 20 5 sigma Lp contrast curve of the clean side note the higher achievable Amag gt 10 5 than with the NB 4 05 filter 8 55 Figure 5 21 Position Angle consideration for APP Imaging No matter what the PA is the PSF pattern remains fixed only the field of view rotates with respect to this pattern 55 Figure 5 22 The APP was manufactured with a strong wedge to avoid spurious reflections The drawback is that it induces a mostly vertical shift of the image in the detector plane The FoV with the 55 Figure 5 23 The APP main commissioning result on Beta Pictoris b Quang S P ApJ 722 LAI 2010 56 Figure 5 24 illustration of the APP spectroscopy concept 58 Figure 5 25 illustration of the prism spectroscopy capability for the Galactic Centre with LGS 60 Figure 5 26 a spectrum of an AO star with the L27 P1 mode The spectrum starts at 0 85 um near the top and extends to 5 5 um near the bottom Note that the change in brightness from 5000 ADU and saturated at 1 um to 20 ADU at 5 um One also notes several electronic and optical ghosts
126. er Legendre polynomial but the coefficients of the polynomial depend on the location of the spectra on the array The traces of spectra that are near to the left edge are straighter than those on the right hand side 60 User s Manual VLT MAN ESO 14200 2761 The prism introduces an offset in x of approximately 120 pixels with the L27 objective For the S13 the offset is almost 200 pixels Figure 5 26 displays a L27_P1 spectrum of a special pinhole There is some scattered light that appears to come from wavelengths longer than 5 5 um that may have been introduced by the use of the pinhole rather than being intrinsic to the prism There are some ghosts but they are most likely reflections Some are well known detector artefacts With prism spectroscopy the wavelength span is very large and hence the atmospheric differential refraction can be large and cannot be properly compensated by the AO system for all wavelength For the L27_P1 mode which spans 0 85 to 5 5 um the system will use 2 5um as central waveleneth to perform the refraction compensation This wavelength accommodates all modes because people are generally interested in the redder part of the spectra otherwise they would likely use another instrument and the index of refraction variation is small between 2 5 and 5 5 um If you plan rather long observations at rather high airmasses please consider this and eventually chose appropriately your position angle PA so align the slit wit
127. er and NACO_img_obs_GenericOffset For these 2 templates a user selectable keyword Observation Category is available and should be set to PRE IMAGE in the above mentioned cases only By default this parameter is set to SCIENCE Failure to set this keyword properly will result in delays to process and deliver the pre imaging data 98 User s Manual VLT MAN ESO 14200 2761 6 8 http the following NACO requirements apply O Finding charts readme files and OB naming conventions www eso org sci observing phase2 SMGuidelines ReadmeFile generic html respectively At least one chart for each observation must be 2 x 2 in size with additional charts showing more details as appropriate All wavefront reference stars must be clearly marked according to the way they are ordered in the preparation software They should be marked R1 R2 R3 etc For imaging the field of view of the selected camera must be drawn For polarimetric and coronagraphic observations the field of view of the selected camera must be drawn and the object that is to be placed behind the mask in the case of coronagraphy or centred in the mask in the case of polarimetry should be clearly indicated For long slit spectroscopy the slit must be drawn For spectroscopic templates the reference star used for preliminary slit centering must be identified For PSF reference stars the OB name must be prefixed with the string PSF For
128. eral it is possible to find a reference star within less than 1 degree in declination and a few minutes in right ascension In these conditions an improvement of a factor 10 can be expected on the averaged contrast A contrast of 9 to 9 5 magnitudes is achievable at 0 5 separation in H and Ks Alternatively as of P82 one can observe in pupil tracking mode setting the position of the telescope spiders to the same fixed angle for both the science and the reference stars In this mode the field of view rotates from one image to the other and frames will have to be restacked during data reduction 48 User s Manual VLT MAN ESO 14200 2761 5 3 3 Annular Groove Phase Mask coronagraph AGPM Following a recent proposal led by the University of Liege AGPM proposing team O Absil D Mawet J Girard A Boccaletti P Baudoz C Delacroix P Forsberg M Karlsson S Habraken J Surdej and M Kasper a successful implementation and validation tests the NACO IS team is delighted to offer a new generation high performance coronagraphic mode for NACO The Annular Groove Phase Mask coronagraph AGPM Mawet Riaud Absil Surdej 2005 ApJ 633 1191 1200 is an optical vortex made out of diamond subwavelength gratings The optical vortex coronagraph is one of the most advanced new generation coronagraphs recently brought to operational level Mawet et al 2012 SPIE 8442 Optical vortices occur when the phase structure of light is affected by a h
129. ere made for both masks and are presented in Figure 5 10 These plots are important to correct the photometry of off axis objects when looking at close companions For instance a companion lying at 0 1 from the primary has its flux absorbed by 50 in the Ks band and 40 in the H band Angular separauon IN A U Angular separauoen IN A U 0 1 2 3 4 5 6 7 O 1 2 3 5 1 2 4QPM in H 4QPM in H Lyot 0 15 data 1 0 5 0 8 E 6 E es D 2 5 gt 0 6 pa 2 D 3 5 4QPM 5 405M lyot 0 15 S 0 4 0 2 0 0 0 0 0 2 0 0 0 1 0 2 05 Angular distance in arcseconds Angular distance in arcsec Figure 5 10 Radial attenuation of an off axis point source moved outwards of the mask centre in H left and Ks right The data are shown as symbols and the lines are from simulations Error bars correspond to the uncertainty in the intensity normalization with respect to the simulations The upper abscissa gives the angular separation in units of A D 5 3 2 2 Contrast of 4QPMs Contrasts were measured on the PSF fibre for the 4QPM_K and the 4QPM_H Azimuthally averaged radial profiles are shown in Figure 5 11 and provide an averaged contrast 45 User s Manual VLT MAN ESO 14200 2761 Another metric commonly used is the maximum attenuation which refers to the ratio of the maximum intensity in the PSF image to that of the coronagraphic image Although maximum intensity is at r 0 on the PSF it is located at 1 5 2 A D on the coronagrap
130. et telescope and acquire for SAMPol NACO_img_acq_SAMPol Imaging Imaging of un crowded fields Imaging of extended objects or crowded fields Imaging requiring special offset sequences Imaging without AO APP or SDI NACO img obs AutolJitter NACO img obs GenericOffset NACO img obs FixedSkyOffset NACO img obs GenericOffset NACO img obs GenericOffsetNoAO NACO app obs GenericOffset Imaging with APP Spectroscopy Spectroscopy of point like or moderately extended objects Spectroscopy of extended objects gt 10 or complex sequences of positions grism amp prism NACO_spec_obs_AutoNodOnsSlit NACO_spec_obs_GenericOffset Polarimetry Imaging Polarimetry NACO_pol_obs_GenericOffset Polarimetry with the Half Wave Plate NACO_pol_obs_Retarder Coronagraphy Coronagraphy Coronagraphy imaging NACO coro obs Stare NACO coro obs Astro SAM SAM includes Pupil Tracking observations NACO sam obs GenericOffset 112 User s Manual VLT MAN ESO 14200 2761 SAMPol SAMPol includes Pupil Tracking observations NACO_sampol_obs_GenericOffset Standard Stars Standard star for imaging NACO img cal StandardStar Standard star for coronagraphy NACO coro cal StandardStar Standard stat for spectroscopy NACO spec cal StandardStar Standard star for polarimetry NACO pol cal StandardStar Night time calibrations Night time coronagraphic flats NACO coro cal NightCalib Night time spectroscopic fla
131. f concentric rings The ghosts can be seen in Figure 5 2 Figure 5 2 Illustration of the ghosts present on CONICA images when observing a bright object In addition to the electronic ghosts there is also an optical ghost characterised by its circular shape The electronic noise visible on the sides of the array as well as the Pias levels of rows 512 amp 513 disappear in the background subtraction 2 The dark current consists of the array dark current which is much lower than the numbers listed here and thermal radiation from the instrument gt Although the array has 1026 rows only the first 1024 are used The last two rows do not contain useful data In most cases the exception being the cube mode images and Mp imaging frames users will receive images that have 1024 pixels in x and y For observations in the Mp the array is windowed to 512 X 514 33 User s Manual VLT MAN ESO 14200 2761 5 12 DIT and NDIT The IRACE controller controls the detector front end electronics and manages pre processing of the data before transferring them to the workstation A single integration corresponds to DIT Detector Integration Time seconds The pre processor averages NDIT of these before transferring the result to disk except in the case of Cube Mode see Section 5 8 Note that the number of counts in the images always corresponds to DIT not to the total integration time i e DIT x NDIT 5 13 Readout Modes and Detector Mode
132. f exposures on sky Sky only Sky offset in RA NODEFAULT RA offset for sky in arcsec Sky offset in DEC NODEFAULT DEC offsets for sky in arcsec Filter NODEFAULT Filter Name Mask Position NODEFAULT Coronagraphic mask Camera NODEFAULT Camera Name NACO coro obs Stare litter Box Width DEC Offset Sky Positions Object Positions RA Offset Figure 7 10 An illustration of how the NACO_coro_obs_Stare template works The dashed line connecting position 10 with 1 is the offset done at the end of the template when the telescope returns to origin The rather erratic bold lines are wires which hold the coronagraphic mask in place The AO loop is off when the sky is observed large filled in circles and on when the object is observed small filled in circles In this example the parameter settings were Number of AB cycles 2 Number of Exposures Object Only 2 Number of offset positions Sky only 3 Jitter Box Width 9 Sky offset in Dec 15 Sky offset in RA 35 Camera S13 If Number of offset positions Sky only is set to zero the sky is not observed In this case the total integration time is DIT x NDIT for the OBJECT positions x Number of Exposures Object Only and all other parameters are ignored In this way the template takes a series of exposures of the target without offsets However sky subtraction is almost always required so this option will probably only be used in very special circumstances 141 User
133. f offsets in X 400400400 List of offsets in Y 2 3 2 3 2 3 0 2 3 2 3 0 2 3 2 3 and List of Position Angle Offsets 0 45 The dashed line connecting position 9 with 5 is the offset done after the 9th and 18th exposures Position 5 corresponds to the position the target was acquired This sequence has been designed so that the entire field of view is covered 7 7 2 NACO pol obs Retarder This template is used for imaging polarimetry exclusively with the half wave plate It can be used with all filters with the exception of J and Mp and with the Wollaston prism This templates works with defined generic offsets It must follow the acquisition template NACO img acq Polarimetry For each given offset position the template runs over the list of half wave plate angles before moving to the next offset position Only at the end of the OB does the telescope move back to the original position and the half wave plate to its default position i e 0 The angles in the list of half wave plate angle are relative one from the other e g 0 22 5 22 5 22 5 would correspond to an absolute rotation of 0 22 5 45 67 5 Note that the first angle provided is absolute since the HWP is always set to its zero position at the beginning of the template Once the template has run over the list of half wave plate angles the telescope can offset according to a user defined list Spatial offsets are defined with the parameters List of offsets in X and li
134. f your OBs should be 1 0 and 30 respectively 6 5 Telescope control Most interactions with the telescope consist of telescope presets for acquisition telescope offsets during observations and M2 chopping for some LW observations Small offsets i e less than one arc minute are usually completed in 10 seconds of time or less It is important to distinguish between the star that is used by the telescope for active optics and the reference object used by NAOS for wavefront sensing The active optics stars which are also used for guiding are automatically selected by the Telescope Control System and users in general do not have to worry about finding them For some specific cases i e large offsets to the sky from a crowded field users might wish to keep the same guide star It is recommended in such a case that they select it by themselves and explicitly indicate its position in one or more dedicated Finding Charts and refer to its use in the text of the README information Appropriate magnitude for guiding stars range from R 11 14 This guide star has to be within a radius of up to 15 arcminutes from the centre of the field field of view of a 96 User s Manual VLT MAN ESO 14200 2761 unit telescope It is recommended to draw a circle on the guide star finding chart to show it lies within this 30 circle The reference object used by NAOS for wavefront sensing and specified within the PS is chosen by the astro
135. fferential imaging SDI coronagraphy polarimetry and sparse aperture interferometry with several different plate scales filters and options e g cube mode for lucky imaging pupil tracking for imaging coronagraphy and SDI The modes offered for P89 are listed in Table 2 1 no changes from P88 NACO can be used in Service SM or Visitor Mode VM The Observatory provides daily calibrations as the NACO Calibration Plan Pipelines for quick look data reduction are available for some modes of the instrument Since P86 it is possible to observe without closing the loop noAO mode and use NACO as a speckle imager which can be useful for some applications and or under bad seeing conditions Table 2 1 Main modes and parameters of NACO Please check NACO public web overview for updates Adaptive Optics Performance 50 Strehl ratio in Ks under good atmospheric conditions NGS good seeing AND coherence time gt 4ms and with a 68 reference object of V 10 mag or K 6 mag Since P93 LGS assisted observations are discontinued for NACO Imaging Broad and narrow band filters in the 1 5 um region with simple 14 56 fields of view and 13 54 mas pixel scales Apodizing Phase Plate Imaging APP in both VM and SM APP Pupil tracking imaging ADJ offered in SM without focal noAO plane mask simple imaging and APP Open loop imaging no AO is offered in SM VM not pipeline supported Simultaneous Differential
136. filter is mounted on a third wheel that also contains the Wollaston prism and the wire grids so J band polarimetric observations are not possible with NACO In this manual filters with central wavelengths longer than 2 5 microns will be referred to as LW filters and filters with wavelengths shorter than 2 5 microns will be referred to as SW filters 35 User s Manual VLT MAN ESO 14200 2761 Not all filter and camera combinations are supported For the 13 S27 and S54 cameras all SW filters can be used For the L27 camera the NB_3 74 NB_4 05 Lp and Mp filters can be used For the L54 camera only the NB_3 74 and NB_4 05 filters can be used Observations with the Mp filter are restricted to a FoV of 14 X14 corresponding to a detector window of 512x512 The FoV is smaller in Mp than in other LW filters because the background in Mp is considerably higher the integration time has to be reduced which can only be done by windowing the array However Mp observations also require chopping that is currently not offered Exceptionally and through a waiver and setup change requests in VM only Mp imaging can be requested attempted for bright sources for which an acceptable SNR can be achieved with extremely low integration time 256x256 windowing and therefore only 7 x 7 FoV with dithering but no chopping Information on the CONICA s broadband filters can be found in Table 5 4 and for narrow and intermediate band filters in Table 5
137. g 7 75 0 23 mag In agreement with Lagrange et al 2010 e Quanz et al 2010 in Prep Delta magnitude NB 4 05 ss o Arcsec Figure 5 23 The APP main commissioning result on Beta Pictoris b Quanz S P ApJ 722 L49 2010 WARNING s APP imaging can only be used with the Lp or NB 4 05 filters The acquisition template has Lp as default filter The FoV with the APP is currently 28x9 using the L27 camera and the default FLM 27 field stop due to an important angular shift caused by the APP wedge Your strategy has to take this into account use small offsets Please provide Finding Charts that clearly take into account the FoV limitation imposed by the APP On the detector the useful FoV spans from p1 80 700 to p2 1024 1024 This is conservative as the lower left corner is not straight When stripped down to 512x514 windowing the remaining FoV is 13 8 x2 5 2 35 on the left and 2 65 on the right We then have p1 0 425 and p2 512 512 Since the concept of the APP is to enhance the contrast on one side of the PSF the instrument has to be rotated to the appropriate angle where the eventual companion is expected If used with pupil tracking i e for Angular Differential Imaging ADJ the initial position angle PA has to be estimated for a given LST so that it accounts for the field rotation with respect to the APP PSF pattern It is recommended to use rather bright stars but not too bright because the APP i
138. g are not biased by the seeing and they obey quasi Gaussian statistics Figure 5 31 left image as obtained on the detector observing a calibrator star with the BB_9Holes mask tight Fourier transform of this image revealing peaks corresponding to the different vector baselines passed by the mask To give an idea of the behaviour of fringe phase for binary star systems Figure 5 32 represents the phases as a function of the baseline in the mask This series of plots was drawn for binary systems with 3 different flux ratios and 3 different angular separations for a grid of 9 plots The maximum baseline available with a mask is 8m while the minimum is the smallest distance between two holes e g 1 17m for the BB 9Holes mask As can be seen the dynamic range of the instrument for faint companions will be directly proportional to the precision with which the phases are measured To achieve a dynamic range of 100 we need phases with a precision of one degree To achieve a dynamic range of 10 000 we need phase knowledge to be around 0 01 degree For high contrast companion detection our goal is simple extract the phases to fit a binary model as shown in Figure 5 32 There are several ways to do so here we give one example The data needed are the science target data data cube and a bad pixel mask and a flat field We also need to know the effective wavelength A the diameter of the holes d and the baselines u 74 User s Man
139. g polarimetry and coronagraphy Left Field orientation on detector at 0 rotation angle on sky Right Field orientation at 45 rotation angle on sky o For imaging polarimetry and coronagraphy East is on the left TX of the images for zero position angle For spectroscopic acquisition East is at the top Y for zero position angle o For imaging polarimetry and coronagraphy North is at the top Y of the images for a zero position angle For spectroscopic acquisition North is on the right X for a zero position angle o Position angle on sky This angle is measured in the standard way i e it is positive from North to East o The slits are oriented along detector rows o For spectroscopy a position angle of zero means that the slit is aligned North South o For polarimetry a position angle of zero means that the mask is aligned East West Position Angle 0 deg Position Angle 45 deg 1024 1024 1024 1024 Y E Conica FoV Conica Foy N 1 1 x 1 1 x Figure 7 2 Orientation for spectroscopic observations Left Field orientation on detector at 09 rotation angle on sky Right Field orientation at 45 rotation angle on sky 114 User s Manual VLT MAN ESO 14200 2761 The templates make extensive use of telescope offsets In some templates the offsets are set automatically e g NACO img obs Autolitter but in others the offsets have to be entered manually as lists In this latter case the co
140. g range of observational parameter space five masks were fabricated and the physical properties of the masks is illustrated in Figure 5 28 They were fabricated by precision laser machining onto 0 2 mm steel stock The outer diameter of the final masks was 20 mm to fit within the CONICA pupil wheel slots 64 User s Manual VLT MAN ESO 14200 2761 Figure 5 28 Mechanical drawings of the four aperture masks installed in the CONICA camera In general the more holes appear in the mask then the smaller the holes must be to preserve non tedundancy and consequently the less light that is passed by the mask The mask to the left shows the 18holes configuration which yields excellent Fourier coverage but which does not pass a large fraction of the incident light In order to access successively fainter targets the 9 and 7 holes configurations may be used although the Fourier coverage becomes markedly worse There are two different 9 hole configurations 9holes and BB_9holes The distinction between these two being that the simple Qholes offers superior Fourier coverage and slightly higher throughput but is not suitable for large fractional bandwidth observations For bandwidths wider than about 10 15 the Oholes mask is unsuited and the BB Oholes should be used The two dimensional layout of the holes specifies the Fourier coverage afforded by the given mask This was optimized with a computer parameter space search algorithm t
141. h the parallactic angle allowing the differential refraction to spread the light along the slit 5 4 4 Slitless spectroscopy Not offered 5 4 5 Slits Two long slits are available for spectroscopy The characteristics are listed in Table 5 11 Shits in CONICA Slit 86mas 86mas x 40 For the S27 and L27 the slit length is 28 Slit_172mas 172mas x 40 For the S27 and the L27 the slit length is 28 The centering of the observed object in the slit is done interactively through an acquisition template Table 5 11 Shits in CONICA Slit 86mas 86mas x 40 For the S27 and L27 the slit length is 28 Slit 172mas 172mas x 40 For the S27 and the L27 the slit length is 28 61 User s Manual VLT MAN ESO 14200 2761 5 4 6 Calibration plan For spectroscopic observations a variety of calibration frames will be taken archived and updated at regular intervals The calibrations are described in detail in the NACO Calibration Plan o Telluric Standard Stars Observations of telluric standards will be performed whenever the orisms are used Whenever possible we will limit the airmass difference between the standard and science target to 0 1 airmasses The standard will be observed with the setup that was used for the science target The stars are generally chosen from the Hipparcos catalogue and are either hot stars spectral type B9 or earlier or solar type stars spectral types GOV to G4V These calibra
142. hat follows from and extends the work of Golay 1970 JOSA 61 272 Exact locations of the holes cut for each mask together with all relevant dimensions and specifications of the physical masks themselves have been provided in the NACO SAM web pages http www eso org sci facilities paranal instruments NACO inst mask_datasheet html A scaled illustration depicting the optical effect of the masks as projected onto the correctly scaled VLT telescope pupil assuming ideal optical alignment is given in Figure 5 29 The large circumscribed circle represents the outline of the VLT primary mirror while the smaller centred circle shows the silhouette of the secondary mirror It is important to note that the spiders which support the secondary mirror are not depicted here but they have an important effect which will be discussed later Figure 5 29 Optical diagrams showing the effect of apodizing the pupil with the four 2 dimensional masks implemented in the CONICA camera 5 6 1 SAM why and when to use it Masking is useful for very narrow fields of view the outer limit is set by the resolution of the shortest baseline in the mask Any advantages it enjoys over conventional full pupil imaging are only manifest at such very high resolutions typically within several resolution elements of the PSF core In the infrared this typically means that the scientific niche is for objects where the entire field of interest lies within several hundr
143. he beam and set to its zero position at the beginning of the template and then it is moved out of the beam at the end of the template This introduces an extra 1 minute overhead per template Table 7 21 Parameters of NACO pol obs Retarder P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DIT s Readout mode Double RdRstRd Readout mode NEXPO per offset position 1 Number of exposures per offset position Number of offset positions NODEFAULT Number of offset positions Observation type O or S NODEFAULT O is in closed loop S in open loop List of offset in X NODEFAULT Offsets in arcsec List of offset in Y NODEFAULT Offsets in arcsec List of position angle offsets NODEFAULT List of HWP angles Filter NODEFAULT Filter Name Polarizer Wheel Wollaston_00 Wollaston_00 or empty Setting to Wollaston_00 default will insert the Wollaston prism and the Wollaston mask Neutral density filter Full Neutral Density filter Camera NODEFAULT Camera Name The template can be restarted with another orientation on the sky for another series of exposures At least two different half wave plate orientations separated by 22 5 degrees are required for computing the Stokes parameters By definition a rotation of the polarisation plane by 45 degrees does correspond to a rotation of the half wave plate by 22 5 degrees To image the entire field of view while observing with the Wollasto
144. he observation of the science target and the PSF reference the brightness and colour of the two should be similar and atmospheric conditions should be stable With NACO the simplest way of ensuring that the instrument configuration does not change is to ensure that the PSF reference T F flag in the acquisition template is set to T When this flag is T the telescope will preset to the target the operator will acquire the target and AO will start without changing the NAOS configuration The time required for PSF reference star observations will be charged to the user For service mode observations we request that all PSF reference OBs are prefixed with the string PSF_ and that clear instructions are written in the README file and the Instrument Comments fields for the science and PSF OBs As of P82 a PSF measurement and its corresponding sky frame can be taken upon request by the acquisition template of SDI and SDI 4 and coronagraphy masks with glass substrate only 100 User s Manual VLT MAN ESO 14200 2761 6 12 Recommended DIT and NDITs Unless the object is bright enough to cause saturation Table 5 2 DITs need to be somewhat larger than those used in ISAAC because the NACO plate scale is considerably finer and it takes longer for exposures to be sky noise limited However if there are bright objects of scientific interest in the field of view then DITs will have to be much smaller than the ones listed in
145. he proper motion to be taken into account it is compulsory to provide both epoch and equinox for which the cootdinates ate provided The corresponding coordinates at the time of observation does correspond to the precessed coordinates at the mean epoch for a given period i e 2007 0 for P78 2007 5 for P79 and so on this is the hard coded epoch of the reference target The epoch of the science target is a free parameter to set between 1850 amp 2100 The target and AO reference star can have different proper motion It is however assumed that the coordinates are given for the same equinox 9 4 Sky Conditions The user characterizes the observing conditions via two parameters the seeing at Zenith and measured at 0 5 um and the airmass The on axis quantities such as the seeing on the reference are automatically computed from these two parameters and some assumptions about the average wind speed and isoplanatic angle on Paranal The Fried parameter r and the isoplanatic angle 9 are also displayed All on axis quantities are computed at 0 5 um 9 5 Reference Objects The information about reference objects is gathered on the right hand part of the main GUL For LGS operations the natural guide star for tip tilt correction TTS has to be specified Ease of operations requires that only one TTS can be specified per LGS OB Users applying for seeing enhancer do not need to specify a TTS 9 5 1 Handling several
146. he total integration time on the sky and on the object can be adjusted so that the S N on the object is optimised Remember that the 30 second per telescope position rule means here that both DIT x NDIT for the OBJECT positions x NEXPO per offset position plus overheads and DIT x NDIT for the SKY positions x NEXPO per offset position plus overheads shall each exceed 30 seconds of time Table 7 14 Parameter of NACO_img_obs_FixedSkyOffset P2PP Label Default Values DIT NODEFAULT Readout mode Double RdRstRd Window Size 1024 Description Detector Integration Time sec Readout mode Size of the window Store Data Cube T F F Data cube flag Jitter box width NODEFAULT Jitter Box Width Number of AB or BA cycles NODEFAULT One cycle is one object sky pair NDIT per object position NODEFAULT Number of DIT s for the OBJECT NDIT per sky position NODEFAULT Number of DIT s for the SKY NEXPO per offset position 1 Number of exposures per offset position Number of offset positions NODEFAULT Number of offset positions Sky offset in RA NODEFAULT RA offset in arcsec Sky offset in DEC NODEFAULT Dec offset in arcsec Filter NODEFAULT Filter name Neutral Density Filter Full Neutral density filter Full none Camera NODEFAULT Camera Name 129 User s Manual VLT MAN ESO 14200 2761 Figure 7 6 illustrates how this template can be used NACO img obs FixedSkyOffset DEC Offset a Sky Positions Object Positions
147. hic image Radial contrast does not reflect directly this value because of azimuthal averaging The maximum attenuation is about 100 a little bit more in the H band probably because the Lyot spot is larger with respect to A D at shorter wavelengths This is comparable to the result obtained in 2004 with the first 4QPM implemented in NACO In this case the limit of contrast is set by the residual static aberrations likely originating from non common path aberrations 5 3 2 3 Chromaticity of 4QPMs Phase shifts as provided by phase masks are chromatic However the chromaticity effect must be balanced with other sources of degradations Chromaticity turns out not to be an issue for NACO Even with the fibre source we observed very small variations as a function of the filter bandwidth as shown in Figure 5 12 The attenuation reaches a factor 60 70 in both Ks and NB 2 17 filters Under atmospheric seeing the effect of chromaticity is totally negligible and a 4QPM designed for the K band can be used with any narrow to broadband filters in the K band and respectively for the 4QPM designed for the H band max attenuation 120 max attenuation 96 Normalized intensity Normalized intensity 1 iy 4 9 a cere es ee enon ae eereanagy L s ee pong 0 0 0 1 0 2 0 3 0 4 0 5 0 0 0 1 0 2 0 3 0 4 0 5 Angular distance in arcsec Angular distance in arcsec Figure 5 11 Radial profiles of the PSF compared to that of the coronagraph
148. hy DIT mg NODEFAULT DIT sec for imaging Readout mode Double_RdRstRd Readout mode Window Size 1024 Size of the window Store Data Cube T F F Store in data cube flag Jitter Box Width NODEFAULT Jitter box width sky only NDIT for object position NODEFAULT Number of DIT s at the object pos under the mask NDIT for sky position NODEFAULT Number of DIT at the sky pos with the mask NEXPO Obj only coro NODEFAULT Number of exp with target under the mask NEXPO per offset pos NODEFAULT Number of exp per imaging position img NOFF sky only coro NODEFAULT Num of offset pos on sky with the mask NOFF img NODEFAULT Number of offset positions for imaging Offset coordinates NODEFAULT SKY or DETECTOR List of offset in X NODEFAULT Offsets in arcsec List of offset in Y NODEFAULT Offsets in arcsec Filter coro NODEFAULT Filter Name for coronagraphy Filter img NODEFAULT Filter Name for imaging Mask Position NODEFAULT Coronagraphic mask Neutral Density Filter Full Neutral Density filter Camera NODEFAULT Camera Name 7 8 4 NACO coro cal NightCalib This template is used for taking nighttime flat fields and it should be placed immediately after the coronagraphic templates If Number of Night Flats is set to n where n can be from 0 to 3 n pairs of exposures are taken Each pair consists of one exposure with the flat field lamp on and one exposure with the flat field lamp off If n is set to zero no lamp flats are
149. ibuted between JitterBoxWidth 2 and JitterBoxWidth 2 It is strongly recommended to define some non zero value for the Jitter Box Width parameter as this allows one to get several images with the spectra lying at different positions on the detector However it should be smaller than the Nod throw otherwise spectra on either side of the throw could overlap 132 User s Manual VLT MAN ESO 14200 2761 1024 1024 Y Acquisition Position Jitter Box 6 23 A 14 5 ee si eo Nod Throw Slit Angle 0 degrees N CONICA FOV S27 28 1 1 X Figure 7 7 An illustration of how the NACO spec obs AutoNodOnsSlit template works with Jitter Box Width 5 Return to Otigin T Number of AB or BA cycles 3 NEXPO per offset position 1 Nod throw 15 To better exploit the jittering facility offered by this template it is also recommended to define the Number of AB or BA cycles to some value higher than 1 e g 4 or 5 so as to get several AB pairs of images with the spectra lying at different positions across the array If the parameter Jitter Box Width is set to zero then the template will just nod between A and B If the parameter Return to Origin T F is set to true T the telescope returns to the starting position If not the telescope is not moved The NEXPO per offset position parameter defines the number of frames stored per A or B position If for example DIT 120s NDIT 1 NEXPO per offset
150. ic image obtained with the 4QPM_K left and the 4QPM_H right 46 User s Manual VLT MAN ESO 14200 2761 1 0000 FN Ks filter SK filter NB 2 17 filter 0 1000 S13 full undersized stop Normalized ntensity Q 0 0010 0 0001 0 00 0 10 0 20 0 30 Angular separation in arcsec Figure 5 12 Chromaticity of the 4QPM_K measured on the 2004 mask with a fibre i e no seeing effects 5 3 2 4 Comparison of the 4QPMs with the classic Lyot masks Measurements were made in 2004 and are still valid for the new masks Figure 5 13 shows data obtained on a natural star The maximum attenuation is only a factor 10 with the 4QPM while it reaches typically 200 with the 0 7 Lyot therefore allowing deeper integrations However the Lyot mask is blind over an area 4 times larger than the 4QPM near the centre and that is precisely the interest of the 4QPMs 5 3 2 5 Observing strategy with the 4AQPMs The precise centering of the science target behind the focal plane mask is critical for the success of the coronagraphic observations and it is done interactively during the acquisition template It can also be tuned during the execution of the observing templates In general the mask centres do not coincide with the centre of the chip and the field of view can be vignetted in complex ways Both the centre and the amount of vignetting depend on the mask and the objective Coronagraphic images with 4QPM and broadband filters prov
151. ich the reference objects are shown will be the one exported to P2PP Sec 9 5 7 and hence the one tried at the telescope o Delete this discards all data pertaining to the selected reference object A confirmation dialog is shown to prevent mistakes o Clear all same as above except that all reference objects of the table will be erased o Duplicate makes a copy of all the characteristics of the currently selected reference object and adds it at the bottom of the list This may prove useful if you want to experiment with a reference object and you want to be able to compare different results of optimization while keeping all of them in the GUI instead of simply overwriting the results 9 5 2 Morphology The Preparation Software and the NAOS instrument can also handle moderately extended objects up to 3 arcsec in diameter to analyze the incoming wavefront Several models are available to define the morphology of the reference object Objects with one of three different morphologies can be used as NAOS reference objects o Point like object 12 User s Manual VLT MAN ESO 14200 2761 o Binary object which requires an angular separation between the two components given in the range 0 2 5 in arcsec and the flux ratio of the two components flux of fainter companion flux of brighter component dimensionless o Disc like object When using a resolved object in the solar system
152. ide a marginal improvement of contrast at a given radius although a significant maximum attenuation 20 200 depending on coronagraphs enable large signal to noise ratio with no need of saturation A large fraction of the flux is therefore left in the focal plane composed with a dynamical halo averaging over time and fluctuating too plus a quasi static halo corresponding to optical aberrations along the optical train from telescope to detector 47 User s Manual VLT MAN ESO 14200 2761 10000 F Lyot vs 4QPM Full Undersized stop PSF 4QPM 1000 Lyot e 0 7 100 Intensity ADU s 0 0 0 2 0 4 0 6 0 8 Angular distance in arcsecond Figure 5 13 Radial profile for the PSF the 4QPM and the 0 7 Lyot obtained with a natural star in 2004 It is recommended here to observe a reference star to calibrate these 2 halos The reference star is chosen with same visible and IR magnitudes to ensure similar AO correction and similar S N in the image More importantly the reference MUST be observed with the same parallactic angle to have the same static speckle pattern which results from interaction between telescope and instrument aberrations and to match the spider spike positions in the images In practice the reference star has the same declination as the target but a right ascension which is that of the star plus or minus the OB duration the reference is observed for the same amount of time as the target In gen
153. iguration file cannot be used for different targets but is fine for different OBs using the same target o The configuration file is inserted into the NAOS parameter file keyword of the relevant acquisition template o The Strehl seeing and airmass constraints and the RA and DEC fields of P2PP will be automatically filled when the configuration file is loaded Do not edit these fields 9 5 8 Exporting OBs from P2PP The export facility in P2PP allows one to export observing blocks For NACO two files are produced one with the extension obx and another with the extension aocfg These files should be kept in the same directory P2PP will report an error if the two files are in different directories 9 5 9 Saving Restoring a PS Session The complete PS session can be saved on local disk and restored The Save Session and Load Session functions available from the File menu of the main panel allow you to save or load the corresponding information on your disk Please be aware that loading a previously saved session file will discard all the data currently stored in the interface However it does not alter any of the configuration files that have been saved to disk Only the files with an extension jnps can be loaded into the PS Once a previous session is loaded into the PS one should run the optimization again before exporting to P2PP otherwise a corrupted file may be exported and the observation may be impossible In case one forgot t
154. ill be rejected at the feasibility assessment stage 102 User s Manual VLT MAN ESO 14200 2761 6 16 Nighttime calibrations For spectroscopic observations users can take spectroscopic flats and arcs immediately after the observation These nighttime calibrations are generally better than the ones taken in the daytime because daytime calibrations are taken with the rotator in a fixed position and a combination of instrument flexure and inhomogeneities along the slit causes the image of the slit on the detector to move by a fraction of pixel when the rotator angle changes For coronagraphic observations with the semi transparent mask and 4QPMs users should take nighttime flats with the NACO_coro_cal_NightCalib template if the flat on off sequence taken during acquisition is not enough for C_0 7_sep_10 and 4QPMs only These nighttime calibrations are significantly better than the ones taken in the daytime because daytime calibrations are taken without the mask Daytime calibrations with the mask are not useful because they are taken with the rotator at a fixed angle and a combination of irregularities on the glass plate holding the mask and instrument flexure means that flats depend on the rotator angle All night time calibrations will be charged to the users with the exception of those explicitly mentioned in the calibration plan of the instrument 6 17 Instrument and telescope overheads The execution time report produced by P2PP comp
155. ime during the acquisition we recommend that users enter an estimate of the position angle into the acquisition template The Alpha offset from Ref Star and Delta offset from Ref Star parameters allow the user to define a telescope offset when the acquisition is made on a bright reference object That is once the reference object has been acquired and centred in the slit the offsets defined here will offset the telescope so as to bring the desired target into the slit Given the accuracy at which the offsets are likely to be defined the smallest slit is only 86 mas wide so the computed offsets have to be better than a few tens of mas we do not recommend this option to users If there is no other option then the position angle of the slit should be set so that both the reference source and science target are not in the slit at the same time to avoid light contamination These offsets should not be confused with the RA offset arcsec and DEC offset arcsec offsets which are used to define the offset between the target and a sky image which is subsequently subtracted from all images This template records between 2 and 5 images to disk On some occasions the operator will record two images of the AO reference which are used to classify the OB If this is the case the image of the slit will be the third frame recorded to disk otherwise it will be first The next image either the 2nd or the 4th image recorded to disk is
156. intain its high contrast capabilities lt 1 100 on the peak i e below the limit imposed by the wavefront quality SR the centering of the star on the AGPM must be within A D 10 or 10 mas third of a pixel at L27 Such a centering capability is now routinely obtained with NACO both in pupil and field tracking modes If a target transits very close to zenith dec 24 10 you might want to fractionate your OB so that a manual recentering of the star is possible every 5 10 minutes 49 User s Manual VLT MAN ESO 14200 2761 5 3 3 1 Contrast of the AGPM As pointed out above the raw contrast will be limited by image quality and pointing errors Under average seeing conditions 1 0 and for reasonably bright stars yielding Lp Strehl ratio between 70 and 80 cf NAOS PS the raw contrast will be around 50 on the brightest peak see Figure 15 The direct benefits of such a starlight attenuation capability are the following e The saturation limit are decreased by 4 magnitudes The level of static speckles pinned to the pupil is decreased accordingly lower speckle noise In the stellar photon noise limited regime close to the center the contrast limit is improved by roughly 2 magnitudes PSF prof e O av rel int coro prof 1 5 0 PCA ADI APA 30 25 5 0 PCA ADI APA gt gt 30 pete e Relative intensity Contrast on te La Ye J 1 0 p 7 5 sa
157. ions without chopping only the NACO img obs Autolitter template should be used The sky subtraction with the other templates is generally unsatisfactory 7 44 1 NACO img obs AutolJitter This template offsets the telescope between exposures according to a random pattern of offsets automatically determined by the template It is ideal for long integrations on sparse fields and does not require a long list of offsets to be defined The offsets are distributed randomly within a box whose size is defined by the parameter Jitter Box Width in arc seconds with the condition that the distance between any two points in a series of ten values is greater than a system determined minimum This is intentionally done to ensure that the 5 frames before and after any frame are spatially not too close and can be safely used for creating skies without residual objects for sky subtraction 1024 1024 Position Angle 45 deg Conica FOV 28 for 527 1 1 X Figure 7 3 An illustration of the NACO img obs Autolitter In this example the jitter box width is set to 10 NEXPO is 1 number of offset position is 7 Return to Origin is T and the camera is 27 The dotted line defines the jitter box width The value of the Jitter Box Width parameter corresponds to the full width of the box in which the offsets are generated Defining too wide a box may lead to poor image overlap Conversely too small a value may lead to poor sky subtraction ne
158. is derived from the PSF and as such it is linked to the observing wavelength The on axis Strehl ratio gives an estimate of the correction of the optical beam in the direction of the reference object i e as seen from the wavefront sensor in NAOS Conversely the off axis Strehl ratio is computed from the estimated PSF on the science object which allows one to estimate the correction provided by NAOS for the target o The full width at half maximum of the PSF is given in arcsec both in the main panel and in the pop up window depicted in Figure 9 6 o Transmission to CONICA is expressed as a fraction of incoming light at the observing wavelength Resulting Performance PointSpread Functon on target 0 0320 x axis 10280 ae Save PSF max 0 0296 3 0240 FWHM xX 0 094 9 0200 FYWHM Y 0 073 Sr 15 30 Dismiss 1 04 60 9 0120 3 0089 3 0040 0 95 0 80 0 64 048 O32 0 15 0 00 0 16 0 32 0 48 0 64 0 50 0 96 arcsec Figure 9 6 Pop up window showing the PSF profile This also gives access to the PSF FITS file The different width of the PSF in x and y direction are due to anisoplanatism The x axis is here defined as the axis that is parallel to the line connecting the reference object with the science target Note the PS takes into account a relatively optimistic turbulence model where the coherence time is large enough to reach nominal AO correction levels i e K band Strehl ratio up to 45 or
159. l TABLE OF CONTENTS 1 SCOPE INQ 2 1 2 2 2 3 INTRODUCTION ADDITIONAL RESOURCES CURRENT VERSION OF THE MANUAL CHANGES IMPLEMENTED DURING THE PRESENT P91 AND PAST PERIODS 3 OBSERVING WITH ADAPTIVE OPTICS IN THE INFRARED 3 1 3 2 3 3 3 4 3 5 3 6 ATMOSPHERIC TURBULENCE ADAPTIVE OPTICS INFRARED OBSERVATIONS WITH AN AO SYSTEM TRANSMISSION AND BACKGROUND BACKGROUND SUBTRACTION SPECTROSCOPY 4 NAOS 4 1 4 2 4 3 4 4 OVERVIEW NAOS PERFORMANCE ANISOPLANATISM LASER GUIDE STAR FACILITY LGSF 5 CONICA 5 1 544 Bk ILI 5 1 4 5 5 5 2 EMA b 52 5 2 4 525 CONICADETECTOR GENERAL CHARACTERISTICS DIT AND NDIT READOUT MODES AND DETECTOR MODES CAMERAS FILTERS IMAGING CALIBRATION PLAN FOR IMAGING AND SDI PIPELINE FOR IMAGING NOAO SPECKLE IMAGING FABRY PEROT IMAGER SIMULTANEOUS DIFFERENTIAL IMAGING SDI VLT MAN ESO 14200 2761 15 17 18 19 19 21 21 21 22 22 23 25 26 26 27 28 28 31 33 33 34 34 35 35 38 38 38 38 40 40 User s Manual 5 2 6 Lal 5 3 Dial D2 5 3 3 5 3 4 5 5 3 6 Ri 5 4 5 4 1 5 4 2 5 4 3 5 4 4 5 4 5 5 4 6 5 4 7 5 4 8 5 5 Dds 5 5 2 5 6 5 6 1 5 6 2 5 6 3 5 6 4 5 6 5 5 6 6 5 6 7 5 6 8 5 6 9 5 6 10 5 6 11 5 6 12 5 6 13 5 6 14 5 6 15 SDI ON SKY PERFORMANCE PIPELINE FOR SDI CORONAGRAPHY SEMITRANSPARENT MASK C_0 7_SEP_10 FOUR QUADRANT PHASE MASKS 4QPMS ANNULAR GROOVE PHASE MASK CORONA
160. l images were stacked together and a MEAN image and a RMS image were created by computing the mean and the rms of each pixel in the stack Then the mean flux per pixel in the core of the PSF was computed in an aperture with a 5 pixel radius The RMS image was divided by the square root of the number of individual images in the stack te 350 The resulting 1 G image Im g contains the 1 0 noise for a single pixel planet To compute the contrast as a function of radius we had to take into account that the flux of a potential companion would be distributed across several pixels and we had to use the same n 5 pixel aperture that we used for the PSF core i e n 5 pixel This will increase the signal to noise by a factor Vn Thus the 5 0 Contrast image Im g in units of magnitudes can be computed as 5 Im 1 n flux n The corresponding contrast curves for NB4 05 and Lp are shown in Figure 5 19 and Figure 5 20 respectively Im 2 5 og 20 pixel NACO APP contrast curve NB4 05 aoe 77777 6 0 6 5 7 0 Fad 8 0 Delta magnitude NB 4 05 0 0 0 5 1 0 1 5 LLL i Arcsec 6000 4000 2000 o 2000 4000 6000 4 Figure 5 19 APP PSF obtained with the NB_4 05 filter and under relatively good seeing conditions and the 5 0 contrast curve of the clean side 54 User s Manual VLT MAN ESO 14200 2761 5 sigma point source detection limit for VLT APP Delta L magnitudes 10 0 0 5 1 1 5 2 Radius a
161. le configurations were tested and if one wishes to use a case not covered some custom tests may be needed Contact NACO eso org for inquiries For DCR HD the overheads are minimal given the fact that no readout is performed until the entire cube has been produced The rule of 0 7 seconds overhead per exposure DITXNDIT is no longer valid in cube mode The time to complete an exposure is typically 1 5 12 The dimension of the cube will be NAXIS3 NDIT 1 See section 5 10 for details Cube mode frame losses go along with time overheads as the system struggles to write the cube ot the disk In this column are displayed approximate writing times for each cube for some known setups The p2pp currently accounts for these overheads only for the full frame minimum DIT cases In case the overhead is negligible 0 here the total OB execution time can be pessimistically estimated by p2pp This part will be refined upon further tests Beware that will such DIT the background might saturate with the L filter 88 User s Manual VLT MAN ESO 14200 2761 times the exposure time DITxNDIT To that one has to add the data cube writing to disk and controller TRACE overheads which are approximately 16 20 seconds per cube When using min DIT and small windows overheads increase but are still of the order of few seconds This is not the case for FowlerNsampling FNS read This technique inevitably introduces large overheads for instance
162. ll occur in pairs that are dithered between two separate quadrants e g bottom left top right Offsets must be given in DETECTOR coordinates to avoid that the changing position angle on sky introduced by the pupil tracking mode in use with SAM puts the objects in ever different locations on the detector or worse outside of the available field The operator always centres the object on pixel 512 512 and the subsequent offset sequence can be of the type offsets in X 1 2 offsets in Y 1 2 with the result that the star goes from upper right to lower left Another possible sequence uses all four quadrants alternatively offsets in X 1 2 0 2 and offsets in Y 1 2 2 2 will move the object from the centre to upper right to lower left to upper left and finally to the lower right quadrant 144 User s Manual VLT MAN ESO 14200 2761 Sky observations will be dealt with as usual open loop offset set by the user in the offset sequence always in DETECTOR coordinates Table 7 26 describes the parameters of this template As always in cube mode DIT 0 will set the minimum integration time allowed for the specific readout mode and window size The NDIT for each frame is limited by the final cube file size set to a maximum of 512 MB For each exposure it can be set to a different number i e list of NDIT can be 2000 50 100 100 Since most SAM objects are bright it is always convenient using cube mode and perform shift and add te
163. lters The transmission curves at the J H Ks Lp Mp and spectroscopic order sorting filters are displayed in Figure 8 1 Electronic versions of the transmission curves of all filters including the NB and IB filters are available from the NACO web pages eso ore sci facilities paranal instruments NACO inst filters html T T T T T T T T SH 0 8 z LNA N 2 og Ww fo a U y E 5 J J H i Ks SK un 0 4 FE 0 2 j n 0 pr ed A LA yi LX 1 0 2 2 0 Wavelength microns 0 8 0 6 0 4 Transmission 0 2 Wavelength microns Figure 8 1 Filter curves for J H Ks Lp and Mp and the order sorting spectroscopic filters SJ SK L The SH and L band filters are also used as order sorting filters in spectroscopy 147 User s Manual VLT MAN ESO 14200 2761 8 2 CONICA Neutral Density Filters CONICA is equipped with a short wavelength 1 to 2 5 um and a long wavelength gt 2 5 um neutral density filter The wavelength dependence of the attenuation is shown in Figure 8 2 Neutral Density Filter 0 925 ND Transmission o Q ff 08 1 12 1 4 16 18 2 22 24 26 28 3 32 34 36 38 4 42 44 4648 5 52 54 56 58 6 Wavelength um Figure 8 2 Transmission curves of the CONICA neutral density filters 148 User s Manual VLT MAN ESO 14200 2761 9 PREPARATION SOFTWA
164. m is at the same position on the two maps A clear minimum appears both in the H and K bands However note that several other local minima exist The best fitting result at the global minimum is plotted in Figure 5 35 76 User s Manual VLT MAN ESO 14200 2761 f gt L 4 w 8 p A p 0 Base m t ra Base meters Figure 5 35 Phases measurement for BD 21 4300 as a function of the baseline length The solid curve is the best fit of a model of a binary star Tuthill et al 2010 SPIE 7735 56 Right panel H band data Left panel K band data The companion position and flux ratio are reported in Table 5 17 Errors on the phases are on average around 0 5 deg in the K band and around 1 deg in the H band Parameters for the best fit detection are presented in Table 5 17 The contrast and separation of this companion 4 magnitudes and 90 mas agree well with the original detection of this companion at Keck Kraus et al 2008 arXiv 0801 2387 This companion lies far beyond the detection limit of direct imaging with or without AO al lhe iy iji IN hi Phan degrees Phase degrees Ph gras Heatuads Recdude Aestiuas Base manara Base rral rs Base metars Figure 5 36 Same as Figure 5 23 but using a point source reference star observed in different filters and masks Left 9 Holes NB_2 17 Middle BB9_Holes NB_2 17 Right BB9_Holes Lp All give statistically null re
165. m the number of elements in the aforementioned lists If the number of spatial offsets is larger than the number of elements in a list the list 1s restarted from the beginning as many times as needed until the correct number of offsets has been done These lists can have any leneth however having lists of different lengths can become extremely confusing It is good practice to use lists of equal length or lists with only one value if one parameter is not changed Unlike other templates this template does not have a Return to Origin T F flag This flag refers to the spatial offsets only and the template will do this automatically before rotating the rotator to the new position Rotator offset angles are entered as a list The angles are relative so a sequence with 0 33 0 33 would result in images that are taken 0 33 33 and 0 degrees from the original rotator position Due to difficulties in compensating for rotator offsets with the FS we are presently requesting observers to keep the relative offset angle to 45 degrees or less Additionally the user can choose to rotate the rotator to the original rotator position once the template has ended with the parameter Return to the Original Rotator Position T F For observations with NAOS CONICA the default value for this flag is False The total number of exposures is given by number of rotator positions x Number of offset positions x NEXPO per offset position With this scheme it
166. metry It can be used with all filters with the exception of J and Mp Rotator offset angles can now be entered as a list The angles are relative so a sequence with 0 45 45 45 would rotate the field by 0 45 90 and 135 degrees from the original rotator position Due to difficulties in compensating for rotator offsets with the FS we are presently requesting observers to keep the relative offset angle to 45 degrees or less Additionally the user can choose to rotate the rotator to the original rotator position once the template has ended with the parameter Return to the Original Rotator Position T F For observations with NAOS CONICA the default value for this flag is False 136 User s Manual VLT MAN ESO 14200 2761 After each rotator offset the telescope can offset according to a user defined list Spatial offsets are defined with the parameters List of offsets in X and List of offsets in Y The offsets are relative to the previous position are in X and Y and are defined in arcsec Additionally the observation type can be defined for each image and is entered as a list in the parameter Observation Type O or S O stands for Object and assigns the DPR TYPE header keyword to OBJECT S stands for Sky and assigns the DPR TYPE header keyword to SKY The AO loop is closed for the former and open for the latter The total number of spatial offsets is defined by the parameter Number of offset positions This number can be differe
167. ming the degrading effects of atmospheric turbulence is real time compensation of the deformation of the wavefront WF by adaptive optics AO Figure 3 1 The wavefront sensor WES measures WF distortions and these measurements are processed by a Real Time Computer RTC The RTC controls a deformable mirror DM and corrects the WF distortions The DM is a continuous thin plate mirror mounted on a set of piezoelectric actuators that push and pull on the back of the mirror Because of the significant reduction in the WF error by AO correction it is possible to record images with exposure times that are significantly longer than the turbulence correlation time The WF error directly determines the quality of the formed image One of the main parameters characterizing this image quality is the Strehl ratio SR which basically corresponds to the amount of light contained in the diffraction limited core relative to the total flux An AO system is a servo loop system working in closed loop The DM flattens the incoming WF and the WES measures the residual WF error The WFS in NAOS uses a Shack Hartmann screen It consists of a lenslet array that samples the incoming WF in a pupil plane Each lenslet forms an image of the object and the displacement of the image gives an estimate of the WF slope at that lenslet A good feature of this WFS is that it works with white light extended sources and very faint stars The performance of an AO system is direc
168. mization is the corresponding estimated performance in terms of image quality It is expressed quantitatively by the computed point spread function PSF and its derived quantities The PSF is returned to the user interface in FITS format It characterizes the quality of the optical beam which is provided by NAOS to CONICA and is thus logically computed at the observing wavelength and is available from the Resulting Performance area of the GUI The provided PSF is computed off axis i e in the direction of the target seen by CONICA The PS computes these data on 128x128 pixels One pixel corresponds to an angle of A 2D and the extracted PSF is assumed to be monochromatic To access the PSF data once the optimization has been performed click on the PSF button This pops up a window that shows the profile of the PSF along the x and y axes Figure 9 6 The FITS file itself can also be saved to the user s local disk for later use If you want to save the file the Save PSF button brings a file browser and allows you to choose the name of the file on your local disk This operation is performed by sending the 157 User s Manual VLT MAN ESO 14200 2761 appropriate request to the central server where your PSF file has been stored under a unique name Depending on your local installation the file retrieval may take a few seconds The other quantities which are outputs of the optimization are o The Strehl ratio is expressed as a percentage It
169. moved from the optical path 115 User s Manual VLT MAN ESO 14200 2761 The detector and readout modes are not parameters of the acquisition templates They are automatically set and they depend on the filter For LW filters the readout mode is set to Uncorr and the detector mode is set to HighDynamic For all other filters the readout mode is set to Double RdRstRd and the detector mode is set to HighDynamic The minimum DIT s for these modes are listed in Table 5 2 For very bright targets a neutral density filter can be inserted into the light path The choices are Full for no neutral density filter ND Long for a LW neutral density filter and ND Short for a SW neutral density filter Filter curves are plotted in Section 8 All acquisition templates can be used to acquire PSF stars In such cases the PSF reference T F flag should be set to true Although the NAOS configuration will be ignored during the acquisition a valid NAOS parameter file is still required the obvious exception to this is acquisition done in no AO mode using NACO img acq MoveToPixelNoAO By default the PSF reference T F flag is F Note that this flag when used with pupil tracking including SAM will additionally keep the pupil angle fixed As of P82 some acquisition templates have been modified to collect useful calibration data free i e at no extra time cost for the users 1 NACO img acq MoveToMask NACOQ ims aeq SDi
170. n SDI from Biller et al Ap J S S 173 143 2007 42 User s Manual VLT MAN ESO 14200 2761 5 3 Coronagraphy 3 P93 the Lyot C_ and 4QPM modes are no longer offered For coronagraphic applications six masks were available until P91 two Lyot coronagraphs opaque masks with diameters of 0 7 and 1 4 arc seconds a semi transparent mask with a diameter of 0 7 arc seconds two 4 quadrant phase masks 4QPM one optimized for K band observations and the other for H band the Apodizing Phase Plate APP see Section 5 3 7 operated with the NB 4 05 and Lp filters just like direct imaging In addition a brand new annular groove phase mask AGPM synthesizing an optical vortex coronagraph tuned for Lp band operation including NB 3 74 and NB 4 05 has been recently installed and successfully validated The available masks and their characteristics are listed in Table 5 6 Table 5 6 CONICA s masks and phase plates for coronagraphy Barred iterm are the discontinued masks since P93 Diameter Comments Opaque held in place by wires 100 extinction over the mask Semi transparent 3 5X10 gt transmission placed on a glass plate 40PM K 0 15 Four quadrant phase mask for K band 13x13 FoV The diameter is that of the central Lyot spot 4QPM H Four quadrant phase mask for H band 8X8 FoV The diameter is that of the central Lyot spot AGPM NA Annular Groove Phase Mask synthesizing an optical vortex coronagraph
171. n prism the same care must be taken as for observation with the NACO_pol_obs_GenericOffset template see Section 7 7 1 The total integration time excluding overheads is defined in seconds by DIT x NDIT x NEXPO per offset pos x number of half wave plate angle x Number of offset pos The angle of the HWP used is reported in the FITS header under INS RETA2 NAME Previously this keyword did not exist The angle of the HWP can be retrieved from INS ADC1 ENC HWP encoder via the following formula HWP angle HWP encoder 205 4096 360 modulo 4096 Example angles of 0 amp 22 5 correspond to INS ADC1 ENC 3891 amp 51 respectively This information remains available from the FITS header Note that the Polarizer Wheel parameter by default is set to Wollaston_00 which will insert both the Wollaston mask and prism If it is set to empty both the Wollaston mask and prism will not be inserted rather the FLM_13 or the FLM_27 normal non polarimetric imaging masks will be selected according to the camera S13 or S27 159 User s Manual VLT MAN ESO 14200 2761 7 71 3 NACO pol cal StandardStar This template should be used to observe polarimetric standards that do not require chopping It is strictly equivalent to the NACO_pol_obs_GenericOffset see 7 7 1 template with the difference that some DPR keywords in the FITS headers of the images are set to different values allowing pipeline processing and archiving 7 8 NACO co
172. nitudes brighter for the N20C80 and N90C10 dichroics For detailed estimates users should use the ETC Table 6 3 Recommended magnitude range of standard stars for observations with the visual dichroic Magnitude Range 101 User s Manual VLT MAN ESO 14200 2761 6 15 Maximum brightness of observable targets Bright targets leave residual images that can take several minutes to disappear Table 6 4 presents the absolute limits acceptable Table 6 4 Magnitude limits for DIV lt 1 sec IR Magnitude Any narrow band filter Any filter plus one neutral density filter Any narrow band filter plus one neutral density filters Please note that the maximum brightness limit is set considering the following limitations o The AO acquisition is done on CONICA in imaging mode i e with no other dimming optical elements in the path o The need to avoid persistence on the CONICA detector These limits apply for DIT lt 1 Such bright objects heavily saturate the detector and cannot be used for science For longer DITs these limits should be increased by approximately 1 magnitude for every 10 fold increase in DIT The careful reader will note that this is not a linear relation When acquiring or when observing targets in imaging or polarimetry a saturation of a factor 10 is the maximum acceptable The saturation level is defined for each detector mode by the full well depth see Table 5 2 Any other expected saturation level for
173. no overlaps between spiders and mask holes occur and use these 6 setups to observe with the pupil at different orientations this technique allows avoiding the spider arms falling onto unwanted areas of the detector and achieving the highest possible dynamic range However the telescope pupil and NACO are not perfectly aligned and only one angle per mask has been found suitable for use 5 6 3 Detector readout and cube mode setup for SAM For bright targets the dominant noise term is in the perturbations from the turbulent atmospheric phase screen Rapid readout of the detector array tends to freeze the motion of the interference fringes reducing the impact of the seeing on the measured coherence of the incoming wavefront Thus seeing drives us to read as many rapid exposure frames as possible but this needs to be traded off against detector readout noise which will rapidly dominate for fainter stars CONICA is ideally suited as a masking camera because it offers a readout mode DCR HD for collecting data cubes of consecutive frames of any given integration time with minimal overheads and high duty cycle These data cubes typically consist of hundreds of short exposure 0 1 sec frames for bright targets or perhaps a few tens of longer exposure frames 1 10 sec More details on cube mode can be found in Section 5 8 66 User s Manual VLT MAN ESO 14200 2761 Given the very small useful science field of view it is generally not necessa
174. nomer See Appendix B It is quite common to offset the telescope very frequently when observing with NAOS CONICA and since there are two stars that are used to control the system one for active optics and the other for adaptive optics as well as the scientific target which may in fact be the same as the adaptive optics star users have to pay very special attention to the restrictions imposed by the system There are essentially two kinds of offsets The first is an offset that results in the NAOS AO loop being closed at the end of the offset The second is an offset that results in the NAOS AO loop being opened at the end of the offset In the first case the field selector FS has to move from where it was when the NAOS AO loop was last closed In the second case the FS does not move The field of view of the FS is a bit less than 2 arcminutes If the offset sequence is such that the positions at which the loop needs to be closed is outside this region the observations will fail It is not possible for the system to know beforehand what offsets it will be asked to perform so if it encounters an offset command which would move the FS beyond its limits it will politely refuse Template parameters which would lead to that happening are checked for possible problems during OB verification When small telescope offsets are used less than one arc minute the telescope keeps the same active optics star If however large t
175. nservative as the lower left corner isn t straight When stripped down to 512x514 windowing the remaining FoV is 13 8x2 5 2 35 on the left and 2 65 on the tight We then have p1 0 425 and p2 512 512 Photometric standard stars will not be taken in Service Mode even for CLR or PHO conditions unless the users specify it in their ReadMe file then taken without APP Standard star OBs with APP can also be provided by the users using this same template 7 4 4 NACO img obs GenericOffsetNoAO This is the speckle mode template allowing cube mode hardware windowing open loop observations It s a copy of NACO_img_obs_GenericOffset all SW filters will be allowed and the Offsets will be optional one can always put 1 and 0 0 to stare Since P88 it is possible to set Return F default was T so that the telescope stays at the position of the last offset of the template instead of coming back to the initial position This is for users who wish to perform quick star hopping cycles between their science and their calibrators at their own risks only VM taking into account the offset sizes with the night astronomer and telescope operator 128 VLT MAN ESO 14200 2761 User s Manual 7 4 5 NACO img obs FixedSkyOffset This template moves the telescope alternatively between object and sky positions The object positions are randomly distributed around the initial telescope position and within a box whose dimen
176. nt from the number of elements in the aforementioned lists If the number of spatial offsets is larger than the number of elements in a list the list is restarted from the beginning as many times as needed until the correct number of offsets has been done These lists can have any leneth however having lists of different lengths can become extremely confusing It is good practice to use lists of equal length or lists with only one value if one parameter is not changed The total number of exposures is given by number of rotator positions x Number of offset pos x NEXPO per offset pos Unlike other templates this template does not have a Return to Origin T F flag This flag refers to the spatial offsets only and the template will do this automatically before rotating the rotator to the new position With this scheme it is possible for the user to sample the object and the sky as desired at several rotator positions It is also possible to code the template so that the object and sky are sampled as desired for one angle only The template can be restarted with another orientation on the sky for another series of exposures At least two different orientations separated by 45 degrees are required for computing the Stokes parameters Table 7 20 Parameters of NACO_pol_obs_GenericOffset P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DIT s Readout mode Double _RdRstRd Read
177. ntauri 30 Figure 5 1 CONICA Schematic overview 32 Figure 5 2 Illustration of the ghosts present on CONICA images when observing a bright object In addition to the electronic ghosts there is also an optical ghost characterised by its circular shape The electronic noise visible on the sides of the array as well as the bias levels of rows 512 amp 513 disappear in the background subtraction 13 Figure 5 3 Some results of the speckle masking experiment Rengaswamy et al 2010 applied on a 0 16 separation binary star Comparison between the reconstructed intensity map bottom left and the closed loop AO image bottom right is given Seeing conditions were excellent for this test 39 Figure 5 4 Speckle holography technique applied to the NGC3603 cluster The holography image on the right is nearly as deep as the AO corrected one on the left the 3 sigma detection limit is Ks 18 in both cases However it is advantageously more suitable for astrometry as every single star of the field appears in its true position unaffected by AO induced distortion effects The holography PSF itself is very clean diffraction limited with a K band Strehl ratio reaching 65 about 2 5 times superior to the closed loop PSF which suffers an obvious waffle mode pattern 39 Figure 5 5 Flat field image of the SDI mode The transmitted wavelengths are 1 6 mm top left 1 575 mm top right and 1 625 mm bottom left and right 41 Figure 5 6 Contrast o
178. nvention is that offsets are relative E g the following list of offsets RA offset list arcsec 0 10 10 20 20 DEC offset list arcsec 00000 will result in a first image without offset a second image in which the telescope was moved 10 arcsec Fast a third image at the original position etc Sometimes offsets may be defined in detector coordinates In that case a positive offset in X will move the image to the right X the telescope offset is therefore in the opposite direction All offsets are defined in arcsec even the offsets that are defined in detector coordinates Therefore an offset of 10 in X will move the object 10 to the right All offsets are relative from the last position entered At the end of the template the telescope will return at the beginning of the sequence if the keyword RETURN is set equal to T 7 2 NACO General templates 7 2 1 NACO all obs Rotate The NACO all obs Rotate template rotates the field of view and it has only one parameter the rotator offset angle The angle is in degrees and a positive angle will rotate the adaptor from North to East Hence objects in an image will rotate from North to West The angle is relative hence the position angle of the field at the end of the rotation will be the position angle of the field before the template was run plus the angle in the template The template can only be followed by imaging templates 7 3 NACO Acquisition templates
179. o save a session it is possible to copy the aocfg file into a jnps file and then import it as a session 9 5 10 Giving names to session P2PP and PSF files Each time a file is about to be saved one is asked to provide a name The default name is based on the target name but one may want to change it This does not affect the operations and may be convenient for the user However remember the files will be used by Unix based machines so one should avoid special characters spaces brackets etc in the names 9 5 11 User s preferences The Preferences menu gives access to configurable functionalities of the PS which are detailed below o Show tool tips every field in the GUI has an attached tool tip Though very useful when starting to use the PS this may be annoying for more experienced users This option allows one to switch them on off 159 User s Manual VLT MAN ESO 14200 2761 o Set working directory you can specify here the name of the directory where the output files are created by the PS the one to be inserted in P2PP OBs are saved The default is your home directory O Set server name this menu item raises a small pop up window that allows one to change the name of the host machine where the PS server can be accessed It is unlikely that normal users will need to use this feature If you do happen to accidentally change the name the server name can be found at http www eso otg sci observing phase2 SM
180. on the ND filter if inserted will be taken out of the path and two images taken one with the star in the field but at least 2 off the mask and one with no star 1 e a sky frame The files created by these templates are saved together with the acquisition image They can be recognized by a unique combination of headers keywords Table 7 2 keywords combinations used for the new calibration frames type Flat on CALIB FLAT LAMP CORONAGRAPHY or INS LAMP2 CURRENT valu IMAGE DIFFERENTIAL e Flat off CALIB FLAT LAMP CORONAGRAPHY or INS LAMP2 CURRENT 0 IMAGE DIFFERENTIAL PSF star CALIB IMAGE PSF CALIBRATOR OBJECT PSF sky CALIB IMAGE PSF CALIBRATOR SKY Users should request that they wish their science target to be observed as PSF calibrator in their README file Alternatively should the science target be unsuitable as PSF calibrator a separate 116 User s Manual VLT MAN ESO 14200 2761 OB for the calibrating target with a name starting with PSF_ should be submitted and it will be observed immediately after the main science target In this case the PSF key in the acquisition template should be ticked on because this will tell NAOS not to change the AO configuration The time needed to observe the PSF target will be charged to the user The NACO img acq MoveToPixelNoAO template will allow an OB to be executed on NaCo without aocfg files because the AO loop will remain open speckle mode 7 3 1 Pupil
181. onversely HighBackground has the largest well depth but has many more hot pixels The former is used for long integrations in low background situations where cosmetic quality and low readout noise are paramount while the latter is used in high background situations where cosmetic quality is less important The detector mode is not a parameter that users can select It is set automatically and depends on the instrument setup For example all observations in FowlerNsamp will use HighSensitivity Details of how the detector modes are assigned are given in Table 5 2 Table 5 2 CONICA detector readout modes for each astronomical use the mode Readout Noise RON gain full well FW capacity and minimum DIT min DIT are given Instrument mode Readout mode Detector Mode RON Gain Full Well Min DIT ADU e ADU ADU sec 7500 1 7927 SW FowlerNsamp 4 4 4 LW Lp imaging Uncort HighWellDepth 44198 22000 0 1750 LW Mp imaging Uncott HighBackground 28000 0 0560 34 User s Manual VLT MAN ESO 14200 2761 The maximum allowed DIT is now unconstrained by the array However in practice the maximum DIT is defined by the need to get sky frames As part of the updated NACO calibration plan photometric standard stars STD will be observed with the same setup dichroic FLM camera filter gain and readout mode as the science observations for all OBs requiring CLR or PHO conditions Full Well refers to the full well
182. oo s TERRO TEATERET Taug En tO ee 0 00 1 0 5 1 1 5 0 0000 0 0050 0 0100 0 0150 0 0200 0 0250 0 0300 0 0350 0 0400 0 0450 0 0500 Ang ular se paratio n Figure 15 left saturated PSF with a DIT of 0 05s Middle residual after the AGPM coronagraph DIT of 0 2s displayed at the exact same linear scale Note the attenuation of the peak brightness the diffraction pattern and the speckles pinned to the PSF including the spiders showing the threefold benefits of coronagraphy Right contrast curves showing the PSF the RAW azimuthally average intensity as well as the 5 6 final contrast after LOCI PCA type speckle subtraction on a typical but short ADI sequence 30 PA variation 200 s of total exposure time on source The purple curve shows the limit for larger PA variations The background limit reached here at 0 4 will be lower for brighter targets and or longer integration times see NACO ETC 5 3 3 2 Observing strategy To stabilize speckles on the science camera CONICA we recommend using the pupil tracking mode It also allows the angular differential imaging ADI strategy to be used or not i e frames can always be simply derotated which is perfectly adapted to the circular symmetry and 360 FoV of the AGPM Pupil tracking is also useful to enable maximum contrast capability as well as minimum background contamination from the telescope obstructing structures mainly M2 and associated support
183. ositions NODEFAULT Number of offset positions List of offsets in X NODEFAULT Offsets in arcsec List of offsets in Y NODEFAULT Offsets in arcsec Filter NODEFAULT Filter name Neutral Density Filter Full Neutral density filter Full none Camera NODEFAULT Camera Name 130 User s Manual VLT MAN ESO 14200 2761 7 4 7 Simultaneous Differential Imaging SDI template discontinued since P93 15 The simultaneous differential imager SDI uses special templates to acquire and observe targets 7 5 1 NACO sdi obs GenericOffset This template is used exclusively with the SDI mode It is similar to the NACO pol obs GenericOffset template in that it allows one to rotate the field of view as well as offset the telescope At each rotator angle the telescope offsets according to a user defined list Offsets are defined with the parameters List of offsets in X and List of offsets in Y They are relative to the previous position are in detector co ordinates and are defined in arcsec Additionally the observation type can be defined for each image and is entered as a list in the parameter Observation Type O or S O stands for Object and assigns the DPR TYPE header keyword to OBJECT S stands for Sky and assigns the DPR TYPE header keyword to SKY The AO loop is closed for the former and open for the latter The total number of spatial offsets is defined by the parameter Number of offset positions This number can be different fro
184. out mode NEXPO per offset position 1 Number of exposures per offset position Number of offset positions NODEFAULT Number of offset positions Observation type O or S NODEFAULT O is in closed loop S in open loop Offset coordinates NODEFAULT SKY or DETECTOR List of offset in X NODEFAULT Offsets in arcsec List of offset in Y NODEFAULT Offsets in arcsec Return to the original rotator F Return to original rotator position at the position T F end of the template List of position angle Offsets NODEFAULT List of rotator offsets in degrees Filter NODEFAULT Filter Name Neutral density filter Full Neutral Density filter Camera NODEFAULT Camera Name To image the entire field of view at one position angle one must take great care with the offsets The opaque and transmitting parts of the mask have slightly different widths The opaque strips have a width of 3 9 and the transmitting strips have a width of 3 1 An example of how one may choose to image the entire field of view is given in Figure 7 9 137 User s Manual VLT MAN ESO 14200 2761 The total integration time excluding overheads is defined in seconds by DIT x NDIT x NEXPO per offset pos x Number of offset pos x number of rotator pos CONICA FOV S827 28 1024 1024 1024 1024 Figure 7 9 An illustration of how the NACO pol obs GenericOffset template works with Number of offset positions 9 NEXPO per offset position 1 Observation Type O or S O List o
185. owing changes were implemented for P88 and still apply e Lyot Coronagraphy offered in SM only in field tracking FT no pupil tracking PT e SDI with PT offered in SM simple imaging only no masks 4QPM The following changes were implemented for P87 and still apply e IB_4 05 NOT Offered the new intermediate band filter centred at 4 05 um showed some 19 User s Manual VLT MAN ESO 14200 2761 bad features strong defocus and less flux than expected Please consider using either the Lp filter or one of the narrow band ones around 4um NB_4 05 or NB_3 74 APP Spectroscopy Offered the Apodizing Phase Plate coronagraph APP can also enhance the spectrum of a faint companion located between 0 2 and 0 7 on one side of its parent star Offered with limited setups and in VM only as explained in Section 5 4 1 Prism Spectroscopy Offered It is offered again for limited setups and VM only The following changes were implemented in P86 and still apply noAO Offered open loop imaging Associated with the cube mode it allows to do speckle interferometry with NACO and recover very good Strehl ratios down to 1 um Offered in VM and SM See Section 5 2 3 for more information APP Offered the Apodizing Phase Plate coronagraph APP which allows direct imaging no mask with an improved companion detection limit between 0 2 and 0 7 on one side of the PSF More information about this mode is available in 5 3 7 Spec
186. pectroscopic templates If Night Arc T F is set to T a pair of exposures one with the arc lamp on and another with the arc lamp off will be taken If set to F no arcs are taken If Number of Night Flats is set n where n can be from 0 to 3 n pairs of exposures are taken Each pair consists of one exposure with the flat field lamp on and one exposure with the flat field lamp off If n is set to zero the default no lamp flats are taken Table 7 19 describes the parameters of this template Table 7 19 Parameters of NACO_spec_cal_NightCahb P2PP Label Default Values Description Night arc T F F Night time arc Number of night flats 0 Number of flat field on off pairs 7 7 NACO polarimetry science templates These templates are for polarimetric observations with the Wollaston prism For SW observations the readout mode of the detector should be set to either Double RdRstRd ot FowlerNsamp For LW observations the readout mode should be set to Uncorr All other combinations will be rejected at the time the OBs are checked For very bright target a neutral density filter can be inserted into the light path The choices are Full for no neutral density filter ND Long for a LW neutral density filter and ND Short for a SW neutral density filter Since the J band filter is in the same wheel as the Wollaston J band polarimetric observations are not feasible 7 7 1 NACO_pol_obs_GenericOffset This template is used for imaging polari
187. position NEXPO IMG and the number of offsets NOFF IMG are free parameters I HI Coronoeraphv i i Coronoeraphv grapn Generic Offset Srapn on target on sky Figure 7 11 Illustration of how the NACO coro obs Astro template works The 3 phases of the template are presented Part I left coronagraphy without moving the telescope Part II middle simple imaging the coronagraphic mask is removed Normally the first offset is zero to measure the exact position of the target out of the mask The last offset of the list NOFF SKY brings you onto the sky position where the original coronagraphic mask is inserted again and on sky coronagraphic images are taken in open loop Part III right diagram In this example NOFF SKY 5 Table 7 23 describes the parameters of this template The total integration time excluding overheads is defined in seconds by the sum of the CORO time and IMAGING time time spent on each mode respectively CORO exposure DIT CORO x NDIT OBJ x NEXPO OBJ DIT CORO x NDIT SKY x NOFF SKY IMG exposure DIT IMG x NDIT IMG NEXPO IMG NOFF IMG When using the 4QPM masks if no neutral density filter is needed it is recommended to use the Full_Uszd mask 142 VLT MAN ESO 14200 2761 User s Manual Table 7 23 Parameters of NACO_coro_obs_Astro P2PP Label Default Values Description NDIT img NODEFAULT Number of DIT s for the imaging DIT coro NODEFAULT DIT sec for coronagrap
188. quency The IRACE controller is able to acquire data with microseconds timing accuracy and it is assumed that the additional frame writing overheads are homogeneously distributed during the exposure time There are stringent limitations to the use of the cube mode in particular it will only be offered in combination with basic imaging including APP SDI coronagraphy and SAM in NGS mode i e no LGS Additional advantage of the cube mode is the much smaller overheads needed to save large quantities of frames When in the past a user would select a certain number of exposures per offset by means of the NEXP parameter now one can select cube mode and save all the images in one frame saving the time needed to save each file 16 17 sec there is only one readout per cube which means that hundreds or thousands of frames can be taken with very little overheads See Section 5 8 1 for more information on overheads The size of each cube is limited by the maximum file size accepted by our flavour of Linux 512 MB Therefore given a certain detector window this fixes the maximum number of planes that can be saved in a cube i e NDIT Cube mode is offered in combination with 5 different window sizes Note that since windowing is done on chip i e hardware windowing NY NX 2 Another feature of hardware windowing is that one cannot choose the position of the window within the full frame array each window is centred on pixel 512 512 and
189. r acquisition o All spectroscopic observations must use NACO_img_acq_MoveToSlit for acquisition o All APP spectroscopic observations must use NACO app acq MoveToSlit for acquisition not offered sin P93 o All coronagraphic observations must use NACO img acq MoveToMask for acquisition only AGPM since P93 o All observations with the SDI must use NACO img acq SDIMoveToPixel for acquisition not offered sin P93 o All observations with the SDI 4 must use NACO img acq SDIMoveToMask for acquisition not offered sin P90 o Al observations with SAM must use NACO img acq SAMMoveToPixel for acquisition o All observations with SAMPol must use NACO img acq SAMPOl for acquisition Oo Itis possible to submit a single OB that comprises several observing descriptions for example one can observe a single target with different filters but most mixed mode observations e g coronagraphy with spectroscopy are generally not allowed Direct imaging after any other mode is allowed but users should note that the position of the object in the CONICA FoV will slightly change when moving from either coronagraphy or spectroscopy to imaging because different flexure compensation models are used for these modes O Some targets saturate the detector with the minimum DIT Consult the ETC o The pixel scale is very small so the readout noise can dominate if the DIT is too small Consult the ETC 111 User s Manual VLT MAN ESO 14200 2761 o
190. r plate is the best option The implementation of these two possibilities it is done via the template At the beginning of the science observation the operator is asked whether the retarder plate should be used making it possible to decide in real time whether the object does have a sufficient rotation to render the use of the retarder plate unnecessary Note that SAMPol does not use the Polarimetry Mask usually needed in classic polarimetry to cover the overlapping parts of the beams because SAM SAMPol are only used for single object targets and there should never be the possibility for confusion between overlapping fields that the mask is intended to avoid 5 7 1 Calibration plan for SAMPol e Twilight flats as described in Section 5 2 1 e Detector darks in all readout modes and DITs 5 7 2 Pipeline for SAMPol SAMPol is not supported by the pipeline 86 User s Manual VLT MAN ESO 14200 2761 5 8 Cube mode Cube mode is a variant of the burst mode offered with VISIR ISAAC and HAWK I In this mode a data cube with each single DIT frame is saved This mode is particularly interesting for lucky imaging type of observations where one wants to select the best frames out of a set before co adding them The mode can be used for time resolved applications provided one selects detector setups that do not lose frames and no single DIT frame time stamping is needed The timing accuracy has been measured in the case of 1 sec sampling fre
191. r possible updates to this manual and for recent news For P93 a drastic reduction of modes due to the installation of NACO on the Nasmyth A platform after 6 months of inactivity P92 The idea is to mitigate risks associated to commissioning training etc and stick to the essential and high performance setups 2 3 Changes implemented during the present P93 and past periods The following change is implemented for P93 and on NACO was disconnected for the whole P92 e Spectroscopy grism and prism is now offered in VM only e AGPM coronagraphy is now offered in VM only e Wollaston Polarimetry is now offered in VM only LGS operations is no longer available e SDI is discontinued e 4QPM and Lyot coronagraphy are discontinued e APP Spectroscopy is discontinued The following change is implemented for P91 and on e A new Annular Groove Phase Mask coronagraph AGPM optimized for Lp band is now offered in pupil tracking PT only The inner working angle of the AGPM is 0 1 and the field of view is clear at 360 and 15 wide e M band imaging is offered in VM only The following changes were implemented for P90 e All coronagraphs Lyot 4QPMs are now offered in SM and VM in field tracking FT AND pupil tracking PT e For technical reasons and the diminishing demand in the past semesters the SDI 4 mode has been decommissioned SDI and 4QPM are still offered separately No changes in P89 The foll
192. rcsec Figure 5 20 5 sigma Lp contrast curve of the clean side note the higher achievable Amag gt 10 5 than with the NB 4 05 filter 8 changing the P rotates the FoV not the APP effect on the PSF Figure 5 21 Position Angle consideration for APP Imaging No matter what the PA is the PSF pattern remains fixed only the field of view rotates with respect to this pattern Telescope PR Collimator APP Filter Camera Detector wedge image 4 OPTI 3 OPTI 5 6 OPTI7 DET L54 M FLM27 APP MELE Figure 5 22 The APP was manufactured with a strong wedge to avoid spurious reflections The drawback is that it induces a mostly vertical shift of the image in the detector plane The FoV with the L27 camera going along with its field limiting stop FLM27 is about 28 wide in X but only 8 high in 55 User s Manual VLT MAN ESO 14200 2761 Y The offset pattern has to take that into account Overall it should not be a problem as the APP is useful to only about 3 further than 1 the rings appear again If using a sub frame of 512x514 thanks to cube mode the FoV is reduced to 2 5 x14 APP coronagraph successful commissioning April 2010 VLT NaCo 4 05 um Contrast curve clean side of the PSF exoplanet Beta Pictoris b demonstration preliminary Beta Pic b confirmed again e Separation 0 354 0 010 6 AU e PA 209 13 deg 2 00 deg e Delta ma
193. recommend this option to users If there is no other option then the position angle of the slit should be set so that both the reference source and science target are not in the slit at the same time to avoid light contamination These offsets should not be confused with the RA offset arcsec and DEC offset arcsec offsets which are used to define the offset between the target and a sky image which is subsequently subtracted from all images This template records between 2 and 5 images to disk On some occasions the operator will record two images of the AO reference which are used to classify the OB If this is the case the image of the slit will be the third frame recorded to disk otherwise it will be first The next image either the 2nd or the 4th image recorded to disk is an image of the acquisition target after it has been centred If reference offsets are used an additional image either the 3rd or the 5th image recorded to disk is taken after the reference offset Table 7 5 parameters of NACO_img_acq_MoveToStit P2PP Label Default Values Description DIT NODEFAULT Petector Integration Time sec NDIT NODEFAULT Number of DITs Type of AO Observation LGS NGS NODEFAULT LGS or NGS observation type PSF Reference T F F Set to T if it is a PSF reference star Pupil Tracking Mode T F F Always set to F PT not supported Alpha offset from Ref star 0 Offset from reference star arcsec Delta offset from Ref star 0
194. reference objects It is possible to keep a list of several possible reference objects for observations in NGS and work alternatively with each of them The list of reference objects is shown as a table at the top of the form containing all the data pertaining to the reference object Each row corresponds to a reference object showing its name if it has been provided and its angular distance to the science target mandatory parameter The other columns are filled when requesting an optimization by the PS server Section 9 5 5 If several reference objects are available in the table you can select the one you want to work with by simply clicking on the corresponding row This will update the contents of the form below the table as well as the Resulting Performance sub panel shown on the bottom left of the GUI Indeed each reference object is attached to its own configuration of the AO system and to the performance estimated when considering this configuration 151 User s Manual VLT MAN ESO 14200 2761 The order is important if the first reference object is acquired successfully then the other reference objects will not even be considered Reference objects should be sorted in decreasing order of expected performance Use the list manipulation buttons Up Down to modify this order as needed Every time you want to add an object to the list you must first fill in the mandatory fields and then click the
195. rential Imager SDI 4 Coronagraphy with 4QPM and Simultaneous Differential Imager Service Mode Strehl Ratio Short Wavelength TBC To Be Clarified TB To Be Defined C Telescope Control Software TIM Time Interface Module TRS Time Reference System F Template Signature File TT Tip Tilt Mirror TTS Tip Tilt Source VLT Very Large Telescope VM Visitor Mode WF Wavefront WES Wavefront Sensor W Workstation ZNVA Zernike Noise Variance J DN DN Z User s Manual VLT MAN ESO 14200 2761 2 INTRODUCTION The Nasmyth Adaptive Optics System NAOS and the High Resolution Near IR Camera CONICA are installed at the Nasmyth B focus of UT4 NACO provides multimode adaptive optics corrected observations in the range 1 5 um NAOS Section 4 is an Adaptive Optics AO system Section 4 1 that is designed to work with natural guide sources NGS point like or extended objects with either a visible or an IR wavefront sensor It can also use a Laser Guide Star LGS beacon and a natural Tip Tilt source TTS to provide AO correction with somewhat degraded performance with respect to NGS As of recently the system is able to be used over the whole sky albeit with poorer correction than with an NGS or the LGS TTS using the LGS alone in seeing enhancer SE mode CONICA Section 5 is an Infra Red IR 1 5 um imager and spectrograph fed by NAOS It is capable of imaging long slit spectroscopy simultaneous di
196. rformance obtained with SAM at NACO 5 6 2 Pupil tracking with SAM One additional aspect of experimental implementation that was requested in advance was the ability to drive the optical rotator and telescope control system in such a fashion that the image of the pupil within the CONICA camera is maintained fixed at a given orientation while the telescope tracks and slews to different stars This pupil tracking mode is crucial for experiments such as aperture masking where the occultation of one of the mask holes by the telescope spiders will cause highly detrimental loss of Fourier coverage and compromise the calibration properties of the experiment Furthermore for observational programs relying on precision calibration it is simply good practice to preserve the optical system in a stable configuration between source and reference Star Although simple in principle the rotator simply has to track the elevation axis ignoring the azimuth axis in practice such a mode can take some effort to fully implement as software driving the pointing tracking and guiding systems together with the AO system all needs to understand the implications of the new sky rotation Pupil tracking mode is the default way to observe with SAM and is implemented in a transparent way for the users The masks have 120 degrees symmetry while the telescope spiders have 180 degrees symmetry In theory it should be possible to find 6 angles at which
197. rmatting Typos Addenda for the new modes sam cube data format pupil tracking New info on new modes after change over to P82 Changes for P83 Phase II Added some more info on overheads Added SAMPol Added info on pupil tracking angles Added details for SAMPol Improved description of Wollaston prisms Chopping conventions SAM and SAMPol acquisition template SAM and SAMPol science templates New revised version for P85 SE and cube imaging in SM added New revised version for P86 APP_coro noAO added PT comments Spectro modified cube mode frame losses More APP information from com report APP Spectroscopy Prism Spectroscopy minor changes in many sections Cube mode for Polarimetry As for CfP88 Lyot Coronagraphy in SM no PT SDI and PT in SM no 4QPM some information about PT astrometric filed orientation calibration Template information fixes Figure tables 5 9 9 1 Section7 some template comments Minor fix to Pol ACQ template description Note about the drift in Pupil Tracking fixed since Oct 15 2011 SDI 4 decommissioned Polarimetric flats clarification Prism Spectroscopy warnings Cube mode time overheads P2PP3 containers for SM Coronagraphy section AGPM Coronagraphy section AGPM update Some modes are not offered anymore SDI Lyot 4QPM LGS and some other modes become VM only AGPM spectroscopy Polarimetry User s Manual VLT MAN ESO 14200 2761 User s Manua
198. ronagraphic acquisition template for all masks supported by a glass substrate C 0 7 sep 10 4QPMs will take one flat on and one flat off image Those can be used for flat fielding of the science data taken afterwards since the mask is not moved out of the beam 52 User s Manual VLT MAN ESO 14200 2761 IMPORTANT NOTE ABOUT AGPM flat field lamp flat fields are not taken at Lp band Instead at least a few sky frames can be used to generate a map flat field of the coronagraph useful for dust imperfections mapping 5 3 6 Pipeline for mask coronagraphy Coronagraphic observations are not supported by the pipeline 5 3 7 Apodizing Phase Plate APP coronagraphy Since P86 there is a new coronagraphic Apodizing Phase Plate APP placed in a pupil plane in the OPTI3 wheel and designed to work in the 3 to 5 um range It is offered to work with the NB 4 05 and Lp filters the IB 4 05 filter showed problems and is decommissioned Since no occulting mask is present in the focal plane it works just like simple direct NB_4 05 or Lp imaging offsets and short DIT required to overcome the thermal background As shown in Figure 5 18 simulations by M Kenworthy it provides higher contrast at small angular separation 0 2 to 0 7 arcseconds from the main star on one side which is suitable for faint companion search in some cases It can be combined with cube mode pupil tracking and saturation within acceptable limits i e 10 times
199. ronagraphic science templates For SW observations the readout mode of the detector should be set to either Double_RdRstRd ot to FowlerNsamp For LW observations with Lyot coronagraphs or the AGPM the readout mode is set to Uncorr 7 8 1 NACO_coro_obs_Stare only with AGPM since P93 7 8 2 This template is used for coronagraphic observations and it moves the telescope alternatively between a fixed object position and a sky position The parameter Number of AB or BA cycles defines the number of times this is done but unlike the NACO_spec_obs_AutoNodOnSht and NACO_img_obs_FixedSkyOffset templates the sequence is ABABAB and not ABBAAB for the example in which the Number of AB or BA cycles is set to 3 The number of exposures at the object position is defined by the Number of Exposures Object Only parameter The telescope does not offset between these exposures The number of exposures at the sky position is defined by the Number of offset positions Sky only and the telescope can offset between these exposures The sky positions are randomly distributed around a position that is set at a constant distance defined by the parameters Sky offset in DEC and Sky offset in RA from the original telescope position and within a box whose dimensions are set by the parameter Jitter Box Width in arcsec It is strongly recommended especially for very bright sources to select an area so that the main target is out of th
200. roscopy Table 5 8 summarizes the main characteristics of the long slit grism spectroscopic modes The resolution R is computed for the 86 mas slit For spectroscopy with the 172 mas slit the spectral resolution is set by the PSF SJ SH SK SHK and SL are special broad band filters for spectroscopic applications They cover a wider wavelength range than the standard J H Ks and L band filters respectively The L band filter is only offered in spectroscopy for imaging applications users should use the Lp filter Table 5 8 Spectroscopic modes The mode name consists of the objective the grism number and the order sorting filter microns mas pixel nm pixel 6 Light from the second order can also be seen but does not contaminate 57 User s Manual VLT MAN ESO 14200 2761 mask mas 2 09 Jam ssas ar 1 te aa 2040 5 4 2 APP enhanced spectroscopy x This mode is no longer offered since P93 IMPORTANT NOTE this is a shared risk mode for high contrast spectroscopy We recommend interested users to contact the APP and NACO IS team for further details Normal L band spectroscopy should be considered instead for non expert users 2 slits 86 and 172 mas POSSIBLE NOT POSSIBLE PA has to be carefully set You can turn the FoV PAs But not the slit wrt APP PSF N PA 0 IMG IG f mj ja Figure 5 24 illustration of the APP spectroscopy concept 58 User
201. rture masking Some useful references specific to masking include o Tuthill P G et al Michelson Interferometry with the Keck I telescope PASP 112 555 2000 o Tuthill P G et al Sparse aperture adaptive optics SPIE 6272 103 2006 o Lloyd J P et al Detection of the Brown Dwarf GJ 802B with Adaptive Optics Masking Interferometry ApJ 650 131 2006 o Tuthill P G et al Sparse Aperture Masking SAM at NAOS CONICA on the VLT SPIE 7735 56 2010 In brief masking is useful for very narrow fields of view the outer limit is set by the resolution of the shortest baseline in the mask Any advantages it enjoys over conventional full pupil imaging are only manifest at such very high resolutions typically within several resolution elements of the PSF core Dynamic ranges obtained within this realm have been demonstrated to be in excess of 200 1 for point source detections To attain this level of precision careful analysis of closure phase signals is required and exhaustive understanding of error sources such as PSF calibration and chromatic effects arising from atmospheric dispersion Furthermore with full recovery of closure phase signals complex and arbitrary flux distributions can be mapped with high fidelity The particular streneths of aperture masking are for relatively bright targets where there is resolved or partially resolved structure within a few resolution elements of bright PSF cores The
202. ry to read the entire 1024 pixel array In fact normally only a 256x258 pixel region would be sufficient In addition to saving on data storage the smaller sub arrays can be read out faster and with a lower noise readout strategy Arrays of size 1024 512 and 256 can be read out in 0 34 0 11 and 0 04 seconds respectively in Double RdRstRd Other windows such as 128x130 and 64x66 are too small to contain the SAM patterns and are not to be used Although for some of the brightest targets there may be good arguments for pursuing a 256x258 sub array the 512x514 sub array is recommended The main advantage of this is that the image of the science target can be dithered between two separate quadrants on successive data cube integrations Thus while collecting data in one quadrant one collects a sky background frame in another quadrant at the same time 5 6 4 SAM with LW filters Operation in the 3 5 um region using the long wavelength filters offered within CONICA is straightforward This was commissioned using the L27 camera which adequately samples the fringes and has optical components optimized for this region For the shorter wavelength operation only the 13 was used again to ensure adequate sampling of the fringes Special strategies such as chopping to remove sky fluctuations are generally not essential for long waveleneth aperture masking One reason is that the masks themselves dramatically cut down the sky background and st
203. s 3 50441 2 60135 3 50441 2 60135 2 00252 1 73423 70 User s Manual VLT MAN ESO 14200 2761 0 500629 4 33558 0 500631 2 60135 0 500631 4 33558 2 50315 0 867115 4 00503 1 73423 4 00503 1 73423 3 Mask BB_9Holes Hole size 0 980 mm diameter Table 5 15 X and Y location of the holes as measured in mm from the centre of the mask BB_9Holes 3 18399 0 0607701 3 53717 1 49530 0 0805017 4 39864 1 64462 212103 3 06355 2 31563 3 76908 2 26903 ics 9 2 78780 0 473616 3 81093 3 84958 2 12960 4 Mask 7Holes Hole size 1 50 mm diameter Table 5 16 X and Y location of the holes as measured in mm from the centre of the mask 7Holes X 3 51064 1 99373 3 51064 2 49014 1 56907 1 36918 71 User s Manual VLT MAN ESO 14200 2761 5 6 10 References and further readings We have tried to give brief notes on the practical use of the aperture masks in the CONICA camera When used correctly these masks transform the single 8 m telescope pupil into a sparse interferometer array and it is therefore necessary to understand the principles of optical interferometry and in particular the recovery of complex Fourier data amplitudes and phases from the Fizeau interference patterns that result A full explanation of the mathematical techniques necessaty to do this task is beyond the scope of the present document The reader is advised to consult sources form the open literature concerning ape
204. s The readout mode refers to the way the array is read out We offer three readout modes Oo Uncorr The array is reset and then read once It is used for situations when the background is high e g LW imaging The minimum DIT without windowing is 0 1750 seconds For observations in Mp the array is windowed to 512x514 and the minimum DIT is 0 0558 seconds Refer to Table 5 21 for minimum DIT values for windowed readout schemes o Double RdRstRd The array is read reset and read again It is used for situations when the background is intermediate between high and low such as SW imaging or LW spectroscopy The minimum DIT is 0 3454 seconds Refer to Table 5 21 for minimum DIT values for windowed readout schemes o FowlerNsamp The array is reset read four times at the beginning of the integration ramp and four times again at the end of the integration ramp Each time a pixel is addressed it is read four times It is used for situations when the background is low such as SW spectroscopy or SW NB imaging The minimum DIT is 1 7927 seconds Refer to Table 5 21 for minimum DIT values for windowed readout schemes The detector mode refers to the setting of the array bias voltage and four modes have been defined HighSensitivity HighDynamic HighWellDepth and HighBackground The well depth and the number of hot pixels are directly related to the detector mode HighSensitivity has the fewest hot pixels but it has the smallest well depth C
205. s a 1 2 5 um filter CutOff_2 5um that may be used to select the non thermal range 8 Based on the 86 mas slit on the central wavelength Fit based on spectra taken were taken with several narrow band filters to create pseudo arc lines The fit is valid from 1 to 4 microns 10 Fit based on telluric absorption features at 5 microns The fit is valid from 4 5 to 5 5 microns 59 User s Manual VLT MAN ESO 14200 2761 LGS Prism Spectroscopy K band image lg ed on the Galactic Center et ve S L band gt as e a et by S Gillessen Figure 5 25 illustration of the prism spectroscopy capability for the Galactic Centre with LGS UT4 LGSF Here are a set of warnings regarding this mode The L27_P1 mode is difficult to use The resolution in J is very low and the background in M is high although it is not so high that normal readout modes cannot be used For targets with blue colours it will be difficult to get good S N at 5 microns without saturating the spectra at 1 micron Data for the S27_P1 have not been taken Figure 5 26 a spectrum of an AO star with the L27 P1 mode The spectrum starts at 0 85 um near the top and extends to 5 5 um near the bottom Note that the change in brightness from 5000 ADU and saturated at 1 um to 20 ADU at 5 um One also notes several electronic and optical ghosts The spectral traces of the prism spectra are quite complex In general one can fit the trace with a 4th ord
206. s discontinued Users can opt for the Wollaston 00 in combination with the retarder plate Special calibrations all observations requesting special calibrations will be moved to VM Exceptions to this rule will be considered on a case by case basis during technical feasibility The following changes were implemented for P80 and still apply Fabry Perot will not be offered Users are encouraged to consider SINFONI as an alternative 20 User s Manual VLT MAN ESO 14200 2761 3 OBSERVING WITH ADAPTIVE OPTICS IN THE INFRARED 3 1 Atmospheric turbulence The VLT Very Large Telescope has a diffraction limited resolution of A D 0 057 at A 2 2 um But the resolution is severely limited by atmospheric turbulence to 1 1 0 7 where r is the Fried parameter The Fried parameter is directly linked to the strength of the turbulence and it depends on the wavelength as For average observing conditions r is typically 60 cm at 2 2 um The correlation time of the turbulence t is related to r and the speed at which the turbulent air travels For a wind speed of 10 m s the correlation time is of the order of 60 ms at 2 2 um Both t and r are critical parameters The larger they are the more stable the atmosphere is and the better the performance of NAOS will be Atmospheric conditions are better suited to AO observations during the summer months in Paranal with larger tand r 3 2 Adaptive optics A powerful technique in overco
207. s located in the same wheel as the ND Long filter 2 5 lt L lt 7 and a L 2 star will saturate the detector with the minimum DIT of 0 175s Uncorr HD FullFrame under nominal conditions The APP imaging finding chart must clearly show the field orientation North East vectors and the position angle at the meridian of the candidate companion if any versus the APP PSF pattern good hemisphere always on the right of the detector For pupil tracking OBs please refer to the Pupil Tracking field orientation issues explained in section 7 3 1 56 User s Manual VLT MAN ESO 14200 2761 Photometric standard stars will not be taken in Service Mode even for CLR conditions unless OBs are provided by the users using this same template see the P89 Calibration Plan No imaging flats will be taken in Service Mode even for CLR conditions unless the users specify it in their ReadMe file P93 Calibration Plan References APP commissioning report APP team S Quanz M Meyer M Kenworthy M Kasper J Girard R Lenzen Kenworthy et al 2010 SPIE Quanz et al 2010 ApJL Girard el at 2010 SPIE 5 4 Long Slit Spectroscopy VM only since P93 Table 5 8 and Table 5 10 summarize the main characteristics of the long slit spectroscopic modes A spectroscopic mode is made up of a grism or a prism an order sorting filter and an objective The mode name is the identifier given to the mode and used in P2PP 5 4 1 Grism Spect
208. s of multiple visits between the science target and a calibrator spanning an interval of several hours may also help to get rid of some of this systematic error Jo User s Manual VLT MAN ESO 14200 2761 Degrees Degrees 100 200 300 400 100 200 300 400 Acquisition Acquisition Figure 5 38 Example of strong systematic effect on the phases Both dataset consists in 400 0 11 ms exposures The only different between these two dataset are the position of the star on the detector In red is plotted the mean phase as well as its statistical rms If the phases could be de biased potential precision on the phase would be 0 1 deg allowing detection with dynamic range of 1 000 5 6 16 Calculating exposure times throughput and sensitivity for selected filters In order to convert from the standard CONICA exposure times given by the online calculator tool ETC into SAM exposure data only two additional numbers are needed These are 1 the fraction of the mirror area passed by the mask and 2 the fraction of the total flux that will be found in the brightest pixel These numbers have been calibrated using the commissioning data for a subset of the total available filter mask combinations For filters that have not been calibrated it should be fairly simple to extrapolate from these numbers to get reasonably close Note that these numbers have been taken from limited observations and some values may not be representative of normal s
209. sets in RA or X and List of offsets in DEC or Y The offsets are relative to the previous position are in RA and DEC or in X and Y depending on the Offset Coordinates parameter and are defined in arcsec Additionally the observation type can be defined for each image and is entered as a list in the parameter Observation Type O or S O stands for Object and assigns the DPR TYPE header keyword to OBJECT S stands for Sky and assigns the DPR TYPE header keyword to SKY The AO loop is closed for the former and open for the latter The total number of offset positions is defined in the parameter Number of offset positions This number can be different from the number of elements in the aforementioned lists Lists do not need to have the same length If the number of exposures is larger than the number of elements in a list the list is restarted from the beginning as many times as needed until the correct number of frames have been acquired The lists can have any length however having lists of different lengths can become extremely confusing It is good practice to use lists of equal length or lists with only one value if one parameter is not changed At the end of the template the telescope is returned to the original position Figure 7 4 and Figure 7 5 illustrate how this template can be used The total integration time is defined in seconds by DITx mer of offset positions ND IT i x NEXPO per offset position 126
210. sions are set by the parameter Jitter Box Width in arcsec e s ositions are randomly distributed around a position that is set at a constant distance The sky posit domly distributed d a position that tat tant dist defined by the parameters Sky offset in DEC and Sky offset in RA from the original telescope position and within a box whose dimensions are set by the parameter Jitter Box Width in arcsec The object positions will be observed with the AO loop closed For the sky positions the AO loop will be open By default there is no telescope offset before the first exposure The telescope moves back to its original position at the end of the template The Number of AB or BA cycles defines the number of OBJECT SKY or SKY OBJECT cycles to be executed These cycles are executed in ABBA sequences E g if Number of AB or BA cycles is set to 3 6 exposures will be taken in an ABBAAB sequence In addition the template provides the flexibility to adjust the number of NDIT sub integrations for the OBJECT and SKY frames NDIT for the OBJECT positions defines the number of sub integrations on the object and NDIT for the SKY positions defines the number of sub integrations on the sky The total integration time excluding overheads is defined in seconds by DIT x NDIT for the OBJECT positions NDIT for the SKY positions x NEXPO per offset position x Number of AB or BA cycles Thus t
211. sks SAM VM only As part of the original design of the CONICA camera provision was made for the possibility of utilizing aperture masking interferometry in order to obtain the very highest angular resolutions at the diffraction limit Following highly successful demonstrations of the technique elsewhere both in the AO corrected and non AO case a proposal was submitted to ESO to install custom fabricated aperture masks into the pupil wheel of CONICA SAM was commissioned in March 2008 after a first attempt in Feb 2007 adversely affected by bad weather by the PI Peter Tuthill School of Physics Sydney University and his Co I Sylvestre Lacour University of Grenoble now at Paris Meudon Observatory The results reported in this manual are taken from their commissioning report The design of aperture masks for a telescope needs to take into account several complicating factors For a given observation there are trade offs between various parameters which means that a range of different masks can be used in order to tailor the experiment to somewhat varying targets and science The factors relevant to mask design include The desired Fourier coverage especially the shortest amp longest baseline required The bandwidth of the optical passband to be used for observations The apparent brightness of the target star The readout noise properties of the detector The degree of correction provided by the AO system In order to span a promisin
212. so large scale changes in the sky background are less noticeable in CONICA than in ISAAC Thus the typical integration time and the typical amount of time between telescope offsets will be larger for CONICA 3 4 Transmission and background The transmission of the Earth s atmosphere in the 1 5 um region is shown in Figure 3 2 The Y J H K L and M bands correspond to atmospheric windows which are approximately centred at 1 22 User s Manual VLT MAN ESO 14200 2761 1 25 1 65 2 2 3 6 and 4 8 um The absorption is mostly due to water and carbon dioxide and it varies with zenith distance and the amount of water vapour Regarding observations with NACO the sky background can be split into two regions Below 2 2 um the sky background is dominated by OH emission that originates at an altitude of 80 km At longer wavelengths the thermal background of the atmosphere and telescope dominate 3 5 Background subtraction Subtraction of the background is critical to the success of observing in the IR and special observing techniques have been developed to do it The techniques depend on the type of observation and on the wavelength region at which one is observing For imaging observations short ward of 4 2 microns and for regions that are relatively un crowded i e tens of point sources in 20 square arcsec or moderately extended objects the standard practice is to resort to the jitter technique and most NACO imagine templates make use of i
213. some occasions the wind can be strong enough to prevent the telescope from pointing in that direction 95 User s Manual VLT MAN ESO 14200 2761 Visitors should also prepare targets with bright V lt 10 reference sources so that telescope time can be effectively used when the turbulence is fast NACO can in principle also observe in open loop should the conditions be unsuitable for adaptive optics but users should consider this only as a last resort unless the noAO mode has been requested 6 3 Active Optics versus Adaptive Optics Active optics is the active control of the primary and secondary mirrors of the telescope its main goal is to correct for dome turbulence and gravity pull on the mirror in order to ensure the same seeing as can be measured outside the dome with the telescope at zenith VLT mirrors have been optimized to make use of this correction hence it is not possible to observe without using the active optics Adaptive optics is the correction of wavefront errors induced by atmospheric turbulence Although the instrument can run in principle in closed loop without the active optics system controlling the primary and secondary mirrors one gets better adaptive optics performance if the active optics system of the telescope is running 6 4 The influence of the moon Moonlight does not noticeably increase the background in any of the CONICA modes so there is no need to request dark or grey time for this reason Ho
214. spec_obs_GenericO ffset P2PP Label Readout mode NEXPO per offset position Number of offset positions Observation type O or S Offset coordinates List of offset in RA or X List of offset in DEC or Y Return to Origin T F Slit Spectroscopic Mode Default Values NODEFAULT NODEFAULT FowlerNsamp 1 NODEFAULT NODEFAULT NODEFAULT NODEFAULT NODEFAULT T NODEFAULT NODEFAULT Description Detector Integration Time sec Number of DIT Readout mode Number of exposures per offset position Number of offset positions O is in closed loop S in open loop SKY or DETECTOR Offsets in arcsec Offsets in arcsec Return to Origin Name of slit Spectroscopic Mode 135 User s Manual VLT MAN ESO 14200 2761 7 6 3 NACO spec cal StandardStar This template is used for spectroscopic standard star observations It is strictly equivalent to the NACO spec obs AutoNodOn Slit template in the definition of the parameters The user is referred to 7 6 1 for the description of the parameters This template should be used by users who need calibrations beyond the ones provided by the Calibration Plan of this mode The differences with NACO spec obs AutoNodOnSlit are that some DPR keywords in the FITS headers of the images are set to different values allowing pipeline processing and archiving 7 6 4 NACO_spec_cal_NightCalib This template is used for taking nighttime arcs and flat fields and it should be placed immediately after the s
215. st of offsets in Y The offsets are relative to the previous position are in X and Y and are defined in arcsec Additionally the observation type can be defined for each image and is entered as a list in the parameter Observation Type O or S O stands for Object and assigns the DPR TYPE header keyword to OBJECT S stands for Sky and assigns the DPR TYPE header keyword to SKY The AO loop is closed for the former and open for the latter The total number of spatial offsets is defined by the parameter Number of offset positions This number can be different from the number of elements in the aforementioned lists If the number of spatial offsets is larger than the number of elements in a list the list 1s restarted from the 138 User s Manual VLT MAN ESO 14200 2761 beginning as many times as needed until the correct number of offsets has been done These lists can have any leneth however having lists of different lengths can become extremely confusing It is good practice to use lists of equal length or lists with only one value if one parameter is not changed The total number of exposures is given by NEXPO per offset pos x number of half wave plate angle x Number of offset pos Unlike other templates this template does not have a Return to Origin T F flag By default at the end of the template the telescope returns at the original position It is important to remember that for technical reasons the HWP is moved into t
216. sults for the presence of a binary companion with best fit limits reported in Table 5 78 Table 5 17 Results from phase fitting of target BD 21 4300 K Band H Band Flux ratio 2 8 0 3 2 4 0 5 Separation 89 8 4 0 91 324 5 5 il User s Manual VLT MAN ESO 14200 2761 Table 5 18 False detections on calibrator stars 9Holes BB 9Holes BB 9Holes NB 2 17 NB 2 17 Lp Flux ratio 0 7 0 2 0 4 0 1 0 8 0 3 Separation 152 8 10 4 100 3 12 5 88 34 7 5 5 6 14 On sky observations AB Dor in H and K 400 400 141 195 200 200 DO W E o E o QO Q ov e D 200 200 129 189 400 400 400 200 0 200 400 400 200 0 200 400 RA mas RA mas Figure 5 37 Likelihood for the presence of a secondary star as a function of its position At maximum likelihood the flux ratio between the main star and its companion is 1 29 0 14 in K band left and 1 47 0 24 in H band tight AB Dor was observed between 1h17 and 1h42UT HD41371 was used for PSF calibration and was observed between 1h54 and 2h12UT For each one of these targets the data consist of two data cubes in each band 2 24 um and 1 75 um The cubes are sets of 100 exposures of 2 seconds integration time using a 512x514 windowing of the detector Seeing was around 1 5 but AO correction was nevertheless stable with occasional disruptions The 9 holes mask was used Correction for dark flat field and bad pixels was applied to our data An important s
217. t The technique basically consists of taking numerous images of the field typically 10 or more with small offsets between the positions The sky is then estimated from all the observations The most critical aspect of jittering is that the size of the offsets should be larger than the spatial extent of the object s one is observing For more crowded fields or extended objects i e covering a large fraction of the array the jittering technique works less well and the sky has to be sampled separately from the object resulting in a loss of observing efficiency which can amount to 50 of the time if the sky has to be sampled as frequently as the object Still all the object positions can be jittered between themselves as well as the sky positions This minimises the effect that poor array cosmetics have on the data In the case of crowded fields where there is no suitable nearby sky field the jittering technique can still give good results as long as the number of offsets is large i e greater than 20 In spectroscopy the classical technique is to observe point sources or moderately extended sources at two or more positions along the slit allowing one to integrate continuously on the object For crowded fields or extended objects the sky has to be sampled separately from the object At thermal IR wavelengths gt 3 um the background is considerably higher and more variable In order to avoid saturation the detector at these waveleng
218. t a relatively low maximum K band Strehl ratio of 55 due to the cone effect Even more severe is the image motion or tilt determination problem Because the paths of the light rays are the same on the way up as on the way down the centroid of the artificial light spot appears to be stationary in the sky while the apparent position of an astronomical source suffers lateral motions also known as tip tilt The simplest solution is to supplement the AO system using the LGS with a tip tilt corrector set on a generally faint close NGS V 17 or brighter Performance is then limited by the poor photon statistics for correcting the tip tilt error The need for a natural guide star for tip tilt sensing is the reason why sky coverage cannot go up to 100 for 28 User s Manual VLT MAN ESO 14200 2761 LGS AO Full sky coverage can be achieved in the so called seesng enhancer mode i e LGS assisted AO observation but without correcting for tip tilt The expected Strehl ratio which can achieved in this mode is given in Table 4 4 Table 4 4 Summary of NACO Strehl ratios at 2 2 microns for LGS without tip tilt correction at two distinct atrmass values These values were derived with the Preparation Software PS and are also used in the CONICA Phase 1 Exposure Time Calculator to estimate signal to noise ratios Seeing Airmass Expected Strehl on axis 14 4 os os The Laser Guide Star Facility LGSF at UT4 is
219. t of view the only difference is that the Wollaston 00 is inserted in the optical path at the end of the acquisition template Given the small field of views of SAM it is not necessary to use the image plane mask In order to get all the Stokes parameters the template uses the half wave plate Since the field of view is now halved offsets in the Y direction have to be very small Table 7 27 describes the parameters of this template Table 7 27 Parameters of NACO sampol obs GenericOffset P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec Readout mode Double RdRstRd Readout mode Window Size 1024 Size of the window Store Data Cube T F T Data cube flag List of NDIT s NODEFAULT List of NDIT s 145 User s Manual NEXPO per offset position Number of offset positions Observation type O or S Offset coordinates List of offsets in RA or X List of offsets in DEC or Y List of position angle offsets Filter SAM Mask Camera 1 NODEFAULT NODEFAULT NODEFAULT NODEFAULT NODEFAULT NODEFAULT NODEFAULT Full NODEFAULT VLT MAN ESO 14200 2761 Number of exposures per offset position Number of offset positions O is in closed loop S in open loop Choose DETECTOR Offsets in arcsec Offsets in arcsec List of HWP angles Filter name Name of SAM mask Camera Name 146 User s Manual VLT MAN ESO 14200 2761 8 FILTER TRANSMISSION CURVES 8 1 CONICA Broad Band Imaging and order sorting fi
220. t overhead Table 6 13 Example 7 LW coronagraphy of a bright source Rene E Oba ron apa Integration Time Execution Time min Preset Be Guide Star Acquisition Initial Setup AO Acquisition Sub Total acquisition i23 Observation 20x 1 3x60 27 35 5 Total min 8 Overheads 140 Observation Integration time minutes x 1 30 x 60 sec Offset Overhead 3 Coronagraphic acquisition 3 4 109 User s Manual VLT MAN ESO 14200 2761 Table 6 14 Example 8 Imaging with chopping Acquisition Template Observation Template Integration Time Execution Time min Guide Star Acquisition Observation Integration time minutes x 1 30 x 60sec Offset Overhead Table 6 15 Example 9 A bright source with SDI Template parameters NACO_img_acq_SDIMoveToPixel NACO sdi obs GenericOffset 10 sec Acquisition Template Observation Template DIT NDIT Number of offset positions NEXPO per offset position Readout Mode List of position angle offsets Double RdRstRd 0 33 Return to original rotator position Execution Time min Preset Se ee Initial Setup AO Acquisition SDI acquisition Sub Total acquisition Rotator Offset 1 Observation at 0 and 33 degrees 2x5x 27 6x10 0 7 2x7 3 14 6 Total Overheads 173 Observation Number of offset positions x Offset overhead NDIT x DIT readout overhead 110 User s Manual VLT MAN ESO 14200 2761 7 NAOS CONICA TEMPL
221. tep was to eliminate exposures where AO correction was unstable The frequency components visibilities and closure phases are then derived A binary system is fitted to the data and the likelihood computed Figure 5 37 gives the likelihood for the presence of a binary companion as a function of its relative position to the star A good fit was obtained for several different positions due to the regular Fourier sampling of the u v plane Because the minimum spacing between two holes is 1 73 meters images are obtained with a modulo 1 73 A rad This cotresponds to 208 mas in H and 267 mas in K By using data from the two spectral bands it is therefore possible to identify the position of the secondary star The position is indicated by the two arrows in Figure 5 37 Data fitting also allows derivation of the flux ratio between the star and its companion These results are summarised in Table 5 19 Table 5 19 result of the observations of AB Dor and its calibrator Wavelength ARA mas 183 6 192 9 ADec mas 192 20 1198 Relative flux 1 29 0 14 1 47 0 24 4 71 0 15 4 58 0 2 78 User s Manual VLT MAN ESO 14200 2761 The results on AB Dor are in agreement with the results obtained by coronagraphic means and with results from the literature see Janson et al A amp A 462 615 2007 Sources of potential errors are 1 Uncertainty on the orientation on the field of view on the pupil Aperture masking req
222. the slit It is very similar to the NACO_img_acq_MoveToPixel 7 3 2 template however it must be followed by a spectroscopic template After the AO reference has been acquired the slit is placed into the beam and an image is recorded The slit position is computed the slit is removed and a drawing of the slit is superimposed on the image of the field The centering of the target is then done interactively The template also allows one to place two objects into the slit without the requirement of calculating the position angle beforehand In such cases the acquisition strategy should be adequately explained in the README file and those targets which should be placed in the slit should be clearly designated on the Finding Chart and their position on the slit clearly indicated To save time during the acquisition we recommend that users enter an estimate of the position angle into the acquisition template The Alpha offset from Ref Star and Delta offset from Ref Star parameters allow the user to define a telescope offset when the acquisition is made on a bright reference object That is once the reference object has been acquired and centred in the slit the offsets defined here will offset the telescope so as to bring the desired target into the slit Given the accuracy at which the offsets are likely to be defined the smallest slit is only 86 mas wide so the computed offsets have to be better than a few tens of mas we do not
223. the STARTX and STARTY parameters are fixed by the chosen window size Table 5 21 lists the available windows the minimum DIT and the maximum NDIT for various teadout and detector modes Cube mode is also offered with FowlerNsamp and Uncorrelated read for NB thermal imaging and Lp without chopping respectively Chopping is indeed incompatible with cube mode since the chopped frames are a different type of cubes by themselves The noise characteristics of the cube mode are similar to the normal frames and temporal noise i e the noise across the cube is at the same levels of spatial noise Some extra noise features fixed pattern 8 pixel noise appear in the cube frames especially when very small windows are used The cosmetic of the detector is also different with more blemishes with smaller windows These patterns can be eliminated during post processing of the data The overall signal to noise in the complete dataset is usually as predicted by the ETC since the cube mode does not add extra noise except of course that the readout noise is much more important given the many reads One can see some additional horizontal additive pattern on the images not stable between cubes or frames this pattern can be removed by subtracting the median of each row M Durant private communication Random drifts jitter in x and y can be seen across the cube For example a star can move from one frame of the cube as much as 1 2 pixels when data
224. through three narrow band filters simultaneously Two images are taken outside the 1 64m methane feature at 1 575 um and 1 600 uum and two images are taken inside the feature both at 1 625 um All filters have a FWHM of 25 nm The plate scale of the SDI camera is 17 32 mas pixel As of P82 SDI has permanently replaced the old SDI now decommissioned In SDI the beam splitting is done by means of a double calcite Wollaston with the four images placed on a square The field of view is 8 X8 see Figure 5 5 Note that the vertical misalignment of the mask varies with time and cannot be corrected for The SDI has been designed to detect methane rich objects near very bright stars To give an approximate idea of the performance contrasts as high as 30 000 between a bright H lt 7 mag primary star and methane rich object IT lt 1000 K can be obtained in 40 min with a signal to noise ratio of 6 40 User s Manual VLT MAN ESO 14200 2761 Figure 5 5 Flat field image of the SDI mode The transmitted wavelengths are 1 6 mm top left 1 575 mm top right and 1 625 mm bottom left and right Since P88 SDI without 4QPM is offered in SM but only in field tracking no pupil tracking 5 2 6 SDI on sky performance Figure 5 6 shows the contrast curves 5 sigma obtained from the reduced SDI images of AB Dor In particular the data was saturated and the first 2 roll angles were used DIT 5s 17 min total exposure
225. ths needs to be read very rapidly which in turn leads to poorer detector cosmetics 23 User s Manual VLT MAN ESO 14200 2761 1 0 TN Jail X ee ug MA af ee NA MA vante O gt or M o EN LT Ts NN iV My i z Hl i 1 i ji cf VA i E nm AY i E i Hh nN il m id Ti i Meg I all N I i m MT 0 6 i i a ol i ni TI i We aa IIIII l f I idl 0 2 j a a B l 4 0 4 2 4 4 4 6 4 8 5 0 Wavelength um Figure 3 2 Model atmospheric transmission between 1 and 5 um for a water vapour column density of 1 6 mm and at airmass 1 Lord 1992 NASA Tech Mem 103957 The standard sky subtraction technique is to use chopping and nodding which is unfortunately not offered on NACO any longer For observations with NACO it is not necessary to use chopping and nodding for LW imaging spectroscopic and polarimetric observations if the central wavelength of the filter is less than 4 2 um the sky is sampled frequently i e more than once per minute and if conditions are clear But for coronagraphic observations where one cannot jitter and for filters with wavelengths greater than 4 2 um efficient subtraction of the sky background would require chopping and nodding 24 User s Manual V
226. tial resolution 73 User s Manual VLT MAN ESO 14200 2761 A Fourier transform of SAM data will reveal a pattern of regular peaks in the frequency plane see Figure 5 31 right Each peak in this complex number array has an amplitude giving a measurement of the contrast visibility of the fringes on that specific baseline and a phase which is a measurement of the position of the fringes Before they can be used scientifically the amplitude measurements need to be calibrated for the average atmosphere telescope transfer function this is achieved by the process of observing a nearby reference star as mentioned earlier Atmospheric turbulence notwithstanding the normalized amplitude of an unresolved point source star should be 1 and the phase 0 Any value different form 1 amplitude or 0 phase indicates the presence of resolved structures These properties were used to achieve the image reconstructions discussed in the previous section Unfortunately calibration of the visibility amplitudes is typically not achieved with high precision performance will vary greatly with conditions but precision better than 5 10 or so cannot be relied upon Under these circumstances visibilities add nothing to the faint companion search and they are discarded Thus our detection of high contrast companions relies entirely on the phases or more precisely on the Closure Phases These are a better observable because they are inherently self calibratin
227. tically supported Neutral Density Filter Full Neutral density Filter Full none DEFAULT Camera S27 Camera name DEFAULT S27 Polarimetric mask Wollaston 00 Wollaston 00 or empty DEFAULT Wollaston 00 NAOS parameter file NODEFAULT NAOS aoctg file from the JNPS 7 3 10 NACO img acq SAMMoveToPixel for SAM and SAMPol This template is used for the acquisition of both SAM and SAMPOl targets The user select whether to use SAM or SAMPol by entering empty or Wollaston 00 in the Polarizer Wheel entry The template does a telescope preset and then sets the pupil tracking mode sending the spiders to a pre defined angle which depends on the SAM mask being used This angle is chosen to prevent the telescope spiders from intersecting any holes in the mask The rest of the acquisition is identical to that of NACO img acq MoveToPixel The template always saves the final acquisition image The operator will centre the object in the centre of the detector at pixel 512 512 since in most cases the following science template will make use of a windowed detector in cube mode recommended setup The window is always centred on 512 512 For SAMPol the final step is the insertion of the Wollaston_00 in the beam The template always saves the final acquisition image Since the J filter and the Wollaston are in the same filter wheel SAMPOL observations with the J broad band are not possible This template can be followed by either
228. tions are taken so that telluric features can be removed from science spectra At this point in time we cannot say how accurate these calibrations will be Should users wish to use telluric standards of a particular spectral type they should express this in the README file during the Phase 2 preparations and this wish will be considered when choosing a star from our database Should users wish to observe a particular star they should provide the corresponding OBs and detailed instructions In this case the time for executing the OBs will be charged to the user and the observatory will not observe a separate telluric standard O Spectroscopic lamp flats in all SW spectroscopic modes slits and readout modes O Spectroscopic arcs in all spectroscopic modes and slits An atlas of lines for the SW modes is available from the NAOS CONICA web page LW spectroscopic arcs are not supported o Detector darks Darks are taken at the end of each night with the DITs and readout modes used during the night 5 4 7 Nighttime arcs and flat fields Imperfections in the slits together with instrument flexure means that day time flat fields and arcs depend on the rotator angle For this reason the template NACO_spec_cal_NightCalib allows one to take nighttime arcs and flat fields immediately after spectra have been taken In general the difference between night and day time calibrations is small and most users will not need to take these calibrations 5
229. tip tilt motions which are not sensed by the LGS The NGS has to be in the V magnitude range 12 17 and can be as far away as 40 from the science target however with decreasing performance with increasing distance At 40 distance about half the Strehl ratio is achieved as compared to having the NGS on axis with the LGS It is also important to remember that due to the Cone Effect the maximum Strehl achievable with the LGS is significantly less than the one obtained with a bright natural guide star 20 against 40 in K band with the AO reference on axis For information the LGS is expected to have a magnitude equivalent to that of a star in the range V 11 13 103 User s Manual VLT MAN ESO 14200 2761 In order to apply for the LGS mode just make sure that you have a natural guide star within 40 from your object and that no other mode can be used It should be stated clearly in the proposal why only this mode can be used and which NGS will be used for tip tilt sensing There are borderline cases when one has to decide whether to select LGS or NGS mode The limiting magnitude is currently my 13 5 14 i e with AO reference stars which are fainter than this limit one should select LGS mode and keep the star as a tip tilt reference Brighter stars offer better performance in NGS mode When using the PS a good rule of thumb is the following if the expected Strehl ratio calculated for the NGS mode is 10 or higher stay with NGS Other
230. tive proper motion fields of P2PP will be automatically filled when the configuration file is loaded Do not edit these fields o There must be one AO configuration file per target The same AO configuration file cannot be used for different targets o For NGS observations of moving targets and where the reference star is itself a moving target you will have to provide two additional files the ephemeris file with the differential tracking expressed in arcsec sec which will be attached to the OB at the moment you check it in The second file is the tracking table i e an ASCII file expressing the offsets in a 6 in arcsec between the moving NGS and the moving target This file must be inserted in the NAOS PS software when you prepare the AO configuration file o Each acquisition science or calibration template that generates files writes three header keywords DPR CATG DPR TYPE and DPR TECH These keywords are used by the pipeline and can be used by the users to classify files or to make queries in the archive for example using the NACO specific query form at http archive eso org wdb wdb eso naco form The complete list of templates and corresponding DPR keywords is given in Section 10 113 User s Manual VLT MAN ESO 14200 2761 7 1 1 Offset conventions and definitions Position Angle 0 deg Position Angle 45 deg 1024 1024 1024 1024 VV Conica FoV Conica FoV 1 1 X 1 1 X Figure 7 1 Orientation for imagin
231. tly related to the number of lenslets in the lenslet array the number of actuators behind the DM and the rate at which WF errors can be measured processed and corrected the server loop bandwidth The performance of an AO system is also directly linked to the observing conditions The most important parameters are the seeing or more explicitly r and t the brightness of the reference source used for WFS and the distance between the reference source and the object of interest In case of good conditions and a bright nearby reference source the correction is good and the resulting point spread function PSF is very close to the diffraction limit A good correction in the K band typically corresponds to a SR larger than 30 At shorter wavelengths particularly in the J band or in the case of poor conditions or a faint distant reference source the correction is only partial the Strehl ratio may only be a few percent 21 User s Manual VLT MAN ESO 14200 2761 Observed object y EN R Uncorrected image vi Plane wavefront Atmospheric turbulence Corrugated wavefront Deformable mirror Tip tilt mirror 5 my Computer A i Beam spliteN Wavefront sensor r AO corrected image Corrected wavefront Camera high resolution image Figure 3 1 Principle of Adaptive Optics 3 3 Infrared Observations with an AO system Observing in the IR with an AO system is in broad terms
232. tral density filter for CONICA when using the visual WFS Additionally we have updated some parameters to better reflect the average conditions of the atmosphere above Paranal 9 1 Starting the PS The NAOS Preparation Software can be downloaded for a number of computer platforms at the following URL http www eso org sci observing phase2 SMGuidelines NAOSPS html After installation a link to the general server situated at ESO will be required i e the local computer has to have access to the Internet In principle JNPS will work within any Java Virtual Machine which supports Java Development Kit JDK 1 5 0 or later It has been reported to work using a variety of Unix and Linux flavours as well as MacOS X Until further notice ESO will only officially support JNPS under Scientific Linux 4 3 The PS client is started by typing the command jnps After initialization the main GUI will appear The start up procedure partly depends on the contents of your preferences file which is created in your home directory when you start the PS for the first time This file called jnpscf contains the user s choices for several items some of which can be accessed via the Preferences menu of the main GUI 9 2 Graphical User Interface Overview The GUI that appears after the initialization phase is depicted in Figure 9 1 The panel is divided into three areas which are from top to bottom o The menu bar giving access to file r
233. troscopy slit grism is now offered in SM as well This applies to grism spectroscopy only Pupil Tracking PT PT is now offered in SM but only for direct imaging and APP no image plane masks New LGS modes 10 3 and 10 4 a new 14x14 lenslet array was successfully installed and commissioned in February 2010 It allows a gain in performance whenever the conditions tau0 seeing laser power etc are acceptable 1 e seeing lt 1 laser power gt 4 W etc The following changes were implemented for P85 and still apply SAMPol Offered sparse aperture mask interferometry SAM can be combined with polarimetry The simultaneous use of the Wollaston 00 together with the SAM masks presents a unique opportunity to examine systems where there may be polarization signals at vety high spatial resolutions SAMPol is similar to SAM and uses pupil tracking and cube modes SAMPol is only offered in VM LGS observations without Tip Tilt star Seeing enhancer mode Offered This will allow a wider sky coverage for laser assisted observations users should be aware however that the expected image quality will be intermediate between simple imaging in the NIR and the full LGS closed loop Lucky imaging Offered Simple imaging in cube mode is offered in SM since P85 the mode is similar to having AO assisted speckle imaging since the user can discard from the cube the images with the worst quality Wire Grid Polarimetry i
234. ts and arcs NACO spec cal NightCalib o With the exception of standards the minimum amount of time between exposutes is 30 seconds This limit is set to allow the telescope Active Optics to at least perform one correction O Ensure that the correct filters are used when acquiring bright targets for spectroscopy o When doing a blind offset from a bright reference object to a faint target we strongly recommend that the position angle be set so that the reference object and target do not fall in the slit at the same time in order to avoid light reflection contaminate the fainter spectrum At the end of the science sequence it might also be a good idea to take an image long enough to allow you to see the faint object in the field Additionally the coordinates of the reference object are the ones that should go into the OB o When using extended objects as AO reference sources make sure that the flux within the specified aperture is correct Users tend to significantly overestimate this flux o The verify button on P2PP checks that individual parameters are within the defined ranges and some additional checking on the global logic of selected OBs Please be very careful the verify button is a logical check only hence it will return no error if for example you typed a DIT of 3600s rather than the 36s you meant originally o The Strehl seeing and airmass constraints as well as the epoch equinox and RA and DEC and respec
235. ual 1 100 P ass Gagress Ej co i o i O 1 1e 4 Phase idag eee O O 2 v v 2 et 8 e T Ta F Figure 5 32 VLT MAN ESO 14200 2761 Aneular separation 100 mas 50 mas 25 mas 201 20 001 5 c s 5 c s 1 0 5 Saseine meters Saseine moters Basoline meters Models of fringe phase as a function of the baseline length A binary system generates phases with a sinusoidal pattern whose amplitude corresponds to the brightness ratio between the primary and the secondary while the frequency is proportional to the angular separation The data reduction steps are 1 Zz Flat field the data Select a 80x80 pixel zone around the PSF could be more depending on the size of the PSF An example is shown in the left panel of Figure 5 33 Fit a model of fringes to each image of the cube separately The frequency of the fringes should be u A with an apodization equivalent to the diffraction figure of a single hole an Airy pattern of size d See the middle panel of Figure 5 33 Derive from the phase and amplitude of the fringes a complex value for each frequency u From these values derive the bispectrum and co add it over all the frames Take the phase of the bispectrum to obtain the closure phase eventually de biased from photon noise Retrieve the phase of the object from the closure phase and fit with binary model 75 User s Manual VLT MAN ESO
236. uires freezing the spider arms in the pupil plane vertical mode The field orientation on the detector is therefore changing with time which requires further sophistication of the software because the recotded data header values become inaccurate 2 Uncertainty on the central wavelength due to the spectral type of the target 3 Uncertainty on the pupil diameter inside the camera filter wheel These soutces of error at present limit the determination of the relative positions to a few percent a value that should improve with further characterization 5 6 15 Additional considerations for faint companion detection 1 2 3 4 What is the best mask to use for faint companions detection It depends primarily on the brightness of the source If the target is faint mag gt 7 the broadband filters should be used Therefore the BB 9Holes mask is recommended or possibly the 9Holes for fractional bandwidths less than 15 If the target is bright the 9Holes mask is recommended a good compromise between Fourier coverage and throughput What is the current limit for the dynamic range We tested the dynamic range of the two 9 holes masks for two different wavelengths K and Lp False detections are represented in Figure 5 36 and results are reported in Table 5 78 This result shows why it is important to have a stringent SNR cut off of 50 for detection of binarity The parameter space being very large false detection is likely at lo
237. ured in the lab left Delacroix et al 2013 in preparation and as demonstrated on sky on a standard star under median to bad seeing conditions right Mawet et al 2013 A amp A gt SAM see Section 5 6 can provide an IWA down to 0 4 lambda D but with contrast of just a few lt 5 magnitudes 51 User s Manual VLT MAN ESO 14200 2761 IMPORTANT NOTE WARNINGS e Since the AGPM is transparent down to its very center the location of the star can be known at any time more precisely than in the saturated regime or of course in Lyot coronagraphy easing astrometric measurements Depending on the brightness of the target saturation will occur when off axis and during acquisition It is therefore recommended to use the ND_long for the acquisition e Photometric standard stars will not be taken in Service Mode even for CLR conditions unless OBs ate provided by the users using this same template see the P93 Calibration Plan e No imaging flats will be taken in Service Mode even for CLR conditions unless the users specify it in their ReadMe file P93 Calibration Plan References e Mawet et al 2005 ApJ 633 1191 1200 Delacroix et al 2012 Appl Opt 51 5897 e Delacroix et al 2013 A amp A Mawet et al 2013 A amp A 5 3 4 Calibration plan for coronagraphy For coronagraphic observations a variety of calibration frames will be taken archived and updated at regular intervals The calibrations are descri
238. utes the overheads according to the rules reported in Table 6 5 Users especially those in service mode should check them and make sure to take them into account for their Phase 1 amp 2 proposal It is possible to simulate the detailed breakdown of the programme in terms of its constituent OBs using the P2PP tutorial accounts see Section 1 4 of the P2PP User Manual available at www eso org sci observine phase2 P2PP P2PPDocumentation html The Execution Time Report option offered by P2PP then provides an accurate estimate of the time needed for the execution of each OB including all the necessary overheads Note that any LGS acquisition lasts 10 minutes longer than the corresponding NGS acquisition i e 22 minutes for a polarimetric acquisition using the LGSF Some examples are given below to illustrate how to compute overheads with NACO In all examples we have assumed that the reference source used for AO and the target are the same Users wishing to make use of Cube Mode should also consult Section 5 8 1 Not all parameters of the listed templates are shown Only those that have an impact on the ovetheads are listed 6 18 Observing with the LGS discontinued since P93 LGS allows AO observations where NGS observations are not possible From past experience one advises to avoid LGS observations for objects with airmass above 1 5 for which the AO correction degrades strongly A NGS is still required to correct for the
239. utgoing laser power over 4W An illustration of the performance can be seen in Figure 4 3 and it is further explained in a Messenger article by Kasper et al 2010 The 7x7 lenslet array remains available for worse atmospheric conditions or lower laser power gt lt EN P93 LGS aided operations are no longer available with NACO 29 User s Manual VLT MAN ESO 14200 2761 Figure 4 2 Illustration of the LGSF set up at UT4 the laser clean room is installed below Nasmyth A note that NACO itself is installed at Nasmyth B The laser beam is propagated via fibre to the launch telescope installed at the back of M2 Improved LGS performances and operations new l4x14 SH array WFS alignment closed loop AO AO gain 3 mag gt EE 35 K band Strehl ratio FVVHM 80 mas seeing 0 7 O Pipeline reduced 10000 stars detected open loop offline tip tilt correction Figure 4 3 Improved performances of the LGS with NACO due to the new 14x14 lenslet array visible on the top left of the Figure four actuators are poked for alignment purposes The image at the bottom left corner shows a promising 35 K band Strehl ratio diffraction limited core obtained with the LGS The centre and right images illustrate the potential of wide field correction with a 1x1 arcmin field centred on the star cluster Omega Centauti 30 User s Manual VLT MAN ESO 14200 2761 5 CONICA CONICA is an IR
240. vailable for acquisition of the target depending on the desired observations it is very important to understand that acquisition and science templates should be consistent i e it is not possible to mix a spectroscopic observation with an image acquisition 6 6 1 Imaging The NACO img acq MoveToPixel template provides interactive tools like dragging arrows to define telescope offsets For SDI users must use template NACO_img_acq_SDIMoveToPixel Users wishing to use the no AO mode must use the NACO img acq MoveToPixelNoAO 9y User s Manual VLT MAN ESO 14200 2761 6 6 2 Spectroscopy It is mandatory to use the NACO_img_acq_MoveToSlit acquisition template for all spectroscopic OBs and the same slit in both the acquisition and observing templates This template provides interactive tools to rotate the field and to centre objects into the selected slit that is overlaid on the Real Time Display RTD It can also be used to place two objects in the slit without having to pre compute the position angle Instructions for specifying this acquisition procedure at Phase 2 are in Section 7 3 4 These instructions must be strictly adhered to 6 6 3 Coronagraphy It is mandatory to use the NACO img acq MoveToMask acquisition template for all coronagraphic OBs and the same mask in both the acquisition and observing templates This template provides interactive tools to centre objects behind the selected mask which is overlaid on the RTD
241. were Number of offset positions 4 NEXPO per offset position 1 Observation Type O or S OS 50 Offset Coordinates DETECTOR List of offsets in RA or X 7 0 14 0 List of offsets in DEC or Y 0 7 07 and Return to Origin T F T 135 Figure 7 9 An illustration of how the NACO pol obs GenericOffset template works with Number of offset positions 9 NEXPO per offset position 1 Observation Type O or S O List of offsets in X 400400400 List of offsets in Y 2 3 2 3 2 3 0 2 3 2 3 0 2 3 2 3 and List of Position Angle Offsets 0 45 138 Figure 7 10 An illustration of how the NACO_coro_obs_Stare template works The dashed line connecting position 10 with 1 is the offset done at the end of the template when the telescope returns to origin The rather erratic bold lines are wires which hold the coronagraphic mask in place The AO loop is off when the sky is observed large filled in circles and on when the object is observed small filled in circles In this example the parameter settings were Number of AB cycles 2 Number of Exposures Object Only 2 Number of offset positions Sky only 3 Jitter Box Width 9 Sky offset in Dec 15 Sky offset in RA 35 Camera 13 141 Figure 7 11 Illustration of how the NACO coro obs Astro template works The 3 phases of the template are presented Part I left coronagraphy without moving the telescope Part I middle simple imaging the coronagraphic mask is removed Normally th
242. wever it is recommended not to observe targets closer than 30 to the moon to avoid problems linked to the telescope guiding active optics system The effect is difficult to predict and quantify as it depends on too many parameters Just changing the guide star often solves the problem Visitors are encouraged to carefully check their target positions with respect to the Moon at the time of their scheduled observations Backup targets are recommended whenever possible and users are encouraged to contact ESO in case of severe conflict i e when the distance to the Moon is smaller than 30 Visitors can use the tools that are available in http www eso org observing sci observing tools ephemerides html select the link Airmasses Calculator which is under User Support Tools to help determine the distance between targets and the moon for given dates However the moon may affect the quality of the adaptive optics correction if the source used for wavefront sensing is fainter than V 16 In these cases reducing the FLI constraint to approximately 0 7 and increasing the distance to the Moon to approximately 50 degrees is generally adequate Even here it is important not to over specify the constraints as this reduces the chances of the Observing Block being executed For wavefront sensing in the IR and for reference sources that are brighter than V 16 the values for Lunar Illumination and Moon Angular Distance in the Constraint Sets o
243. wise move to LGS Starting with P85 a new mode the so called seeing enhancer mode is offered with the LGS this mode does not need a tip tilt star and will allow better image quality than simple imaging but worse than what can be obtained with full adaptive optics correction For an idea of the expected performances users are encouraged to consult Table 4 4 The mode is particularly useful for observations of extended objects or for distant targets without any suitable nearby tip tilt star Any request for this mode should be explicitly mentioned in the proposal Table 6 5 NACO Overheads 104 User s Manual VLT MAN ESO 14200 2761 Acquisition Templates Overhead 3 min 0 75 min 2 min 5 10 min Description Comment Telescope Preset Guide star acquisition Initial setup NAOS CONICA AO acquisition Depends on the brightness of the source used for AO 4 min Strehl measurement Not charged to the user Imaging acquisition 0 5 min Polarimetric acquisition 1 min Spectroscopic acquisition 1 5 min Depends on target brightness Coronagraphic acquisition 2 3 min SDI 4 acquisition LGSF acquisition Depends on target brightness 10 min Accurate centering is mandatory 10 min On top of the classical ACQ time Observation templates Readout overhead per DIT FowlerNsamp Readout overhead per DIT x NDIT Double_RdRstRd Readout overhead per DIT Uncorr Telescope Offsets NAOS header Stop and Start AO Start an

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