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VERY LARGE TELESCOPE NACO User Manual

1. 0 2 a j 0 Ja L 1 I JV I Lj Ne l LX l 1 5 2 2 0 Wavelength microns 1 p i 1713 r I rr r AQ Fa N g 9 8 Q i nm 0 6 E J l M co 0 4 S 802 f o be N 3 3 0 4 4 5 5 Wavelength microns Figure 7 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 7 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 7 2 141 User s Manual VLT MAN ESO 14200 2761 Neutral Density Filter 0 025 ND2 short 0 02 Lb 2 Fe 0 01 0 005 0 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 7 2 Transmission curves of the CONICA neutral density filters 142 User s Manual VLT MAN ESO 14200 2761 8 PREPARATION SOFTWARE 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
2. To select a sub wavelength range an additional filter can be used There is a 1 2 5 um filter CutOff_2 5um that may be used to select the non thermal range The spectral traces of the prism spectra are quite complex I general one can fit the trace with a 4th order 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 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 4 29 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 artifacts 6 Based on the 86 mas slit on the central wavelength 7 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 8 Fit based on telluric absorption features at 5 microns The fit is valid from 4 5 to 5 5 microns 57 User s Manual VLT MAN ESO 14200 2761 2 n gt g R n e ur i du ag om UT4 LGSF R 7 JET e gt OR a M 4 aa Illustration by S G
3. Telescope spiders at PA 95 Telescope spiders at PA 90 Figute 4 46 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 nor SAM masks When observations take place close to zenith the pupil rotation compensation is faster and a drift of the order of 1 pix minute is observed on the detector plane at airmass of 1 05 It can easily be corrected for if the DIT is small i e cube mode in the case of simple imaging by shift and add methods However it s not yet understood enough to offer PT associated with coronagraphy or SAM in SM In some cases it is better to saturate 87 User s Manual VLT MAN ESO 14200 2761 the detector instead of using a focal plane mask because every frame is then useful and the drifts can be recovered a posteriori 4 14 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 NAX
4. 113 VPT INVAGO JMN 114 Table ra PNI DMT 115 VPT NEO NNN 116 Table PSN IO NNN IP 117 TT TE PSTN TE E OOA UO ON eE EEEE 118 Tabie TAN PR GO TODS TO 666666 119 T RT SDS FOP LOG DUDE SOW IN LOOS A keen cited taneitetiads 120 TD TT TS SOW I TONIC TOD sures 666 121 Table TE Parametr i NACO IE 008 FR EO SCL 122 TT PR NTV SN LT 666 123 TaeT TG PGS NTE OSEN NAD OE 666 124 1207 AL Parameters o NACO Spee ODS sAn oN OMS oi 126 E OE AK UA A SOF A EE T E E TE O T 126 Taner To darii ani Of NACO D US AG NTA I T EEEE NEEE IEEE Pith EEEE OO Ueto iliac edd tod 128 E E A EE CAD E E ETN O E A A E T 128 Tamer LTAT Of NAC OPO DE ITTO SOU ox bass ay ar ices NG 130 Jane da PN TENNE Ree sandsteinen 131 Te PST NAC O IN E 133 Fe PT NACO AOO T SO KAG 135 TGC La NACO TOTO T NIE ais alta eos iste Sabah Pi te lle a ud a din Redd danene 136 LE PN NENNE 136 LP NOI 138 T NNE NNN 139 Fe Fal PSTN TEEN Ad 139 User s Manual VLT MAN ESO 14200 2761 LIST OF FIGURES Figure 3 1 Principle of Adaptive Optics 19 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 21 Figure 4 1 A view of the NAOS optical train 2 Figure 4 2 lllustration 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 27 Fig
5. Ln 2 5 3 3 5 Waelength microns Figure 4 30 Transmission as a function of wavelength for the Wollaston prism The big absorption feature at 3 4 microns is due to the resin material 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 At this stage we do not know how accurately the instrument induced polarisation can be removed from data 4 9 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 4 5 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 No internal lamp flats are taken since the calibration mirror in the light path changes the level of polarization o Detector darks in all readout modes and DITs 4 9 2 Pipeline for polarimetry Pola
6. Observation Number of offset positionsx Offset overhead NDIT DIT readout overhead Table 5 11 Example 5b Polarimetry of bright source with the Wollaston and HWP Template parameters Acquisition Template Observation Template DIT NDIT Number of offset positions NEXPO per offset position Readout Mode List of HWP offsets NACO img acq Polarimetry NACO pol obs Retarder FowlerNsamp D ale D g Un Execution Time min Preset Guide Star Acquisition Initial Setup Setting HWP in out AO Acquisition Polarimetric acquisition Sub Total acquisition Observations at 0 and 22 5 degrees 2x 5x 27 6x 10 2 2x8 3 16 4 HWP rotation 0 25 Total min 29 6 Overheads 196 Observation Number of offset positionsx Offset overhead NDITx DIT readout overhead Preset P Guide Star Acquisition 1075 InitialSeup Setting HWP in out o N AO Acquisition o 5 Polarimetric acquisition o S Sub Total acquisition 11275 Observations at 0 and 22 5 degrees 2x 5x 27 6x 10 2 2x8 3 164 gt HWP rotation 25 296 S 19 S 101 User s Manual VLT MAN ESO 14200 2761 Table 5 12 Example 6 SW coronagraphy of a bright source with Double_RdRstRd NACO_img_acq_MoveToMask NACO coro obs Stare 10 sec Double R RsR Execution Time min Observations 6 2x 10x 6x10 0 7 9x16 27 4x 5x10 0 7 27 9 3 Observation Number of AB cycles x Number of exposures OBJECT
7. Reset form Register Object Update Object Cancel Reset All Figure 8 1 PS GUI 8 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 dichroic can also be selected with the visible WFS 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 144 User s Manual VLT MAN ESO 14200 2761 There are borderline cases when one has to decide whether to selec
8. 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 4 6 4 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 4 14 and provide an averaged contrast 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 coronagraphic 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 4 6 5 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
9. 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 9 107 User s Manual VLT MAN ESO 14200 2761 6 1 1 Offset conventions and definitions Position Angle 0 deg Position Angle 45 deg 1024 1024 1024 1024 V Conica FoV Conica FoV 1 1 X 1 1 X Figure 6 1 Orientation for imaging 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 X 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 al
10. 1024x1024 Rockwell Hawaii 1024x1024 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 24 User s Manual VLT MAN ESO 14200 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 I Exposure Time Calculator to estimate signal to noise ratios V magnitude 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
11. 120 User s Manual VLT MAN ESO 14200 2761 Table 6 13 parameters for the example shown in Figure 6 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 0080 8 808 6 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 filters will be allowed The readout mode will be automatically set to Uncorr HighDynamic L27 or L54 camera are both options for this mode 6 4 4 NACO noAO obs GenericOffset 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 6 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 dimensions are set by the parameter Jitter Box Width in arcsec 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
12. Tip tilt mirror Real time ys Computer lt N 5 Beam splitter 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 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 go
13. 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 As for P86 a new 14x14 lenslet array has been commissioned successfully Feb 2010 and gives better performances than the actual 7x7 one whenever the atmospheric conditions are good to very good and the outgoing laser power over 4W new version of JNPS will allow the new 10 3 and 10 4 modes to be selected under strict conditions seeing lt 1 tau0 gt 4 ms CL or PH etc An illustration of the performance can be seen on Figure 4 3 and it is further explained in a Messenger atticle by Kasper et al 2010 The 7x7 lenslet array remains available for worst atmospheric conditions or lower laser power 26 User s Manual VLT MAN ESO 14200 2761 E 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 5 lt n a nd 35 K band Strehl ratio FYVHM 80 mas seeing 0 7 i Di ud et GS Omega Cen K band FoV I x1 Pipeline reduced 10000 stars detected offline tip tilt correction open loop Figure 4 3 Improved performances of th
14. 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 4 35 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 71 User s Manual 1 100 I1 1e 4 FLUX ratio Le 6 VLT MAN ESO 14200 2761 Angular separation J 100 mas 50 mas 25 mas 1 1 1 r D m a a 1 1 1 5 8 D 5 D 5 ool ool oo F ono 300 0 00 a 201 20i 0J 5 gt 8 1 pa 2 D 5 7 q 1 fo lot e z G c a E 1 5 o 8 1 o 8 D 5 Saseine moters Sascine motars Easolno motors Figure 4 35 Models of f
15. 0 7 100 Intensity ADU s 0 0 0 2 0 4 0 6 0 8 Angular distance in arcsecond Figure 4 16 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 important 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 spikes position 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 45 User s Manual VLT MAN ESO 14200 2761 plus or minus the OB duration the reference is observed for the same amount of time as the target In general 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 mags 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 o
16. 0 8 to 1 arcsec Figure 4 36 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 4 10 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 4 36 Left CONICA image of a binary star Center 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 x 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 4 37 200 100 100 f 100 RA mas Figure 4 37 x2 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 73 User s Manual VLT MAN ESO 14200 2761 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 4 38 f f b Base meters Base meters
17. 073 9 0160 Sr 19 30 0 0240 Dismiss 0 0120 0 0080 0 0040 0 95 0 60 0 64 046 0 32 0 15 0 00 0 16 0 32 0 48 0 64 0 60 0 96 arcsec Figure 8 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 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 151 User s Manual VLT MAN ESO 14200 2761 8 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 To call the ETC load this file into your favorite web browser and click on the Call CONICA ETC button at the bottom of the page 8 5 7 Exporting to P2PP All NACO acquisition templates Section 6 3 require a configuration file whi
18. 14200 2761 User s Manual Please refer to Section 4 10 for information on the available setups Table 6 27 Parameters of NACO_sam_obs_GenericOffset P2PP Label Default Values Description DIT Readout mode NODEFAULT Double RdRstRd Detector Integration Time sec Readout mode Window Size 1024 Size of the window Store Data Cube T F T Data cube flag List of NDITs NODEFAULT List of NDITs 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 6 10 2 NACO_sampol_obs_GenericOffset The science template is similar to NACO_sam_obs_GenericOffset From an operational point 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 6 28 describes the parameters of this template Table 6 28 Parame
19. 4 must use NACO img acq SDIMoveToMask for acquisition 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 o In the NACO_spec_obs_AutoNodOnSlht template the jitter width should be smaller than the throw same thing for NACO app spec obs AutoNodOnsSlit o Cube mode is a feature that can be turned on for science templates not acquisition by means of the flag in the P2PP file 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 Le the user cannot set STARTX and STARTY the lower left coordinates for the detector window 104 User s
20. 5 5 Simultaneous Differential Imaging SDI The SDI mode of CONICA obtains four images through three narrow band filters simultaneously Two images are taken outside the 1 6um 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 8X8 see Figure 4 8 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 Figure 4 8 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 38 User s Manual VLT MAN ESO 14200 2761 4 5 6 SDI on sky performance Figure 4 9 shows the contrast curves 5 sigma obtained from the reduced SDI images of AB Dor In particular this is for the first two roll angles of saturated data DIT 5s 17 min total exposure time We ar
21. 58 58 59 59 59 60 61 61 62 63 63 64 64 65 User s Manual VLT MAN ESO 14200 2761 4 10 6 CALIBRATIONS FLAT FIELDS AND DATA CLEANING 66 4 10 7 PSF CALIBRATIONS STRATEGIES 66 4 10 8 SAM IMAGING TESTS 67 4 10 9 U V COVERAGE 67 4 10 10 REFERENCES AND FURTHER READINGS 69 4 10 11 ONSKY OBSERVATIONS VY CANIS MAIORIS 69 4 10 12 FAINT COMPANION DETECTION THEORY 70 4 10 13 ON SKY OBSERVATIONS BD 21 4300 73 4 10 14 ONSKY OBSERVATIONS AB DOR IN H AND K 75 4 10 15 ADDITIONAL CONSIDERATIONS FOR FAINT COMPANION DETECTION 76 4 10 16 CALCULATING EXPOSURE TIMES THROUGHPUT AND SENSITIVITY FOR SELECTED FILTERS 77 4 10 17 PSF AND MTF 83 4 10 18 CALIBRATION PLAN FOR SAM 83 4 10 19 PIPELINE FOR SAM 83 4 11 SAMPOL 83 4 11 1 CALIBRATION PLAN FOR SAMPOL 83 4 11 2 PIPELINE FOR SAMPOL 84 4 12 CUBE MODE 84 4 12 1 CUBE MODE OVERHEADS 85 4 13 PUPIL TRACKING PT MODE 86 4 14 NACO DATA FORMAT 88 5 OBSERVING WITH CONICA AT THE VLT 89 5 1 VISITOR MODE VM OPERATIONS 89 5 2 ACTIVE OPTICS VERSUS ADAPTIVE OPTICS 89 5 3 THE INFLUENCE OF THE MOON 90 5 4 TELESCOPE CONTROL 90 5 5 TARGET ACQUISITION 91 5 5 1 IMAGING 91 5 5 2 SPECTROSCOPY 91 5 5 3 CORONAGRAPHY 91 5 5 4 SDI 4 92 5 5 5 POLARIMETRY 92 5 5 6 SAM 92 5 5 7 SAMPOL 92 5 6 PRE IMAGING 92 5 7 FINDING CHARTS README FILES AND OB NAMING CONVENTIONS 92 User s Manual 5 8 REFERENCE SOURCES FOR WAVEFRONT SENSING 5 9 STREHL RATIO AND CLASSIFICATION OF OBS IN SERVICE MODE SM 5 1
22. Density Filter Full Neutral density filter Full none Camera NODEFAULT Camera Name 6 5 Simultaneous Differential Imaging SDI template The simultaneous differential imager SDI uses special templates to acquire and observe targets 6 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 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 lis
23. Figure 4 38 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 as presented in Error Reference source not found Right panel H band data Left panel K band data The companion position and flux ratio are reported in Table 4 20 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 4 20 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 GH i r Mit i iy H nt i ait 4 Phase degrees aw cers Phase degrees Heatuads Recduds Restiuas Base nanara Base raters Base metars Figure 4 39 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 results for the presence of a binary companion with best fit limits reported in Table 4 21 74 User s Manual VLT MAN ESO 14200 2761 Table 4 20 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 Table 4 21 False detections on calibrator stars 9Holes BB
24. I J H K 90 VALLH K 10 WES and observations 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 23 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 visual dichroic can only be used with the visual WES and the other dichroics can only be used with the IR WFS 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 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 natural guide star NGS can be selected anywhere within a 110 arcsec diameter field of view FoV facilitating a target to reference distance of up to 55 arcsec NAOS allows WF
25. Integration Time seconds The pre processor averages NDIT of these before transferring the result to disk Note that the number of counts in the images always corresponds to DIT not to the total integration time i e DIT x NDIT 4 4 3 Readout Modes and Detector Modes 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 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 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 addtessed 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 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
26. Lp contrast curve of the clean side note the higher achievable Amag gt 10 than with the NB_4 05 filter 8 48 Figure 5 15 Position Angle consideration for APP Imaging 49 Figure 5 16 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 useful field of view FoV with the L27 camera going along with its field limiting stop FLM27 is about 28 wide in X but only 8 high in Y The offset pattern has to take that into account Overall it should not be a problem as the APP useful is 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 4 x14 49 Figure 5 19 The APP main commissioning result on Beta Pictoris b 50 Figure 5 14 Flat field of the SDI 4 corrected from detector flat field taken with the H filter only not SDI filters The FoV is 8 for each quadrant 51 10 User s Manual VLT MAN ESO 14200 2761 Figure 5 15 Radial profiles for the PSF solid the 4OPM image dotted and the SDI processing for PSFs dash dotted and 4OPM images dashed Colors are for Ao red Ag green A gt blue purple Left plot is for SDI and right plot is for SDT 52 Figure 5 16 5 0 detection level for different processing techniques 40 and 40 ref stand for direct corona graphic imaging
27. Manual VLT MAN ESO 14200 2761 o Pupil tracking mode is set in the acquisition template by means of the correspondent flag in P2PP Note that all the acquisition templates including the ones for modes that are not offered with pupil tracking contain this flag Table 6 1 NACO template suite Action General to all observing modes Turn the field telescope rotator NACO all obs Rotate Preset telescope and acquite for imaging Preset telescope and acquire for APP imaging Preset telescope and acquire for SDI Preset telescope and acquire for polarimetry Preset telescope and centre object s in the slit Preset telescope and centre object behind a mask NACO img acq MoveToMask Preset telescope and centre object in SDI 4 Preset telescope and acquire for SAM Preset telescope and acquire for SAMPol Imaging of un crowded fields Imaging of extended objects or crowded fields NACO img obs GenericOffset of NACO img obs FixedSkyOtfftset Imaging requiring special offset sequences NACO img obs GenericOffset Imaging with SDI NACO sdi obs GenericOffset Spectroscopy grism amp prism Spectroscopy of point like or moderately NACO spec obs AutoNodOnsSlit extended objects Spectroscopy of extended objects gt 10 or NACO spec obs GenericOffset complex sequences of positions Spectroscopy of point like source using the APP NACO_app_spec_obs_AutoNodOnsSlit Tages MN Coronagraphy NACO coro obs Stare Coronagraphy imaging NACO coro obs A
28. 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 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 5 14 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 observations without chopping only the NACO img obs Autolitter template should be used The sky subtraction with the other templates is generally unsatisfactory 6 4 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 saf
29. PS this may be annoying for more experienced users This option allows one to switch them on off 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 CSO 019 observing etc NaOsps doc 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 155 User s Manual VLT MAN ESO 14200 2761 9 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 identificatio
30. Roll averaging improves also the detection capability of the instrument dashed red The standard SDI processing that consists in 2 observations at 2 roll angles separated by 33 is also given in blue but for 25 apart This results in a small improvement with respect to SDI green line Another technique which is called double roll subtraction has been tested dashed blue It consists in using only SDI data of the star and subtracting the SDI star data to themselves but with different angular separations For example we calculate the images that have a separation of 25 SDI O SDI 25 and SDIG SDIG0 and SDI 10 SDI 35 etc up to SDI 25 SDIGO0 Adding them after having rotated them by the right amount will add up the information of the companion However we have only added 6 times the information of the companion while we have a total of 11 images and subtracted out 6 images To add up the other 5 images we can for example subtract from the 5 images that have not been added yet SDI 30 to SDI 50 note that they were used for subtraction though the images that show an angle difference of 25 SDI 50 SDI 25 SDI 45 SDI 20 etc to SDI 30 SDI 5 Adding all these roll subtracted images corrected for the instrument angle will create a typical spatial structure made of a positive PSF at the companion position and 2 negative PSF located at 25 on each side of the companion The profile in
31. acquired This sequence has been designed so that the entire field of view is covered 6 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 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 ass
32. 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 6 1 provides a short summary of the templates offered for P85 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 6 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 o All APP imaging observations must use the NACO app img acq MoveToPixel template for acquisition o All polarimetric observations must use NACO img acq Polarimetry for acquisition o All spectroscopic observations must use NACO img acq MoveTOSlit for acquisition o All coronagraphic observations must use NACO img acq MoveToMask for acquisition o All observations with the SDI must use NACO img acq SDIMoveToPixel for acquisition o All observations with the SDI
33. angle Filter NODEFAULT Filter name e g Ks Neutral Density Filter ND_Short 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 6 3 6 NACO img acq_MoveToMask This template does a telescope preset and is followed by interactive centring of the object behind the coronagraphic 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 centring 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 centring 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 Table 6 6 describes the parameters of this template 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 4
34. 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 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 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 is restarted from the beginning as many times as needed until the correct number of offsets has been done These lists can have any length however having lists of different lengths can become extremely confusing It is good pract
35. by the mask 74 Figure 5 22 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 pa Figure 5 23 Left CONICA image of a binary star Center best fit artificial fringe pattern giving the Fourier amplitudes and phases Right the fitting residual shows the discrepancy between data and model Z3 Figure 5 24 X maps showing detection of the binary BD 21 4300 Left H band data Right K band data The general X minimum is at the same position on the two maps 79 Figure 5 25 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 as presented in Error Reference source not found Right panel H band data Left panel K band data The companion position and flux ratio are reported in Table 5 14 74 Figure 5 26 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 results for the presence of a binary companion with best fit limits reported in I able 5 13 74 Figure 5 27 Likelihood for the presence of a secondary star as a function of its position At maximum likelihood the flux ratio between the mai
36. 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 4 10 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 seeing conditions being biased by small sample statistics Table 4 23 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 4 42 Figure 4 43 Figure 4 44 and Figure 4 45 ot
37. filler sses 55 Tareh 18 Romm DE EE EE E AE 94 Table 6 2 IR Backgrounds The hyphens mark invalid combinations of a NAOS dichroic CONICA filter ssec 95 Table 6 3 Recommended magnitude range of standard stars for observations with the visual dichroic 95 TAO OF VEGA TES SR inal deisbeeeocaidelan 95 Table 6 6 Example 1 Imaging a faint source V 15 for visual WES or K 10 for IR WES with FowlerNsamp ossec 99 Table 6 7 Example 2 Imaging a bright source V 11 with the VIS WES or K 7 with the IR WFS with Double_RdRstRd 99 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 100 Tableb 9 Examplea Specaroscopy of faini source WILD FOWLOVIN SAID iwedsunarcissetistviatsbeves TE R 100 12010105 Example 3 3 W Polatimeiri of brihi source WILD Ihe W OUASIOW carevessiresesdisaucnns ninii inen i aE NEEE A 101 Table 6 11 Example 5b Polarimetry of bright source with the Wollaston and HVD 101 Table 6 12 Example 6 SW coronasraphy of bright source with Double RRSI RI 102 TOT BE LE Tonara A Or SONNO 6 102 EE SERGE SLT EG ERE NE 103 GO VT 25 AUG TAN DVO SOUT COI SADT RR MN te choke sah etl 103 TAER INFN ee Gera that tit te EO 105 Fable J lt 2 ROWOTAS COMUVINGATIONS USCA JOR IDE NEW GN TAPE at 110 LIER 29 Par Of NAC O ET VOU CV OF rand AN 112 Me Paramore of NAG O Hed SPD NTN 112 User s Manual VLT MAN ESO 14200 2761 ale FDS Paramereys 07 IN AAC MN
38. 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 75 User s Manual VLT MAN ESO 14200 2761 meters images are obtained with a modulo 1 73 A rad This corresponds 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 4 40 Data fitting also allows derivation of the flux ratio between the star and its companion These results are summarised in Table 4 22 Table 4 22 result of the observations of AB Dor and its calibrator ARA mas 6 9 ADec mas 75 6 771 8 Relative flux 1 29 N 0 14 1 47 0 24 4 71 0 15 4 58 0 2 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 requires 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 dia
39. 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 4 11 Spectroscopic modes The mode name consists of the objective the grism number and the order sorting filter microns un B nm pixel 0 91 1 40 BEIN Sor ee RJ RE 4 smasH 1392 3 7 om o ES msa oi a or saasa 13020 1 s ia 0 ss 17928 2 a or 10 ss 192m 2 a7 os 10 sa 3sK 17237 2 10 10 smask 2002 2 a7 0 f o saa sk 179237 1 34 19 o rats 260420 2 3 36 f oo TS 2040 foja or w 15428 30040 1 a om no 17281 3442 1 27 f o 1711 3203 2 7 180 w 13421 3203 1 20 mo w 38040 2 raze 33040 1 sm 20 nm iaae 35040 1 27 100 nm Jed fo Light from the second order can also be seen but does not contaminate 55 User s Manual VLT MAN ESO 14200 2761 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 4 8 2 APP enhanced
40. for wavefront sensing The brighter the reference source is and the closer it is to the science target the better the correction will be It can even be the science target itself if it is sufficiently bright and point like 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 development of operations the user is restricted to a single Tip Tilt Star per LGS OB or 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 5 9 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 setvice mode the Strehl Ratio of the reference source will be measured with the NB_2 17 filter during acquisition or at the observed wavelength using a dedicated IDL or else tool The measurement during the acquisition process is automatic Use
41. 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 directly 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 18 User s Manual VLT MAN ESO 14200 2761 Observed object y EN Uncorrected image vi Y Plane wavefront i Atmospheric turbulence Corrugated wavefront Deformable mirror
42. 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 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 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 4 10 9 18 Holes 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 m
43. 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 6 8 2 NACO coro obs Astro 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 on 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 def
44. 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 Table 6 14 describes the parameters of this template 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 121 VLT MAN ESO 14200 2761 User s Manual Thus the 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 t
45. other dichroics will be taken when these modes are used Observations in J H and Ks will be done with the detector in Double_RdRstRd and observations in Lp and Mp will be done in Uncorr Zero points in all other filters and readout modes are not supported by the calibration plan and users should prepare the necessary OBs These calibrations aim to provide a photometric accuracy of 5 Users needing higher accuracy should provide standard stars OBs that will be executed either immediately before or after their observations The time spent doing these observations will be charged to the user 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 Internal Flat Fields in all filters and weekly J H Ks S27DCR for instrument checks Long waveleneth flats will be taken on the sky but only when observations with the corresponding set up ate executed during the night Observations in J H and Ks will be taken with the detector in Double RdRstRd observations in Mp Lp NB_3 74 IB 4 05 and NB_4 05 will be done in Uncott Detector darks in all readout modes and DITs as required 4 5 2 Pipeline for imaging The NACO img obs Autolitter and the NAC
46. polarisation a second set of images with the Wollaston prism rotated by 45 degrees with respect to the first pair are required This can be achieved 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 4 15 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 4 15 Beam separation of the Wollaston prism on the sky arcsec and in pixels as a function of the camera pp fw37 nn ps h g ES f i 87 1122 gt S po ee ee A e 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 4 30 60 User s Manual VLT MAN ESO 14200 2761 Wollaston Prism Transmission o o c v O 2 c
47. 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 6 4 and Figure 6 5 illustrate how this template can be used The total integration time is defined in seconds by DITx number of offset positions ND IT i x NEXPO per offset position Table 6 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 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 NO
48. sensing with faint NGS and extended objects but with lower performance Observations of very bright objects are possible with the visible WFS 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 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 5 15 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 5 105 7x7 12 16 7 9 12 10 5 13 5 128x128 EEV CCD
49. spectroscopy 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 Figure 4 26 illustration of the APP spectroscopy concept Table 4 12 APP Spectroscopic modes The mode name consists of the objective the grism number and the order sorting filter Mode Spectral domain Order Spatial scale Linear Dispersion microns SV dam ee L54 2 L APP 3 50 4 10 raspe 380 tf er 27_1_LP_APP 350410 541_LP_APP 350410 e order 2 visible also but does not contaminate 56 User s Manual VLT MAN ESO 14200 2761 Figure 4 27 illustration of the APP spectroscopy concept 4 8 3 Prism spectroscopy 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 4 13 The spectral resolution varies from about 40 in the J band to 250 in the M band 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 Table 4 13 Prism spectroscopic modes Mode Filter Dispersion Wavelength R Fit Fit RMS Name nm pixel microns Order nm 57 P CuOm2sum 82 08250
50. telescope spiders have 180 degrees symmetry In theory it should be possible to find 6 angles at which 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 at the time of writing the telescope pupil and NACO are not well aligned and only one angle per mask has been found suitable for use Better pupil alignment is one of the goals of upcoming intervention s during 2010 4 10 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 f
51. 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 center to upper right to lower left to upper left and finally to the lower right quadrant Sky observations will be dealt with as usual open loop offset set by the user in the offset sequence always in DETECTOR coordinates Table 6 27 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 techniques during post processing of the data 138 VLT MAN ESO
52. 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 8 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 146 User s Manual VLT MAN ESO 14200 2761 o Point like object 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 you are asked to enter its diameter in arcsec This morphology is modeled by a limb darkened disk 8 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 yo
53. the detector The degree of correction provided by the AO system In order to span a promising range of observational parameter space five masks were fabricated and the physical properties of the masks is illustrated in Figure 4 31 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 Figure 4 31 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 Oholes 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 w
54. the pixel to pixel sensitivity variations by using a flat that is taken without the coronagraphic plate but this kind of flat does not remove dust features that are on the plate As of P82 a new version of the coronagraphic 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 4 6 10 Pipeline for mask coronagraphy Coronagraphic observations are not supported by the pipeline 46 User s Manual VLT MAN ESO 14200 2761 4 6 11 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 Lp imaging offsets and short DIT required to overcome the thermal background As shown on Figure 4 17 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 APP Apodizi
55. 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 neighbor The order in which the reference objects are shown will be the one exported to P2PP Sec 8 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
56. 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 respective 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 jnps software when you prepare the AO configuration file
57. 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 imaging templates make use of it 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 fittered 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 mo
58. x DITxNDIT teadout overhead Number of exposures OBJECT 1 x time between frames without offset Offset overhead Number of offset positions SKY x DITxNDIT readout overhead offset overhead Table 5 13 Example 7 LW coronagraphy of a bright source Acquisition Template Observation Template Tntegration Time Execution Time min Preset Guide Star Acquisition Initial Setup 2 AO Acquisition 5 el Sub Total acquisition 12 75 Observation 20x 1 3x00 27 3 Total min 4 Overheads 140 Observation Integration time minutes x 1 30 x 60 sec Offset Overhead 102 User s Manual VLT MAN ESO 14200 2761 Table 5 14 Example 8 Imaging with chopping Acquisition Template Observation Template Integration Time Execution Time min Observation Integration time minutes x 1 30 x 60sec Offset Overhead Table 5 15 Example 9 A bright source with SDI NACO img acq SDIMoveToPixd NACO sdi obs GenericOffse 10 sec i Double RARSIRA 03 Return to original rotator postion F Execution Time min Observation Number of offset positions x Offset overhead NDIT x DIT readout overhead 105 User s Manual VLT MAN ESO 14200 2761 6 NAOS CONICA TEMPLATES The instrument detector and telescope are controlled by Observing Blocks OBs which are made up of templates Templates are divided into three categories acquisition observation and calibration Usually OBs consist of an
59. 0 5 11 5 12 5 13 5 14 5 15 5 16 5 17 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 6 NAOS CONICA TEMPLATES 6 1 6 1 1 GENERAL REMARKS AND REMINDERS OFFSET CONVENTIONS AND DEFINITIONS 6 2 NACO GENERAL TEMPLATES 6 2 1 6 3 6 3 1 6 3 2 6 3 3 6 3 4 6 3 5 6 3 6 6 3 7 6 3 8 6 3 9 6 4 6 4 1 6 4 2 6 4 3 6 4 4 6 4 5 6 4 6 6 5 6 5 1 6 6 6 6 1 NACO ALL OBS ROTATE NACO ACQUISITION TEMPLATES PUPIL TRACKING PT IN THE ACQUISITION TEMPLATES NACO IMG ACQ MOVETOPIXEL NACO IMG ACQ SDIMOVETOPIXEL NACO APP ACQ MOVETOPIXEL NACO IMG ACQ MOVETOSLIT NACO IMG ACQ MOVETOMASK NACO IMG ACQ SDIMOVETOMASK 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_NOAO_OBS_GENERICOFFSET 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 VLT MAN ESO 14200 2761 93 93 94 94 94 95 95 96 96 97 104 104 108 109 109 109 111 111 112 113 113 114 115 116 116 117 117 119 121 121 121 123 123 123 124 12
60. 100 0 100 100 0 100 Milliarcseconds Milliarcseconds 200 ML aaa 100 Milliarcseconds O 200 amp 200 100 0 100 200 Milliarcseconds Figure 4 33 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 4 10 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 spatial resolution A Fourier transform of SAM data will reveal a pattern of regular peaks in the frequency plane see Figure 4 34 right Each peak in this complex number array has an amplitude giving a 70 User s Manual VLT MAN ESO 14200 2761 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 ca
61. 18 Holes mask Left panel shows throughput with three narrowband filters in J H and K bands respectively while the longer wavelengths are given to the right panel Various integration times are shown annotated on the plot 79 VLT MAN ESO 14200 2761 User s Manual 10000 2 1000 5 O x O v a 100 1000 Peak Counts 100 Magnitude Figure 4 43 Same as Figure 4 42 but for the 9 Holes mask VLT MAN ESO 14200 2761 User s Manual 10000 1000 2 Q ait O v a 100 1000 Peak Counts 100 Magnitude Figure 4 44 Same as Figure 4 42 but for the BB 9 Holes mask VLT MAN ESO 14200 2761 User s Manual 2 1000 5 OO a 100 J NNYNNYNNN O 2 1000 OO x a 100 Magnitude Figure 4 45 Same as Figure 4 42 but for the 7 Holes mask User s Manual VLT MAN ESO 14200 2761 4 10 17 PSF and MTF Information on PSF and MIF can be found in the NACO SAM web pages http www eso ore sci facilities paranal instruments NACO inst sam html 4 10 18 Calibration plan for SAM Twilight flats as described in section 4 5 and internal flats without the masks e Detector darks in all readout modes and DITs 4 10 19 Pipeline for SAM SAM is not supported by the pipeline 4 11 SAMPol The simultaneous use of the Wollaston together with the SAM masks presents a unique opportunity with CONICA to examine syste
62. 2761 8 5 9 SAVING RESTORING A PS SESSION 152 8 5 10 GIVING NAMES TO SESSION P2PP AND PSF FILES 152 8 5 11 USER S PREFERENCES 153 9 APPENDIX DPR KEYWORDS FOR NACO 154 LIST OF TABLES LAU ZV NMAN OBES GNA TN 15 TN ae eee 23 E E NNN ee 24 Table 4 3 Summary of NACO Strehl ratios at 2 2 microns for an AO reference star at an airmass 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 We CONICA Phase L Exposure Time Calculator to K MARE SIONAL TO NOSE TANO barken 25 Table 44 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 I Exposure Time Calculator to estimate NACI TONO PALO AEE 26 Table 5 2 CONICA detector readout modes for each astronomical use the mode Readout Noise RON gain full well FW capacity ina MMe TILT INN 31 Table 5 3 List of available Cameras with plate scales fields of view and wavelength ranges 32 Te LIS OF ROTON NN 34 Taon I GO OE DAKS TOC CONON GON ADI EER E E N 40 Table 5 7 Spectroscopic modes The mode name consists of the objective the grism number and the order sorting
63. 5 User s Manual VLT MAN ESO 14200 2761 6 6 1 NACO_APP_ SPEC OBS AUTONODONSLIT 6 6 2 NACO SPEC OBS GENERICOFFSET 6 6 3 NACO SPEC CAL STANDARDSTAR 6 6 4 NACO SPEC CAL NIGHTCALIB 6 7 NACO POLARIMETRY SCIENCE TEMPLATES 6 7 1 NACO POL OBS GENERICOFFSET 6 7 2 NACO POL OBS RETARDER 6 7 3 NACO POL CAL STANDARDSTAR 6 8 NACO CORONAGRAPHIC SCIENCE TEMPLATES 6 8 1 NACO CORO OBS STARE 6 8 2 NACO CORO OBS ASTRO 6 8 3 NACO coro cCaL NIGHTCALIB 6 8 4 NACO CORO CAL STANDARDSTAR 6 9 NACO SDI 4 SCIENTIFIC TEMPLATES 6 9 1 NACO SDI4 OBS STARE 6 10 NACO SAM AND SAMPOL SCIENCE TEMPLATES 6 10 1 NACO_SAM_OBS_GENERICOFFSET 6 10 2 NACO SAMPOL OBS GENERICOFFSET 7 FILTER TRANSMISSION CURVES 7 1 CONICA BROAD BAND IMAGING AND ORDER SORTING FILTERS 7 2 CONICA NEUTRAL DENSITY FILTERS 8 PREPARATION SOFTWARE 8 1 STARTING THE PS 8 2 GRAPHICAL USER INTERFACE OVERVIEW 8 3 TARGET AND INSTRUMENT SETUP 8 4 SKY CONDITIONS 8 5 REFERENCE OBJECTS 8 5 1 HANDLING SEVERAL REFERENCE OBJECTS 8 5 2 MORPHOLOGY 8 5 3 PHOTOMETRY 8 5 4 TRACKING TABLE 8 5 5 OPTIMIZING NAOS AND GETTING A PERFORMANCE ESTIMATION 8 5 6 EXPORTING TO THE EXPOSURE TIME CALCULATOR 8 5 7 EXPORTING TO P2PP 8 5 8 EXPORTING OBS FROM P2PP 126 126 128 128 129 129 151 132 132 132 134 136 136 137 157 138 138 139 140 140 141 143 143 143 144 145 145 145 146 147 147 148 152 152 152 User s Manual VLT MAN ESO 14200
64. 8 38 User s Manual VLT MAN ESO 14200 2761 4 5 6 SDI ON SKY PERFORMANCE 4 5 7 PIPELINE FOR SDI 4 6 CORONAGRAPHY 4 6 1 PERFORMANCE OF THE SEMITRANSPARENT MASK C 0 7 SEP 10 4 6 2 PERFORMANCE OF THE 4QPMS 4 6 3 RADIAL ATTENUATION OF 4QPMS 4 6 4 CONTRAST OF 4QPMs 4 6 5 CHROMATICITY OF 4QPMS 4 6 6 COMPARISON WITH THE CLASSIC LYOT MASKS 4 6 7 OBSERVING STRATEGY WITH THE 4QPMS 4 6 8 CALIBRATION PLAN FOR CORONAGRAPHY 4 6 9 NIGHT FLAT FIELDS FOR CORONAGRAPHY 4 6 10 PIPELINE FOR MASK CORONAGRAPHY 4 6 11 APODIZING PHASE PLATE APP CORONAGRAPHY 4 7 SIMULTANEOUS DIFFERENTIAL IMAGING PLUS CORONAGRAPHY SDI 4 4 7 1 CONTRAST WITH SDI 4 4 7 2 TESTS WITH 4QPM SDI 4 AND ROTATION 4 7 3 CALIBRATION PLAN FOR SDI 4 4 7 4 NIGHT FLAT FIELDS FOR SDI 4 4 7 5 PIPELINE FOR SDI 4 4 8 LONG SLIT SPECTROSCOPY 4 8 1 GRISM SPECTROSCOPY 4 8 2 APP ENHANCED SPECTROSCOPY 4 8 3 PRISM SPECTROSCOPY 4 8 4 SLITLESS SPECTROSCOPY 4 8 5 SLITS 4 8 6 CALIBRATION PLAN 4 8 7 NIGHTTIME ARCS AND FLAT FIELDS 4 8 8 PIPELINE FOR SPECTROSCOPY 4 9 POLARIMETRY 4 9 1 CALIBRATION PLAN FOR POLARIMETRY 4 9 2 PIPELINE FOR POLARIMETRY 4 10 SPARSE APERTURE INTERFEROMETRIC MASKS SAM 4 10 1 SAM WHY AND WHEN TO USE IT 4 10 2 PUPIL TRACKING WITH SAM 4 10 3 DETECTOR READOUT AND CUBE MODE SETUP FOR SAM 4 10 4 SAM WITH LW FILTERS 4 10 5 CHOOSING WHICH MASK TO USE 39 40 40 41 41 42 43 43 44 45 46 46 46 47 51 51 52 54 54 54 55 55 56 57
65. 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 4 10 14 On sky observations AB Dor in H and K 400 400 141 195 200 200 W W E o E o Q Q ov ov DVD e 200 200 129 189 400 400 400 200 0 200 400 400 200 0 200 400 RA mas RA mas Figure 4 40 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 step 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 4 40 gives the likelihood for the presence of a binary companion as a function of its relative position to the star A good
66. DEFAULT 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 119 User s Manual VLT MAN ESO 14200 2761 1024 1024 N Position Angle 45 deg CONICA FOV 28 for 27 1 1 x Figure 6 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 6 12 parameters for the example shown in Figure 6 4 NEXPO per offset position 1 Observation Type O or S O Number of offset positions 8 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 1024 1024 N Position Angle 45 deg 3 CONICA FOV 28 for 27 1 1 x Figure 6 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 ate given in Table 6 13
67. EUROPEAN SOUTHERN OBSERVATORY Organisation Europ enne pour des Recherches Astronomiques dans I 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 87 0 Date 10 10 2010 Prepared J Girard for the IOT E Pompei P Amico C Lidman 10 09 2010 Name Date Signature Approved C Dumas Name Date Signature Released A Kaufer NameA Date Signature User s Manual VLT MAN ESO 14200 2761 CHANGE RECORD ISSUE DATE SECTIONS REASON INITIATION AFF 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 08 2010 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 reformatting 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 mote info on overheads Added SAMPol Added info on pupil tracking angles Add
68. Error Reference source not found clearly shows an improvement of about 1 mag with respect to standard SDI data reduction SDI 2 rolls 10 4Q 3 4th of the data SDI roll SDI ref 3 4th of the data SDI ref roll 3 4th of the aos SDI Standard roll subtraction 25d eg SDI double roll subtraction 2 deg 5 detection level ve s N g A a GE NPR OP AG tee e F POR rae Ne Oso Ss N Pa Lanne Ny I A KE 0 0 0 5 1 0 1 5 2 0 Angular distance in arcseconds Figure 4 25 5 0 detection level for different processing techniques 4Q and 4Q ref stand for direct corona graphic imaging respectively not using and using reference subtraction For all the lines that are called SDI we are studying the spectral subtraction image at 1 575um image at A 53 User s Manual VLT MAN ESO 14200 2761 1 625um SDI and SDI roll show the results of SDI subtraction with and without roll averaging It is the same for SDI ref and SDI ref roll but using also the subtraction of the SDI image of a reference star at the same parallactic angle The SDI double subtraction is described in details in the text For the detection level estimation we supposed that the companion has a contrast of 100 in the methane band no flux in the image at A 1 625um Obviously for a companion located at close angular separation the PSFs may overlap and subtract themselves In our case
69. 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 Mask should always be set to Wollaston 00 6 7 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 6 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 6 8 NACO coronagraphic science templates For SW observations the readout mode of the detector should be set to either Double_RdRstRd ot to FowlerNsamp 6 8 1 NACO coro obs Stare 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 Num
70. IS 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 produced by the NAOS RTC that can 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 WFS used the 14x14 or the 7x7 subapertures The variance vector has dimension 35 Datacubes are 3 D FITS files Ge 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 rema
71. Infra red Array Control Electronics I Instrument Summary File IWS Instrument Workstation JNPS Java NACO Preparation Software LAN Local Area Network C 3 F F F F 15 User s Manual VLT MAN ESO 14200 2761 MTF Modulation Transfer Function N A Not Applicable NAOS Nasmyth Adaptive Optics System NACO NAOS CONICA arrow Band Z Ss VZ 4 D DIT umber of Detector Integration Time GS Natural Guide Source noAO Open loop no AO correction Observation Block A Preliminary Acceptance Europe P2PP Phase 2 Proposal Preparation Preparation Software F eutral Density H S Z 4 4 F O ey ge PD ge T J DY O Paranal Science Operations ae N Point Spread Function Pupil Tracking ae ge lt Random Access Memory RON Read Out Noise RTAP Real Time Application Platform RTC Real Time Computer TD Real Time Display SAM Sparse Aperture interferometric Mask SAMPol Sparse Aperture interferometric Mask Polarimetry D SDI Simultaneous Differential Imager SDI 4 Coronagraphy with 4QPM and Simultaneous Differential Imager Service Mode Strehl Ratio Short Wavelength To Be Clarified To Be Defined Telescope Control Software TIM Time Interface Module R Time Reference System TSF Template Signature File Tip Tilt Mirror Tip Tilt Source Very Large Telescope Visitor Mode Wavefront Wavefront Sensor Workstation ZNVA Zernike Noise Variance Simultaneous Differ
72. Integration Time sec Number of DIT s LGS or NGS observation type Set to T if it is a PSF reference star Set to true for PT observations RA offset for sky image DEC offset for sky image Position angle or pupil angle in degrees Filter name e g Ks Neutral density Filter Full none Camera Name e g S27 NAOS aocfg file from JNPS This template is very similar to NACO_img_acq_MoveToPixel 6 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 centring 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 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
73. 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 8 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 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 8 4 and an estimation of the resulting PSF The Strehl ratio is always computed for the reference object on axis at the 148 User s Manual VLT MAN ESO 14200 2761 observing wavelength and at 2 166 um For the science target off axis the Strehl ratio is given at the observing wavelength only Tracking Table D Data RA DEC 10 0 12 0 13 0 15 0 12 0 13 0 Figure 8 3 An example of tracking table window acquisition and observation of moving objects Offsets in RA
74. 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 90 User s Manual VLT MAN ESO 14200 2761 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 telescope 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 5 5 Target acquisition Irrespective of the observing mode the acquisition sequence is composed by 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 l
75. O img obs FixedSkyOtfset templates are suppotted by the pipeline The NACO img obs GenericOffset is only partly suppotted Sequences of observations with offsets larger than the field of view mosaicking 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 35 User s Manual VLT MAN ESO 14200 2761 4 5 3 noAO speckle imaging As for P86 and onwards we decided to offer an open loop imaging mode with NAOS CONICA Associated with hardware windowing and fast readouts cube 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 allowing to get Strehl of 10 40 speckle masking image reconstruction a a Weigelt 1977 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 R Sridharan srengasw eso org and gave promising results on close binaries high strehl ratios speckle holography Petr 1998 allowing very precise astrometry over a somewhat large field of view Figure 4 7 lead R Sch del rainer iaa es Etc noAO mode sp
76. ONICA FOV S827 28 1 1 X Figure 6 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 7 0 14 0 List of offsets in DEC or Y 0 707 and Return to Origin T F T 127 User s Manual VLT MAN ESO 14200 2761 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 Table 6 18 Parameters of NACO_spec_obs_GenericOffset P2PP Label Default Values Description DIT NODEFAULT Petector Integration Time sec NDIT NODEFAULT Number of DITs Readout mode FowlerNsamp Readout mode NEXPO per offset position 1 Number of exposutes per offset position Number of offset positions NODEFAULT Number of offset posit
77. P is currently 8 x28 using the L27 camera 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 APP can also be used with the L54 camera and then the FoV limitation is less of a problem The image is just shifted up by 19 Y and 2 right X 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 ADI the APP is affected by the same drift problem mentioned in Section 6 3 1 It is recommended to use rather bright star but not too bright because the APP is located in the same wheel as the ND_Long filter 2 5 lt L lt 7 and a L 2 star is about to saturate the detector with the minimum DIT of 0 175s Uncorr HD FullFrame 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 50 User s Manual VLT MAN ESO 14200 2761 4 7 Simultaneous Differential Imaging plus coronagraphy SDI 4 SDI 4 is a new mode of NACO offered as of P81 April 2008 It was commissioned together with the new 4QPMs by a team from LESIA Observatoire de Paris led by A Boccaletti
78. 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 8 5 7 an estimate of the performance in terms of Strehl a 2 dimensional PSF and an HTML formatted file Sec 8 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 neutral 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 8 1 Starting the PS The NAOS Preparation Software can be downloaded for a number of computer platforms at the
79. Parameters of NACO 18 acg SDIMovel oMask 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 itis a PSF reference star Pupil Tracking Mode T F P Set to T for Pupil tracking 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 Uszd Neutral density Filter Full Uszd none BB filter wheel H Filter name H or empty NAOS Parameter file NODEFAULT NAOS aocfg file from the JNPS 115 User s Manual VLT MAN ESO 14200 2761 6 3 8 NACO_img acq Polarimetry This template does a telescope preset and is followed by interactive centring 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 centring 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 compl
80. R 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 22 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 FoV to CONICA Two off axis parabolas re image 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 li mirror Dichroic 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 VRI 90 J H K L M 90 Near IR observations N20C80 V R LJ H K 20 VARLLH K 80 WES and observations N90C10 V R
81. SF 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 confirmation the ND filter if inserted will be taken off 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 i 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 6 2 keywords combinations used for the new calibration frames type Flat on CALIB PLAT 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 110 User s Manual VLT MAN ESO 14200 2761 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 OB for the calibrating target 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 ti
82. 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 44 User s Manual VLT MAN ESO 14200 2761 mask is blind over an area 4 times larger than the 4QPM near the centre and that is precisely the interest of the 4QPMs 4 6 7 Observing strategy with the 4QPMs The precise centring 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 provide 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 10000 F Lyot vs 4QPM Full Undersized stop PSF 4QPM 1000 Lyot d
83. a simple simulation using the real PSF image has been used to estimate the attenuation of the positive PSF For an angle of 25 the PSF is attenuated by 20 at 150 mas and less than 4 at 300 mas The blue curve showed in Figure 4 25 has been corrected for this effect by dividing the detection level calculated on the double roll subtraction images by the theoretical attenuation This last technique is outperforming all the others except at very short angular separation less than 0 15 where the SDI subtracted by an SDI reference is better However since it does not use a reference image the exposure time on the studied star is doubled for a given observing time For this reason we advise users to save images with rotation steps of the instrument and use this double roll subtraction technique to improve the efficiency of the instrument In terms of operations the rotation of the instrument is already implemented in the templates and is not time consuming However during the rotation the position of the star is changed compared to the coronagraph mask and a re centering is mandatory albeit time consuming 4 7 3 Calibration plan for SDI 4 Darks with the same DIT are the only supported calibration See also Section 4 7 4 4 7 4 Night flat fields for SDI 4 SDI 4 is even more affected by dust than those of 4QPMs The same recommendations issued for 4QPMs hold for SDI 4 Imperfections on the plates that hold the 4QPMs together with instrume
84. action area gathering general actions such as requests for optimization or creation of the P2PP parameter file and the HTML file for the ETC NAOS Preparation Software v 1 103 EE File Objects Adaptive Optics Preferences r farget Instrument Setup rReference Objects CONICA Filter Ks om Observing Wavelength 2 18 microns Status Name Distance sr 36 ME 36 Dichroic FREE 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 Prop Mot DEC arcsec year pSky 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 Same Z RA Prop Mot RA arcsec year Windspeed 12 m s G5 v Theta on reference object 1 49 arcsec DEC JE Prop Mot DEC arcsec year ThetaO at zenith 2 0 medium oe _ Tracking Table VIS Background full moon v 20 0 V mag arcsec2 Morphology IPgint like v Photometry Mag Spectral Type v IR Background median we 13 8 H mag arcsec2 Observed Magnitude Band y Resulting Performance g Y Lz Sr on reference object User Information Sr 2 166 on ref objecd Spectral Type B3V w Sr on targev FWHM on reference object arcsec Transmission
85. alibrations 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 observed 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 Adaptive Optics Performance 40 Strehl ratio in K under good atmospheric conditions seeing AND coherence time and with a reference object of V 10 mag or K 6 mag Imaging Broad and narrow band filters in the 1 5 um region with 14 56 fields of view and 13 54 mas pixel scales Simultaneous Differential Imaging SDI in VM Apodizing Phase Plate Imaging APP in both VM and SM Open loop imaging no AO is offered in SM VM not pipeline supported Coronagraphy Occulting masks of various diameters 4 quadrant phase masks AQPM H 4QPM_K VM only Simultaneous Differential Imaging plus Coronagraphy SDI amp 4QPM_H VM only Spectroscopy Long slit spectroscopy with 4 grisms of resolving power 400 1400 over the covered spectral range Spectroscopy is now offered both in VM and SM APP Spectroscopy Limited setups see web pages only LW and only VM Prism Spectroscopy Limited setups see web pages and only VM een ei a E SAM Sparse Aperture Interferometry with 4 different masks SAM is only offered in VM SAMPol SAM with polarimetry offered in VM This
86. an achieved in this mode is given in Table 4 4 Table 44 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 I Exposure Time Calculator to estimate signal to noise ratios Seeing Aitmass Expected Strehl on axis 14 4 08 08 The Laser Guide Star Facility LGSF at UT4 is a joint project in which ESO built the laser room beam relay and launch telescope while MPE and 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 A 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
87. and collaborators J Baudrand P Riaud and P Baudoz The SDI mode of CONICA can be combined with the 4 quadrants phase mask optimized for the H band to achieve high contrast and improve the detectability of faint sub stellar companions near bright stars ideally down to massive extra solar giant planets by reducing the photon noise at small angular separations The advantages of this new mode are o It allows deeper integration by about a factor 50 100 with respect to conventional imaging with SDI unsaturated o It allows getting closer to the central star An example flat field is shown in Figure 4 23 This mode is now completely commissioned and is offered only in VM as of P81 Figure 4 23 Flat field of the SDI 4 corrected from detector flat field taken with the H filter only not SDI filters The FoV is 8 for each quadrant 4 7 1 Contrast with SDI 4 The contrast when combining the 4QPM_H with SDI and SDI was measured The measurements were done as follows Gaussian fitting was used to determine accurately the position of the PSFs in order to measure the relative positions between the 4 images These images were 51 User s Manual VLT MAN ESO 14200 2761 extracted and re centred at the sub pixels precision using the result of the Gaussian fitting Sub images were over sampled to improve alignment if needed and to allow better spectral rescaling Images are numbered from 0 to 3 starting from the lower left corner
88. and DEC are given in arcsec Figure 8 4 Performance subpanel the AO optimal configuration and the PSF is available from buttons in this panel 149 User s Manual VLT MAN ESO 14200 2761 The optimal Adaptive Optics configuration can be displayed by clicking on the AO Config button in the subpanel depicted in Figure 8 4 An example is shown in Figure 8 5 WS Figure 8 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 optimization 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 th
89. and turning anticlockwise with Aj 1 625um 1 575um and s 1 600um We computed Ao Ao As An M s normalization to total intensity The results are displayed in The dotted line corresponding to the 4QPM alone is identical to Figure 4 24 except near the centre because the bandwidth is much smaller than previously and therefore the spectral leakage at the centre is smaller with SDI There is a clear improvement of almost a factor of 10 to use a 4QPM with SDI at high Strehl regime In addition to the fact that the signal to noise ratio is improved since longer integration times are possible the use of a coronagraph is known to be theoretically more favourable to differential imaging as demonstrated here 10 SDI SDI max attenuation 140 max attenuation 130 107 107 oO D PSF PSF 4QPM_H 4QPM_H_SDI 4QPM_H_SDI io Normalized intensity Normalized intensity 1074H r RR eS 8 oa ESS Seen OG ve ar mm se 0 0 i 0 0 0 1 0 2 0 3 0 4 0 5 Angular distance in arcsec Angular distance in arcsec Figure 4 24 Radial profiles for the PSF solid the 4QPM image dotted and the SDI processing for PSFs dash dotted and 4QPM images dashed Colors are for Ao Ax red Ao As green Ai blue s purple Left plot is for SDI and right plot is for SDI 4 7 2 Tests with 4QPM SDI 4 and rotation In the following section the re
90. 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 ty and to 3 2 Adaptive optics A powerful technique in overcoming 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 WFS 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
91. ask 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 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 filter 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 65 User s Manual VLT MAN ESO 14200 2761 4 10 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 o
92. ave 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 to save a session it is possible to copy the aocfg file into a jnps file and then import it as a session 8 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 152 User s Manual VLT MAN ESO 14200 2761 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 8 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
93. bandwidth as shown in Figure 4 15 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 43 User s Manual eT Tr max attenuation 96 O I ae a al T TT TT Normalized intensity Normalized intensity oO ba 107 morrir 1 jor LI 1 T S jj i it LI PL i tt l i i j i 4 Lit 1 i t 0 0 0 1 0 2 0 3 0 4 0 5 Angular distance in arcsec io jor CV ee TT TTT T T rn 7 PT oere I a sk VLT MAN ESO 14200 2761 max attenuation TV VRV VA 120 ea 0 0 0 1 0 2 0 3 0 4 0 5 Angular distance in arcsec Figure 4 14 Radial profiles of the PSF compared to that of the coronagraphic image obtained with the 4QPM_K left and the 4QPM_H right 1 0000 Fs Ks filter SK filter NB 2 17 filter 9 1000 13 full undersized stop 0 0100 E Normalized ntensity 0 0010 0 0001 0 00 0 10 0 20 Angular separation in arcsec Figure 4 15 Chromaticity of the 4QPM_K measured on the 2004 mask with a fibre i e no seeing effects 4 6 6 Comparison with the classic Lyot masks Measurements were made in 2004 and are still valid for the new masks Figure 4 16 shows data obtained on a natural star
94. ber 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 132 VLT MAN ESO 14200 2761 User s Manual especially for very bright sources to select an area so that the main target is out of the 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 o
95. 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 13 camera severely limits the availability of the field of view due to vignetting induced by mask mis alignment see Figure 4 11 This should discourage the use of this mask with the smallest scale camera except for very experienced users Figure 4 11 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 4 6 2 Performance of the 4QPMs The two four quadrant phase masks 4QPM reduce the intensity of a source by adding a phase shift of x to the wavefront Unlike the classical Lyot masks a phase mask coronagraph splits the focal plane into four equal areas two of which are phase shifted by m As a consequence a 41 User s Manual VLT MAN ESO 14200 2761 destructive interference occurs in the relayed pupil and the on axis starlight rejected outside the geometric pupil is filtered with a diaphragm a Lyot stop of 0 15 diameter 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 cfr Boccaletti et al The four quadrant phase mask coronagraph PASP 116 p 1061 2004 There are two such masks available Figure 4 12 e AQPM H optimi
96. 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 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 An attempt should be made as far as possible to preserve the same AO parameters between source 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 wi
97. cation of the holes as measured in mm from the centre of the mask 9 Holes 3 Mask BB Holes Hole size 0 980 mm diameter Table 4 18 X and Y location of the holes as measured in mm from the centre of the mask BB 9Holes x 4 Mask 7Holes Hole size 1 50 mm diameter Table 4 19 X and Y location of the holes as measured in mm from the centre of the mask 7 Holes x 3 51064 1 99373 3 51064 2 49014 1 56907 1 36918 68 User s Manual VLT MAN ESO 14200 2761 4 10 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 necessary to do this task is beyond the scope of the present document The reader is advised to consult sources form the open literature concerning aperture 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 Adapti
98. ch 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 configuration 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 8 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 8 5 9 Saving Restoring a PS Session The complete PS session can be saved on local disk and restored The S
99. commended magnitude range of standard stars for observations with the visual dichroic Magnitude Range SW broad band filters 10 12 SWNB filers FP 5 14 Maximum brightness of observable targets Bright targets leave residual images that can take several minutes to disappear Table 5 4 presents the absolute limits acceptable Table 5 4 Magnitude limits for DIT lt 7 sec IR Magnitude MGE 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 95 User s Manual VLT MAN ESO 14200 2761 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 4 6 Any other expected saturation level for field stars should be accepted prior to observation In service mode waiver reque
100. cope will return at the beginning of the sequence if the keyword RETURN is set equal to T 6 2 NACO General templates 6 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 Fast 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 6 3 NACO Acquisition templates Telescope presets can only be done via acquisition templates and all observing blocks must start with one There are seven acquisition templates one for imaging and one each for SDI imaging spectroscopy coronagraphy SDI 4 polarimetry and SAM They are listed in Table 6 1 All acquisition templates preset the telescope to the AO reference star set up NAOS and CONICA close the loop and acquire the science target All acquisition templates require a NAOS parameter file a k a aocfg 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 ima
101. copic 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 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 5 16 Instrument and telescope overheads The execution time report produced by P2PP computes the overheads according to the rules reported in Table 5 5 Users especially those in service mode should check them and make sure to take them i
102. cover very good strehl ratios down to 1 um Offered in VM and SM See section 4 5 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 4 6 11 Spectroscopy 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 since 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
103. ctor 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 6 6 1 NACO_app_spec_obs_AutoNodOnSlit Exactly the same as NACO_spec_obs_AutoNodOnSlit but allowing the APP in with limited setups see 4 8 2 6 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 Table 6 18 describes the parameters of this template 126 User s Manual VLT MAN ESO 14200 2761 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 RA 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
104. d AO reference star can have different proper motion It is however assumed that the coordinates are given for the same equinox 8 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 8 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 ITS 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 8 5 1 Handling several 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 f
105. d 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 6 3 parameters of NACO_img_acq_MoveToSht 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 Always set to F PT not supported Alpha offset from Ref star 0 Offset from reference star arcsec 113 User s Manual VLT MAN ESO 14200 2761 Delta offset from Ref star 0 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
106. d objects or for distant targets without any suitable nearby titp tilt star Any request for this mode should be explicitly mentioned in the proposal 97 User s Manual Table 5 5 NACO Overheads VLT MAN ESO 14200 2761 Acquisition Templates Description Telescope Preset Guide star acquisition Initial setup NAOS CONICA AO acquisition Strehl measurement Imaging acquisition Polarimetric acquisition Spectroscopic acquisition Coronagraphic acquisition SDI 4 acquisition LGSF acquisition Overhead 3 min 0 75 min 2 min 5 10 min 4 min 0 5 min 1 min 1 5 min 2 3 min 10 min 10 min Comment Depends on the brightness of the source used for AO Not charged to the user Depends on target brightness Depends on target brightness Accurate centring is mandatory 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 and completion overheads for IRACE 1 2 3 4 typical offset 2 4 time between frames without offsets Change in instrument configuration HWP in or out HWP angle setup Rotator offset for polarimetry and SDI Re centring for 4QPM and SDI 4 All observations using chopping Night time spectroscopic flats Night time spectroscopic arcs Night time coronagraphic flats 2 sec 0 7 sec Negligibl
107. diagram In this example NOFF SKY 5 Table 6 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 Table 6 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 coronagraphy DIT img NODEFAULT DIT sec for imaging Readout mode Double RdRstRd Readout mode Window Size 1024 Size of the window Store Data Cube T F p Store in data cube flag Jitter Box Width NODEFAULT Jiter box width sky only NDIT for object position NODEFAULT Number of DITs at the object pos under the mask NDIT for sky position NODEFAULT Number of DITs 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 Li
108. e 9 sec 7 sec 2 sec 9 sec 27 sec 16 sec 1 min 30 sec 15 sec 1 2 min 2 min 30 6 min 6 min 6 min Add to the exposure time per on off pair per on off pair 98 User s Manual VLT MAN ESO 14200 2761 Table 5 6 Example 1 Imaging a faint source V 15 for visual WES or K 10 for IR WES with FowlerNsamp NACO eee Move Topical NACO_img_obs_AutoJitter 3 sec 20 60 1 F Execution Time min Guide Star Acquisition owlerNsamp Observation 60x 27 20x 3 2 Observation Number of offset positionsx Offset overhead NDITx DIT readout overhead Table 5 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 Obsetvation 20x 27 2x16 3x 30x2 0 7 Total min Overheads Observation Number of offset positions Offset overhead NEXPO per offset position 1 tume between frames without offset NEXPO per offset positionx DITxNDIT readout overhead 99 User s Manual VLT MAN ESO 14200 2761 Table 5 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 Templat
109. e 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 center and right images illustrate the potential of wide field correction with a 1x1 arcmin field centered on the star cluster Omega Centauri 27 User s Manual VLT MAN ESO 14200 2761 CONICA CONICA is an IR 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 4 4 for a drawing of the instrument 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 4QPM in H and K the coronagraphic masks 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 gr
110. e PSF 150 User s Manual VLT MAN ESO 14200 2761 along the x and y axes Figure 8 6 The FITS file itself can also be saved to the uset 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 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 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 8 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 y axis 8 1 0280 Save PSF max 0 0296 FWHM X 0 094 3 0200 FYVHM Y 0
111. e 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 4 10 It is important to note that the contrast curve 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 4 10 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 CONICA PSF Optimized Conyentional AO SDI AF 1 50 0 0 0 5 1 0 1 5 2 0 arcsec from primary Figure 4 9 Contrast obtained on AB Dor with the new Wollaston SDI DU User s Manual VLT MAN ESO 14200 2761 AB_Dor DX_leo GJ799A GJ799B GJ803 GJ862 HD155555AB HD181321 HD48189A 4 84500 5 24200 ssssscscsees 5 20100 5 20000 4 83100 5 28500 4 90700 5 05000 4 74700 H H H H H H H H H H AF1 50 0 0 a HO 19 2 0 arcsec from primary Figure 4 10 obtained on AB Dor with the old Wollaston SDI from Biller et al Ap J S S 173 143 2007 4 5 7 Pipeline for SDI The SDI mode of CONICA is not supported by either a pipeline or an ETC 4 6 Coronagraphy For co
112. e 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 5 1 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 some occasions the wind can be strong enough to prevent the telescope from
113. e calibration plan they should submit their own OBs Full Well refers to the full well 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 4 4 4 Cameras The characteristics of the cameras of CONICA are described in Table 4 7 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 are well in agreement with the previously measured values using galactic center data R Schedel Thesis S27 and S13 B Sicardy private communication 54 C Lidman Table 4 7 List of available Cameras with plate scales fields of view and wavelength ranges re mas pixel arcsec microns 4 4 5 Filters All but one of the CONICA filters Error Reference source not found and Table 4 9 are mounted on two filter wheels Transmission curves of several filters are given i
114. e found in the sections below detailing the on sky performance obtained with SAM at NACO 4 10 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 63 User s Manual VLT MAN ESO 14200 2761 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
115. e is offered in combination with 5 different window sizes Note that since windowing is done on chip 1 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 centered on pixel 512 512 and the STARTX and STARTY parameters are fixed by the chosen window size Table 4 24 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 in 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 patte
116. e 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 50 Offset Coordinates DETECTOR List of offsets in RA or X 7 0 14 0 List of offsets in DEC or Y 0 7 0 7 and Return to Origin T F T 127 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 anf List of Position Angle Offsets 0 45 130 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 13 134 Figu
117. e parameters Acquisition Template NACO img acq MoveToPixel Observation Template NACO img obs Autolitter DIT 0 2 sec NDIT 150 Number of offset positions 120 NEXPO per offset position 1 Readout Mode Uncorr Execution Time min Observation Number of offset positionsx Offset overhead DITXNDIT Table 5 9 Example 4 Spectroscopy of faint source with FowlerNsamp Acquisition Template Observation Template DI NDIT Neas NEXPO per offset position Readout Mode Return to Origin Jitter Box Width Execution Time min Preset 3 Guide Star Acquisition Initial Setup AO Acquisition Spectroscopic acquisition Through slit Sub Total acquisition Observation 2x6x 27 300 3 Total min Overheads Observation 2xNumber of AB or BA cyclesx Offset overhead DIT readout overhead ze 100 User s Manual VLT MAN ESO 14200 2761 Table 5 10 Example 5 SW Polarimetry of bright source with the Wollaston Template parameters NACO_ime_acq_Polarimetry NACO pol obs GenericOffset 10 sec Acquisition Template Observation Template DI NDIT Number of offset positions NEXPO per offset position Readout Mode List of position angle offsets z FowlerNsamp 0 45 Execution Time min Preset ET VET Initial Setup AO Acquisition Polarimetric acquisition Sub Total acquisition Observations at 0 and 45 degrees 2x 5x 27 6x 10 2 2x8 3 16 4 Rotator offset in between angles Total min 2505 Overheads 193 5
118. east 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 center it in the middle of the field of view of the wavefront sensor indicated by a white box overlayed on the CONICA detector Once the centring 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 available 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 5 5 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 acq img SDIMoveToPixel 5 5 2 Spectroscopy It is mandatory to use the NACO img acq_MoveToSlit acquisition template for all sp
119. eb pages as the reports come along If you are interested by this mode just consider the cube mode and 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 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 star 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 37 User s Manual VLT MAN ESO 14200 2761 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 to reach K 18 see Figure 4 7 4 5 4 Fabry Perot Imager Since P86 Fabry Perot imaging is not offered 4
120. eckle masking technique Weigelt s Bispectrum method adapted by S Rengaswamy noAO speckle masking reconstruction VLT NaCo Sub field bad image best image r J band seeing 0 4 r NGC3603 mean image closed loop AO 90 J band Strehl ratio obtained 22 J band Strehl ratio Figure 4 6 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 36 User s Manual VLT MAN ESO 14200 2761 noAO mode speckle holography technique Work in progress on crowded fields by R Sch del VLT NaCo 13 Field Ks band RA Figure 4 7 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 More information will be published on the NaCo w
121. ect 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 exposutes 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 Table 6 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 6 6 NACO spectroscopic science templates For SW observations the readout mode of the detector can be 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 regula
122. ectroscopic 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 II are in Section 6 3 5 These instructions must be strictly adhered to 5 5 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 ot User s Manual VLT MAN ESO 14200 2761 This template provides interactive tools to centre objects behind the selected mask which is overlaid on the RTD 5 5 4 SDI 4 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 5 5 5 Polarimetry It is mandatory to use the NACO img acq Polarimetry acquisition template 5 5 6 SAM It is mandatory to use NACO_img_acq_SAMMoveToPixel and use the same mask in both the acquisition and the science templates 5 5 7 SAMPol It is mandatory to
123. ed 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 User s Manual TABLE OF CONTENTS 1 SCOPE INQ 2 1 2 2 2 53 INTRODUCTION ADDITIONAL RESOURCES CURRENT VERSION OF THE MANUAL CHANGES FOR P87 3 OBSERVING WITH ADAPTIVE OPTICS IN THE INFRARED 3 1 3 2 33 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 CONICA DETECTOR 4 4 1 4 4 2 4 4 3 4 4 4 4 4 5 4 5 4 5 1 4 5 2 4 5 3 4 5 4 4 5 5 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 13 15 16 16 16 18 18 18 19 20 20 22 23 23 24 25 25 30 30 31 31 52 32 35 35 35 36 3
124. egion 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 stellar 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 4 10 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
125. ely 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 4 8 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 59 User s Manual VLT MAN ESO 14200 2761 4 9 Polarimetry A MeF 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 is inserted at the focal plane In a single exposure at least half the field will be missing so that three exposures with 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
126. ely used for creating skies without residual objects for sky subtraction 117 User s Manual VLT MAN ESO 14200 2761 1024 1024 Position Angle 45 deg je 96 j gt ball j Conica FOV 28 for 527 1 1 x Figure 6 3 An illustration of the NACO img obs Auto itter 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 near 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 The total integration time excluding overheads is defined in seconds by DIT x NDIT x NEXPO per offset position X Number of offset positions Table 6 10 describes the parameters of this template Table 6 10 Parameters of NACO_img_obs_AutoJitter P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Numb
127. ential Imaging Nn Z Z NM NM AIO O J ap ze ge DN be lt Z T z 14 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 sensors 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 Recently the system is able to provide even more degraded correction using the LGS without TTS the so called seeing enhancer SE mode allowing full sky coverage CONICA Section 0 is an Infra Red IR 1 5 um imager and spectrograph fed by NAOS It is capable of imaging long slit spectroscopy simultaneous differential 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 P87 are listed in Table 2 1 NACO can be used in Service SM or Visitor Mode VM The Observatory provides daily c
128. er of DITs 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 Return 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 118 User s Manual VLT MAN ESO 14200 2761 6 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 Table 6 11 describes the parameters of this template Telescope offsets are defined as lists with the parameters List of offsets 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
129. ers 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 sources 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 7 2 34 User s Manual VLT MAN ESO 14200 2761 IB 4 05 was decommissioned due to a not recoverable defocus and therefore it is not offered in P87 and on While the exoplanet s flux rapidly drops towards wavelengths note the log scale shorter than about 4 microns the atmospheric L band closes at around 4 1 microns Hence an intermediate bandwidth filter with a bandpass around 4 4 1 micron is most effective for planet detection Please use NB_4 05 instead 4 5 Imaging Imaging and SDI Simultaneous Differential Imaging uses different combinations of filters and cameras 4 5 1 Calibration Plan for imaging and 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 O Nightly zero points provided it is clear in J H and Ks with the 27 or 13 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 or S54 objectives and
130. et 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 6 9 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 S27 28 1024 1024 1024 1024 Figure 6 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 anf List of Position Angle Offsets 0 45 130 User s Manual VLT MAN ESO 14200 2761 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
131. eted 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 6 8 describes the parameters of this template Table 6 8 Parameters of NACO_img_acq_Polarimetry 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 itis a PSF reference star Pupil Tracking Mode T F F Always set to F PT not suppotted 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 Neutral Density Filter Full Neutral density Filter Full none Camera S27 Camera name NAOS parameter file NODEFAULT NAOS aocfg file from the JNPS 6 3 9 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 alwa
132. 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 Fabry Perot will not be offered Users are encouraged to consider SINFONI as an alternative Wire Grid Polarimetry is 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 17 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 t 0 7 where to 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 To 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 ty and r
133. f 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 rejected 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 4 10 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 Center have calibrator finding
134. f 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 5 11 Recommended DIT and NDITs Unless the object is bright enough to cause saturation Table 4 6 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 Table 5 1 For DITs larger than 60 seconds users should consider using FowlerNsamp and not Double_RdRstRd With DITs larger than 60
135. fect 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 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 Otherwise 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 titp tilt star and will allow better image quality than simple imaging but worst 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 extende
136. fewest hot pixels but it has the smallest well depth Conversely 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 4 6 Table 4 6 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 S SW sv peneana ravnen 12 1 0 fm vat 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 and this will be around 900 seconds 31 User s Manual VLT MAN ESO 14200 2761 Users should be aware that some of the observatory provided calibrations are only done in one readout mode For example standard star observations in the SW broad band filters will only be done in Double_RdRstRd If users want to observe a standard in a mode that is not supported in th
137. ffset positions Sky only x Number of AB cycles Table 6 22 describes the parameters of this template Table 6 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 DITs for SKY Number of exposures NODEFAULT Number of exposures on target Object only Number of offset positions NODEFAULT Number of 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 133 User s Manual VLT MAN ESO 14200 2761 NACO coro obs Stare Jitter Box Width DEC Offset Sky Positions Object Positions RA Offset Figure 6 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
138. following URL http www eso org observing etc naosps doc 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 flavors 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 8 2 Graphical User Interface Overview The GUI that appears after the initialization phase is depicted in Figure 8 1 The panel is divided into three areas which are from top to bottom o The menu bar giving access to file related operations and other miscellaneous functionalities see following sections 143 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
139. ges 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 109 User s Manual VLT MAN ESO 14200 2761 where the mask cannot change from acquisition to science SDI 4 and the 4QPMs which once inserted are never removed from the optical path 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 DITs for these modes are listed in Table 4 6 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 7 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 By default t
140. h the new Wollaston SDI 39 Figure 5 7 obtained on AB Dor with the old Wollaston SDI from Biller et al Ap J S S 173 143 2007 40 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 41 Figure 5 9 Flat field images of the 40PM K Ks filter left and of the 4OPM_H H filter right The many dust particles observed in the flats generate flat field variations of 10 20 locally 42 Figure 5 8 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 43 Figure 5 9 Radial profiles of the PSF compared to that of the coronagraphic image obtained with the 4OPM_K left and the 4OPM H right 44 Figure 5 10 Chromaticity of the 4OPM_K measured on the 2004 mask with a fibre i e no seeing effects 44 Figure 5 11 Radial profile for the PSF the 4OPM and the 0 7 Lyot obtained with a natural star in 2004 45 Figure 5 14 Azimuthally averaged flux of the VLT and VLT APP point spread functions simulations 47 Figure 5 14 APP PSF obtained with the NB 4 05 filter and under relatively good seeing conditions and contrast curve of the clean side 48 Figure 5 15
141. hat the scientific niche is for objects where the entire field of interest lies within several hundred milli arcsecs from a bright star Although there may be ways to mosaic larger fields together these have never been successfully demonstrated 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 4 10 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 b
142. he 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 NACO img acq SDIMoveToPixel and NACO img acq SDIMoveToMask these templates set the instrument in coronagraphic mode in SDI and SDI 4 mode 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 is 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 nternal lamp taken during the day or obtain niet calibrations by means of NACO_coro_NightCalib 2 NACO img acq MoveToMask and NACO_img_acq_SDIMoveToMask 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 P
143. he 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 6 14 Parameter of NACO_img_obs_FixedSkyOffset P2PP Label Default Values DIT Readout mode NODEFAULT Double RdRstRd Description Detector Integration Time sec Readout mode Window Size 1024 Size of the window Store Data Cube T F F Data cube flag Jitter box width NODEFAULT Jiter Box Width Number of AB or BA cycles NODEFAULT One cycle is one object sky pair NDIT per object position NODEFAULT Number of DITs for the OBJECT NDIT per sky position NODEFAULT Number of DITs 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 Densty Filter Full Neutral density filter Full none Camera NODEFAULT Camera Name Figure 6 6 illustrates how this template can be used NACO img obs FixedSkyOffset l I l i a AT 1 DEC Oftset pr Sky Positions Object Positions RA Offset Figure 6 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 S13 The AO loop i
144. he typical overhead is 1 8xNDIT seconds 4 13 Pupil Tracking PT mode Pupil tracking mode is a new option for imaging applications 4QPM coronagraphy classic coronagraphy SDI SDI 4 Pupil tracking mode was originally implemented to support SAM but given the demand from the community it is now offered for a wider range of applications In this mode the telescope independently from NACO tracks the pupil orientation instead of the field This new tracking mode opens the possibility to improve Angular Differential Imaging ADD a high contrast imaging technique that reduces quasi static speckle noise and facilitates the detection of nearby companions 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 4 46 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 a
145. 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 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 1024 1024 Acquisition Position C
146. ice 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 Table 6 20 describes the parameters of this template 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 exposutes 129 User s Manual VLT MAN ESO 14200 2761 At least two different orientations separated by 45 degrees are required for computing the Stokes parameters Table 6 20 Parameters of NACO_pol_obs_GenericOffset P2PP Label Default Values Description DIT NODEFAULT Detector Integration Time sec NDIT NODEFAULT Number of DITs 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 Offset coordinates NODEFAULT SKY or DETECTOR List of offs
147. iew rotates with respect to this pattern Telescope P Collimator APP Filter Camera Detector focus wedge image 4 OPTI 3 OPTI5 6 OPTI7 DET BOE OE EOE EEE EEE EEE EERE EEE EEE EEE EEE EE EEE EEE EE EEE EE EEE EEE REESE EEE EEE Figure 4 21 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 useful field of view FoV with the L27 camera going along with its field limiting stop FLM27 is about 28 wide in X but only 8 high in Y The offset pattern has to take that into account Overall it should not be a problem as the APP useful is 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 4 x14 49 User s Manual VLT MAN ESO 14200 2761 APP coronagraph successful commissioning April 2010 VLT NaCo Contrast curve clean side of the PSF exoplanet Beta Pictoris b demonstration preliminary 6 0 o Un Beta Pic b confirmed again e Separation 0 354 0 010 6 AU e PA 209 13 deg 2 00 deg Delta mag 7 75 0 23 mag In agreement with Lagrange et al 2010 e Quanz et al 2010 in Prep 7 5 Delta magnitude NB 4 05 ss 8 0 f Arcsec Figure 4 22 The APP main commissioning result on Beta Pictoris b WARNINGs The useful field of view with the AP
148. igned 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 Fov N 1 1 x 1 1 x Figure 6 2 Orientation for spectroscopic observations Left Field orientation on detector at 0 rotation angle 108 User s Manual VLT MAN ESO 14200 2761 on sky Right Field orientation at 45 rotation angle on sky 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 convention 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 teles
149. igns 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 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 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 the 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 6 21 describes the parameters of this template Table 6 21 Parameters of NACO pol obs Retarder P2PP Label Default Val
150. igurations were tested and if one for cases not covered and some custom tests may be needed in case one wants to use a special configuration Contact NACO eso org for inquiries 1 The dimension of the cube will be NAXIS3 NDIT 1 See section 4 14 for details 85 User s Manual VLT MAN ESO 14200 2761 For DCR HD the overheads are minimal given the fact that no readout is performed till 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 times the exposure time DITxNDIT To that one has to add the data cube writing to disk and controller RACE 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 tread This technique inevitably introduces large overheads for instance 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 t
151. illed when requesting an optimization by the PS server Section 8 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 145 User s Manual VLT MAN ESO 14200 2761 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 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 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
152. illessen Figure 4 28 illustration by S Gillessen of the prism spectroscopy capability for the Galactic Center with LGS Figure 4 29 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 4 8 4 Slitless spectroscopy Not offered 4 8 5 Slits Two long slits are available for spectroscopy The characteristics are listed in Table 4 14 Slitless spectroscopy is done with the FLM_13 mask which is the field mask used for imaging with the S13 objective and it is available for the SW grism modes only The centring of the observed object in the slit or to the centre of the mask in the case of slitless spectroscopy is done interactively through an acquisition template 58 User s Manual VLT MAN ESO 14200 2761 Table 4 14 Slits 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 4 8 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 Whe
153. in degrees Filter NODEFAULT Filter name e g Ks Mask NODEFAULT Coronagraphic mask Neutral Density Filter Full Neutral density Filter Full none Camera NODEFAULT Camera Name e g S27 NAOS Parameter file NODEFAULT NAOS aocfg file from JNPS 6 3 7 NACO img acq_SDIMoveToMask This template does a telescope preset which is followed by interactive acquisition of the object behind the 4QPM_H in combination with the SDI camera It must be followed by the dedicated SDI 4 template which uses the same instrument setup with the possible exception for the use of the neutral density filter ND Short for the acquisition of very bright targets The use of the H band filter is recommended The template records the following frames 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 specified in the initial setup and an image of the sky these images can be used as PSF calibrator Then the following steps are performed o Rough offset to position the star behind the mask o Removal of the ND_Short filter if used The Full Uszd mask is inserted instead o Adjustment of DIT if needed o Fine centring behind the mask O Record the final acquisition image of the star finely centered behind the mask Error Reference source not found describes the parameters of this template Table 6 7
154. in unchanged Chopping mode saves data in cubes of NAXIS3 2 a cube of two frames corresponding to the two average half cycles frames 88 User s Manual VLT MAN ESO 14200 2761 5 OBSERVING WITH CONICA AT THE VLT As with other ESO instruments users prepare their observations with P2PP Acquisitions observations and calibrations are coded via templates Section 6 and two or more templates make up an Observing Block 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 Exposure Time Calculator ETC and P2PP use the output from PS to determine feasibility and to prepare observations For phase II 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 PS For the former the ETC now calls the NAOS PS server itself to retrieve the performance estimate For phase I preparation users can use either access route although we strongly recommend the use of the PS for phase I preparation as well At the telescope OBs are executed by the instrument operator 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 provid
155. ine 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 position NEXPO IMG and the number of offsets NOFF IMG are free parameters 134 VLT MAN ESO 14200 2761 User s Manual HI Coronoeraphv i Coronoeraphv grapn Generic Offset erapny on target on sky Figure 6 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
156. ion 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 des 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 More information about SAMPol will be available after the commissioning run Interested users ate encouraged to consult the web pages for updates and news and to contact NACO eso org in case of questions 4 11 1 Calibration plan for SAMPol e Twilight flats as described in section 4 5 1 e Detector darks in all readout modes and DITs 83 User s Manual VLT MAN ESO 14200 2761 4 11 2 Pipeline for SAMPol SAMPol is not supported by the pipeline 4 12 Cube mode Cube mode is a variant of the burst mode already offered with VISIR and ISAAC 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 se
157. ions Observation type O or S NODEFAULT O isin closed loop S in open loop Offset coordinates NODEFAULT SKY or DETECTOR List of offset in RA or X NODEFAULT Offsets in arcsec List of offset in DEC or Y NODEFAULT Offsets in arcsec Return to Origin T F T Return to Origin Slit NODEFAULT Name of slit Spectroscopic Mode NODEFAULT Spectroscopic Mode 6 6 3 NACO spec cal StandardStar This template is used for spectroscopic standard star observations It is strictly equivalent to the NACO spec obs AutoNodOnsSlit template in the definition of the parameters The user is referred to 6 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 FTTS headers of the images are set to different values allowing pipeline processing and archiving 6 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 spectroscopic 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
158. is 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 symmettic 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 4 10 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 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 Table 4 16 X and Y location of the holes as measured in mm from the centre of the mask 18 Holes 67 User s Manual VLT MAN ESO 14200 2761 3 25047 2 11124 3 85992 2 46311 0 812615 2 11124 1 01577 3 16686 2 84415 2 81498 0 203153 4 57435 2 Mask 9Holes Hole size 1 156 mm diameter Table 4 17 X and Y lo
159. isms 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 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 and the order sorting filters used in spectroscopy The camera wheel which contains all the objectives 28 User s Manual VLT MAN ESO 14200 2761 Adapter Callbratlon Source tH p Cryogenle Shutter Fabry Perot UPS Mask Wheel Colllmator Closed Cycle Cooler Detector METTET I N2 Cyecllng Radlatlon Shleld Figure 4 4 CONICA Schematic overview 29 User s Manual VLT MAN ESO 14200 2761 CONICA detector 4 4 1 General characteristics The CONICA detector is a Santa Barbara Research Center 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 4 5 Table 4 5 CONICA detector characteristics Detector Format Pixel Size Dark Current Wavelength range um ADUs pixel um Aladdin 3 10262x1024 0 05 0 15 0 8 5 5 0 8 0 9 The new detector is more sensitive to heavily saturated sources The limiting magnitudes that are observable are specified in Table 5 4 Please check carefull
160. ith a computer parameter space search algorithm that 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 62 User s Manual VLT MAN ESO 14200 2761 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 4 32 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 4 32 Optical diagrams showing the effect of apodizing the pupil with the four 2 dimensional masks implemented in the CONICA camera 4 10 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 t
161. itional charts showing more details as appropriate o 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 o For imaging the field of view of the selected camera must be drawn 92 User s Manual VLT MAN ESO 14200 2761 o 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 o For long slit spectroscopy the slit must be drawn o For spectroscopic templates the reference star used for preliminary slit centring must be identified o For PSF reference stars the OB name must be prefixed with the string PSF_ o For pre imaging the OB name must be prefixed with the string PRE_ o For PSF observations which are to be done as pre imaging the OB name must begin with PRE_PSF_ o The magnitude of the brightest object in all fields including standard stars must be explicitly given in the README file and indicated on the finding charts o For LGS observations the TTS magnitude and distance from the target must be explicitly given in the README file and indicated on the finding charts o For LGS in SE mode this must be explicitly written on the finding chart and in the README 5 8 Reference sources
162. lamp off If n is set to zero the default no lamp flats are taken Table 6 19 describes the parameters of this template Table 6 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 128 User s Manual VLT MAN ESO 14200 2761 6 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 6 7 1 NACO_pol_obs_GenericOffset This template is used for imaging polarimetry 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
163. lative merits of different observing techniques with 4QPM and SDI 4 are discussed this analysis was performed by the commissioning team The tests were performed on sky on a star and a reference and the results presented in Figure 4 25 In this figure we compare the detection levels that can be reached with the classical no SDI coronagraphic imaging using reference subtraction or not with SDI 4 using subtraction of SDI images of the reference or not The effect of roll averaging is also studied The reference subtraction is only done on 3 4th of the data 8 images out of 11 to match the parallactic angle of the star and its reference In Figure 4 25 the SDI processing solid green appears to be slightly better for the short angular separation less than 0 4 than the coronagraphic imaging using subtraction of a reference star dotted black To see the effect of the rotation we added the different images we recorded after correcting for the instrument rotation in order to add up companion signal while averaging out speckle and readout noise The effect is clearly an improvement of the detection capability especially at large angular distances dashed green The subtraction of the SDI image of the star with the SDI image of the reference star solid red was also investigated This technique is more efficient than the SDI image at angular distance 52 User s Manual VLT MAN ESO 14200 2761 shorter than 1 and is the same further away
164. lects 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 frequency It is believed but has not been tested yet that 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 te no LGS This mode is only offered for VM runs even though waivers for simple cases are possible 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 4 12 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 mod
165. ll 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 1s 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 Table 6 17 Parameters of NACO_spec_obs_AutoNodOnS fit P2PP Label Default Values Description DIT NODEFAULT Dete
166. ll 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 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 66 User s Manual VLT MAN ESO 14200 2761 4 10 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 large fraction of the success of the images depicted in this section is due to the relatively good Closure Phase data Th
167. mal configuration of the AO system 150 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 151 12 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 Acronym Meaning 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 Adaptive Optics D D AO i AT AT C O PU C C F IT M P SO T N oV P S W U B D S W W W CS S R SF Detector Integration Time HighWellDepth H H H H P R S R S S R Data Product C S I D P IB Intermediate band I Instrument Control Software IN Instrumentation Software Package I O input output I Infra red IRACE
168. manual is organized as follows 15 2 1 User s Manual VLT MAN ESO 14200 2761 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 NACO contributed library NACO Call for Proposal NAOS Preparation Software Exposure Time Calculator Catalogues for adaptive optics reference objects 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 proposals 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 Phase 2 Proposal http www eso org observing p2pp NACO NACO P2PP html Preparation User Support Department NACO Quality Control http www eso org org dmd usg http www eso org observing dfo quality index_NACO html For any q
169. me needed to observe the PSF target will be charged to the user The NACO_noAO_acq_MoveToPixel template will allow an OB to be executed on NaCo without aocfg files because the AO loop will remain open speckle mode 6 3 1 Pupil 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 img acq SDIMoveToPtixel usually F T is optional NACO img acq SDIMoveToMask usually F T is optional NACO img acq MoveToPixel usually F T is optional NACO img acq MoveToMask usually F T is optional NACO APP acq MoveToPtixel 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 In the remaining templates NACO img acq MoveToSlit and NACO img acq Polarimetry even though the flag is still present it must remain set to F Rotator angle offsets work the same way as in normal rotator mode A positive angle moves the spiders clockwise See Figure 4 46 for an illustration 6 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 re
170. meter 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 4 10 15 Additional considerations for faint companion detection 1 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 2 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 4 39 and results are reported in Table 4 21 This result shows why it is important to have a stringent SNR cutoff of 50 for detection of binarity The parameter space being very large false detection is likely at 10 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 soutce 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 illu
171. mode of the detector should be set to either Double_RdRstRd or to FowlerNsamp 6 9 1 NACO sdi4 obs Stare This template is used for SDI 4 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_AutoNodOnSlit 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 This part of the template works identically to NACO_coro_obs_Stare 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 the field of view for sky measurements to avoid saturation effects The coronagraphic mask is left in the beam for the sky exposure
172. ms where there may be polarization signals at very high spatial resolutions This is straightforward in principle and only requires further testing and verification no additional hardware or software except modifying the observing template to allow the Wollaston to be put into the beam which will take place during a short commissioning run in March 2009 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 retarder plate is the best option The implementat
173. n 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 normaly 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 TECH 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 154
174. n Section 7 1 The J band 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 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 IB_4 05 Lp and Mp filters can be used For the L54 camera only the NB_3 74 and NB IB_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 32 User s Manual VLT MAN ESO 14200 2761 Mp is considerably higher the integration time has to be reduced which can only be done by windowing the array Information on the CONICA s broadband filters can be found in Table 4 8 and for narrow and intermediate band filters in Table 4 9 Table 4 8 CONICA Broad Band Imaging filters um um 33 User s Manual VLT MAN ESO 14200 2761 Table 4 9 List of narrow and intermediate band filters um um 7 IB 2 45 2 450 0 060 57 mapaj oao IB_2 48 2 480 0 060 53 mapaj oao sm m Additionally there are two neutral density filt
175. n 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 calibrating are not biased by the seeing and they obey quasi Gaussian statistics Figure 4 34 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 To give an idea of the behavior of fringe phase for binary star systems Figure 4 35 represents the
176. n is computed the slit is removed and a drawing of the slit is superimposed on the image of the field The centring 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 Table 6 5 describes the parameters of this 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 avoi
177. n on detector at O rotation angle 108 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 27 The dotted line defines the jitter box width 118 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 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 120 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 13 120 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 13 122 Figure 7 7 An illustration of how the NACO spec obs AutoNodOnS lit template works with 125 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 th
178. n star and its companion is 1 29 0 14 in K band left and 1 47 0 24 in H band right 75 Figure 5 28 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 KF Figure 5 29 Throughput for the 18 Holes mask Left panel shows throughput with three narrowband filters in J H and K bands respectively while the longer wavelengths are given to the right panel Various integration times are shown annotated on the plot ee Figure 5 30 Same as Figure 5 29 but for the 9 Holes mask 50 Figure 5 31 Same as Figure 5 29 but for the BB 9 Holes mask 81 Figure 5 32 Same as Figure 5 29 but for the 7 Holes mask 82 Figure 5 33 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 87 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 108 11 User s Manual VLT MAN ESO 14200 2761 Figure 7 2 Orientation for spectroscopic observations Left Field orientatio
179. never 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 calibrations 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 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 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 4 8 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 immediat
180. ng Phase Plate coronagraph theory amp practice Expected gain in contrast close to the parent star o Ao go E p VLT NaCo S o 4 05 um F o 7 o 0 0 5 1 Radius arcsec Figure 4 17 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 1 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 throughout is simply the ratio of the count rates with and without the APP It shows that for the NB4 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 To compute de contrast curves all 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
181. ngle 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 on sky at the start of exposure ADA POSANG END specifies the position angle on sky at the end of exposure ADA PUPILPOS specify the pupil angle Note that this value does not coincide with the position angle specified by the user PUPILPOS position angle C C 88 99 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 Asa consequence all files taken before that date are missing those keywords Since the mode was officially offered as of Oct 5th the number of affected files is rather small 86 User s Manual VLT MAN ESO 14200 2761 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 typically of the order of 1 deg For example if one sets position angle 0 in the acquisition template ADA PUPILPOS may report 90 8
182. nt flexure means that flat fields depend on the rotator angle For this reason the template NACO coro cal NightCalib allows one to take nighttime flat fields immediately after SDI 4 data have been taken We strongly recommend that these calibrations are taken for the said setup In addition the acquisition template for SDI 4 NACO img acq SDIMoveToMask takes the following calibration frames o One flat on and one flat off image with the mask inserted Those can be used for flat fielding of the science data taken afterwards since the mask is not moved out of the beam o Two images of the bright star off the mask with ND Short inserted if needed in acquisition The second image is meant to be used as sky 4 7 5 Pipeline for SDI 4 SDI 4 observations are not suppotted by the pipeline or by the ETC 54 User s Manual VLT MAN ESO 14200 2761 4 8 Long Slit Spectroscopy Table 4 11 and Table 4 13 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 it is used in P2PP 4 8 1 Grism Spectroscopy Table 4 11 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
183. nto account for their Phase 1 amp 2 proposal Note that any LGS acquisition will last 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 96 User s Manual VLT MAN ESO 14200 2761 Not all parameters of the listed templates are shown Only those that have an impact on the ovetheads are listed 5 17 Observing with the LGS At the time of updating this manual the LGS mode of NAOS is still poorly characterised Its use is for the time being recommended only for science programs that can take advantage of moderate Strehl ratios seeing enhancements to achieve their scientific goals From the past commissioning experience one advises to avoid LGS observations for objects with airmass above 1 5 for which the AO correction degrades strongly A natural guide star NGS is still required to correct for the 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 ef
184. 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 8 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 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 changed your mind and do not want the tracking table anymore just deselect the Tracking Table check button 147 User s Manual VLT MAN ESO 14200 2761 i L i _ SE P rs G 25 Figure 8 2 Illustration of the extinction curve used when giving a non zero value to the extinction Ay The J H
185. od 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 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 19 User s Manual VLT MAN ESO 14200 2761 3 4 Transmission and background The transmission of the Earth s atmosphere in the 155 um region is shown in Figure 3 2 The X J H K L and M bands correspond to atmospheric windows which are approximately centred at 1 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 As regards 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
186. of view Table 6 4 describes the parameters of this template Table 6 4 Parameters of NACO_img_acg_SDIMoveToPixel 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 Neutral Density Filter NAOS parameter file Default Values NODEFAULT NODEFAULT NODEFAULT F F 5 5 0 Full NODEFAULT 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 true for PT observations RA offset for sky image DEC offset for sky image Position angle or pupil angle in degrees Neutral density Filter Full none NAOS aocfg file from JNPS 112 User s Manual VLT MAN ESO 14200 2761 6 3 4 NACO app acq MoveToPixel Template very similar to the NACO img acq MoveToPtixel but created specially for the APP coronagraph pupil plane The default and acquisition filter is NB 4 05 The acquisition images are taken without the APP which is placed in the optical path afterwards 6 3 5 NACO img acq MoveTosSlit This template does a telescope preset and is followed by interactive centering of the object in the slit It is very similar to the NACO img acq MoveToPixel 6 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 positio
187. on 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 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 positions NODEFAULT Num of DITs per object position NDIT for SKY positions NODEFAULT Num of DITS per sky position Number of exposures object NODEFAULT Number of exposures on target only Number of offset positions sky NODEFAULT Number of exposures on sky only Sky offsets in RA NODEFAULT RA offset in arcsec Sky offsets in DEC NODEFAULT DEC offset in arcsec 6 10 NACO SAM and SAMPol science templates Starting in P83 there are two science templates one for SAM observations and the other for SAMPol 6 10 1 NACO sam obs GenericOffset The science template is similar to NACO img obs GenericOffset 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 will occur in pairs
188. on 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 these case that they select it by themselves and insert the coordinates in their OB Appropriate magnitude for guiding stars range from 11 to 14 The reference object used by NAOS for wavefront sensing and specified within the PS is chosen by the astronomer 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 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
189. on 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 1024 1024 Acquisition Position Jitter Box 14 5 Nod Throw Slit Angle 0 degrees N CONICA FOV S827 28 1 1 X Figure 6 7 An illustration of how the NACO spec obs AutoNodOnSlit template works with Jitter Box Width 5 Return to Origin 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 25 User s Manual VLT MAN ESO 14200 2761 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 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 wi
190. pe 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 support html select the link airmass 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 of your OBs should be 1 0 and 30 respectively 5 4 Telescope control Most interactions with the telescope consist of telescope presets for acquisiti
191. pointing in that direction 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 5 2 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 it can be measured outside the dome with the telescope at zenith VLT mirrors have been 89 User s Manual VLT MAN ESO 14200 2761 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 5 3 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 However it is recommended not to observe targets closer than 30 to the moon to avoid problems linked to the telesco
192. r 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 10 124 User s Manual VLT MAN ESO 14200 2761 6 6 1 NACO_spec_obs_AutoNodOnSlit 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 Table 6 17 describes the parameters of this template 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 ATE ATE B Es BHEs ATE ATE B EJB EJ A E where EF 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 distributed between JitterBoxWidth 2 and JitterBoxWidth 2 It is strongly recommended to define some n
193. rames 1 10 sec More details on cube mode can be found in section 4 12 Given the very small useful science field of view it is generally not necessary 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 4 10 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 Hardware windowing with the CONICA array requires NY NX 2 where NX and NY are the number of pixels in X and Y respectively 64 User s Manual VLT MAN ESO 14200 2761 fringes and has optical components optimized for this r
194. re 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 wavelengths needs to be read very rapidly which in turn leads to poorer detector cosmetics 20 User s Manual VLT MAN ESO 14200 2761 W tg ye Vas las dl Ny B EN P Vi j i i yi l dada i iN I a a hi i kill TN P ul p S i 2 eld F 0 eV 1 od g gt Fa W die ad 1 n u Ay HIN VI AA J er iij ill ij M r Transmi o a oO I t T MAN AL i i NN i I i FE 94 vr 4 0 4 2 4 4 4 6 4 8 5 0 Wavelength um fi 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 unfortunatel
195. re 7 11 IMustration 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 the 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 LI right diagram In this example NOFF SKY 3 135 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 141 Figure 8 2 Transmission curves of the CONICA neutral density filters 142 Figure 9 1 PS GUI 144 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 148 Figure 9 3 An example of tracking table window acquisition and observation of moving objects Offsets in RA and DEC are given in arcsec 149 Figure 9 4 Performance subpanel the AO optimal configuration and the PSF is available from buttons in this panel 149 Figure 9 5 Pop up window showing an opti
196. respectively not using and using reference subtraction For all the lines that are called SDI we are studying the spectral subtraction image at 1 57 5um image at 22 Figure 5 18 illustration of the APP spectroscopy concept 56 Figure 5 24 illustration of the APP spectroscopy concept 57 Figure 5 25 illustration by S Gillessen of the prism spectroscopy capability for the Galactic Center with LGS 58 Figure 5 17 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 58 Figure 5 17 Transmission as a function of wavelength for the Wollaston prism The big absorption feature at 3 4 microns is due to the resin material 61 Figure 5 18 Mechanical drawings of the four aperture masks installed in the CONICA camera 62 Figure 5 19 Optical diagrams showing the effect of apodizing the pupil with the four 2 dimensional masks implemented in the CONICA camera 63 Figure 5 20 Canis Majoris images reconstructed from 18 hole masking data top and from a set of shift and add stacked full pupil AO frames bottom 70 Figure 5 21 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
197. rimetry is not supported by the ETC or the pipeline 61 User s Manual VLT MAN ESO 14200 2761 4 10 Sparse Aperture interferometric Masks SAM 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 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
198. ringe 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 i P 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 4 36 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 4 36 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 User s Manual VLT MAN ESO 14200 2761 7 Retrieve the phase of the object from the closure phase and fit with binary model 4 10 13 On sky obsetvations 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 ie a total integration time of 6 minutes It was observed with the H and K broad band filters and with the BB_9holes mask Seeing was average between
199. rn on the 84 User s Manual VLT MAN ESO 14200 2761 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 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 Table 4 24 characteristics of cube mode PDER HD 1024x1026 oso 16 06 DCR HD 512x514 009 3 o Dam zos ooo lor 06 Damb s30 oos s oo PDCR HD ex o0 m 0 Note DCR min DIT 05 60 always loses frames 0 5 sec docs not Efficient L Nor FNS always one frame is Tost Large overheads PUcR AD oaos oss 1 0 UCR AD azs4 o 3 0 PUCR HD zez o or 0 PUCR HD 128x130 0008 s oo o PUCR AWD T024x1026 030 16 06 UCR AWD si2xsi4 oo lse oo PUCR AWD 256x258 002 2 06 o UCR AWD 128x130 0008 s o PUcR HWD ex6 00 sm oo o 5 kes T T an Kas has an an oo pas GIGI GIGI 4 12 1 Cube mode overheads Overheads in cube mode depend on the readout mode and on the observing setup DIT NDIT Not all possible conf
200. ronagraphic applications a Lyot type coronagraph with a circular focal plane mask and an undersized pupil plane mask can be rotated into the beam of CONICA Five masks are available two opaque masks with diameters of 0 7 and 1 4 arc seconds a semi transparent mask with a diameter of 0 7 arc seconds and two 4 quadrant phase masks 4QPM one optimized for K band observations and the other for H band In addition a new Apodizing Phase Plate APP see Section 4 6 11 has been installed in the pupil plane and is operated at 4 05 um NB and IB filters just like direct imaging The available masks and their characteristics are listed in Table 4 10 Table 4 10 CONICA s masks and phase plates for coronagraphy C07 Opaque held in place by wires 100 extinction over the mask 4QPM_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 C_0 7_sep_10 Semi transparent 3 5X10 gt transmissivity placed on a glass plate 0 1 40 User s Manual VLT MAN ESO 14200 2761 HE central Lyot spot Pupil Plane Apodizing Phase Plate for NB 4 05 and IB 4 05 28x28 FoV NEW 4 6 1 Performance of the 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
201. rs 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 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 performance of the RTC cannot give a valid estimate which is the case for slow 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 93 User s Manual VLT MAN ESO 14200 2761 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 We are considering a similar classification scheme for the LGS operation Check for updates on the NACO webpages http www eso org instruments NACO news html 5 10 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 the observation of the science target and the PSF reference the brightness o
202. s The object positions will be observed with the AO loop closed The sky positions will be observed with the AO loop open Table 6 26 describes the parameters of this template 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 x Number of Exposures Object Only NDIT for the SKY positions x Number of offset positions Sky only x Number of AB cycles 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 Note that an additional overhead of 2 minutes for target re centring has to be considered every time that Number of Exposures Object Only is greater than 1 137 User s Manual VLT MAN ESO 14200 2761 Table 6 26 Parameters of NACO_sdi4_obs_Stare P2PP Label Default Values Descripti
203. s 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 gt User s Manual VLT MAN ESO 14200 2761 6 4 6 NACO img cal StandardStar This template is used for imaging standards and is similar to the NACO img obs GenericOtffset 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 6 15 describes the parameters of this template Table 6 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 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 Neutral
204. seconds the number of hot pixels in Double_RdRstRd is noticeably larger Table 5 1 Recommended DIT and NDIT range DIT sed DITXNDIT sed J SW NB filters 60 300 120 300 H and Ks 20 120 60 240 o om a These recommendations do not necessarily hold for cube mode where the choice of DIT and NDIT will depend on the application 5 12 IR background Background is a function of the filter and the dichroic They are listed in Table 5 2 Users should note that the RON of the array can dominate if DIT is too small 94 User s Manual VLT MAN ESO 14200 2761 Table 5 2 IR Backgrounds The hyphens mark invalid combinations of a NAOS dichroic CONICA filter Background magnitude sq arcsec Vis N20c80 N90C10 JHK K_ 8 1158 58 a 140 140 140 140 Xs 128 125 io ip po so I Mp 05 os 5 13 Recommended magnitude ranges for Standard Stars The recommended magnitude range for standard stars in imaging and spectroscopy is given in Table 5 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 magnitudes brighter for the N20C80 and N90C10 dichroics For detailed estimates users should use the ETC Table 5 3 Re
205. spect 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 Table 6 3 describes the parameters of this template 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 111 User s Manual Table 6 3 Parameters of NACO 1799 acg MoveToPixel 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 Neutral Density Filter Camera NAOS parameter file Default Values NODEFAULT NODEFAULT NODEFAULT F F 5 5 0 NODEFAULT Full NODEFAULT NODEFAULT 6 3 3 NACO img acq_SDIMoveToPixel VLT MAN ESO 14200 2761 Description Detector
206. st 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 best 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 will be rejected at the feasibility stage 5 15 Nighttime calibrations For spectros
207. st of offset in Y NODEFAULT Offsets in arcsec Filter coro NODEFAULT Filter Name for coronagraphy Filter img NODEFAULT Filter Name for imaging 135 User s Manual VLT MAN ESO 14200 2761 Mask Position NODEFAULT Coronagraphic mask Neutral Density Filter Full Neutral Density filter Camera NODEFAULT Camera Name 6 8 3 NACO coro cal NightCalib This template is used for taking nighttime flat fields and it should be placed immediately after the coronagraphic or the SDI 4 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 taken The default is one This template should be used to take flats with the 4QPM the semi transparent coronagraphic mask and SDI 4 Only the SW filters are supported LW lamp flats are not possible For the LW filters the only alternative is to use a sky frame to flat field the data Table 6 24 describes the parameters of this template Table 6 24 Parameters of NACO_coro_cal_NightCahb P2PP Label Default Values Description Number of night flats 1 Night time flat field 6 8 4 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 key
208. strated in Figure 4 41 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 76 User s Manual VLT MAN ESO 14200 2761 3 What can be done about it The bias that can be observed on the phases see Figure 4 41 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 consists 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 g dr b O Oh p D O O 100 200 300 400 100 200 300 400 Acquisition Acquisition Figure 4 41 Example of strong systematic effect on the phases Both
209. stro SDI 4 4QPM H coronagraphy SDI NACO sdi4 obs Stare SAM includes Pupil Tracking observations NACO sam obs GenericOffset 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 star for spectroscopy NACO spec cal StandardStar Standard star for polarimetry NACO pol cal StandardStar Night time calibrations Night time coronagraphic and SDI 4 flats NACO coro cal NightCalib Night time spectroscopic flats and arcs NACO spec cal NightCalib 105 User s Manual VLT MAN ESO 14200 2761 106 User s Manual VLT MAN ESO 14200 2761 o With the exception of standards the minimum amount of time between exposures 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
210. t 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 will require chopping and nodding 21 User s Manual VLT 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 I
211. t 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 the 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 an
212. ted 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 at 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 of a natural guide star for tip tilt sensing is the reason why sky coverage cannot go up to 100 for LGS AO Full sky coverage can be achieved in the so called seesng enhancer mode i e LGS assisted 25 User s Manual VLT MAN ESO 14200 2761 AO observation but without correcting for tip tilt The expected Strehl ratio which c
213. ters of NACO_sampol_obs_GeneriwcOffset 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 List of position angle offsets NODEFAULT List of HWP angles Filter NODEFAULT Filter name SAM Mask Full Name of SAM mask Camera NODEFAULT Camera Name 159 User s Manual VLT MAN ESO 14200 2761 7 FILTER TRANSMISSION CURVES 7 1 CONICA Broad Band Imaging and order sorting filters The transmission curves at the J H Ks Lp Mp and spectroscopic order sorting filters are displayed in Figure 7 1 Electronic versions of the transmission cutves of all filters including the NB and IB filters are available from the NACO web pages http www eso org sci facilities paranal instruments NACO inst filters html 140 User s Manual VLT MAN ESO 14200 2761 1 T T T T T T T T ij 1 T ij T 1 T SH 0 8 FN n 0 6 i E E H Ks SK 0 4 T
214. th 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 specified in the initial setup and an image of the sky these images can be used as PSF calibrator Then the following steps are performed o Rough offset to position the star behind the mask o Removal of the ND Shott filter if used For 4QPM the Full Uszd mask is used All other masks use Full o Adjustment of DIT if needed o Fine centring behind the mask o Record the final acquisition image of the star finely centred behind the mask without the ND filter Table 6 6 Parameters of NACO_tmg_acq_MoveToMask 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 114 User s Manual VLT MAN ESO 14200 2761 PSF Reference T F F Set to T if it is a PSF reference star Pupil Tracking Mode T F F Set to T for Pupil tracking 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
215. the square root of the number of individual images in the stack te 350 The resulting 1 6 image contains the 1 6 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 47 User s Manual VLT MAN ESO 14200 2761 5 0 Contrast image in units of magnitudes can be computed using 2 5xlog 5 Im 1 0 Vn 1 flux n 20 pixel NACO APP contrast curve NB4 05 6 0 L 7 55 Delta magnitude NB 4 05 8 0 E 7 Or a oo e e toep poa 0 0 0 5 1 0 1 5 Arcsec 6000 4000 2000 o 2000 4000 6000 4 Figure 4 18 APP PSF obtained with the NB_4 05 filter and under relatively good seeing conditions and contrast curve of the clean side 5 sigma point source detection limit for VLT APP Delta L magnitudes 10 0 0 5 1 1 5 2 Radius arcsec Figure 4 19 Lp contrast curve of the clean side note the higher achievable Amag gt 10 than with the NB 4 05 filter 8 48 User s Manual VLT MAN ESO 14200 2761 changing the PA rotates the FoV not the APP effect on the PSF Figure 4 20 Position Angle consideration for APP Imaging No matter what the PA is the PSF pattern remains fixed only the field of v
216. ther and frames will have to be restacked during data reduction Given the above the use of the four quadrant phase mask is restricted to Visitor Mode observations 4 6 8 Calibration plan for coronagraphy For coronagraphic 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 and daytime lamp flats as described in 4 5 These calibrations are done without the focal plane masks For additional details see also Section 4 6 9 o Detector darks in all readout modes and DITs 4 6 9 Night flat fields for coronagraphy 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 transmissivity 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
217. ts 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 123 User s Manual VLT MAN ESO 14200 2761 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 Table 6 16 describes the parameters of this template 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 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 obj
218. 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 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 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 Natural Guide Stars 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 crea
219. u 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 8 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 modeled 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 due to the broad bandwidth of the wavefront sensor detectors We adopted a standard extinction law represented in Figure 8 2 as defined by Cardelli Clayton amp Mathis AJ 345 245 1989 section IIb 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 8 5 4 Tracking table For
220. uced 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 4 33 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 4 33 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 diffraction limited structures appearing in the masking data 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 69 User s Manual VLT MAN ESO 14200 2761 100 u go ka O O 2 0 100 1 75um
221. ues 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 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 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 131 User s Manual VLT MAN ESO 14200 2761 Filter NODEFAULT Filter Name Mask NODEFAULT Set to Wollaston 00 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 exposutes 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 Wollaston prism the same care must be taken as for observation with the NACO_pol_obs_GenericOffset template see Section 6 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
222. uestion 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 87 0 of the NACO User Manual applicable for phase I and phase II preparation of P87 Since NACO is being constantly improved and modes are constantly refined especially the new ones it is advisable to check the NACO web page for possible updates to this manual and for recent news 2 3 Changes for P87 The following changes are implemented for P87 IB_4 05 NOT Offered the new intermediate band filter centered at 4 05 um showed some 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 16 User s Manual VLT MAN ESO 14200 2761 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 Preliminary results were promising limited setups and VM only as explained in section 04 8 2 Prism Spectroscopy Offered It is offered back for limited setups and VM only The following changes were implemented since P86 and still apply noAO Offered open loop imaging Associated with the cube mode it allows to do speckle interferometry with NACO and re
223. ure 5 1 CONICA Schematic overview 29 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 level of rows 512 amp 512 disappear in the background subtraction 30 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 36 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 of 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 38 Figure 5 6 Contrast obtained on AB Dor wit
224. use NACO_img_acq_SAMPol and use the same mask in both the acquisition and the science templates 5 6 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_AutoJitter and NACO_img_obs_GenericOffset For these 2 templates a new user selectable keyword Observation Category has been introduced and should be set to PRE IMAGE in the above mentioned cases only By default this parameter is set to SCIENCE Failure set this keyword properly will result in delays to process and deliver the pre imaging data 5 7 Finding charts readme files and OB naming conventions In addition to the general instructions on finding charts and README files that are available at http www eso org observing p2pp ServiceMode html the following NACO requirements apply O At least one chart for each observation must be 2 x 2 in size with add
225. ve Optics Masking Interferometry Ap 650 131 2006 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 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 4 10 16 gives calibrations of the counts expected for varying mask filter combinations 4 10 11 On sky obsetvations VY Canis Maioris VY Canis Majoris is a bright M supergiant which has prod
226. ve 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 colored 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 TT 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 1 18e 3 4 42e 3 4 75e 3 Total area Peak Pixel 1 53e 3 37e 3 95e 3 7 2e 3 NON Fe Total area Peak Pixel 2 67e 3 2 53e 3 5 52e 3 use VLT MAN ESO 14200 2761 Table 4 23 Mask area and peak flux ratios for 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 78 User s Manual VLT MAN ESO 14200 2761 2 1000 c 3 5 O x pv A 100 4 Magnitude 10000 2 1000 c 3 5 O x O Q A 100 Magnitude Figure 4 42 Throughput for the
227. words in the FITS headers of the images are set to values that allow pipeline 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 Table 6 25 describes the parameters of this template Table 6 25 Parameters of NACO_coro_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 exposures per offset position Number of offset positions NODEFAULT Number of offset positions 136 User s Manual VLT MAN ESO 14200 2761 List of offsets in X NODEFAULT Offsets in arcsec List of offsets in Y NODEFAULT Offsets in arcsec Filter NODEFAULT Filter name Mask psition C_0 7_sep_10 Coronagraphic mask Camera NODEFAULT Camera Name 6 9 NACO SDI 4 scientific templates For SDI 4 observations the readout
228. y section 0 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 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 of concentric rings The ghosts can be seen in Figure 4 5 Figure 4 5 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 level of rows 512 amp 512 disappear in the background subtraction The dark current consists of the array dark current which is much lower than the numbers listed here and thermal radiation from the instrument 2 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 30 User s Manual VLT MAN ESO 14200 2761 4 4 2 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
229. ys saves the final acquisition image The operator will center the object in the center 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 116 User s Manual VLT MAN ESO 14200 2761 This template can be followed by either NACO sam obs GenericOffset or NACO sampol obs GenericOtfftset Table 6 9 describes the parameters of this template Table 6 9 Parameters of NACO_img_acq_SAMMove Tl oPixel 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 itis 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 aocfg file from JNPS 6 4
230. zed 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 Figure 4 12 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 4 6 3 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 were made for both masks and are presented in Figure 4 13 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 42 User s Manual VLT MAN ESO 14200 2761 Angular separauon IN A U Anguiar separauon IN A U 2 3 4 9 2 3 4QPM in H 4QPM in H Lyot 0 15 data 4QPM 4QPM lyot 0 15 Coronagraph attenuation Intensity variation 0 2 0 0 0 1 0 2 0 3 Angular distance in arcseconds Angular distance in arcsec Figure 4 13 Radial attenuation of an off axis point source moved outwards of the mask centre in H left and Ks right

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