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1. P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs Observation Category SEQ CATG SCIENCE Observation category science or preimaging Number of Exposures SEQ NEXPO Number of exposures List of NDIT SEQ NDIT LIST NDIT List Return to Origin SEQ RETURN Return to Origin Flag Obs Type 0 or S SEQ OBSTYPE LIST Observation type list S or O List of offsets X or RA SEQ OFFSET1 LIST List of offsets Y or DEC SEQ OFFSET2 LIST er a X or RA offset list arcsec Y or DEC offset list arcsec Offset Coordinates SEQ OFFSET COORDS SKY or DETECTOR coordinates LW Filter wheel 1 INS FILT3 NAME Filter wheel 1 LW Filter wheel 2 INS FILT4 NAME Filter wheel 2 of exposure NEXPO is larger than 1 There is not jittering during the observation creation of a data cube The keywords EVENT DATE and EVENT TIME are ignored whenever BURST F On the con trary in Burst mode by setting the value 0 default no EVENT time is considered during the template execution and the exposure start as soon as the acquisition and the instrument set up have been completed Last the keywords WIN STARTX Y cannot take any value The window is always centred in the Aladdin detector and is not possible to place it say in just one quadrant Therefore please refer to Table 26 to get the appropriate values for the selected window size Table 61 Parameters of ISAACLW_img_obs_FastPhot P2PP label
2. Execution time s 18 30 41 54 66 77 89 102 113 126 137 162 174 187 198 246 388 199 114 37 Data cube Size Mb 4 1 8 2 12 3 16 4 20 5 24 6 28 7 32 8 36 9 41 0 45 0 53 3 57 4 61 5 65 6 82 0 131 1 262 2 262 2 262 2 ISAAC User Manual VLT MAN ESO 14100 0841 48 A Template description A 1 General remarks and reminders how to avoid common sources of error e Only parameters specific to ISAAC are described The description of other parameters can be found in the http www eso org sci observing phase2 e We strongly recommend that you consult the http www eso org sci facilities paranal instruments isaac for the latest information e Templates using the Aladdin and templates using the Hawaii must not be mixed in the same OB e All SW spectroscopic OBs must use the ISAACSW_img_acq MoveToSlit or ISAACSW_img_acq MoveToSlitrrm template for acquisition and all LW spectroscopic OBs must use either the ISAACLW_img_acq MoveToSlit or ISAACLW_img_acq MoveToSlitNoChop templates e The SW polarimetric OBs must use the ISAACSW_img_acq Polarimetry template for acquisition e LW imaging chopping templates must use either ISAACLW_img_acq_Preset or ISAACLW_img_acq_MoveToPixel for acquisition and LW imaging no chopping templates must use either ISAACLW_img_acq Preset or ISAACLW_img_acq MoveToPixNoChop e In those templates where 2 filters have to be defined SW Filter wheel 1 and SW Filter wheel 2 or
3. ISAAC User Manual VLT MAN ESO 14100 0841 88 B Filter curves See the on line version of the User Manual http www eso org sci facilities paranal instruments isaac for transmission curves in ASCII format Fiter SH trananission arve Fiter SK traremisdon arve 1 1 as as as ae Taremaio Tamman as a4 a2 16 17 Worstereth iria ore Ater SL rams mssi cuve Tamman as Wienslereth mior Figure 19 Filter curves for order sorting filters ISAAC User Manual VLT MAN ESO 14100 0841 Toeman Toremasion Toeman 45 205 46 PO aN XA ter SZ transmission curve A smission Ater H torem don arve AR A f poten Toremssion 1 2 1 25 13 1 35 14 145 1 45 15 1 55 16 1 65 17 1 75 18 185 Wonelerath mirot Wonslercth mia ora Alta Ke tranamnission curve Filter L ranamission curve Toeman 21 215 22 25 23 235 24 Wonelercth iria ora Filter M tranamission arve 47 48 49 s s1 s2 Wonelercth micrors Figure 20 Filter curves for broad band filters 89 ISAAC User Manual VLT MAN ESO 14100 0841 NB 1 06 NA 1 08 12 12 10 10 uw on of 06 o DA OF 03 ee 00 44 03 1 009 1 044 1 099 1 004 10 1 089 1 099 1030 1060 Lon 1 080 Law 1 100 1110 Werder h Caen Vaselengih Quer NB 1 19 NO 121 12 T Ad T rr T T 12 T a Y APP T hd T y 10 10 e 08 oe 08 ou DA oz 08 oo oo Ar AA AAA A oz SS A A Lie 1 1
4. 1 For NB_3 21 amp NB_3 28 non chopping observations with this mode the minimum DIT is 0 3447s ISAAC User Manual VLT MAN ESO 14100 0841 11 3 Observing in the NIR 3 1 Atmospheric Transmission The transmission of the Earth s atmosphere from 0 8 to 5 1 um is shown in Figures 3 and 4 and overplotted are the transmission curves of most of the filters available in ISAAC The J H K L and M bands correspond to the main transmission windows All bands particularly J L and M are also affected by atmospheric absorption within the band The amount of telluric absorption varies with zenith distance and the amount of precipitable water vapour PWV 3 2 Background Emission There are two regimes in the sky background emission Below 2 2 wm the sky emission is dominated by OH emission taking place at an altitude of 80 km Detailed sky spectra with OH line identifications are available on the http www eso org sci facilities paranal instruments isaac Beyond 2 24m the thermal background dominates The thermal background consists of at mospheric and telescope emission An overall telescope emissivity of 17 has been recently measured Between the OH lines in J and H the background is very low and has been measured to be 0 1 to 0 15 e s during dark conditions It is a sensitive function of the Moon phase and the distance to the Moon Even with DIT values of 900s the performance in MR spectroscopy is limited by the reado
5. 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 13000 14000 15000 16000 7000 6000 1000 2000 3000 4000 5000 6000 8000 10000 7000 1000 2000 3000 4000 5000 6000 10000 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000 26000 28000 30000 32000 14000 12000 2000 4000 6000 8000 10000 12000 16000 20000 14000 2000 4000 6000 8000 10000 12000 20000 Execution time s 20 37 42 81 112 109 139 174 216 377 431 495 501 562 636 642 143 114 20 29 42 61 84 112 183 374 143 12 31 47 67 92 122 270 300 Data cube Size Mb 4 1 8 2 12 3 16 4 20 5 24 6 28 7 32 8 36 9 41 0 53 3 57 4 61 5 65 6 28 7 24 6 4 1 8 2 12 3 16 4 20 5 24 6 32 8 41 0 28 7 16 4 32 8 49 2 65 6 82 0 98 4 163 9 Table 28 FastJitter mode technical info Note that the reported execution times are just indicative and may vary depending on the net connection Window Size pxs 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 64x64 128x128 256x256 DIT ms 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12 14 37 NDIT N Frames 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 13000 14000 15000 16000 20000 32000 16000 4000 1000 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 13000 14000 15000 16000 20000 32000 16000 4000 1000
6. ISAAC User Manual VLT MAN ESO 14100 0841 86 Note 2 OB requirements Finding charts OBs making use of the acquisition template ISAAC_img_acq_Preset do not need an attached finding chart It will be responsibility of the user to double check his her coordinates A 11 6 ISAACLW spec_obs AutoNodOnSlit This template works in an identical manner to ISAACSW_spec_obs AutoNodOnSlit Please refer to Sec A 8 1 for a description of what the template does This mode is available for MR spectroscopy only Table 62 Parameters of ISAACLW_spec_obs_AutoNodOnS1lit P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of sub integrations Jitter Box Width SEQ JITTER WIDTH Jitter box width arcsec Return to Origin SEQ RETURN T Return to Origin flag Nod Throw Along Slit SEQ NODTHROW Throw of the nod arcsec Number of AB or BA cycles SEQ NABCYCLES Number of AB or BA cycles NINT SEQ NINT Number of frames at each position Instrument Mode INS MODE Instrument Mode Slit INS SLIT Which slit e g slit_1 Central Wavelength microns INS GRAT WLEN Central Wavelength microns A 11 7 ISAACLW spec_obs GenericOffset This template works in an identical manner to ISAACSW_spec_obs GenericOffset Please refer to Sec A 8 2 for a description of what the template does This mode is available for MR spectroscopy only Table 63 Parameters of ISAACLW_spec_obs Generic
7. 49 A 3 Chopping conventions and definitions ee o 49 AA Offset conventions and definitions 2 25 ee bbe ee eee ee be ee 50 AD PUSUSMES lt lt ke CA RE HE AA ORG wR Ew ROS 51 AO Haw i Acquisition Templates c se paa se 24426 Oa kG ea dG es 53 AGI Introduction AN 53 A G2 ISAC ing acq Preset o a wwe a e AR ES 53 A 6 3 ISAACSW_img acq Presetrrm aoaaa 54 A 6 4 ISAACSW_img_acqMoveToPixel oaaae 54 AOS ISAACSW img acq MoveToSlit s lt ssa 48 eee oe catan is 56 A 6 6 ISAACSW_img acqMoveToSlitrrm lt 55 4442 a 56 A 6 7 ISAACSWime acq Polarimetry aoaaa lt o 57 AT Hae Imaging Templates osos ARA RE C4 58 Act ISAACSW Img obs AUMOJ BREL ocioso ebd eee bees 58 A 7 2 ISAACSW_img obsAutoJitter0ffset cria a4 oe bay ox 60 A 7 3 ISAACSW_img_obs_FixedSkyOffset 2 62 A 7A ISAACSW img obs GenericDffset 1 bbe ee ee errauts 64 ATO ISAACSW_ime obs Polarimetry lt e 24654454556 e be bee es 66 A 7 6 ISAACSW_img_cal_GenericOffset o o 67 ATIT ISAACS WN imp cal Polarimetry lt 4 244220465444 444 04 67 A 8 Hawaii Spectroscopy templates o oo a e a 69 A S ISAACSW spec obs AutoNodOnSlit gt o sss so cere a ee 69 A 8 2 ISAACSW_spec_obs GenericOffset aaau aa 71 A 8 3 ISAACSW_spec_cal_AutoNodOnSlit amp ISAACSW_spec_cal_GenericOffset 72 ABA ISAACSW spec cal WiehtCslth lt ance a cessa teadid orad is 72 A 9 Aladdin acqu
8. Chopping and Nodding The Aladdin templates are divided into those that use chopping LW and those that do not SW amp LW Chopping can be used for all LW observations gt 3um It is the only mode of operations for imaging in L and M and LR spectroscopy The Aladdin templates that use chopping are listed in Table 52 Table 52 Aladdin templates that use chopping P2PP Template Name ISAACLW_img_obs_AutoChopNod ISAACLW_spec_obs_AutoChopNod ISAACLW_img_cal_AutoChopNod ISAACLW_spec_cal_AutoChopNod If an observation is done with chopping then the calibration should be done with chopping as well Do not mix observing templates that use chopping with calibration templates that don t and vice versa Chopping is always combined with telescope nodding This is illustrated on figure 18 orion i Figure 18 Combination of chopping and nodding in the opposite direction On the left is a schematic of a chopped image so called position A with one star image positive in white and one star image negative in black The chop throw is assumed here to be smaller than the field size In the central figure the telescope has been nodded to the B position in the opposite direction of the chop There are background residuals on both A and B chopped images Subtracting the B from A right image provides an image free of background residuals with a central positive image twice as bright as the 2 negative image
9. Detector Integration Time secs Observation Category SEQ CATG SCIENCE Observation category science or preimaging Jitter Box Width SEQ JITTER WIDTH Random offset box width arcsec Return to Origin SEQ RETURN T Return to Origin Sky Offset Throw SEQ SKYTHROW Sky Throw arcsec Rotate Pupil SEQ ROTPUPIL T Pupil rotation compensation Number of AB or BA cycles SEQ NABCYCLES Number of AB or BA cycles NDIT for the OBJECT positions SEQ NDIT OBJECT NDIT used on OBJECT positions NDIT for the SKY positions SEQ NDIT SKY NDIT used on SKY positions SW Filter wheel 1 INS FILT1 NAME Filter name in wheel 1 SW Filter wheel 2 INS FILT2 NAME Filter name in wheel 2 Figure A 7 2 illustrates what the template does By default there is no telescope offset before the first exposure If the parameter Return to Origin 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 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 The template provides the possibility of rotating the instrument between object and sky frames so that pupil ghosts can be minimised all object frames have the same position angle on sky The technique has proved to be efficient with SOFT It is
10. in the Burst FastJitter Sec 83 1 Nov 23 2008 A 6 A 9 remove add vel parameters 83 2 Nov 23 2008 A 6 A 9 added paragraph on target parameter section 84 0 Feb 26 2009 all changed all references to location UT1 UT3 changed all web links to match the pages in the new ESO web structure 84 1 Jul 07 2009 12 2 Calibration plan of burst fast jitter changed 85 0 Nov 25 2009 all minor corrections 85 1 Dec 11 2009 12 1 A 11 5 added comments about jitter 0 for burst 86 0 March 06 2010 none only change of version number for P86 87 0 August 26 2010 none only change of version number for P87 88 0 March 2011 none only change of version number for P88 88 1 May 27 2011 minor changes to comply with EVM changes minimum time between off sets changed to 30s 89 0 Aug 12 2011 major overhaul of the manual with huge input from Monika Petr Gotzens 90 0 Feb 22 2012 none only change of version number for P90 ISAAC User Manual VLT MAN ESO 14100 0841 This page was intentionally left blank ISAAC User Manual VLT MAN ESO 14100 0841 v Acknowledgements This manual had been first drafted and written by J G Cuby and C Lidman who worked in the commissioning of the instrument defining most of the current procedures and operations They deserve the merit of the authorship Successive Instrument Scientists R Johnson A O Jaunsen E Mason and V Ivanov also significantly contributed to the improvement of
11. scription of the mode The mode has been originally implemented for lunar occultations LOs which are short and time critical events We also created an acquisition template which is particularly suitable to LO observations This template ISAACLW_img_acq_FastPhot can be used only in combination with the observing template ISAACLW_img_obs_FastPhot On the other hand the observing template ISAACLW img obs FastPhot can be alternatively combined with any of the other LW imaging acquisition templates in no chopping mode i e ISAACLW_img_acq_Preset and ISAACLW_img_acq _MoveToPixNoChop as needed ISAAC User Manual VLT MAN ESO 14100 0841 24 The ISAACLW_img_acq_FastPhot template minimises the time for the target acquisition by skipping active optics corrections good image quality is not critical to LO observations It is suitable for the acquisition of very bright targets as it allows the use of the windowed detector The user is recommended to provide accurate and correct target coordinates as the template though allowing to refine the centring of the target will not allow to check the field of view particularly in the case of a very small window The Finding Chart is not required for this specific template See Section A 9 6 for a description of the template parameters 5 4 Maximum Brightness of Observable Targets Direct imaging of very bright objects in the Hawaii arm results in residual flux that can last up to several hours due to
12. should they need it Note that starting from period 78 the time for such an observation will be charged to the user The stars are generally chosen from the Hipparcos catalogue and are either hot stars spectral type BOV to B4V or solar type stars spectral types GOV to G4V These calibrations are taken so that telluric features can be removed from science spectra They can also be used for flux calibration with a relative accuracy of 5 10 and an absolute accuracy of 5 20 A detailed discussion on this topic is given in Sec 3 4 Should users need more accurate results or require telluric standards of a particular spectral type they should provide the corresponding OBs and detailed instructions The spectroscopic standard star templates e g _cal_ must be used to prepare these OBs In this case the time executing the OBs will be charged to the user and the observatory will not observe a separate telluric standard ISAAC User Manual VLT MAN ESO 14100 0841 43 e Darks Darks are taken at the end of each night with the DIT values and readout mode used during the night e Spectroscopic Flats corresponding to the set ups used during the night are taken by the operation staff the next day e LR arcs LR arcs are taken in the L band In M it is not possible to take arcs with the grating in the 1st order so they are taken with the grating in 3rd order However the accuracy is poorer than using the telluric features imprinted on the scienc
13. the observation type can be defined for each image and is entered as a list in the parameter Obs Type 0 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 ISAAC User Manual VLT MAN ESO 14100 0841 65 ISAACSW_img_obs_GenericOffset 1024 1024 Position Angle Sky 30 Ts N Template Parameters Number of exposures 8 Obs Type D List of Offsets in X or RA 07 50 7 5 0 0 7 5 List of Offsets in Y or DEC 0045 0 45 45 0 45 Offset Coordinates SKY ISAAC field of view 1 1 Figure 14 Illustration of the ISAACSW_img obs GenericOffset template The black dots represent the position of a star which was originally at the centre of the field In this example Offset Coordinates is set to SKY and the telescope is moved in RA and DEC according to the list of offsets the stars move in the opposite direction The total number of exposures is defined in the parameter Number of Exposures 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 goo
14. 1 3 NB 2 34 CO 2 34 0 03 1 3 Filters available with the Aladdin J Block Same as Hawaii blocking filter with mean transmission of 75 H Same as Hawaii Ks Same as Hawaii Hl The central wavelength varies slightly across the field of view 21 This filter is primarily used as an order sorting filter however it can be used for imaging as well B This filter has leaks in the K band and the atmosphere defines the red edge of the filter For accurate photometry the Js filter is recommended 4 The narrow band 1 06m and 1 19pm filters correspond to regions of low OH emission and therefore enhanced sensitivity 5 The blocking filter is to prevent red leaks Table 3 LW Imaging filters See appendix B for the filter curves Name Line Central wavelength um Width um Width LEI 3 78 0 58 15 NBM 4 66 0 10 2 NB 3 21 3 21 0 05 1 6 NB 3 28 PAH 3 28 0 05 1 6 NB 3 80 3 80 0 06 1 6 NB 4 07 Bra 4 07 0 07 1 7 H the central wavelength varies slightly across the field of view 2 the ESO L filter is centred at 3 8m and is closer to L filter Bessell and Brett 1988 than it is to the original Johnson L filter ISAAC User Manual VLT MAN ESO 14100 0841 5 Table 4 ISAAC Spectroscopic Modes H Mode Array Spectral Range Pixel Scale Resolution for arcsec 1 arcsec slit SWSI1 LR Hawaii 0 98 2 5 ym 0 147 500 SWS1 MR Hawaii 0 98 2 5 ym 0 147 3000 LWS3 LR Aladdin 3 0 5 1 pm 0 147 400 LWS3
15. 135 Q i 0 1 90 U i 45 i 135 where a is the intensity of the source which transmits light that is polarised at angle a We have assumed that the rotator is at a position angle of O degrees for the first measurement This need not be the case The degree of polarisation and the polarisation angle are given by p VU Alda U 0 0 5 tan Q To derive the correct value of 0 attention needs to be paid to the signs of U and Q This algorithm neglects instrumental polarisation Preliminary measurements with ISAAC indicate that the instrument polarisation is 1 5 As this is partially caused by the tertiary mirror the vector defining the instrument induced polarisation will rotate relative to the sky A method to eliminate the instrumental polarisation is outlined by Sperello di Serego Alighieri 1989 Proceedings of 1st ESO ST ECF Data Analysis Workshop Table 7 shows the main characteristics of the Polarimetric Mode of ISAAC The filters available in the Polarimetric Mode are a subset of the filters available in imaging the Wollaston prism is on one of the two filter wheels making the filters on this wheel unavailable Available filters in SWP1 mode are listed in table 8 ISAAC User Manual VLT MAN ESO 14100 0841 8 Table 8 SW Polarimetry filters See appendix B for the filter curves Name Central wavelength um Width um Width szl 1 06 0 13 13 Js 1 24 0 16 13 Je 1 25 0 29 23 H 1 65 0 30 18
16. PARO ME Throw offset 0 OFFSET wollaston kls fe d Pos Angle offset o OFFSET ee DIT sec JG MASK s xo v OFFSET NDIT 5 XY via RTD ND Samples 2 Readout Mode Double Cor AMIE Matet Sidereal time 06 29 46 950 SETUP STOP MORE CANCEL SETUP DATA CANCEL Rotator on sky 4 Comments 4 ActionLog w w Disk Space w Exposure History OS SETUP finished 0 12 sec OS RIDDRAW command received l i OS SETUP function OCS RTD DRAW ST F 7 CLEAR OS RTDDRAW finished CANCEL Figure 5 OS Graphical User Interface Left panel instrument control Middle panel detector control Right panel telescope control 5 2 The Real Time Display RTD The Real Time Display is central to observing with ISAAC Like a video camera every frame taken by the detector is continuously displayed on the RTD It is important to realise that the continuous display of images on the RTD is not related to saving the data to disk An image is stored to disk only if the adequate action is taken to do so i e when a Start Exposure is sent This is what the templates do The RTD provides a number of tools for measuring statistics measuring the position and FWHM of objects in the field and for storing an image to be subtracted from incoming ISAAC User Manual VLT MAN ESO 14100 0
17. SW filters than in the LW filters If the ISAACLW_img_acq MoveToSlit acquisition template is used then chopping is set by default even if SW filters are used during the acquisition A defect on the objective in the Aladdin arm produces a patch of lower counts in the bottom left quadrant of the array In order to avoid the subsequent spectra being at the same position on the array as this patch objects are acquired 150 pixels away from the centre of the slit 5 3 4 Rapid Response Mode RRM The rapid response mode RRM offered since P74 allows approved RRM programs to au tomatically trigger target of opportunity ToO observations Please see http www eso org sci observing phase2 RRMObservation html for more in formation about RRM To facilitate the RRM two acquisition templates are provided ISAACSW_img_acq Presetrrm and ISAACSW_img_acq MoveToSlitrrm It is required that any RRM OB contains one of these acquisition templates The templates are essentially identical to the ISAACSW_img acq Preset and ISAACSW_img acq MoveToSlit templates but contain fewer parameters See Section 5 4 for brightness limits applied to RRM observations 5 3 5 Burst mode and Lunar occultation Since P79 we offer an observing mode capable to deliver ultra fast photometry down to the order of a few millisecond for short time intervals See Section 12 or the link http www eso org sci facilities paranal instruments isaac tools burst_fastjitter html for a de
18. Seed eee ndar Ee ee RE Oe eS 9 Short Wavelength Spectroscopy 1 SWS1 DLL Characteristics lt lt o s kee wk we ee ke EEE a Se eee 92 Recommended DITs and NUITs 2 coso cies ew ae eee ee ee DE eS Oo Calibrahon PAn esco rre ease DERG eRe Ed ewe Ba os We PIPE os cs oe RR A AS ARA A ee ee 95 Performante 2 2 4 4 484462483 eee A OR RES REESE EES 10 Long Wavelength Spectroscopy 3 LWS3 ID teres ee BROKE dara 10 2 Recommended DiTs and NDITs 2 22 4 44424 4408 ba wpe ea eee 10 39 Calibration Plame corces Ope be ek we Eee eR EE ORE Re eR 10A Pipeline cs ee ee g Cee OR Eye Oe ee Ob ee Oh BE Eo A AMA 11 Short Wavelength Polarimetry 1 SWP1 TI AAC e c s erais RR SA AR A OE Bo Bee we h 11 2 Recommended DITs and NOITes 4 4 224 be bee REE EERE EERE ES 113 Salat PIAR s coce cane m OR sia EE EER SEES EOE SHES LE III 115 Performance ceci ewe ee ewe eke ESS ee de ee oe 12 Aladdin Fast Photometry Burst and FastJitter modes IL Aer oc oh eee WA OSS Se OR EE eee a vill 27 28 28 30 35 35 35 35 36 36 37 37 37 37 37 38 39 39 39 40 41 41 42 42 42 42 43 43 44 44 44 44 44 44 45 ISAAC User Manual VLT MAN ESO 14100 0841 ix 1272 Corot Plan ocres DS RED SS ee eee eee Ss BS C4 46 T23 Pipelne e ea A A A a BeBe Bad wo 46 A Template description 48 A 1 General remarks and reminders how to avoid common sources of error 48 A 2 Orientation conventions and definitions o o e
19. and in particular have not clarified some issues regarding flat fielding and photometric accuracy For these reasons we strongly suggest that users carry out SW imaging observations with the Hawaii arm The main cause of concern for Aladdin JHK observations is the photometric accuracy In test observations we find a difference of up to 0 1 mag rms between Hawaii and Aladdin magnitudes of the same field The reason for this is unknown For JHK imaging with the Hawaii we achieve a photometric accuracy of 5 or better In addition the Aladdin array is intrinsically more non linear The Aladdin JHK images are more complicated to flat field because the flat field contains scattered light and also a central light concentration In some cases we have found that flat ISAAC User Manual VLT MAN ESO 14100 0841 4 Table 2 SW Imaging filters See appendix B for the filter curves Name Line Central wavelength um Width um Width Filters available with the Hawaii sz 1 06 0 13 13 Js 1 24 0 16 13 Jl 1 25 0 29 23 H 1 65 0 30 18 Ks 2 16 0 27 13 NB 1 0611 1 06 0 01 94 NB 1 08 He I 1 08 0 016 1 5 NB 1 191 1 19 0 01 0 8 NB 1 21 1 21 0 018 15 NB 1 26 Fe II 1 26 0 019 1 5 NB 1 28 PG 1 28 0 019 1 5 NB 1 64 Fe II 1 64 0 025 1 5 NB 1 71 1 71 0 026 1 5 NB 2 07 He I 2 07 0 026 1 5 NB 2 09 2 09 0 02 1 0 NB 2 13 H2 S1 2 13 0 028 1 3 NB 2 17 Bry 2 17 0 028 1 3 NB 2 19 2 19 0 03 1 3 NB 2 25 2 25 0 03 1 3 NB 2 29 2 29 0 03
20. angle beforehand There is no way of checking if the slit that is chosen in the acquisition template and the slit that will be used subsequently in the observation template are the same It is therefore of utmost importance that users ensure that they are identical Users should also ensure that the correct set of filters are used when acquiring bright targets See Section 5 4 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 reference objects 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 These offsets should not be confused with the Alpha offset arcsec and Delta offset arcsec offsets which are used to define a sky reference for the first telescope position in order to subtract a fixed pattern Table 34 Parameters of ISAACSW_img_acq MoveToSlit P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of DITs Alpha offset arcsec TEL TARG OFFSETALPHA 10 RA offset arcsec Delta offset arcsec TEL TARG OFFSETDELTA 10 DEC offset arcsec Angle on Sky deg TEL ROT OFFANGLE 0 Position angle DDD TTT Preset Telescope SEQ PRESET T Preset telescope Alpha offset from Ref Star SEQ REF OFFSETALPHA 0 Offset from Ref Star arcsec Delta offset f
21. arcs taken with the ISAACSW_spec_cal_NightCalib or ISAACLW _spec_cal NightCalib templates see Section 5 5 6 2 Overheads Since Period 65 overheads are charged to the users Special care should therefore be taken when estimating the overheads The execution time report produced by P2PP computes the overheads according to the rules given in this manual Users especially those in service mode should check it to make sure that the overheads have been taken into account Preset operations The overhead for preset and acquisition depends on the template as shown in Table 15 These times include the telescope preset closing the active optics loop and acquiring the target if necessary Hawaii overheads During the execution of an Observation Template most of the overheads come from frequent telescope offsets inherent to IR observations One should allow for approximately 15 seconds of time for the telescope to offset a few arcseconds and for the next exposure to start A strict minimum of 30s per telescope position including overheads is recommended in order to maintain image quality see Section 4 Another source of overheads is the detector read time which lasts approximately 2 3 4 1 seconds per DIT for Hawaii imaging observations and 4 0 7 6 seconds per DIT for Hawaii spectroscopic observations The overheads then depend on the nature of the observations In Ks imaging for instance DIT is typically 10s Assuming NDIT 6 the ela
22. e g photometric calibration In the Hawaii array the minimum DIT has alternated in the past between 3 55 and 1 77s This is due to changing the detector read speed to reduce the amplitude of the odd even column effect The current value of the minimum DIT in the Hawaii array can be found http www eso org sci facilities paranal instruments isaac tools oddevencol html For service mode observations with the Hawaii array the allowed minimum DIT is 3 55s Users requiring shorter DITs should consider using the Aladdin array see Section 2 2 1 Note that DIT NDIT are not template parameters for the LW templates where chopping is used They are hard coded in the templates Features ISAAC suffers from a number of features that are discussed in the ISAAC data reduction guide and in the ISAAC web pages Users are encouraged to consult these documents before submitting an ISAAC proposal and to assess carefully how these features may affect their scientific goals For example the Hawaii SW detector suffers from electrical ghosts along detector lines which are somehow proportional to the intensity integrated along the lines A procedure ghost to partially get rid of these features when reducing the data has been implemented in the http www eso org sci software eclipse data reduction package not longer supported Note that the new pipeline http www eso org sci software cpl1 esorex html does not offer any more such a recipe ISAAC
23. in Delta arcsec Rotate Pupil SEQ ROTPUPIL T Pupil rotation compensation Number of AB or BA cycles SEQ NABCYCLES Number of AB or BA cycles NDIT for the OBJECT positions SEQ NDIT OBJECT NDIT used on OBJECT positions NDIT for the SKY positions SEQ NDIT SKY NDIT used on SKY positions LW Filter wheel 1 INS FILT3 NAME Filter name in wheel 1 LW Filter wheel 2 INS FILT4 NAME Filter name in wheel 2 A 11 4 ISAACLW_img obs_GenericOffset This template works in an identical manner to ISAACSW_img_obs_GenericOffset Please refer to Sec A 7 4 for a description of what the template does This mode is available for imaging with the J Block H amp Ks broadband filters and 3 21 and 3 28 narrow band filters only A 11 5 ISAACLW_img obs_FastPhot This template allow Fast Photometry either in Burst or FastJitter mode In order to select one mode or the other the keyword DET BURST MODE should be set to T or F respectively For details about the difference between the two modes please refer to Section Other important keyword that need to be set in both modes are the detector windowing DET WIN NX and DET WIN NY the DIT and the NDIT parameters Note that the JITTER WIDTH parameter is ignored if BURST T For convenience please set it to 0 Random telescope offsets jitter will be executed only in FastJitter mode if the number ISAAC User Manual VLT MAN ESO 14100 0841 85 Table 60 Parameters of ISAACLW_img obs GenericOffset
24. make the best choice as this depends on the science users wish to do If you think that a specific spectral type suits your program better than others we recommend that you submit calibration OBs The observatory selects telluric standards from four catalogues the IRIS Photometric Stan dards the MSSSO photometric standards a composite list of bright spectroscopic standards and the Hipparcos Catalogue The majority of the standards come from the Hipparcos Cat alogue Although the Hipparcos Catalogue is an excellent source of telluric standards for ISAAC most of the stars in the catalogue do not have IR magnitudes which means that IR magnitudes have to be inferred from the spectral type Such an extrapolation leads to an uncertainty of 5 20 in the absolute flux calibration If users wish to have a more certain absolute flux calibration they should provide their own standards ISAAC User Manual VLT MAN ESO 14100 0841 14 For absolute calibration slit losses have to be estimated This is usually a difficult task as the spectroscopic standard which is usually the telluric standard and the program object may not be positioned at exactly the same place in the slit If the object is a point source it can be assumed that the slit losses for the standard and the program object are the same If the program object is not a point source the slit losses have to be estimated on the basis of its morphology If your observations need an estimate of
25. of filters are used when acquiring bright targets for SW spectroscopy See Section 5 4 Ensure that spectra do not overlap when offsetting the telescope or nodding the sec ondary In particular make sure that jitter width is smaller than the nod throw Observation templates that use chopping should only be calibrated with calibration templates that use chopping Likewise observation templates that do not use chopping should only be calibrated with calibration templates that do not use chopping For observations that use chopping the bias voltage of the array is set so that the well depth is large This leads to a very large number of hot pixels whose flux is changing on the timescale of a few seconds Thus it is very important in long exposures to set Jitter Box Width to some non zero value so that these hot pixels can be removed When doing a blind offset from a bright reference object to a faint target the co ordinates of the reference object are the ones that should go into the acquisition template Orientation conventions and definitions East is to the right X of the images for zero position angle North is to the bottom Y of the images for a zero position angle Position angle on sky This angle is measured in the standard way i e it is positive from North to East The slits are oriented along detector columns y axis on the figures In fact there is a small angle which ensures that night sky lines and arc lines are ver
26. secs NDIT DET NDIT Number of DITs Number of Exposures SEQ NEXPO Number of exposures Return to Origin SEQ RETURN X offset list arcsec SEQ OFFSETX LIST X offset list arcsec Y offset list arcsec SEQ OFFSETY LIST Y offset list arcsec SW Filter wheel 1 INS FILT1 NAME Filter wheel 1 SW Filter wheel 2 INS FILT2 NAME Filter wheel 2 Return to Origin Flag A 7 7 ISAACSW_img_cal Polarimetry This template is used for standard star observations in SW polarimetry It is strictly equivalent to the ISAACSW_img obs Polarimetry template with the only difference that some DPR key words in the FITS headers of the images are set to different values allowing pipeline processing and archiving The user is referred to the description of the ISAACSW_img_obs_Polarimetry template for the description of the parameters ISAAC User Manual VLT MAN ESO 14100 0841 68 Acquisition template Angle on Sky deg 45 PS N E Observation template parameters Number of exposures 9 X Offset List 1515150 15 1501515 Y Offset List 300030003000 Rotator Offset List 045 DO S N E E 24 20 Figure 15 Illustration of the ISAACSW_img obs Polarimetry template The rotator angle set in the acquisition image is 45 degrees The crosses represent the position of a star which was originally at the centre of the field With this sequence the entire field of view would be imaged first at position angle of 45 degr
27. the manual and ISAAC operations ISAAC User Manual VLT MAN ESO 14100 0841 This page was intentionally left blank vi ISAAC User Manual VLT MAN ESO 14100 0841 Contents 1 Introduction Aid 1 2 1 3 DA a ARA A ee ET ec et ek we Content of this manual es a s as eee we a RA Re e a CODIO os hoe Seah a ed a dra ada ad ra 2 ISAAC Infrared Spectrometer and Array Camera 2 1 22 2 3 2 4 2 9 Optical Layout lt cir tee Eee wy ES AAA a HES Ma we as a eR Ee ee Ewe oe we es 2 2 1 Comparison of JHK imaging in Hawaii and Aladdin arms Spectroscopic Modes s se e wao OR Se e Ree eee OS Palmer MAS et a eee a hee ae e eR ES Detectors and Acquisition System 2 2 000 eee ee eee 3 Observing in the NIR 3 1 3 2 3 3 3 4 3 0 4 1 4 2 Atmospheric Transmission 6G Ae ROR iaa eR Background Emission lt s s ses ps ee ew eh aS Oe HSE SR SE s TO ce ee ee eye ee Bee ee ee ee Hh ee Bee oe Be ee ee PURO o s s ch he EOE E RE HE eR BE BE Ee Bae Ea Influence of the Moom es sbros s sedis deora e hs eae ep head wa Observing at the VLT Viitor Mode Operations Y dvs ew a a A A A The Telescope A 5 Observing with ISAAC 5 1 5 2 5 3 5 4 5 9 5 6 5 7 Observation Software ch ek EER ER RELEASE REED EE EER ED The Real Time Display RID 44442444684 hoe ie SRE wR ES Target Acquisition lt lt he we Be bh OER RES ee ES Be Ok eR Sab DAS iy coce se be eee poe eee Ge See RSE EE OSE
28. the default configuration with ISAAC In addition the template provides the flexibility to adjust the number of NDIT subintegrations for the OBJECT and SKY frames NDIT for the OBJECT positions defines the number of subintegrations on the object and NDIT for the SKY positions defines the number of subintegrations 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 Number of AB or BA cycles 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 1 minute per telescope position rule means here that both DIT x NDIT for the OBJECT positions plus overheads and DITx NDIT for the SKY positions plus overheads shall each exceed one minute of time ISAAC User Manual VLT MAN ESO 14100 0841 61 ISAACSW_img_obs_AutoJitterOffset Sky positions Sky offset throw Template Parameters Obj ct positions Number of AB or BA cycles 3 Jitter box Width 40 Sky offset throw 250 Rotate Pupil F Figure 11 Illustration of the ISAACSW_img obs_AutoJitter0ffset template The black dots in the central square represent the position of a star which was originally at the centre of the field The other squares represent the position of the SKY frames ISAAC User Manual VLT MAN ESO 14100 0841 62 A 7 3 ISAACSW_img obs FixedSkyUOffset This template mo
29. transmission curves are overplotted The atmospheric spectrum is represented here with a FWHM of 8 A The atmospheric spectrum is a model corresponding to the typical situation at Paranal The Narrow Band Filters can be easily identified through the central wavelength of their response curves In green is part of the Z filter not offered since P70 in yellow the J filter in magenta the SH filter in blue the H filter in green the SK filter and in orange the Ks filter ISAAC User Manual VLT MAN ESO 14100 0841 17 a y f E S gt w gt gt i A a wi 18 mj o gt le C 1 i t m a SSS a IF a a is a 5 a a nN gt 4 w o 4 Pe i s W 3 z de Ss 2 T m T Ee Y 5 3 5 5 5 e 3 F xo o 4 E G E a E E em ES g gt amp o Y 2 mj Q 5 g E 2 nm 3 o o S i m a 2 m 4 4 o o re r 5 k WT 5 _ A t 4 A e A gt g m a lt nm lt N w a 4 f O 4 m9 e gt m lt MD E 4 2 Y ha u H EE EJE o Mm E oe ewe wees us vuran bLiob ost 7 S o 0 L oo 0 S o o UDISS USUDS LOIS US UDS UDJSSI USUD Figure 4 Atmospheric Transmission spectrum in the LW region Most of the LW filter transmission curves are overplotted The atmospheric spe
30. use chopping with calibra tion templates that do and vice versa A 11 1 ISAACLW_img obs_AutoJitter This template works in an identical manner to ISAACSW_img_obs_AutoJitter Please refer to Sec A 7 1 for a description of what the template does This mode is available for imaging with the J Block H amp Ks broadband filters and 3 21 and 3 28 narrow band filters only Table 57 Parameters of ISAACLW_img_ obs_AutoJitter P2PP label Keyword Default Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of sub integrations Observation Category SEQ CATG SCIENCE Observation category science or preimaging Number of Exposures SEQ NEXPO Number of exposures Jitter Box Width SEQ JITTER WIDTH Random offset box size arcsec Return to Origin SEQ RETURN T Return to Origin LW Filter wheel 1 INS FILT3 NAME Filter name in wheel 1 LW Filter wheel 2 INS FILT4 NAME Filter name in wheel 2 A 11 2 ISAACLW_img obs_AutoJitter0ffset This template works in an identical manner to ISAACSW_img_obs_AutoJitter0ffset Please refer to Sec A 7 2 for a description of what the template does This mode is available for imaging with the J Block H amp Ks broadband filters and 3 21 and 3 28 narrow band filters only ISAAC User Manual VLT MAN ESO 14100 0841 84 Table 58 Parameters of ISAACLW_img obs _AutoJitterOffset P2PP label Keyword Def Description DIT DET DIT Detector Integration Ti
31. 00 0841 2 2 ISAAC Infrared Spectrometer and Array Camera 2 1 Optical Layout Figure 1 shows the ISAAC optical layout Array detector Filter wheels Figure 1 ISAAC Optical Layout In imaging mode light enters the entrance window on the left hand side of the figure the slit is then out of the beam The Telescope Focal Plane is 80 mm behind the entrance window The Mode Selector Mirror M1 directs the light to the collimator and the collimated beam is sent to the M7 mirror which selects between the Hawaii SW and Aladdin mostly LW but also JHK imaging arms The collimated beam is then imaged onto the detector by the objective in place on the Hawaii or Aladdin arm There are two filter wheels just in front of the objective wheels ISAAC User Manual VLT MAN ESO 14100 0841 3 Table 1 ISAAC Imaging Modes Mode Array Spectral Range Pixel Scale Maximum Field Of View Detector Size arcsec arcsec pixels SWI Hawaii 0 98 2 5 um 0 1484 152 x 152 1024 x 1024 LWI3 3 Aladdin 1 1 5 1 pm 0 1478 151 x 151 1024 x 1024 LWI14l Aladdin 3 0 5 1 pm 0 0709 73 x 73 1024 x 1024 H LWI3 is used for J Block H Ks NB_3 21 and NB_3 28 imaging without chopping and for acquisition of LW spectroscopic targets 21 LWI4 is used for LW imaging with chopping L NB M NB_3 21 NB_3 28 NB_3 80 and NB_4 07 3 The LWI3 objective setup is used also by the FastPhot Burst and FastJitter modes which therefore ha
32. 74 Rapid Response Mode Real Time Display Son Of Isaac Short Wavelength Short Wavelength Imaging Short Wavelength Spectroscopy Short Wavelength Spectroscopy Low Resolution Short Wavelength Spectroscopy Medium Resolution Target of Opportunity Un Correlated Read Unit Telescope Very Large Telescope 95
33. 8 190 jae 114 140 122 a Vavelergih sen Varelengih um NB 1 20 NA 1 28 AA A A 1 134 130 138 Varelengih um NA 1 71 109 ae LB 106 108 158 1 7 1m 17 178 Wavalangih Con Warelengin um Figure 21 Narrow band filter curves 90 ISAAC User Manual VLT MAN ESO 14100 0841 NB 2 07 12 10 g g 2 g g zm em zu zw zw 210 ew ew Wervelengih een NB 2 13 12 10 o ou oo E g 2 206 208 210 212 ei 210 218 an Vavelergih an NB 2 19 12 10 b oe p g gt 212 2 14 216 218 120 ee am 246 Wavalergih am NB 2 29 14 10 E E p e lp p zm zw tx um zw 228 2m Woealengsn em xa 200 oa DA oo S r a gt te 20 on aos 208 2 10 ae 2M 216 Vaselengih ques NB 217 10 08 08 ot 08 oo 02 210 213 ald 216 aw an 22 an Varelengih um NH 225 10 os os n4 oz au 140 ae ee an a3 22 Warelergih um xa 24 os os ns oe oo 225 zw tm am om Warrlengihn Gum Figure 22 Narrow band filter curves 91 ISAAC User Manual VLT MAN ESO 14100 0841 Tremain Torem Toremain a2 222 224 23m 22m as as2 234 as Wovelertth ina or B4 1 as 06 6 8 E a4 a2 AY ra 0 0 hacia a sn Ao 3 3 70 3 75 3 80 L 90 3 95 o Wovelength m 205 4 4 05 41 415 42 Wassran ina or NBM 1 T T T T as aoe 04 02 o 45 4 55 46 465 47 475 48 Wonelertsh oricrors Figure 23 Narrow ban
34. 841 21 images This latter tool is referred to as store a fixed pattern and is very frequently used during acquisition quality control etc To center of slit TOSLIT Store FIXPAT SW FIXPAT On Off SW Rapid Frame Data Figure 6 Real Time Display 5 3 Target Acquisition 5 3 1 Imaging The pointing accuracy of the VLT is very good and usually a blind preset to the field is suffi cient in imaging the templates for the Hawaii and Aladdin arms are ISAACSW_img_acq Preset and ISAACLW_img_acq Preset respectively If users would like a finer pointing so as to posi tion an object in a particular region of the detector they should use ISAACSW_img_acq MoveToPixel for the Hawaii arm and ISAACLW_img_acq MoveToPixel if chopping or ISAACLW_img_acq MoveToPixNoChop non chopping for the Aladdin arm These templates provide interactive tools such as arrows to define telescope offsets see figure 6 Use of the finer pointing acquisition templates should be accompanied by precise instructions in the Phase 2 README file Observers in service mode shall provide together with their OBs all necessary information regarding the centring of the field if they have special requirements ISAAC User Manual VLT MAN ESO 14100 0841 22 5 3 2 SW Spectroscopy Blind centring of objects in the slits based on coordinates is not supported Neither the pointing accuracy of the telescope nor the coordinate accuracy of most targe
35. AC User Manual VLT MAN ESO 14100 0841 15 for MR and LR spectroscopy and has proved to be as accurate as using the arcs 3 5 Influence of the Moon The Moon is usually not a problem in the IR In Broad Band SW and LW imaging most of SW Narrow Band imaging LW Narrow Band imaging SWS LR spectroscopy LWS LR and LWS MR spectroscopy moonlight does not significantly affect the background There is therefore no point in requesting gray or dark time for programs that involve these modes However the moonlight contributes to the sky background when observing between the OH lines in J and H i e NB imaging in J in the low background NB filters NB 1 06 NB 1 19 and SWS MR spectroscopy in J and H Measurements done during an eclipse of the Moon showed that at more than 70 from the Moon the sky background remains approximately constant regardless of the phase Typically when ultimate performances are sought in MR spectroscopy below 2 0 um it is advisable to constrain the distance to the Moon to be above 50 70 while the Fractional Lunar Illumination can remain relatively unconstrained lt 0 7 ISAAC User Manual VLT MAN ESO 14100 0841 16 mm a w a o o o f ns o 3 gt gt E E an o an 5 5 9 a 5 ri ES S E a o E gt 09 bd Apo T M r v T IA A A s0 o UDISSIUSUDJ LOS JU DS Figure 3 Atmospheric Transmission spectrum in the SW region Most of the SW filter
36. EUROPEAN SOUTHERN OBSERVATORY Organisation Europ ene pour des Recherches Astronomiques dans l H misphere Austral Europ ische Organisation ftir astronomische Forschung in der s dlichen Hemisphare ESO European Southern Observatory Karl Schwarzschild Str 2 D 85748 Garching bei Miinchen Very Large Telescope Paranal Science Operations ISAAC User Manual Doc No VLT MAN ESO 14100 0841 Issue 90 0 Date 22 02 2012 L Schmidtobreick and the IOT Prepared L can ool nae ap aed ee deel y Ae Ge Bek e Sec Date Signature A Kaufer PROVE A A A iter ree RA Date Signature C Dumas o II OIR Date Signature ISAAC User Manual VLT MAN ESO 14100 0841 This page was intentionally left blank ISAAC User Manual VLT MAN ESO 14100 0841 111 Change Record Issue Rev Date Section Parag affected Reason Tnitiation Documents Remarks 75 Feb 15 2005 all Update for new web pages 76 Feb 27 2005 all Updated for P76 CfP 77 Sep 1 2005 all Updated for P77 CfP T7 Dec 1 2005 9 3 10 3 A 6 to A 11 Updated for P77 Phase 2 78 Jun 6 2006 9 2 A 7 A 10 and A 11 Updated for P78 Phase 2 79 Sep 9 2006 none Version changed to P79 79 Nov 30 2006 5 3 5 5 4 6 2 12 A 9 6 Included all info for the new observing A 11 5 plus many tables modes Fast Photometry 80 May 25 2007 A 11 5 Included details about the naming con ventions previously on the p2pp web page 81 Aug 30 2007 12 Reviewed Table 26 and added few notes
37. Eas eta o o ee bk kee eda es bade wee Ear ee saders Doas L See ye ho eee ee SEE ee ee we 5 3 4 Rapid Response Mode RRM o ooo 5 3 5 Burst mode and Lunar occultation o o Maximum Brightness of Observable Targets 5 4 1 SW Imaging Aladdin and Hawaii 046 54A2 SW Spectroscopy lt o ee rasp i pe eee Bee BEY Re RES Es DAS LW Imaging and Specirostopy o ece i sos pie a oh EE eS Night Flat telus sid ACS Yo arar ar a a a D CIO o s cots santue a AREA RA e Ee Calibration Plans o eoi ace ado a a iaa AAA vii Se ee o Nh MA A NN Wd 11 11 11 11 12 15 18 18 18 ISAAC User Manual VLT MAN ESO 14100 0841 DS PIDIE AAA 6 Template cookbook and overhead calculations 6 1 Templates General description and summary O2 Overheads s e aaa a ada L a A 7 Short Wavelength Imaging Hawaii SWI1 amp Aladdin LWI3 TL Characteristics cisco des ira we Eee EEE RES Fe Recommended DITS and NDITSs 464 6464 eis rr e eR oweED fe Cabhbraton PISE lt e ee sgo Eee GEER ERR EERE SE REE Te Pipe II To AO ee a we oe he Se G di ae ee a 8 Long Wavelength Imaging LWI3 and LWI4 EL CINACIOOSIS cos bMS ee OSE ERE AS ERE BS 8 2 Recommended DITs and NOITs gt re sd de Heike a a ES Oo Cabbration Plam lt sa ro s eb ro eae AE RR DES OR OOS BS Om Penne 224 44444 miches r edhe aa per aaa EDEL HERES EH 8 5D Performante s ssa lt 4 4 be Sete
38. INS FILT3 NAME Filter wheel 1 LW Filter wheel 2 INS FILT4 NAME Filter wheel 2 Slit INS SLIT Long Slit e g slit_1 i e using J Block H Ks NB_3 21 or NB_3 28 Acquisition using LW broad band filters is allowed however in this case the detector may have to be windowed down to a field of view of 1 arcmin to avoid saturation The template presets the telescope and allows the operator to interactively centre the field This template is functionally identical to the ISAACSW_img_acq MoveToPixel template so users should refer to Sec A 6 4 for details Table 49 Parameters of ISAACLW_img_acq MoveToPixNoChop P2PP label Keyword Default Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of DITs Alpha offset arcsec TEL TARG OFFSETALPHA 10 RA offset arcsec Delta offset arcsec TEL TARG OFFSETDELTA 10 DEC offset arcsec Angle on Sky deg TEL ROT OFFANGLE 0 Position angle DDD TTT Preset Telescope SEQ PRESET T Preset telescope LW Filter wheel 1 INS FILT3 NAME LW Filter wheel 1 LW Filter wheel 2 INS FILT4 NAME gt LW Filter wheel 2 A 9 6 ISAACLW_img_acq_FastPhot As specified in Section 5 3 5 the template can be used only in combination with the ISAA CLW_img obs FastPhot The acquisition is interactive as it allow the instrument operator to centre the target by applying small offsets The template however does not check nor wait for active optics or ONECAL correc
39. It is strictly equivalent to the ISAACLW_img_obs_AutoChopNod template with the only difference that some DPR keywords in the FITS header of the images are set to different values This allows pipeline processing archiving and quality control The user is referred to the description of the ISAACLW_img obs AutoChopNod template for the description of the parameters This template should not be used to calibrate observations that were taken with Aladdin templates that do not use chopping A 10 4 ISAACLW_spec_cal_AutoChopNod This template is used for standard star observations in spectroscopy It should only be used to calibrate observations that were taken with the Aladdin templates that use chopping It is strictly equivalent to the ISAACLW_spec_obs_AutoChopNod template with the only difference that some DPR keywords in the FITS header of the images are set to different values This allows pipeline processing archiving and quality control The user is referred to the description of the ISAACLW_spec_obs_AutoChopNod template for the description of the parameters This template must be used by users requesting calibrations beyond the ones provided by the Calibration Plan of this mode This template should not be used to calibrate observations that were taken with Aladdin templates that do not use chopping A 10 5 ISAACLW_spec_cal_NightCalib This template allows one to take night time calibrations right after any Aladdin spectroscopic template Se
40. Jitter0ffset ISAACLW_img_obs_GenericOffset ISAACLW_img_obs_FixedSky0ffset Fast Photometry J Block H Ks Burst or FastJitter ISAACLW_img_obs_FastPhot Spectroscopy Spectroscopy with chopping and nodding ISAACLW_spec_obs_AutoChopNod MR spectroscopy without chopping ISAACLW_spec_obs_AutoNodOnSlit ISAACLW_spec_obs_GenericOffset Standard Stars Standard Star imaging with chopping ISAACLW_img_cal_AutoChopNod Standard Star imaging without chopping ISAACLW_img_cal_GenericOffset Standard Star spectroscopy with chopping ISAACLW_spec_cal_AutoChopNod Standard Star spectroscopy without chopping ISAACLW_spec_cal_AutoNodOnSlit ISAACLW_spec_cal_GenericOffset Spectroscopic Night Time Calibration Night time flat fields and or arcs ISAACLW_spec_cal_NightCalib The allowed imaging acquisition templates for subsequent science observations have changed since P70 The sim ple preset ISAACLW_img_acq Preset can be used for any subsequent imaging observation The chopping preset ISAACLW_img_acq MoveToPixel can only be used for subsequent imaging observations with chopping and the non chopping preset ISAACLW_img_acq MoveToPixNoChop can only be used for subsequent imaging observations without chopping 6 Template cookbook and overhead calculations 6 1 Templates General description and summary The instrument detector and telescope are controlled by Observing Bloc
41. Keyword Def Description BURST DET BURST MODE T Toggle Burst mode DIT DET DIT Detector Integration Time secs List of NDIT SEQ NDIT LIST NDIT List WINX DET WIN NX 1024 number of column WINY DET WIN NY 1024 number of rows STARTY DET WIN STARTX 1 1024 first column of window STARTY DET WIN STARTY 1 1024 first row of window EVENT DATE EVENT DATE 0 UT date of event YYMMDD EVENT TIME EVENT TIME 0 UT time of event HHMMSS Number of Exposures SEQ NEXPO Number of exposures JITTERBOX JITTER WIDTH Jitter Box Width Return to Origin SEQ RETURN T Return to Origin Flag LW Filter wheel 1 INS FILT3 NAME Filter wheel 1 LW Filter wheel 2 INS FILT4 NAME Filter wheel 2 Note 1 OB Naming Convention e FastJitter OBs BURST F should start with the prefix FAST in their name e Burst OBs BURST T which do not make use of the EVENT keywords EVENT DATE 0 and EVENT TIME 0 should start with the prefix BURST in their name e Burst OBs BURST T which make use of the EVENT keywords EVENT DATE YYMMDD and EVENT TIME HHMMSS need to include the time at which the science template not the acquisition should start i e the UT time of the EVENT time minus half the total exposure time For example let s assume that you are exposing for 30 sec in total and let s assume that your event occurs at UT date YYMMDD and UT time HH MMSS then your OB name should include the following prefix BURSTUTYYMMDD HHMMss where ss 55 30 2 55 15
42. Ks 2 16 0 27 13 NB 1 0614 1 06 0 01 94 NB 1 1914 1 19 0 01 0 8 NB 2 09 2 09 0 02 1 0 NB 2 19 2 19 0 03 1 3 Hl The central wavelength varies slightly across the field of view 21 This filter is primarily used as an order sorting filter however it can be used for imaging as well B This filter has leaks in the K band and the atmosphere defines the red edge of the filter For accurate photometry the Js filter is recommended 4 The narrow band 1 06um and 1 19um filters correspond to regions of low OH emission and therefore enhanced sensitivity 2 5 Detectors and Acquisition System Characteristics The detectors are an Hawaii 1024 x 1024 array from Rockwell used for SW observations and a 1024 x 1024 Santa Barbara Research Center SBRC Aladdin array used mainly for LW observations but also for JHK imaging from P70 onward They are controlled by the ESO IRACE controller The main characteristics of the detectors are summarised in table 9 DIT and NDIT The IRACE controller controls the detector front end electronics and manages pre processing of the data before transferring it to the workstation The pre processor among other tasks averages the NDIT individual DIT integrations This significantly lowers the data rate between the IRACE controller and the instrument workstation were the images are finally stored on disk particularly for L band imaging where the DIT is only a hundred milliseconds Note that the number of counts in the im
43. LW Filter wheel 1 and LW Filter wheel 2 it is essential that at least one filter be set This includes acquisition templates e The slit that is chosen in the acquisition template and the slit that will be used subse quently in the observation template must be the same e If imaging and spectroscopic templates are combined in one OB it is required that the imaging template follows the spectroscopic template e It is possible to submit a single OB which comprises several observing descriptions for example to observe a single target with different filters e Night time calibration templates are not autonomous They must follow a spectroscopic observation Furthermore they only calibrate the wavelength setting that is used in the preceding template and not the wavelength settings in all preceding templates e Some targets we are asked to observe saturate the detectors with the minimum DIT Please pay close attention to source brightnesses to ensure that this does not happen e Use the verify button in P2PP this checks that individual parameters are within the defined ranges and also runs scripts to check the global logic of an OB e With the exception of standards the minimum amount of time between telescope offsets is 30 seconds ISAAC User Manual VLT MAN ESO 14100 0841 49 A 2 Remember that for short wavelength imaging objects brighter than 11th magnitude must be justified in the README file Ensure that the correct set
44. LW_spec_cal_AutoNodOnSlit amp ISAACLW spec_cal GenericOffset 87 A IL IOTSAACLN spec cal NightCalib ei oo ssaa hb see Ree eee 87 B Filter curves 88 C Standard stars 93 C1 SW Photometric Standards es cos rider eh ewe eS eee Sa Re ed 93 C2 OW Tellure Standards s s s ce ee eae bd aw oe ae RE eee eed ex 93 C 3 Bright standards for LW imaging and spectroscopy 93 D Acronyms 95 ISAAC User Manual VLT MAN ESO 14100 0841 1 1 Introduction 1 1 ISAAC ISAAC is an IR 1 5 um imager and spectrograph that is mounted at the Nasmyth A focus of UT3 Melipal Until P84 it was mounted at the Nasmith B focus of UT1 Antu ISAAC has two arms one equipped with a 1024 x1024 Hawaii Rockwell array and the other with a 1024 x 1024 InSb Aladdin array from Santa Barbara Research Center The Hawaii arm is used at short wavelengths 1 2 5 um Prior to P70 the Aladdin arm was used exclusively at long wavelengths 3 5 um From P70 onward this arm is also offered for JHK imaging ISAAC has several modes imaging and spectroscopy in both short wavelength SW and long wavelength LW FastPhot Burst and FastJitter imaging in LW only and imaging polarimetry in SW only All modes are offered for both Service and Visitor Programs Target acquisitions observations and calibrations are done via templates A number of calibrations are regularly performed by ESO for general use Calibration Plan Finally data reduction pipelines are av
45. Low and Medium Resolution LR and MR respectively spectroscopy 6 slits and order sorting filters for each spectroscopic band The main characteristics of the spectroscopic modes of ISAAC are summarised in table 4 Slits with widths ranging from 0 3 to 2 arcsec see table 5 are available The 0 8 slit has two defects on the slit which produce regions of reduced transmission in the spectra Figure 2 shows a plot of the transmission along the slit The two defects at 93 and 688 pixels from the bottom of the slit are clearly seen It is recommended that observers choose nod throws that avoid using these parts of the slit This limits the usable length of the 0 8 slit to 1 5 arcmin A calibration unit allows calibration lamps to be used for both wavelength calibration and flat fielding in spectroscopy only The lamps used for wavelength calibration are Xenon and Argon Special acquisition templates are used for the spectroscopic modes in order to ensure that objects are properly acquired in the slits The spectroscopic arm of ISAAC involves additional mirrors which cause the spatial axis the vertical one to be flipped with respect to imaging Table 6 shows the correspondence between wavelength range grating order filter and spectral ISAAC User Manual VLT MAN ESO 14100 0841 6 IA NN ingen mm N T W ih WP Wi rr Wii awh yw i in on 0 8 Transmiss 0 6 Figure 2 Transmission along 0 8
46. MR Aladdin 3 0 5 1 um 0 147 2500 1 See Sections 9 and 10 for more detailed information fielding can actually decrease the photometric accuracy of the observation Without illumi nation corrections the flat fielding accuracy is 23 improving to 1 5 with illumination corrections The corresponding values for the Hawaii are 22 without and 1 with illumi nation corrections Ks images taken with the Aladdin contain scattered LW light observed as circular arcs which is probably due to the open filter position which is immediately adjacent The scattered light is removed by normal IR sky subtraction techniques however sky subtraction is still better with the Hawaii The main advantage of JHK Aladdin observations is that they are much more efficient due to the negligible readout time This can mean a significant reduction in overheads for users with short DITs This also means that the minimum DIT is reduced compared to the Hawaii 0 3447s compared to 1 77 3 55 s The Aladdin arm also has higher throughput than the Hawaii arm in tests SW imaging with the Aladdin reached 0 15 mag fainter than with the Hawaii in the same exposure time In summary users who require very short integration times or who do not require such accu rate photometry may be interested in using the Aladdin arm for JHK observations however most users will probably want to use the Hawaii arm 2 3 Spectroscopic Modes ISAAC is equipped with 2 gratings for
47. OFFSETX LIST X offset list arcsec Y offset list arcsec Obs Type 0 or S SEQ SEQ OFFSETY LIST OBSTYPE LIST Y offset list arcsec List of observation types S or O Instrument Mode INS Slit INS Central Wavelength microns INS MODE SLIT GRAT WLEN Instrument Mode Long Slit Central Wavelength microns Figure 17 illustrates what the template does ISAACSW_spec_obs_GenericOffset 25 E OBJ N Position angle on the Sky 30 Isaac field of view 1 1 Figure 17 Slit broadened 1024 1024 Template Parameters Number of exposures 6 X offset list 00 60 0 60 0 Y offset list 0 40 0 90 0 30 Obs Type oossoo X Illustration of the ISAACSW_spec_obs_GenericOffset template The black dots represent the position of a star moved according to the lists of offsets in X and Y irrespective of the position angle on sky Telescope offsets are defined as lists with the X offset list arcsec and Y offset list arcsec parameters Telescope offsets are relative defined along detector lines X ISAAC User Manual VLT MAN ESO 14100 0841 72 and columns Y and are in arcsec Offsets in Y are along the slit offsets in X are perpen dicular to the slit 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 w
48. Offset P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of sub integrations Number of Exposures SEQ NEXPO Number of exposures Return to Origin SEQ RETURN T Return to Origin flag X offset list arcsec SEQ OFFSETX LIST X offset list arcsec Y offset list arcsec SEQ OFFSETY LIST Y offset list arcsec Obs Type 0 or S SEQ OBSTYPE LIST List of observation types S or O Instrument Mode INS MODE Instrument Mode Slit INS SLIT Long Slit Central Wavelength microns INS GRAT WLEN Central Wavelength microns A 11 8 ISAACLW img cal GenericOffset This template is used for standard star observations in imaging It should only be used to calibrate observations that were taken with the Aladdin templates that do not use chopping The template is very similar to ISAACLW_img_obs_GenericOffset with the difference that the offsets are defined in detector coordinates ISAAC User Manual VLT MAN ESO 14100 0841 87 Table 64 Parameters of ISAACLW_img cal GenericOffset P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT E Number of DITs Number of Exposures SEQ NEXPO Number of exposures Return to Origin SEQ RETURN X offset list arcsec SEQ OFFSETX LIST X offset list arcsec Y offset list arcsec SEQ OFFSETY LIST Y offset list arcsec LW Filter wheel 1 INS FILT3 NAME Filter wheel 1 L
49. Q JITTER WIDTH Random offset box size arcsec Return to Origin SEQ RETURN T Return to Origin Chop Throw arcsec SEQ CHOP THROW M2 Chop Throw arcsec ChopNod PARA of PERP to Slit SEQ CHOP SPEC Chopping along or perpendicular to slit Integration time minutes SEQ TIME Integration time minutes Instrument Mode INS MODE Instrument Mode Central Wavelength microns INS GRAT WLEN Central Wavelength microns Slit INS SLIT Which slit e g slit_1 The total integration time excluding overheads is defined in minutes In general the user will get slightly more or slightly less time that what was specified in the OB This is because the DIT is set so that the detector does not saturate the number of NDITs is set by the chopping frequency and the number of cycles is set so that approximately one minute is spent at each end of the nod To compute the actual integration time from the information provided in the FITS header you need to compute ISAAC User Manual VLT MAN ESO 14100 0841 82 DIT x NDIT x 2 x Number of cyclesx Number of AB or BA cyclesx 2 Note again that if chopping nodding is done in the direction perpendicular to the slit only half of this time will be spent on target A 10 3 ISAACLW_img cal_AutoChopNod This template is used for standard star observations in imaging It should only be used to calibrate observations that were taken with the Aladdin templates that use chopping
50. SKY positions SEQ NDIT SKY NDIT used on SKY positions SW Filter wheel 1 INS FILT1 NAME Filter name in wheel 1 SW Filter wheel 2 INS FILT2 NAME Filter name in wheel 2 Figure 12 illustrates what the template does By default there is no telescope offset before the first exposure If the parameter Return to Origin 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 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 The template provides the possibility of rotating the instrument between object and sky frames so that pupil ghosts can be minimised all object frames have the same position angle on sky The technique has proved to be efficient with SOFI It is the default configuration with ISAAC In addition the template provides the flexibility to adjust the number of NDIT subintegrations for the OBJECT and SKY frames NDIT for the OBJECT positions defines the number of subintegrations on the object and NDIT for the SKY positions defines the number of subintegrations 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 Number of AB or BA cycles Thus the to
51. SW_img_acq_Preset 6 times incl active optics ISAACSW_img_acq_Presetrrm 6 ISAACLW_img acq Preset 6 ISAACSW_img_acq_MoveToPixel 7 ISAACSW_img_acq_Polarimetry 7 ISAACLW_img_acq_MoveToPixNoChop 7 ISAACLW_img_acq MoveToPixel 7 5 ISAACLW_img acq FastPhot max depending on tel offset ISAACSW_img acq MoveToSlit 10 ISAACSW_img_acq MoveToSlitrrm 10 ISAACLW_img_acq_MoveToSlitNoChop 10 ISAACLW_img_acq MoveToSlit 10 Both Instrument Setup Spectroscopy 2 Average Both Instrument Setup Imaging 0 5 Average Both Instrument Setup per additional 1 Average after the 1st template in the same OB Both Telescope Offset 0 25 Average Hw imaging Detector readout per DIT 0 04 0 071 Approximately Al nochop imaging Detector readout per DIT Negligible Hw spectroscopy Detector readout per DIT 0 07 0 13 Approximately Al nochop spectroscopy Detector readout per DIT Negligible Al LW Imaging with chopping 40 Al LW Spectroscopy with chopping 30 Both Night time flat 4 For one on off pair Both Night time arc 3 For one on off pair T Depends on read speed see text 2 Global overheads in percent should be used for LW chopping observations time between two consecutive exposures is 0 4 x 150 15 75 seconds corresponding to overheads of about 25 Table 15 provides some generic values for the main operations involved during operations They should be used when computing the ISAAC overheads In the new Fast Photometry observi
52. T MAN ESO 14100 0841 51 direction All offsets are given in arcseconds even the offsets that are defined in detector coordinates Therefore an offset of 10 in X will move the object 10 arcsec to the right of the image Reminder the minimum time between telescope offsets is 30 seconds A 5 File names The names of the FITS files produced are fixed for each template and have names of the format ROOT _ nnmn ext fits where ROOT depends on the template used and is given in Table 29 nnnn is a 4 digit incremental number and ext is a possible extension e g CUBE1 for LW observations and SAMPLE or DIT for the Burst and FastJitter observations respectively Table 29 FITS files names Template ROOT ISAACSW_img_obs_AutoJitter ISAAC_SWLSCI ISAACSW_img_obs_AutoJitterOffset ISAACSW_img_obs_GenericOffset ISAACSW_img_obs_Polarimetry ISAAC_SWP_SCI ISAACSW_spec_obs_AutoNodOnSlit ISAAC_SWS_SCI ISAACSW_spec_obs_GenericOffset ISAACSW_img_cal_GenericOffset ISAAC SWLSTD ISAACSW_spec_cal_AutoNodOnSlit ISAAC_SWS_STD ISAACSW_img_cal_Polarimetry ISAAC_SWP_STD ISAACSW_spec_cal_NightCalib ISAAC_SWS_NIGHTCALIB ISAACLW_img_obs_AutoChopNod ISAAC_LWI_SCI ISAACLW_img_obs_AutoJitter ISAACLW_img_obs_AutoJitterUOffset ISAACLW_img_obs_GenericOffset ISAACLW_img_obs_FastPhot Burst mode ISAAC_LWI_SCI_nnnn_SAMPLE_ ISAACLW_img_obs_FastPhot FastJitter mode ISAAC_LWI_SCI_nnnn_DIT_ ISAACLW_spec_obs_AutoChopNo
53. T Number of DITs SW Filter wheel 1 INS FILT1 NAME Filter wheel 1 SW Filter wheel 2 INS FILT2 NAME Filter wheel 2 A 6 4 ISAACSW_img_acq_MoveToPixel This template presets the telescope and allows the operator to interactively centre the field In visitor mode the interactive part of the template will be executed by the instrument operator under the supervision of the visiting astronomer In service mode it is mandatory that users send detailed information for the field centring see Section 5 3 In general one should not put the object at the very centre of the array One should aim to place it a few tens of pixels away In order for objects to be clearly seen one fixed pattern image is acquired in an offset position defined by the Alpha offset arcsec and Delta offset arcsec parameters This image is then subtracted from all images that are subsequently displayed on the RTD The telescope first goes to the offset position the operator is prompted to store a fixed pattern and when stored the telescope moves to the preset position The image displayed on the RTD then displays an image of the field minus the fixed pattern The integration time for these acquisition images is defined by the DIT and NDIT parameters and should be set according to the guidelines discussed in section 7 At this point in time the user can change DIT and NDIT If the user changes these values the telescope offsets again and the user is required to stor
54. User Manual VLT MAN ESO 14100 0841 10 Table 9 ISAAC detectors Detector Format Pixel Size Q E RON Gain Well capacity pixels um e7 e7 ADU 7 Hawaii 1024 x 1024 18 5 0 65 10 4 6 200 000 Aladdin 1024 x 1024 27 0 8 40 7 8 DCR HB UCR 290 000 8 7 DCR LB 170 000 Table 10 ISAAC detector readout modes Instrument mode configuration Detector readout mode Hawaii Hawaii SW Imaging SWI1 Double Correlated DCR Hawaii SW Polarimetry SWP1 Double Correlated DCR Hawaii SW Spectroscopy SWS1 Non Destructive Read NDR Aladdin with chopping Aladdin LW Imaging LWI4 L M NB Uncorrelated UCR Aladdin LW Imaging LWI4 NB 3 21 3 28 3 80 4 07 Double Correlated High Bias DCR HB Aladdin LW Spectroscopy LWS3 MR and LR L band Double Correlated High Bias DCR HB Aladdin LW Spectroscopy LWS3 LR M band Uncorrelated UCR Aladdin without chopping Aladdin SW Imaging LWI3 J Block H Ks Double Correlated Low Bias DCR LB Aladdin FastPhot LWI3 J Block H Ks Double Correlated Low Bias DCR LB Aladdin LW Imaging LWI3 NB 3 21 NB 3 28 Double Correlated High Bias DCR HB Aladdin LW Spectroscopy LWS3 MR Double Correlated Low Bias DCR LB Table 11 Minimum DIT for the Hawaii and Aladdin Arrays Detector Readout Mode Minimum DIT s Hawaii SW DCR and NDR 1 77 3 55 Aladdin LW DCR LB 0 3447 Aladdin LW DCR HB 0 27711 Aladdin LW UCR 0 1073
55. W Filter wheel 2 INS FILT4 NAME Filter wheel 2 Return to Origin Flag A 11 9 ISAACLW_spec_cal_AutoNodOnSlit amp ISAACLW_spec_cal_GenericOffset These templates are used for standard star observations in spectroscopy They should only be used to calibrate observations that were taken with the Aladdin templates that do not use chopping They work in an identical manner to ISAACLW spec obs AutoNodOnSlit amp ISAACLW_spec_obs GenericOffset The only difference is that some keywords in the FITS headers are set to different values allowing pipeline processing and archiving These templates must be used by users requesting calibrations beyond the ones provided by the Calibration Plan of this mode A 11 10 ISAACLW_spec_cal_NightCalib This template allows one to take night time calibrations right after any Aladdin spectroscopic template See section 5 5 for more information regarding the need for night time calibrations This template is not autonomous It must follow a spectroscopic observation Furthermore it only calibrates the wavelength setting that is used in the preceding template and not the wavelength settings in all preceding templates Table 65 Parameters of ISAACLW_spec_cal_NightCalib P2PP label Keyword Def Description Exposure Name DET EXP NAME 1 Exposure Base filename Flatfield at end of template SEQ FLATFIELD T Night flat field at end of template Arc at end of template SEQ ARC F Night arc at end of template
56. W_img_obs_GenericOffset ISAACSW_img_obs_FixedSky0ffset Imaging requiring special telescope offset sequences ISAACSW_img_obs_GenericOffset Imaging Polarimetry ISAACSW_img_obs_Polarimetry Spectroscopy Spectroscopy of point like or moderately extended objects ISAACSW_spec_obs_AutoNodOnSlit Spectroscopy of extended objects i e wider than 1 arcminute or complex sequences of slit positions ISAACSW_spec_obs_GenericOffset Standard Stars Standard Star imaging ISAACSW_img_cal_GenericOffset Standard Star polarimetry ISAACSW_img_cal_Polarimetry Standard Star spectroscopy ISAACSW_spec_cal_AutoNodOnSlit ISAACSW_spec_cal_GenericOffset Spectroscopic Night Time Calibration Night time flat fields and or arcs ISAACSW_spec_cal_NightCalib ISAAC User Manual VLT MAN ESO 14100 0841 30 cover their needs they must contact the User Support Department usd helpleso org well before the observations start The template parameters are extensively described in appendix A for Phase II Preparation Note calibration templates dealing with darks flats and arcs are not available in the ISAAC Instrument Package for P2PP All such required calibrations are executed by the Operation Staff at the end of the night according to the setups that were used during the night The only calibrations that can be taken at night if desired are spectroscopic flat fields and
57. _spec_obs AutoNodOnSlit and ISAACSW_spec_obs GenericOffset templates in the definition of the parameters The user is referred to the description of these templates for the description of the parameters appendix A 8 1 amp A 8 2 These templates must be used by SWS1 MR and SWS1 LR users requesting cal ibrations beyond the ones provided by the Calibration Plan of this mode The differences with ISAACSW_spec_obs_AutoNodOnSlit amp ISAACSW_spec_obs_GenericOffset are 1 some DPR keywords in the FITS headers of the images are set to different values allowing pipeline processing and archiving 2 In the list of available slits Slit parameter a slitless slit can be selected for observation of the standard star in a slitless mode for absolute spectrophotometric cali bration Note that the Nod Throw Along Slit parameter when selecting the slitless must be lt 20 arcsec Note also that this particular slit is not offered in the list of available slits in the ISAACSW_img_acq MoveToSlit template Any slit can be defined for the acquisition when slitless is selected in the present template A 8 4 ISAACSW_spec_cal NightCalib This template allows one to take night time calibrations after the ISAACSW_spec_obs_AutoNodOnSlit ISAACSW_spec_obs GenericOffset and ISAACSW_spec_cal_AutoNodOnSlit templates See ISAAC User Manual VLT MAN ESO 14100 0841 73 section 5 5 for more information regarding the need for night time calibrations This te
58. ads is defined in minutes In general the user will get slightly more or slightly less time that what was specified in the OB This is because the DIT is set so that the detector does not saturate the number of NDITs is set by the chopping frequency and the number of cycles is set so that approximately one minute is spent at each end of the nod To compute the actual integration time from the information provided in the FITS header you need to compute DIT x NDIT x 2 x Number of cyclesx Number of AB or BA cyclesx 2 Depending on the chop throw and whether or not the object is within the field of view in both chop positions the total integration time on the object may be reduced by a factor 2 ISAAC User Manual VLT MAN ESO 14100 0841 81 A 10 2 ISAACLW spec_obs AutoChopNod This template combines chopping and telescope nodding The number of nodding cycles is referred to as the Number of AB or BA cycles and one cycle commonly called an AB or BA cycle consists of two exposures one at each end of the nod Additionally it is possible to jitter between ABBA cycles but not between AB or BA cycles The amount of jitter between ABBA cycles is defined by the Jitter Box Width parameter in arcseconds For the removal of hot pixels it is essential that Jitter Box Width be set to a non zero value Chopping and therefore nodding can be either along the slit or perpendicular to it ChopNod PARA of PERP to Slit parameter It is important to reali
59. ages always correspond to DIT not to the total integration time i e DIT x NDIT Readout Modes The offered readout modes with the Hawaii are Double Correlated Read DCR and Non Destructive Read NDR The offered readout modes with the Aladdin are Uncorrelated Read UCR Double Correlated Read with High Bias DCR HB and Double Correlated Read with Low Bias DCR LB DCR first resets the array and then performs two reads one at the beginning and one at the end after DIT seconds of integration The difference between these two reads is the image NDR first resets the array and then non destructively reads the array N 1 times during the DIT seconds of integration where N depends on the DIT and is set by the software Longer DITs will result in more reads For each pixel a line is fit to the N reads the first read is discarded and the slope of the fit gives the pixel value in the image The readout modes are not parameters defined by the users The readout mode is auto matically set according to the instrument mode Table 10 lists the detector modes that are ISAAC User Manual VLT MAN ESO 14100 0841 9 assigned to instrument modes configurations LW observation modes Chopping is the default mode of operation for LW observations it is not used for SW obser vations Chopping is achieved by synchronising the detector with the secondary mirror of the telescope M2 and by subtracting the images from the respective beams The resu
60. ailable for most modes of the instrument Important additional information to consult before preparing Phase I or Phase II proposals can be found at the following URLs e http www eso org sci facilities paranal instruments isaac e http www eso org sci observing proposals e http www eso org sci observing phase2 1 2 Content of this manual This User Manual is organised as follows Section 2 describes the optical layout the offered modes the detectors the control software and the templates of ISAAC Section 3 gives an overview of observing in IR Section 4 presents some general features of observing at the VLT and section 5 introduces observing with ISAAC Section 6 gives a cookbook of the ISAAC templates and has a discussion of overhead calcu lation Sections 7 to section 11 give details of the different ISAAC instrument modes Finally the appendices present a detailed description of the templates appendix A the filter curves appendix B and a list of acronyms appendix D The standard star lists previously in the appendices are now available at http www eso org sci facilities paranal instruments isaac tools 1 3 Contact Should you have any questions regarding the operation of ISAAC the point of contact is the User Support Department usd help eso org in Garching Questions related to the visitor mode VM observations should be addressed to the ISAAC team isaac eso org ISAAC User Manual VLT MAN ESO 141
61. aturation levels 5 7 Calibration Plans The calibrations that the observatory takes are discussed in detail in sections 7 to 11 Users are requested to read these sections carefully The time spent doing these calibrations is not charged to the user If the user wishes to do calibrations that are not specifically mentioned or if the user wishes to do calibrations in excess of those specified in the calibration plan then users must submit the OBs to do these calibrations together with precise instructions in the README file The time spent doing these calibrations will be charged to the user 5 8 Pipelines It is our long term aim to produce pipelines that reduce ISAAC data accurately At this point in time this is not the case and experienced observers will be able to do better than the pipeline Thus we recommend that users use pipeline products as a means of quickly assessing the data The pipeline recipes and their limitations are discussed in more detail in the http www eso org sci facilities paranal instruments isaac Documentation See Sections 7 to 11 for details of the pipelines associated with each template For the tem plates supported by the pipeline service observers will receive reduced data processed by the pipeline in Garching by the Quality Control Group Visitors will have direct access to the data processed automatically on line Note however that in the latter case the data are not calibrated e g flat fielded as the
62. bs_AutoNodOnSlit template The black dots represent the different positions of a star originally at the centre of the slit Note that the template starts with a telescope offset to move the star to one end of the nod along the slit The mean size of the nod is defined by parameter Nod Throw Along Slit in arcsec The first exposure A is taken after offsetting the object along the slit by EIA arcsec ISAAC User Manual VLT MAN ESO 14100 0841 70 NodThrowAlongS1it 2 The second exposure B is therefore arcsec 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 1 B EJ A es A es B es B 3 A 4 A e B e5 B e5 A where e are random offsets In general should be much smaller than the nod throw The random offsets are generated inside an interval defined by the parameter Jitter Box Width in arcsec Offsets are randomly distributed between e2 Boxeth and HSA It is strongly recommended to define some non zero value for the Jitter Box Width parameter as this allows one to get several images with the spectra lying at different po sitions on the detector However it should be smaller that the Nod Throw Along Slit otherwise spectra on either side of the throw could overlap To better exploit the jittering facility offered by t
63. bservations that use chopping DIT and NDIT are not parameters they are automatically set in the templates based on the instrument mode in use For non chopping observations the optimal DIT values are between 0 35 and 5 seconds NDIT should be set so that the total exposure at any one position is between one and a few minutes Users should note that some spectral regions in the M band will saturate the detector with the minimum integration time More detailed information is provided on the http www eso org sci facilities paranal instruments isaac 10 3 Calibration Plan For the LR grating only two grating settings that correspond to 3 55 and 4 75 um are supported Users should not use any other central wavelength in LR mode In LR mode telluric standards spectroscopic flats and arcs will only be taken at the supported wavelengths The calibrations provided according to the instrument calibration plan are the following e LR and MR Telluric Standard Stars according to the night time observations The tel luric standard is taken at similar airmass than the science observations the observatory guarantees that the airmass difference between the standard and science target is lt 0 2 airmasses The standard will be observed with the slit that was used during the obser vations Starting from period 77 we do not observe any more the telluric standard with the 2 slit Therefore the users should explicitly required it within their README files
64. circular arrow indicates the direction the field will rotate after a positive position angle is applied direction of the chop on the array depends on the position angle of the instrument on the sky Ifthe Chop Angle Coordinate is set to DETECTOR the chopping will be in detector coordinates The convention is that chopping will be along the X axis if Chop Position Angle is set to 0 and to the Yt axis if Chop Position Angle is set to 90 This is independent of the position angle of the instrument on the sky e Chop Angle Coordinate Either SKY or DETECTOR See figure 9 for an illustration of the chopping orientation conventions A 4 Offset conventions and definitions The templates make extensive use of telescope offsets In some templates the offsets are set automatically e g ISAACSW_img_obs_AutoJitter but in others the offsets have to be en tered 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 will result in a first image at initial position in RA telescope offset 10 arcsec East for the second telescope offset 10 arcsec West for the third image i e the telescope is back to the initial 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 ISAAC User Manual VL
65. cted slit In visitor mode the interactive part of the template will be executed by the night operator based on the indications provided by the user In service mode it is mandatory that the users send detailed information for centring the object into the slit The instrument mode for this template is LWI3 which is not an offered imaging mode Con sequently the detector may have to be windowed down to a field of view of 1 arcmin if the acquisition filter is either L or narrow band M Therefore acquisitions involving objects ISAAC User Manual VLT MAN ESO 14100 0841 76 separated by more than 1 arcmin should be acquired with either the narrow band LW or SW filters This template uses chopping All LW spectroscopic templates that use chopping should use this template The template can also be used for LW spectroscopic templates that do not use chopping although we recommend that the ISAACLW_ img _acq MoveToSlitNoChop template is used for acquiring such targets The chopping parameters to be defined are e Chop Throw arcsec This is the throw of the chopping in arcsec it is limited to the 10 30 arcsec range A chop throw of lt 20 arcsec is recommended e Number of Chop Cycles This is the number of chop cycles to be averaged in the acquisition system preprocessor The higher the value the better the detection limit but the longer the integration time One chop cycle will typically last 2 to 10 seconds of time depending o
66. ctrum is represented here with a FWHM of 2 5 The atmospheric spectrum is a model corresponding to the typical situation at Paranal The Narrow Band Filters can be easily identified through the central wavelength of their response curves In magenta is the SL filter the absorption dip at 3 1 um is not real in blue the L filter in yellow the M filter ISAAC User Manual VLT MAN ESO 14100 0841 18 4 Observing at the VLT 4 1 Visitor Mode Operations Visitors arrive on Paranal 2 days ahead of their observing run and receive support from Paranal Science Operations PSO to prepare their OBs Users are requested to read the P2PP and ISAAC User Manuals before arriving During the night users do not have direct interaction with the instrument and the telescope The execution of their OBs is undertaken by the Telescope Instrument Operator and or the nighttime support astronomer Visitors should be aware that at least part of the twilight will be used by the observatory ac cording to the instrument calibration plan This usually consists in twilight flat fields and low airmass SW photometric standards For spectroscopic observations in VM the observatory will not automatically take telluric standards although they are essential in removing telluric features and calibrating the data Visitors should think carefully about which telluric stan dards they should observe and observatory staff will help them make the right choice A brief overview of s
67. d ISAAC_LWS _SCI ISAACLW_spec_obs_AutoNodOnS1it ISAACLW_spec_obs_GenericOffset ISAACLW_img_cal_AutoChopNod ISAAC_LWI_STD ISAACLW_img_cal_GenericOffset ISAACLW_spec_cal_AutoChopNod ISAAC_LWS_STD ISAACLW_spec_cal_AutoNodOnSlit ISAACLW_spec_cal_NightCalib ISAAC_LWS_NIGHTCALIB ISAAC User Manual VLT MAN ESO 14100 0841 52 y y A A 1024 1024 1024 1024 Y Y N N AN 1 lt i ho L gt a Slit a Slit x 1 1 1 1 a b y y A A 10241024 1024 1024 It MN a Ma Slit Slit 1 1 LD c d Figure 9 Chopping orientation convention The star image in white is positive the star image in black is negative a 0 rotation on sky 0 chopping angle for SKY chopping coordinates or 90 chopping angle for DETECTOR coordinates b 0 rotation on sky 30 chopping angle for SKY chopping coordinates or 60 chopping angle for DETECTOR coordinates c 30 rotation on sky 0 chopping angle for SKY chopping coordinates or 60 chopping angle for DETECTOR coordinates d 30 rotation on sky 60 chopping angle for SKY chopping coordinates or 0 chopping angle for DETECTOR coordinates ISAAC User Manual VLT MAN ESO 14100 0841 93 A 6 Hawaii Acquisition Templates A 6 1 Introduction Telescope presets can only be done via acquisition templates Note however that as of version 2 12 of P2PP all information on the target coordinates additi
68. d filter curves 92 ISAAC User Manual VLT MAN ESO 14100 0841 93 C Standard stars See the http www eso org instruments isaac for a list of standard stars C 1 SW Photometric Standards Only stars fainter than K 12 mag should be used as standards to calibrate the broad band filters A number of stars in the JHK Persson and UKIRT fundamental and extended lists are suitable Note however that many stars in these lists are too bright and may saturate the detector especially when the seeing is good C 2 SW Telluric Standards Telluric standards are used to remove telluric absorption features In most cases they can also be used for flux calibration A more detailed discussion as to which stars are best to use is given in Sec 3 4 We prefer to use very hot stars earlier than type B4 or solar analogues The Hipparcos catalogue is an excellent source for such stars Many of the stars in the Hipparcos catalogue have IR magnitudes from either the 2MASS or DENIS IR surveys See also section C 3 for more star lists The optimal magnitude ranges for SW LR and MR spectroscopic standards are K 7 to K 9 and K 5 to K 7 respectively Stars brighter than this will saturate the detector C 3 Bright standards for LW imaging and spectroscopy This section mentions several standard star lists that can be used for LW observations either for imaging or for spectroscopy They can also be used for SW spectroscopy The optimal magnitude ranges fo
69. d 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 if the parameter Return to Origin is set to true T If not the telescope is not moved at the end of the template The total integration time is defined in seconds by NumberofExposures DIT x 5 NDIT i 1 where NDIT i are the elements of the List of NDIT ISAAC User Manual VLT MAN ESO 14100 0841 66 A 7 5 ISAACSW_img obs Polarimetry This template is used for imaging polarimetry Telescope offsets are defined with the parameters X offset list arcsec and Y offset list arcsec and are defined along detector rows and columns so that users can move the object easily along the strips of the polarimetric mask which are along detector columns A list of rotator offsets is defined with the parameter Rotator Offset list The rotator offsets are relative to the current rotator position All the spatial offsets are performed for each rotator offset At the end of the sequence of spatial offsets at one rotator position the telescope is returned to its original spatial position The parameter Number of Exposures gives the number of exposures at each rotator position The offsets in X offset list arcsec and Y offset list arcsec will be repeated un til SEQ NEXPO exposures have been taken Note that the telescope is only returned to its
70. data and these are the only calibrations provided by the observatory If the user needs a polarimetric standard he she must provide the OBs and the time will be charged to him her 11 4 Pipeline This mode is not supported by a pipeline 11 5 Performance This mode is not supported by an ETC However the performance can be confidently esti mated from the imaging case see section 7 by considering that the light from the object and from the sky is divided into two by the Wollaston To reach a given limiting magnitude in the background limited case therefore requires twice the time required in imaging ISAAC User Manual VLT MAN ESO 14100 0841 45 12 Aladdin Fast Photometry Burst and FastJitter modes Since Period 79 Fast Photometry imaging is offered which can be used in Burst or FastJitter mode It is intended for fast relative photometry from a few ms to a few tens of ms Origi nally implemented and tested for lunar occultations they are suitable for any fast variable phenomena where time resolution is a must 12 1 Characteristics Imaging is possible in three SW filters J Block H and Ks using the Aladdin array located in the ISAAC s LW arm Hardware windowing of the array allows very short DITs The Burst and FastJitter modes are offered both in VM and in SM However in the case of occultations only disappearances are offered in SM VM must be requested in the case of appearances The two modes differ only in the way a
71. e 3 SW Standard star in spectroscopy Template parameters Acquisition Template ISAACSW_img_acq MoveToSlit Observation Template ISAACSW_spec_cal_AutoNodOnSlit DIT 20 seconds NDIT 3 Number of AB or BA cycles 1 NINT 1 Return to Origin T Night time Calibration Template ISAACSW_spec_cal_NightCalib Flatfield at end of template T Arc at end of template T Execution time minutes Preset amp Acquisition 10 0 Instrument setup 2 0 int time detector overhead 0 33 0 13 x 3 NDIT x 2 1 AB cycle Telescope offsets 0 75 3 telescope offsets Flat field 4 Arc 3 Total 22 5 minutes for 2 minutes of integration Table 19 Overheads Example 4 SW Spectroscopy of fainter object Template parameters Acquisition Template ISAACSW_img_acq MoveToS1lit Observation Template ISAACSW_spec_obs_AutoNodOnSlit DIT 300 seconds NDIT 1 Number of AB or BA cycles 6 NINT 1 Return to Origin T Night time Calibration Template ISAACSW_spec_cal_NightCalib Flatfield at end of template T Arc at end of template F Execution time minutes Preset 10 0 Instrument setup 2 0 int time detector overhead 5 0 13 x 1 NDIT x 12 6 AB cycles Telescope offsets 0 25 x 8 8 offsets for 6 cycles Flat field 4 Total 79 5 minutes for 60 minutes of integration ISAAC User Manual VLT MAN ESO 14100 0841 33 Table 20 Overheads Example 5 LW Imaging with chopping L band Template parameter
72. e another fixed pattern before the telescope returns to the nominal position This loop can continue until the user has identified the target The observer is then prompted to define an offset This is simply done by drawing an arrow on the screen with the left hand button of the mouse At this point a window which lists the pixel co ordinates at the start and the end of the arrow will appear see figure 6 The user can either accept the offsets cancel or edit the co ordinates directly If the offsets are accepted the telescope offsets by the desired amount Finally the user is given the possibility to redraw the arrow for refining the position of the object if necessary Once the user is satisfied the template finishes If the Preset Telescope 7 parameter is set to F then the telescope will not move This can be useful in visitor mode to use the functionality of the template without presetting the telescope The interactive pop up windows are usually displayed before new images have arrived on the RTD Therefore users are strongly advised to carefully check that a new image has arrived before clicking on these windows e g for storing a fixed pattern for changing the DIT and NDIT The image displayed on RTD at the end of the template is dumped on disk ISAAC User Manual VLT MAN ESO 14100 0841 Table 33 Parameters of ISAACSW_img_acq MoveToPixel P2PP label Keyword Default Description DIT DET DIT Detec
73. e exposure which are ubiquitous in M band spectra e MR arcs Arcs corresponding to the setups used during a night are taken by the daytime astronomer during the following day As in LR arcs are taken with the grating in 1st order for L and with the grating in 3rd order for M Alternatively the ubiquitous telluric features can be used This has been tested for all spectroscopic modes and has proved to be as accurate as using the arcs e Star traces are taken every 3 6 months or after an instrument intervention to trace the spectra at different positions along the slit and provide the co ordinate transformation between imaging and spectroscopy They are archived for both the LR and MR modes 10 4 Pipeline All chopping and most non chopping templates are supported The GenericOffset templates are not supported 10 5 Performance The user should refer to the ETC for estimating the performance of this mode http www eso org observing etc ISAAC User Manual VLT MAN ESO 14100 0841 44 11 Short Wavelength Polarimetry 1 SWP1 11 1 Characteristics See Section 2 4 for a description of this mode 11 2 Recommended DITs and NDITs Since light is divided in two by the Wollaston prism the DIT values used in the SWI1 mode see Section 7 should be doubled 11 3 Calibration Plan This mode is only partly supported within the ISAAC Calibration Plan The normal twilight flat fields without the Wollaston can be used to flat field the
74. e section 5 5 for more information regarding the need for night time calibrations This template is not autonomous It must follow a spectroscopic observation Furthermore it only calibrates the wavelength setting that is used in the preceding template and not the wavelength settings in all preceding templates Table 55 Parameters of ISAACLW_spec_cal_NightCalib P2PP label Keyword Def Description Flatfield at end of template SEQ FLATFIELD T Night flat field at end of template Arc at end of template SEQ ARC F Night arc at end of template ISAAC User Manual VLT MAN ESO 14100 0841 83 A 11 Aladdin Observation and Calibration Templates Without chopping For some modes one can take data in the Aladdin arm without chopping These modes are broadband imaging with the J Block H amp Ks filters NB imaging with the NB 3 21 and NB 3 28 filters and MR spectroscopy at all wavelengths The Aladdin templates that do not use chopping are listed in Table 56 Table 56 Aladdin templates that do not use chopping P2PP Template Name ISAACLW_img_obs_AutoJitter ISAACLW_img_obs_AutoJitter0ffset ISAACLW_img_obs_FixedSky0ffset ISAACLW_img_obs_GenericOffset ISAACLW_spec_obs_AutoNodOnSlit ISAACLW_spec_obs_GenericOffset ISAACLW_img_cal_GenericOffset ISAACLW_spec_cal_AutoNodOnSlit If an observation is done without chopping then the calibration should also be done without chopping Do not mix observing templates that do not
75. ees and then with 90 degrees ISAAC User Manual VLT MAN ESO 14100 0841 69 A 8 Hawaii Spectroscopy templates A 8 1 ISAACSW_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 43 Parameters of ISAACSW_spec_obs AutoNodOnSlit P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of sub integrations Jitter Box Width SEQ JITTER WIDTH Jitter box width arcsec Return to Origin SEQ RETURN T Return to Origin flag Nod Throw Along Slit SEQ NODTHROW Throw of the nod arcsec Number of AB or BA cycles SEQ NABCYCLES Number of AB or BA cycles NINT SEQ NINT Number of frames at each position Instrument Mode INS MODE Instrument Mode Slit INS SLIT Which slit e g slit_1 Central Wavelength microns INS GRAT WLEN Central Wavelength microns Figure 16 illustrates what the template does ISAACSW_spec_obs_AutoNodOnslit 1024 1024 Position angle on sky 180 Jitter box A Template Parameters ae Nod throw Jitter box Width 20 Acquisition Nod Throw along Slit 70 position Number of AB or BA cycles 4 2 3 6 7 B ISAAC field of view Slit broadened 1 1 Figure 16 Illustration of the ISAACSW_spec_o
76. efining too wide a box may lead to poor image overlap Conversely too small a value may lead to poor sky subtraction near extended objects A value of 30 arcsec or less is adequate for empty fields The minimum value is set to 10 arcsec By construction there is no telescope offset before the first exposure If the parameter Return to Origin 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 Number of Exposures ISAAC User Manual VLT MAN ESO 14100 0841 60 A 7 2 ISAACSW_img obs AutoJitter0ffset This template moves the telescope alternatively between object and sky positions The object positions of the telescope are randomly distributed around the object initial telescope position and within a box whose dimensions are set by the parameter Jitter Box Width in arcsec The minimum value for this parameter is 10 arcsec The sky positions are at a constant distance defined by the parameter Sky Offset Throw from the original telescope position but at an angle randomly distributed between 0 and 360 degrees i e the sky exposures are distributed on a circle surrounding the initial telescope position Table 38 Parameters of ISAACSW_img obs _AutoJitterOffset P2PP label Keyword Def Description DIT DET DIT
77. eld Figure 15 illustrates what the template does Only the filters in filter wheel 1 are available for this template Table 41 Parameters of ISAACSW_img_obs_Polarimetry P2PP label Keyword Def Description DIT DET DIT a Detector Integration Time secs NDIT DET NDIT Number of sub integrations Number of Exposures SEQ NEXPO Number of exposures at each rotator position X offset list arcsec SEQ OFFSETX LIST X offset list arcsec Y offset list arcsec SEQ OFFSETX LIST Y offset list arcsec Rotator Offset list SEQ ROT OFFLIST 0 Rotator offset list degrees Return to original rotator position SEQ RETROTOFF T Return to original rotator position Flag SW Filter wheel 1 INS FILT1 NAME Filter name in wheel 1 The total integration time excluding overheads is defined in seconds by DIT x NDIT x Number of Exposuresx number of rotator offsets ISAAC User Manual VLT MAN ESO 14100 0841 67 A 7 6 ISAACSW_img cal GenericOffset This template is used for imaging standards and is similar to the ISAACSW_img_obs_GenericOffset template appendix A 7 4 with the difference that the offsets are defined in detector coordi nates This template should be used by all SWI1 users requesting calibrations beyond the ones provided by the Calibration Plan of this mode Table 42 Parameters of ISAACSW_img_cal_GenericOffset P2PP label Keyword Def Description DIT DET DIT Detector Integration Time
78. emplate e Chop Throw arcsec This is the chopping throw in arcsec it is limited to the 10 30 arcsec range However we strongly recommend that users limit the throw to 20 arcseconds or less e Chop Position Angle See section A 2 This parameter can be defined in either SKY or DETECTOR coordinates e Chop Nodding Coordinate Either SKY or DETECTOR Depending on which value is selected the chopping angle will be defined either on sky or relatively to the detectors rows and columns The nodding is slaved to the direction of the chopping If the parameter Return to Origin 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 Table 53 Parameters of ISAACLW_img_obs_AutoChopNod P2PP label Keyword Default Description Observation Category SEQ CATG SCIENCE Observation category science or preimaging Integration time minutes SEQ TIME Integration time minutes Jitter Box Width SEQ JITTER WIDTH Random offset box size arcsec Return to Origin SEQ RETURN T Return to Origin Chop Throw arcsec SEQ CHOP THROW M2 Chop Throw arcsec Chop Position Angle SEQ CHOP POSANG Chop Position angle deg Chop Nodding Coordinate SEQ CHOPNOD COORDS SKY or DETECTOR coordinates LW Filter wheel 1 INS FILT3 NAME e Filter wheel 1 LW Filter wheel 2 INS FILT4 NAME Filter wheel 2 The total integration time excluding overhe
79. entre 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 along 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 Along Slit 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 correspond to the product Number of AB or BA cycles x NINT x 2 The total integration time excluding overheads is defined in seconds by ISAAC User Manual VLT MAN ESO 14100 0841 71 DIT x NDIT x NINT x 2 x Number of AB or BA cycles A 8 2 ISAACSW_spec_obs_GenericOffset This template is for spectroscopy and has the flexibility to allow any sequence of telescope offsets It is essentially intended for programs requiring large offsets off the slit or slit scanning across one object Table 44 Parameters of ISAACSW_spec_obs_GenericOffset P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of sub integrations Number of Exposures SEQ NEXPO Number of exposures Return to Origin SEQ RETURN Return to Origin flag X offset list arcsec SEQ
80. er identification of the field these filters are not available for the subsequent observation templates 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 reference objects 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 At the end of the template the image displayed on the RTD consisting of Number of Chop Cycles chopped images is dumped on disk A 9 5 ISAACLW_img_acq MoveToPixNoChop The instrument mode for this template is LWI3 This template does not use chopping and can only be used to acquire targets for subsequent imaging observations that do not use chopping ISAAC User Manual VLT MAN ESO 14100 0841 77 Table 48 Parameters of ISAACLW_img_acq MoveToSlit P2PP label Keyword Default Description Preset Telescope SEQ PRESET T Preset telescope Chop Throw arcsec SEQ CHOP THROW M2 Chop Throw arcsec Number of Chop Cycles SEQ CHOP NCYCLES Number of chop cycles ChopNod PARA of PERP to Slit SEQ CHOP SPEC Chopping along or perpendicular to slit Alpha offset from Ref Star SEQ REF OFFSETALPHA 0 Offset from Ref Star arcsec Delta offset from Ref Star SEQ REF OFFSETDELTA 0 Offset from Ref Star arcsec Angle on Sky deg TEL ROT OFFANGLE 0 Position angle DDD TTT LW Filter wheel 1
81. for Burst mode executions black is for window 32x32 and DIT 3 2ms blue is for window 32x32 and DIT 5ms red is for window 64x64 and DIT 6 4ms Empty squares are for the FastJitter mode executions window 32x32 and DIT 12 ms ISAAC User Manual VLT MAN ESO 14100 0841 35 7 Short Wavelength Imaging Hawaii SWI1 amp Aladdin LWI3 7 1 Characteristics See Section 2 2 for a description of this mode JHK imaging is possible with the Aladdin as well as the Hawaii See section 2 2 1 for a comparison of these two modes For most users JHK imaging with the Hawaii will be superior 7 2 Recommended DITs and NDITs Table 23 gives some recommended values for DIT and NDITxDIT These values are a compro mise between being background limited and maximising efficiency while limiting the exposure level to below 10 000 5 000 ADU Hawaii Aladdin and not staring at the same position for too long It is important that the sky is sampled frequently and many times Users should rather observe too many sky frames than too few Exposure levels can be derived by using the http www eso org observing etc Table 23 Recommended DIT in seconds and NDIT ranges for mode SWI1 amp LWI3 J Js J Block H Ks NB filters in J NB filters in H and K DIT seconds 30 451 10 127 10 15 60 120 50 100 NDITx DIT seconds 60 180 60 120 60 120 180 300 120 300 1 For visitor mode programs the ranges for the Js and H filters are 30 60 and 10 15 seconds
82. ghter than 11th magnitude BB imaging or 8th magnitude NB imaging cannot be guaranteed in service mode and in shared visitor nights ESO reserves the right to lower the overall priority of the OB in question in service and not to execute the observations in shared visitor nights Imaging observations not compliant with these limits must be approved via submission of a http www eso org sci observing phase2 WaiverChanges html If the waiver is ap proved this should be stated in the README file along with an estimate of the brightest object in the field of view ESO will try to devise strategies so that the observations can be done for example scheduling the observations for the end of the night or scheduling other imaging OBs after the observations in question ISAAC User Manual VLT MAN ESO 14100 0841 25 5 4 2 SW Spectroscopy Table 12 indicates the filter settings that must be used when acquiring targets This depends on the brightness of the sources in the instrument field of view during a spectroscopic acquisition Note that this typically applies not only to standard stars but also to science fields when there are bright objects in the field of view Table 12 Acquisition filters versus object magnitude IR Magnitude Filters to use gt 11 Any gt 8 and lt 11 Any Narrow Band filter gt 6 and lt 8 Two close Narrow Band Filters on each filter wheel E g NB_2 19 on filter wheel 1 and NB_2 17 on filter wheel 2 lt 6 Two dis
83. his template it is also recommended to define Number of AB or BA cycles to some value higher than 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 At the end of the template the telescope returns to the original position if the parameter Return to Origin is set to true T If not the telescope is not moved at the end of the template Users of the SWS1 LR mode are requested to set the central wavelength to one of the following values 1 06 1 25 1 65 or 2 20 Other values are not supported by the calibration plan see section 9 The NINT parameter defines the number of frames stored per A or B position If e g DIT 120s NDIT 1 NINT 8 8 images will be stored for each position If in addition Number of AB or BA cycles is set to 2 the template will deliver in total 32 images 8 for the first A position 16 for the B position and 8 for the second A position The total integration time excluding overheads is 64 minutes Note in the case where there are several OBs using this template on the same target for several hours of integration on the same target it is recommended to modify the Nod Throw Along Slit parameter by a few arcseconds between each OB This is for the following reason the acquisition is always done at the same position on the array i e c
84. hould be obtained separately Important note We had reports of incorrect visible magnitudes in this list Users are encouraged to choose only standard stars for which the IR magnitude is available in the pho tometric band corresponding to their observations and not to rely on the visible magnitude The table will be corrected for the errors as time permits ISAAC User Manual VLT MAN ESO 14100 0841 D Acronyms ASM BB BOB CCD DCR DCR LB DCR HB DIT ETC GUI ISAAC LR LW LWI LWS LWS LR LWS MR MR NB NDIT NDR NINT NTT OB OS P2PP P70 P71 P72 P74 RRM RTD SOFI SW SWI SWS SWS LR SWS MR ToO UCR UT VLT Astronomical Site Monitor Broad Band Broker for Observation Blocks Charge Coupled Device Double Correlated Read Double Correlated Read Low Bias Double Correlated Read High Bias Detector Integration Time Exposure Time Calculator Graphical User Interface Infrared Spectrometer and Array Camera Low Resolution Long Wavelength Long Wavelength Imaging Long Wavelength Spectroscopy Long Wavelength Spectroscopy Low Resolution Long Wavelength Spectroscopy Medium Resolution Medium Resolution Narrow Band Number of Detector Integration Time Non Destructive Read Number of integrations New Technology Telescope Observation Block Observation Software Phase 2 Proposal Preparation ESO Observing Period 70 ESO Observing Period 71 ESO Observing Period 72 ESO Observing Period
85. ill instruct the operator to resume guiding If the guide star has changed during an offset the accuracy of the offset will be poorer than the offset 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 operator will make sure that the original guide star is reselected so that pointing accuracy is maintained while on the object Additionally the observation type can be defined for each image and entered as a list Obs Type 0 or S O stands for Object and assigns the DPR TYPE to OBJECT S stands for Sky and assigns the DPR TYPE header keyword to SKY This template allows slit scanning across an object by defining a list of offsets in the X direction At the end of the template the telescope returns to the original position if the parameter Return to Origin is set to true T If not the telescope is not moved at the end of the template 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 The total integration time excluding overheads is defined in seconds by DIT x NDIT x Number of Exposures A 8 3 ISAACSW_spec_cal_AutoNodOnSlit amp ISAACSW_spec_cal_GenericOffset These templates are used for standard star observations in spectroscopy at SW They are strictly equivalent to the ISAACSW
86. inally there is the possibility to redraw the arrow for refining the position of the object if necessary Once the user is satisfied the template finishes The Preset Telescope parameter if set to F allows to use the functionality of the template without presetting the telescope It is possible in this template to use the J Block H or Ks filters which are likely to allow an easier identification of the field these filters are not available for the subsequent observation templates Table 47 Parameters of ISAACLW_img acq_MoveToPixel P2PP label Keyword Default Description Preset Telescope SEQ PRESET T Preset telescope Chop Throw arcsec SEQ CHOP THROW M2 Chop Throw arcsec Number of Chop Cycles SEQ CHOP NCYCLES Number of chop cycles Chop Position Angle SEQ CHOP POSANG Chop Position angle deg Chop Angle Coordinate SEQ CHOP COORDS SKY or DETECTOR coordinates Angle on Sky deg TEL ROT OFFANGLE 0 Position angle DDD TTT LW Filter wheel 1 INS FILT3 NAME Filter wheel 1 LW Filter wheel 2 INS FILT4 NAME Filter wheel 2 At the end of the template the image displayed on the RTD consisting of Number of Chop Cycles chopped images is dumped on disk A 9 4 ISAACLW_img_acq_MoveToSlit All LW spectroscopy OBs that use chopping must use this template for target acquisition This template presets the telescope and allows the operator to interactively centre objects into the sele
87. ing and spectroscopic modes In general it is not necessary for the acquisition and the subsequent observation templates to have the same DIT and NDIT A 6 2 ISAACSW_img_acq Preset This template does a simple telescope preset It is the easiest template to use when objects can be easily identified against the sky background An identical version for RRM observa tions is available see Section A 6 3 It should NOT be used for subsequent spectroscopic observations and it should not be used if the user wants a pointing accuracy that is better than few arcsec Table 31 describes the parameters of this template Table 31 Parameters of ISAACSW_img_acq Preset P2PP label Keyword Default Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT 7 Number of DITs Position Angle on Sky Deg TEL ROT OFFANGLE 0 Position angle DDD TTT SW Filter wheel 1 INS FILT1 NAME Filter wheel 1 SW Filter wheel 2 INS FILT2 NAME Filter wheel 2 No RTD image is dumped on disk at the end of this template ISAAC User Manual VLT MAN ESO 14100 0841 54 A 6 3 ISAACSW_img acq Presetrrm This template is functionally identical to ISAACSW_img_acq Preset apart from not allowing to set the position angle see Table 32 and is intended for acquisition of RRM imaging OBs Table 32 Parameters of ISAACSW_img_acq Presetrrm P2PP label Keyword Default Description DIT DET DIT Detector Integration Time secs NDIT DET NDI
88. ing the night e Spectroscopic screen flats are taken on the following morning for any set up used during the night e Wavelength calibrations are taken on the following morning for any set up used at night e Star traces are taken every 3 6 month or after an instrument intervention to trace the spectra at different positions along the slit and provide the co ordinate transformation between imaging and spectroscopy They are archived for both the LR and MR modes and can be downloaded from the archive eso org ISAAC User Manual VLT MAN ESO 14100 0841 41 9 4 Pipeline The AutoNod0nS1it templates are supported by the pipeline The GenericOffset templates are not supported by the pipeline Further details are given in the http www eso org sci facilities paranal instruments isaac doc drg html drg html 9 5 Performance The user should refer to the ETC for estimating the performance of this mode http www eso org observing etc ISAAC User Manual VLT MAN ESO 14100 0841 42 10 Long Wavelength Spectroscopy 3 LWS3 10 1 Characteristics See Section 2 3 for a description of the mode Chopping is essential for LR observations and can be used for all observations For more information about chopping see Section 5 6 The chopping templates produce a data cube for each nod position which contains the two half cycle frames For MR observations non chopping observations can also be taken 10 2 Recommended DITs and NDITs For o
89. isition Templates 2 2 2 2 0 0 eee ee eee ee 74 A IRONIA ea opea sa A eR A ke a A 74 AE ISRACLW img acg Preset oce Ohba ra OL EER OL EE EY 74 AOS ISAACLW ime aoq MoveloPinel occ 6a 4 a4 cera ee hae OS 74 A 9 4 ISAACLW_img_acqMoveToSlit o o 75 A 9 5 ISAACLW_img_acqMoveToPixNoChop 2200 76 AO ISAACIN img acq_FastPhot s o ct esmi eed A SRE OR a 77 A 9 7 ISAACLW_img_acq MoveToSlitNoChop ooa aa TT A 10 Aladdin Observation and Calibration Templates With Chopping 79 A 10 1 ISAACLW_img_obs_AutoChopNod oaoa a 79 A 10 2 ISAACLW spec_obs_AutoChopllod s s ecescs s era es 81 ISAAC User Manual VLT MAN ESO 14100 0841 x A 10 3 ISAACLW_img cal AutoChopNod oaoa a 82 A 10 4 ISAACLW spec cal AutoChoplod 2 22545 06h edd eee bees 82 A 10 5 ISAACLW spec cal NightCalib 4 468 4048 pede bay da 82 A 11 Aladdin Observation and Calibration Templates Without chopping 83 ALI ISAACLW img obs AutolJitter s c e 6nh Seed Rowe SRE HES 83 A 11 9 ISAACLW_img obs_AutoJitter0ffset 2 54 44 6 5b 83 A 11 3 ISAACLW_img obs_FixedSkyOffset o e 84 A 11 4 ISAACLW_img_obs_GenericO set o 84 A 11 5 ISAACLW img obs FastPhot 2 6 cocos 84 A 11 6 TSAACLW spec 0bs AutoNodOnSlit gt o sess ee ee to ee Se 86 A 11 7 ISAACLW_spec_obs GenericOffset aoaaa aaa 86 A 11 8 ISAACLW_img cal GenericOffset aoaaa 86 A 11 9 ISAAC
90. jects which are brighter than this limit These reference objects can either be positioned in the slit together with the target by defining the appropriate position angle on sky the recommended procedure or be used for initial centring on slit followed by a blind offset to move the target into the slit The ISAACSW_img_acq MoveToSlit template allows one to define relative offsets from the reference star These reference objects should be stars or point like objects Blind offsets from a reference object should be limited to approximately 1 arcminute Offsets that are too large could cause the TCS to change the guide star which would result in a less accurate acquisition Experience has shown that the offsets from the reference star are often inaccurately defined For example if the offsets are computed from a previously taken ISAAC image the distortion at the edges of the field can affect the accuracy of the offsets if one has assumed a constant plate scale Also users tend to choose the brightest object in the field which can be far from the target Fainter reference objects still bright enough to satisfy the limits mentioned above are often closer to the target and make much better choices To minimise offset errors users should use reference objects that are as close as possible to the target rather than trying to use the brightest reference objects It is recommended to position a reference object in the slit together with the target so o
91. ks OBs which are made up of templates Templates are divided into three categories acquisition observation and calibration Usually OBs consist of an acquisition template and one or more observation templates for science frames and one or more calibration templates for calibration frames One and only one acquisition template is allowed in an OB and therefore only one preset on sky It is not possible for example to group in the same OB observation templates on the science object and calibration templates on a standard star Tables 13 and 14 provide a short summary of the templates currently offered These templates should cover most needs Should observers who have observing time with ISAAC consider that these templates do not ISAAC User Manual VLT MAN ESO 14100 0841 29 Table 14 Hawaii Templates cookbook Action Template s to use Acquisition Simple telescope preset same for RRM ISAACSW_img_acq Preset ISAACSW_img_acq Presetrrm Preset telescope and center field ISAACSW_img_acq MoveToPixel Preset telescope and center object s in slit spectroscopy same for RRM ISAACSW_img_acq MoveToSlit ISAACSW_img_ acq MoveToSlitrrm Preset telescope and center field polarimetry ISAACSW_img_acq Polarimetry Imaging Imaging of uncrowded fields ISAACSW_img_obs_AutoJitter Imaging of extended objects or crowded fields ISAACSW_img_obs_AutoJitterUOffset ISAACS
92. lt of a chopped image is therefore a background subtracted image with positive and negative images It is described in more detail in Section 5 6 We deliver the two half cycle frames for each chopped image ie an ON frame and an OFF frame both averaged over the number of chop cycles These data are stored in a cube For LW narrow band imaging observations below 3 5 microns and for MR spectroscopic ob servations it is possible to get reasonable sky subtraction without resorting to chopping We have provided 6 observing templates 2 acquisition templates and 2 calibration templates that can be used to jitter and nod the telescope without chopping These templates are identical to those used for SW imaging in the Hawaii arm The advantages of jittering and nodding over chopping are twofold Firstly the overheads are less and secondly there are no negative images so that unlike when chopping the whole field of view becomes available for science For all LW broad band and LR spectroscopic observations chopping is the only offered mode Windowing Windowing is not offered for either SW or LW observations except for the FastPhot modes Sec 12 In some cases acquisition frames in the L band and some LW calibrations win dowing may be used but this is automatically setup and transparent to the user Minimum DIT Table 11 indicates the minimum integration times for the Hawaii and Aladdin arrays which limit the magnitude of the stars to be used for
93. me secs Observation Category SEQ CATG SCIENCE Observation category science or preimaging Jitter Box Width SEQ JITTER WIDTH Random offset box width arcsec Return to Origin SEQ RETURN T Return to Origin Sky Offset Throw SEQ SKYTHROW Sky Throw arcsec Rotate Pupil SEQ ROTPUPIL T Pupil rotation compensation Number of AB or BA cycles SEQ NABCYCLES Number of AB or BA cycles NDIT for the OBJECT positions SEQ NDIT OBJECT NDIT used on OBJECT positions NDIT for the SKY positions SEQ NDIT SKY NDIT used on SKY positions LW Filter wheel 1 INS FILT3 NAME Filter name in wheel 1 LW Filter wheel 2 INS FILT4 NAME Filter name in wheel 2 A 11 3 ISAACLW_ img obs_FixedSky0ffset This template works in an identical manner to ISAACSW_img_obs_FixedSkyOffset Please refer to Sec A 7 3 for a description of what the template does This mode is available for imaging with the J Block H amp Ks broadband filters and 3 21 and 3 28 narrow band filters only Table 59 Parameters of ISAACLW_img obs_FixedSky0ffset P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs Observation Category SEQ CATG SCIENCE Observation category science or preimaging Jitter Box Width SEQ JITTER WIDTH Random offset box width arcsec Return to Origin SEQ RETURN T Return to Origin Sky Offset in Alpha SEQ SKYOFFSET ALPHA Sky Offset in Alpha arcsec Sky Offset in Delta SEQ SKYOFFSET DELTA Sky Offset
94. me observations The tel luric standard is taken at similar airmass than the science observations the observatory guarantees that the airmass difference between the standard and science target is lt 0 2 airmasses The standard will be observed with the slit that was used during the obser vations Starting from period 77 we do not observe any more the telluric standard with the 2 slit Therefore the users should explicitly require it within their README files should they need it Note that starting from period 78 the time for such an observation will be charged to the user The stars are generally chosen from the Hipparcos catalogue and are either hot stars spectral type BOV to B4V or solar type stars spectral types GOV to G4V These calibrations are taken so that telluric features can be removed from science spectra They can also be used for flux calibration with a relative accuracy of 5 10 and an absolute accuracy of 5 20 A detailed discussion on this topic is given in Sec 3 4 Should users need more accurate results or require telluric standards of a particular spectral type they should provide the corresponding OBs and detailed instructions The spectroscopic standard star templates e g _cal_ must be used to prepare these OBs In this case the time executing the OBs will be charged to the user and the observatory will not observe a separate telluric standard e Darks are taken on the following morning for any DIT value used dur
95. metric field to determine the distortion of the instrument See http www eso org sci facilities paranal instruments isaac inst field_distortion html for a list of these observations e Detector darks taken during the following morning for any DIT used at night 7 4 Pipeline All AutoJitter and AutoJitterOffset templates are supported by the pipeline ISAACLW_img obs GenericOffset is not supported ISAACSW_img obs GenericOffset is only partly supported sequences of observations with offsets larger than the field of view mosaic ing are not reduced by the pipeline The SWI1 and LWIS pipelines also calculate zero points and the read out noise and create master twilight flats and master dark frames See http www eso org projects dfs papers jitter98 for a description of the pipeline algorithm This pipeline has been used successfully since the start of the operations 7 5 Performance The user should refer to the ETC for estimating the performance of this mode http www eso org observing etc ISAAC User Manual VLT MAN ESO 14100 0841 37 8 Long Wavelength Imaging LWI3 and LWI4 8 1 Characteristics See Section 2 2 for a description of this mode Chopping is essential for observations with wavelengths gt 3 5um and can be used for all LW observations Chopping will always give a better sky subtraction For more information about chopping see Section 5 6 The imaging mode for observations with chopping is LWI4 The chopping
96. mplate is not autonomous It must follow a spectroscopic observation Furthermore it only calibrates the wavelength setting that is used in the preceding template and not the wavelength settings in all preceding templates Table 45 Parameters of ISAACSW_spec_cal_NightCalib P2PP label Keyword Def Description Flatfield at end of template SEQ FLATFIELD T Night flat field at end of template Arc at end of template SEQ ARC F Night arc at end of template ISAAC User Manual VLT MAN ESO 14100 0841 74 A 9 Aladdin acquisition Templates A 9 1 Introduction Telescope presets can only be done via acquisition templates Note however that as of version 2 12 of P2PP all information on the target coordinates additional velocities proper motion are not provided in the acquisition template but in the target package of the P2PP GUI see Table 30 Telescope presets move the telescope to the requested coordinates and allow the telescope operator to select a guide star and start active optics Additionally these templates set up the detector and the instrument Conversely observation templates only deal with telescope offsets and not with telescope presets In general acquisition templates dump an image to disk only the ISAACLW_img_acq Preset template does not These dumped images are aimed at keeping track of the field position and orientation before starting the observation The acquisition templates to use depend upon the subsequent
97. n chopping frequency The minimum number of chop cycles is 1 This parameter may be adjusted by the operation staff at execution time if the object is too faint it si recommended to use at least 10 chop cycles to average out the atmospheric jitter and thus ensure a good centring on the slit e ChopNod PARA of PERP to Slit This parameter allows the user to define chop ping as either parallel or perpendicular to the slit If set to PARA the object will be continuously in the slit After completion of the preset the instrument and detector are set The observer is then prompted to either define an offset to the slit a drawing of which is overlaid on the RTD or to rotate the field by clicking on two objects Offsetting is simply done by drawing an arrow on the screen with the left hand button of the mouse If the offset is accepted the telescope offsets by the desired amount Finally the user is given the possibility of refining the position of the object Once the user is satisfied the template finishes An identical iteration loop is performed for rotating the field by clicking on 2 objects These 2 objects will be centred in the slit If the Preset Telescope parameter is set to F then the telescope will not move This can be useful in visitor mode to use the functionality of the template without presetting the telescope It is possible in this template to use the J Block H or Ks filters which are likely to allow an easi
98. n during the following day 8 4 Pipeline Chopping and most non chopping observations are supported by the pipeline The ISAACLW_img obs_GenericOffset template is not supported ISAAC User Manual VLT MAN ESO 14100 0841 38 8 5 Performance The user should refer to the ETC for estimating the performance of this mode http www eso org observing etc ISAAC User Manual VLT MAN ESO 14100 0841 39 9 Short Wavelength Spectroscopy 1 SWS1 9 1 Characteristics See Section 2 3 for a description of the mode 9 2 Recommended DITs and NDITs ISAAC has always suffered from electronic pickup which could occasionally dominate the readout noise The work around was to use recommended DITs which were observed to have small or insignificant pickup noise However a recent intervention Feb 2006 on the Infrared Array Control Electronic IRACE cabinet has solved the problem By replacing a fan the well known pickup noise at 51Hz has been eliminated and only a weak residual pickup noise at 75 and 152 Hz can be observed through a power spectrum analysis Therefore there are no longer particular limitations on the choice of the DIT values Reappearance of pickup noise will be posted on the http www eso org sci facilities paranal instruments isaac which we suggest to check at the moment of your OB preparation In case a thumbnail rule would be to select a DIT value which is not multiple of the pickup frequency i e avoid DIT n f sec where f i
99. n image is processed and transferred from IRACE InfraRed Array Control Electronics to the instrument workstation This difference affects the technical capabilities of each mode Specifically e The shortest DITs possible are 3 2 ms Burst mode and 12ms FastJitter with the smallest window size of 32x32 pixels corresponding to a 4 7 x4 7 FOV e The readout mode is Double Correlated Read Reset Read Read in this mode each image or DIT unit is made of two reads The data are stored in single fits files each containing a data cube The Burst mode produces a data cube comprised of single reads which have to be combined two by two to reconstruct an image DIT A script which allows image reconstruction is available For the smallest window the size of the data cube is therefore 32x32x2xNDIT The FastJitter mode usually produces a data cube of DITs i e already recon structed images For the smallest window the size of the data cube is therefore 32x32xNDIT e In Burst mode the telescope is staring at the target for the duration of the integration INT NDITxDIT and only one data cube is produced Any value for jittering set in the template is ignored In FastJitter mode the telescope can jitter on the sky and several data cubes can be produced within one template e In Burst mode it is possible to set the absolute time on which the observation has to be centred For example if one wants to observe an event at time T a
100. nd sets a total integration of 60 seconds the template will start to collect data at time T 30 and end at T 30 Both modes are subject to some limitations e The data cube can contain a maximum of 32000 planes frames i e the maximum NDIT is 16000 in Burst mode and 32000 in Fast Jitter mode e The maximum data cube size is 262Mb Once the window size has been selected this limits the number of frames reads and vice versa The data cube size in bytes is given ISAAC User Manual VLT MAN ESO 14100 0841 46 by the relation Xpixx Ypixx4xNDIT Table 26 reports some conservative upper limits for the data cube size Data cubes too close in size to the limit of 262Mb can results in the loss of few frames NDIT A summary table with the hardware windowing characteristic is given in Table 26 The detector characteristics are the same as for SW imaging with the LW array see the User s Manual The maximum and minimum observable magnitudes can roughly be estimated through the ETC by scaling the obtained counts to the actual DIT As a general rule targets brighter than 1 mag cannot be observed in any mode or filter Table 27 reports some technical information for the Burst mode Table 28 reports some technical information for the FastJitter mode 12 2 Calibration Plan For both modes we provide a set of windowed darks taken with the same DIT of the science template Twilight flats are taken in full readout mode with the same filters combina
101. ne can determine the position of the target on the spectral image It also allows one to monitor the image quality across the spectrum and to monitor the flux through the slit etc In service mode it is mandatory that all the relevant information is given in advance to the operation staff This information should consist of e Finding charts with clear definition of the field orientation and of the scale e Overlay of the slit e Clear identification of the object ISAAC User Manual VLT MAN ESO 14100 0841 23 e Clear identification of the reference object to be used for preliminary slit centring e The offset to be applied between the reference and the target This offset has to be entered in the ISAACSW_img_acq_MoveToSlit template See http www eso org sci observing phase2 SMGuidelines html for more detailed in formation on the format of the finding charts and README files to be provided at the time of OB submission Should this detailed information be missing the observations will not be scheduled 5 3 3 LW spectroscopy The same interactive tools available in ISAACSW_img_acq MoveToSlit are provided in the ISAACLW_img_ acq MoveToSlit and ISAACLW_img_acq MoveToSlitNoChop templates Although the subsequent spectroscopic observations are at long wavelengths gt 3um short wavelength broad band filters J H and Ks are available for object acquisition It is believed that most of the targets will be acquired more easily in these
102. ng all the images from all OBs one will be able to adequately remove bad pixels In this case it is recommended to place the object at different positions along the slit The easiest way to do this is to give the different OBs slightly different values for the Nod Throw Along Slit parameter see Section A 8 1 The ISAACSW_spec_obs_AutoNodOnSlit template provides the possibility of storing individual frames at each telescope position NINT It is therefore preferable to use a high NINT rather than a high NDIT At Low Resolution the noise is essentially limited everywhere by the photon noise from the OH lines after 1 minute of integration Therefore DITs of a few minutes e g from 1 to 3 are adequate It is then advisable to offset the telescope as many times as possible during the execution of the template ISAAC User Manual VLT MAN ESO 14100 0841 40 Table 25 Recommended range for DIT in seconds and NDIT for SWS1 LR and SWS1 MR modes LR MR DIT recommended 60 200 300 900 NDIT 1 1 1 no more than 180s for 2 2um 9 3 Calibration Plan For the LR grating only four grating settings that correspond to 1 06 1 25 1 65 and 2 2 um are supported Users should not use any other central wavelength in LR mode In LR mode telluric standards spectroscopic flats and arcs will only be taken at the supported wavelengths The guarantee calibrations in SM are e LR and MR Telluric Standard Stars according to the night ti
103. ng modes the overheads dominate the total execution time assuming a DIT of few millisec They increase with the requested NDIT i e the size of the data cube to be created delivered and they also depend on the selected mode Burst or FastJitter In particular they increase parabolically in the case of the Burst mode and linearly in the case of the FastJitter one see Figure 7 Some examples tables 16 to 21 are given below to illustrate how to compute overheads with ISAAC Table 16 Overheads Example 1 SW Imaging with the Hawaii Template parameters Acquisition Template ISAACSW_img_acq_Preset Observation Template ISAACSW_img_obs_AutoJitter DIT 10 seconds NDIT 10 Number of Exposures 36 Execution time minutes Preset 6 0 Instrument setup 0 5 int time detector overhead 0 167 0 07 x 10 NDIT x 36 Telescope offsets 0 25 x 36 Total 101 minutes for 60 minutes of integration ISAAC User Manual VLT MAN ESO 14100 0841 32 Table 17 Overheads Example 2 SW Imaging with the Aladdin Table Template parameters Acquisition Template ISAACLW_img_acq_Preset Observation Template ISAACLW_img_obs_AutoJitter DIT 10 seconds NDIT 10 Number of Exposures 36 Execution time minutes Preset 6 0 Instrument setup 0 5 int time detector overhead 0 167 x 10 NDIT x 36 Telescope offsets 0 25 x 36 Total 76 minutes for 60 minutes of integration 18 Overheads Exampl
104. observation For imaging the simple preset ISAACLW_img_acq Preset can be used for any subsequent observation The chopping preset ISAACLW_img_acq MoveToPixel1 can only be used for subsequent imaging ob servations with chopping and the non chopping preset ISAACLW_img_acq MoveToPixNoChop can only be used for subsequent imaging observations without chopping For spectroscopy observations using chopping must use ISAACLW_ img acq MoveToSlit for acquisition Non chopping observations can use either ISAACLW_img_acq MoveToSlit or ISAACLW_img_acq_MoveToS1itNoChop A 9 2 ISAACLW_ img acq Preset This template does a simple telescope preset It is the easiest when a pointing accuracy of a few arcsec is enough for the purposes of the program It should NOT be used for subsequent spectroscopic observations No light reaches the detector during this template to avoid accidental imaging of warm objects as the telescope is presetting Consequently an image of the field will not be seen on the RTD when this template is used Table 46 describes the parameters of this template Table 46 Parameters of ISAACLW_img_acq Preset P2PP label Keyword Default Description Angle on Sky deg TEL ROT OFFANGLE 0 Position angle DDD TTT No RTD image is dumped on disk at the end of this template A 9 3 ISAACLW_img_acq_MoveToPixel The instrument mode for this template is LWI4 The template uses chopping and can only be used to acquire targets for s
105. of the night is measured In any case the zero points are aimed at providing photometric calibration accurate to 5 10 Hawaii Aladdin Should users need higher accuracy they should provide OBs for standards close to the object that will be executed either immediately before or after their observations In this case the time spent doing these observations will be charged to the user The same holds for imaging OBs that use other filters i e NB filters These are not supported by the calibration plan and users should prepare the necessary OBs e The observatory does not measure the extinction every night Instead the observatory has calculated the average extinction for the J Js H and Ks filters with the Hawaii detec tor since the start of operations See http www eso org sci facilities paranal instruments isaac tools imaging_standards html Extinction Extinction coeffi cients for the SW broad band filters in the Aladdin detector were not determined e Every 3 6 month or after an intervention on the instrument the observatory takes illumi nation frames for the illumination correction These frames are taken only in photometric conditions and serve to determine large scale difference between the true flat field and the twilight sky flat field These are determined in the Aladdin and the Hawaii for Js J J Block H and Ks only e At least once per year or after an intervention on the instrumnet the observatory takes images of an astro
106. on the spectroscopic images It is strongly recommended to the extent this is possible to orient the field so as to have a moderately bright object in the slit simultaneously with the program object This allows one to monitor slit losses during a long exposure while providing an extra means of locating the object spectrum through its position relative to this reference object The bright object can also be used as a secondary standard for the removal of telluric lines Wavelength calibration As mentioned in section 2 3 ISAAC is equipped with a calibration unit allowing one to take arc spectra of Xenon and Argon However it is standard practice to use the OH lines for wavelength calibration The technique works very well at medium spectral resolution below 2 2um At low resolution the lines are too highly blended but can still be used for a zero point correction from a calibration performed with the arc lamps Detailed sky spectra with OH line identifications are available on the http www eso org sci facilities paranal instruments isaac Above 2 2 um the OH lines are very weak and cannot be used so arc spectra should be used Telluric features can also be used Above 4 2 um Xenon and Argon lines are too faint to be observed Although it is possible to use the grating in 3rd order to do the wavelength calibration the calibration is not very accurate An alternative method is to use the numerous telluric features This has been tested ISA
107. onal velocities proper motion are not provided in the acquisition template but in the target package of the P2PP GUI see Table 30 Telescope presets move the telescope to the requested coordinates and allow the telescope operator to select a guide star and start active optics Additionally these templates set up the detector and the instrument Conversely observation templates only deal with telescope offsets and not with telescope presets In general acquisition templates dump an image to disk only the ISAACSW_img_acq Preset template does not These dumped images are aimed at keeping track of the field position and orientation before starting the observation All Hawaii acquisition templates use the SWI1 mode Table 30 Parameters of target package in the P2PP GUI P2PP label Key Word Default Description Right Ascension 00 00 00 RA of target Declination 00 00 00 Dec of target Equinox TEL TARG EQUINOX 2000 Equinox expressed as yr from 2000 to 3000 Epoch TEL TARG EPOCH 2000 0 Epoch expressed as yr from 2000 to 3000 Proper Motion Alpha TEL TARG PMA 0 proper motion in yr from 10 to 10 Proper Motion Delta TEL TARG PMD 0 proper motion in yr from 10 to 10 Add Velocity Alpha TEL TARG ADDVELALPHA 0 Additional tracking vel in RA Add Velocity Delta TEL TARG ADDVELDELTA 0 Additional tracking vel in DEC Tn arcsec sec See also sections 5 3 7 and 9 for more information on target acquisition and on the Hawaii imag
108. ope between exposures according to a random pattern of offsets automatically determined within the template It is ideal for long integrations on empty fields and does not require a long list of offsets to be defined Table 37 Parameters of ISAACSW_img obs AutoJitter P2PP label Keyword Default Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of sub integrations Observation Category SEQ CATG SCIENCE Observation category science or preimaging Number of Exposures SEQ NEXPO Number of exposures Jitter Box Width SEQ JITTER WIDTH Random offset box size arcsec Return to Origin SEQ RETURN T Return to Origin SW Filter wheel 1 INS FILT1 NAME Filter name in wheel 1 SW Filter wheel 2 INS FILT2 NAME Filter name in wheel 2 Figure A 7 1 illustrates what the template does 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 ISAAC User Manual VLT MAN ESO 14100 0841 59 points in a series of ten values is greater than a certain minimum This is intentionally done to ensure that the 5 frames before and after any frame are spatially not too close and can be safely used for creating skies without residual objects for sky subtraction The value of the Jitter Box Width parameter corresponds to the full width of the box in which the offsets are generated D
109. ope does an offset During the offset the guide star is lost for the duration of the offset Consequently offsetting the telescope too frequently can result in a significant loss of signal for the active optics and degraded performance This has the following important operational consequence The minimum time between telescope offsets must be at least 30 seconds Obser vations not complying with this rule will be rejected by the operation staff at the time of execution Note that this rule does not apply to standard stars imaging or spectroscopy since some image degradation can usually be tolerated Provided that the previous rule is followed the ISAAC User Manual VLT MAN ESO 14100 0841 19 control of the telescope active optics is totally transparent to the users Other important facts are e the offsetting accuracy of the telescope is 0 1 arcsec RMS as long as the same guide star is used when offsetting Offsets larger than a few arc minutes may involve a guide star change and in such a case the offsetting accuracy is less e defocusing the telescope is not an operational procedure e Scanning along the slit in spectroscopy during one exposure is not supported Guide Stars Guide stars are automatically found by the Telescope Control System and the users do not have to worry about finding them When small telescope offsets are used a few arcseconds to a few arcminutes the telescope keeps the same guide star this depends in
110. original spatial position after Number of Exposures exposures Be very careful if the lengths of X offset list arcsec and Y offset list arcsec are not equal to the number of exposures If the cumulative offset at the end of the list is not equal to zero it is easy to inadvertently move the object behind the polarimetry mask At the end of the template the rotator offset can optionally be returned to the value at the beginning of that template by setting Return to original rotator position to true T note that this option only returns the rotator to its original position at the end of the entire template With this scheme it is possible for the user to sample the object and sky as desired for a se quence of rotator positions within one template At least two different orientations separated by 45 degrees are required for computing the Stoke s parameters The most likely situation will be to set the Rotator Offset list parameter to 0 45 The template has been coded so the rotation occurs about the centre of the mask which is approximately at x y 512 540 To image the entire field of view at one position angle one must take great care with the spatial offsets The opaque and transmitting parts of the mask have slightly different widths 24 arc seconds for the opaque ones and 20 arcseconds for the transmitting ones Thus three exposures with offsets of about 15 arcseconds in between the exposures are needed to cover the whole fi
111. pectrophotometric calibration which includes the removal of telluric features is given in Sec 3 4 Dealing with the moon If the object is very close to the moon less than 20 degrees away moonlight can prevent the telescope active optics system from working 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 4 2 The Telescope Telescope Focus This is a burden of the past In fact the telescope cannot be defocused For standard stars we can degrade the IQ by using a calibrated solution for the optics since standards are often too bright for the VLT However this procedure is not offered for science targets Telescope control Most interactions with the telescope consist of telescope presets for acquisition telescope offsets during observations and M2 chopping in LW observations Small offsets i e less than 1 arcminute are usually completed in 10 to 15 seconds of time The guide star is used for field stabilisation and optimising the performance of the optics active optics The active optics system runs continuously even when the telesc
112. persistence effects in the Hawaii detector In service mode this problem can affect subsequent observations of other programs In visitor mode and provided that the nights are not shared the potential problems related to the persistence effects are left to the responsibility of the user We have less experience with the effect of bright stars on the Aladdin array Hence we request that users follow the same SW imaging rules as with the Hawaii Note RRM observations will be turned down if the field contains objects brighter than 9th magnitude in J H or K This is done in order to protect the array from remnant effects and changes in the gain properties resulting from saturation As the field and OB contents is not known a priori a general rule must be applied to all ISAAC RRM observations The brightness of field stars will be checked automatically with the final release of the 2MASS catalogue See Sections 5 4 1 and 5 4 2 for more information on general brightness limits in service mode Note 2 When using the ISAACLW_img_acq_FastPhot template and the Burst FastJitter mode the maximum brightness of the observable target depend on the minimum DIT that is possible for the selected mode Burst or FastJitter and on the detector windowing It should be extrapolated by using the ETC In no case targets brighter than 1 mag will be observed in any filter or mode 5 4 1 SW Imaging Aladdin and Hawaii Observations involving fields with objects bri
113. practice on the position of the guide star in the Nasmyth field of view The offset accuracy is then excellent at the level of 0 1 arcsecond However if large telescope offsets are used the guide star changes The telescope will not resume guiding automatically and the operator will be prompted to resume guiding More importantly after changing guide stars the telescope may not come back to precisely the same position This is a potential problem when doing spectroscopy of extended objects This particular problem will be dealt with by the operator during such observations by ensuring that the same guide stars are used when the telescope returns back to the object Flexures and tracking stability The flexure of ISAAC at the detector plane is very small around 0 5 pixel over a full instrument rotation In most circumstances the image stability of both telescope and instrument is so good that there is usually no need to reacquire the target during long integrations up to two hours in spectroscopy This is not the case when crossing the meridian near Zenith and it is advised not to schedule trans meridian observations on fields with Zenith distances lower than 10 For such fields it is advised to do e g standard star observations during the 15 minutes surrounding the transit ISAAC User Manual VLT MAN ESO 14100 0841 20 5 Observing with ISAAC 5 1 Observation Software OS is the high level software controlling the instrument I
114. psed time between 2 consecutive exposures including one telescope offset is therefore about 6 x 10 4 1 15 100 seconds corresponding to overheads of about 66 Shorter DITs will accordingly increase the overheads In medium resolution spectroscopy in J or H the DIT can be as high as 15 minutes leading to readout time limited overheads of 2 only Aladdin overheads For the templates that involve chopping the overheads are given as a fraction of total integra tion time For imaging this fraction is 40 and for spectroscopy the overheads are 30 The Aladdin templates that do not involve chopping used for J Block H Ks NB 3 21 amp NB_3 28 imaging and LW MR spectroscopy are more efficient The overheads come from instrument setups telescope presets object acquisitions and telescope offsets The overhead from detector readout is negligible Assuming DIT 0 4 seconds and NDIT 150 the elapsed For service mode observations a read time of 4 1s should be assumed The Hawaii read time has alternated between these two values because of changes in the chip read speed made to reduce the amplitude of the odd even column effect Refer to the ISAAC web pages http www eso org sci facilities paranal instruments isaac Documentation for the current value ISAAC User Manual VLT MAN ESO 14100 0841 31 Table 15 Overheads Channel Operation Time Comment minutes Both Full Preset amp acquisition varies with acq template ISAAC
115. r filter spectral coverage AA and spectral resolutions for the SWS1 and LWS3 LR and MR modes See appendix B for the filter curves Wavelength Or Fi LR MR Range de It AA R 0 3 R 0 6 R 0 8 AA R 0 3 R 0 6 R 0 8 um r er um R 1 R 1 5 R 2 um R 1 R L 5 R 2 SWS1 0 98 1 1 5 SZ full 1800 900 750 550 420 270 0 046 11500 5700 5000 3400 2700 1700 1 1 1 4 4 J full 1700 860 730 500 390 250 0 059 10500 5200 4700 3100 2500 1500 1 4 1 82 3 SH full 1600 840 690 500 380 250 0 079 10000 5100 4500 3000 2400 1500 1 82 2 5 2 SK full 1500 750 600 450 330 200 0 122 8900 4400 3900 2600 2100 1300 LWS3 2 55 4 2 SL full 1200 600 480 360 270 180 0 255 6700 3300 2600 2000 1500 1000 445 51 1 M full 1600 800 650 500 370 250 0 237 10000 5000 4000 3000 2300 1500 BR Table 7 ISAAC Polarimetric Mode Mode Spectral Range Pixel Scale Field Of View Detector Size arcsec arcsec pixels SWP1 0 98 2 5 ym 0 1484 3x 20 x 150 1024 x 1024 of the image the separation varies by 3 pixels To measure the Stokes parameters and hence the degree and position angle of polarisation a second set of images with the Wollaston prism rotated 45 degrees with respect to the first pair are required The rotation is done by rotating the entire instrument The Stokes parameters are then determined as follows I i 90 i 0 i 45 i
116. r LR and MR spectroscopic standards are L 4 to L 6 and L 2 to L 4 respectively For L band imaging standards should be fainter than L 6 magnitude and for narrow band imaging standards should be fainter than L 5 e the MSSSO infrared photometric standards McGregor 1994 PASP 106 508 Trans formations from the Cal Tech system to the original MSSSO and AAO systems are given in McGregor 1994 PASP 106 508 e the IR photometric data of ESO calibration stars van der Bliek et al 1996 A amp AS 119 547 e Anextensive list of bright stars of known spectral type and magnitude taken from a vari ety of sources MSSSO photometric standards IRPS FIGS G dwarfs spectroscopic stan dards UKIRT spectroscopic standards NASA Infrared Catalog Bright Star Catalog and have correspondingly uncertain photometric magnitudes Photometric magnitudes in this list come from the following references M McGregor 1994 PASP 106 508 C Carter 1990 MNRAS 242 1 B Bouchet Manfroid amp Schmider 1991 A amp A Suppl 91 409 A Allen amp Cragg 1983 MNRAS 203 777 Stars with magnitudes listed but lacking a reference annotation are taken from the NASA Catalog and their photometry should be considered uncertain at the 0 05 mag level Other stars lacking ISAAC User Manual VLT MAN ESO 14100 0841 94 measured photometric magnitudes should be used only as telluric standards to remove terrestrial absorption features flux calibration s
117. ral the spectroscopic standard and the telluric standard are the same star but this does not need to be the case The most prominent feature in IR spectra are the telluric lines of the Earth s Atmosphere Unfortunately many of the telluric lines do not scale linearly with airmass so it is necessary to observe a standard at the same airmass and with the same instrument setup as that used for the science target Furthermore the strength of the telluric lines varies with time so it is also necessary to observe the standard soon after or soon before the science target The spectrum of the telluric standard is divided directly into that of the science target Ideally the spectrum of the telluric standard should be known so that features belonging to it can be removed However this is never the case so one has to use standards in which the spectrum is approximately known Within the observatory s calibration plans we use either hot stars main sequence B0 B4 stars or solar analogs as telluric standards and generally these stars are selected from the Hipparcos Catalogue The spectra of hot stars those hotter than B4 are relatively featureless and are well fitted by blackbody curves So by knowing the spectral type of the star one uses a blackbody curve with the appropriate temperature to fit the continuum of the standard The spectra of stars that are cooler than AO start to have many more features and cannot be fitted with a blackbody cur
118. ransparent way with the M2 chop ping e One chop cycle corresponds to one ON OFF cycle i e one period of the M2 chopping motion Only the acquisition frame is saved on disk as the subtracted ON OFF image e Several chop cycles can be averaged by the pre processor to deliver only one image This is referred to as the Number of chop cycles in the template parameters and applies only to acquisition templates For the observing templates this parameter is automatically set e LW chopping data From P69 onward we have delivered the two half cycle frames for each chopped image i e an ON frame and an OFF frame both averaged over the number of chop cycles These data are stored in a cube There is one cube containing these two half cycle frames for each chopped image This change is transparent at the template level for the user The pipeline has been updated accordingly ISAAC User Manual VLT MAN ESO 14100 0841 27 The subtracted image ON OFF image can still be displayed on the RTD but is not saved on disk Storing the half cycle frames allows checking of the sky background levels to operate the detector at the optimum level ranges and easier application of the non linearity corrections during data reduction The format of the data issued from non chopping templates are un changed e DIT and NDIT are not parameters of the LW chopping templates as they are auto matically set to the optimal values imposed by the chopping frequency and s
119. respectively If the observations are to be done at the beginning of the night when the background in these filters is high then DITs at the lower end of the range should be used 2 For K band observations of objects that are crossing the meridian near Zenith within 10 degrees of Zenith it is better to use NDITx DIT that is nearer to the lower bounds of the recommended range This will result in better sky subtraction 7 3 Calibration Plan According to the observatory s calibration plan in SM we provide the following calibrations e Twilight Flat Fields in all filters as they are used Note that due to the limited number of narrow bands NB which can be observed during twilight i e one each science OB is restricted to include at most two NB filters e Nightly zero points in the Hawaii Js J H and Ks filters using a low airmass standard star On a semi regular basis we also take a photometric standard star at high airmass in the same filters Typically both the low and the high airmass standard are taken during twilight In VM only the low airmass standard will be taken Note that for the Aladdin J Block H and Ks filters SWLW zero points will be taken only in those nights when these filters are used Imaging OBs that use broad band filters and require PHO conditions will be bracketed by photometric standard stars taken within 3h before and after the OB Like this the ISAAC User Manual VLT MAN ESO 14100 0841 36 stability
120. roblem only affects observations at high signal to noise ratio S N gt 100 It is therefore recommended that users use the night time calibration templates if they want high signal to noise data In this case one should also take night time flats for the telluric standards As this is not part of the ISAAC calibration plan users will have to provide the appropriate OBs To get the highest signal to noise ratio one should set the nod throws of the telluric standard and the science target to be the same Observers who do not wish to obtain such high signal to noise data this applies to most observations done with ISAAC can safely ignore the night time flat field calibrations Requesting night time arcs is usually not necessary for observations below 2 2m since the OH lines provide an in situ wavelength calibration Above 2 2 microns there are few OH lines but there are many telluric features and they can either be used as in situ wavelength ISAAC User Manual VLT MAN ESO 14100 0841 26 calibration or as a means of determining the wavelength offset for observations calibrated with the daytime arcs Little experience has been obtained with similar problems in the LW arm However the same template has been created for the LW channel in case users feel they need accurate flat fields or arcs Note that the arcs should usually not be necessary since the sky leaves plenty of telluric features for wavelength calibration In the M band it is not pos
121. rom Ref Star SEQ REF OFFSETDELTA 0 Offset from Ref Star arcsec SW Filter wheel 1 INS FILT1 NAME Filter wheel 1 SW Filter wheel 2 INS FILT2 NAME Filter wheel 2 Slit INS SLIT Slit e g slit_1 The image displayed on RTD at the end of the template is dumped on disk A 6 6 ISAACSW_img_acq MoveToSlitrrm This template is functionally identical to ISAACSW_img_acq MoveToSlit apart from having fewer available parameters see Table 35 and is intended for acquisition of RRM spectroscopy OBs ISAAC User Manual VLT MAN ESO 14100 0841 57 Table 35 Parameters of ISAACSW_img_acq MoveToSlit P2PP label Keyword Def Description DIT DET DIT NDIT DET NDIT SW Filter wheel 1 INS FILT1 NAME SW Filter wheel 2 INS FILT2 NAME slit INS SLIT Detector Integration Time secs Number of DITs Filter wheel 1 Filter wheel 2 Slit e g slit_1 A 6 7 ISAACSW_img_acq Polarimetry All SW polarimetric OBs must use this template for target acquisition This template is very similar to the ISAACSW_img_acq MoveToPixel template The polarimet ric mask is displayed on the RTD and is superimposed on the image of the field Therefore the offset can be defined so as to properly position the object into the transparent region of the mask The template has been coded so that the field of view will rotate around pixel x y 512 540 If the aim of the user is to measure the polarisation of a single target as opposed to measuring the polarisa
122. rved for the Aladdin arm above 3 um and it consists of moving the secondary mirror of the telescope M2 once every few seconds The typical throw is about 20 arcseconds Therefore in most circumstances the images corresponding to the two beams have some overlap An essential requirement of this technique is to combine chopping with telescope nodding i e offsetting in the direction opposite to that of the chop The chopped images usually leave strong residuals on the detector that are due to the different optical paths of the two beams These residuals subtract well between two chopped images taken with a telescope nod in between In addition chopping and nodding may be combined with jittering i e the telescope is slightly offset between nod cycles Photometric Calibration Because the strong IR atmospheric absorption varies with airmass and water vapour content see section 3 1 in a slightly non linear manner accurate photometric calibration is more difficult in the IR than in the visible An accuracy of 1 can be obtained during stable nights provided that standard stars are observed frequently and with the same airmass as the object Standard stars have to be observed at least twice with a telescope offset in between allowing for the sky to be subtracted A list of photometric standard stars is provided in appendix C 1 The observatory maintains a list of standard star OBs which visiting astronomers can use Flat fielding The VLT dome
123. s Acquisition Template ISAACLW_img_acq Preset Observation Template ISAACLW_img_obs_AutoChopNod Integration time minutes 60 Execution time minutes Preset 6 0 Instrument setup 0 5 Integration time 60 Global overheads 40 x 60 Total 90 5 minutes for 60 minutes of integration Table 21 Overheads Example 6 LW Spectroscopy with chopping Template parameters Acquisition Template ISAACLW_img_acq_MoveToSlit Observation Template ISAACLW_spec_obs_AutoChopNod Integration time minutes 60 Execution time minutes Preset 10 0 Instrument setup 2 0 Integration time 60 Global overheads 30 x 60 Total 90 minutes for 60 minutes of integration Table 22 Overheads Example 7 LW Spectroscopy without chopping Template parameters Acquisition Template ISAACLW_img_acq_MoveToS1itNoChop Observation Template ISAACLW_spec_obs_AutoNodOnSlit DIT 0 4 seconds NDIT 150 Number of AB or BA cycles 30 NINT 1 Return to Origin T Execution time minutes Preset 10 0 Instrument setup 2 0 int time 60 0 Telescope offsets 15 25 61 telescope offsets Total 87 25 minutes for 60 minutes of integration ISAAC User Manual VLT MAN ESO 14100 0841 34 600 Ti ime sec O S 200 0 10 2x10 3x10 NDIT Figure 7 Execution times of the ISAACLW_img acq FastPhot template depending on the the data cube size and the selected mode Burst or FastJitter Filled squares are
124. s For observations that use chopping the bias voltage of the array is set so that the well depth is large This leads to a very large number of hot pixels whose flux is changing on the timescale of a few seconds Thus it is very important in long exposures to set Jitter Box Width to some non zero value so that these hot pixels can be removed A 10 1 ISAACLW_img_ obs_AutoChopNod This template combines chopping and telescope nodding The number of nodding cycles is referred to as Number of AB or BA cycles and one cycle commonly called an AB cycle ISAAC User Manual VLT MAN ESO 14100 0841 80 consists of two exposures one at each end of the nod Additionally it is possible to jitter between ABBA cycles but not between AB or BA cycles The amount of jitter between ABBA cycles is defined by the Jitter Box Width parameter in arcseconds For the removal of hot pixels it is essential that Jitter Box Width be set to a non zero value The orientation of the chopping is defined with the Chop Position Angle parameter This parameter can be defined in terms of SKY or DETECTOR coordinates with the Chop Nodding Coordinate parameter see section A 3 The parameters dealing with chopping and nodding are e Integration time minutes This parameter allows one to define the total integra tion time excluding overheads See section 6 2 for how to compute the overheads The number of chop and nod cycles will be determined automatically in the t
125. s are not equipped with calibration screens so dome flats are not possible In imaging twilight flats are for the time being the only possibility offered to ISAAC observers Regular twilight flat fields are taken by the ISAAC operation staff as part of the Calibration Plan and are made available through the ESO archive ISAAC does have a calibration unit equipped with a tungsten lamp however the unit is adequate for spectroscopic flat fields only 3 4 Spectroscopy Nodding The classical technique in spectroscopy is to observe object s at two or more positions along the slit The sky is effectively removed by subtracting one frame from the other registering the two beams and then subtracting again This process is sometimes called double subtraction If the field is crowded or if the object is extended then a blank sky may be necessary and in this case the double subtraction is done slightly differently Spectrophotometric Calibration Calibration of spectroscopic data in the IR is a complicated procedure that requires care It is generally done in three steps The first step removes telluric features with what is commonly called a telluric standard the second step removes the spectral features of the telluric standard that are imprinted onto the science spectrum because of the first step and the third step sets the absolute scale with what one may call a spectroscopic standard In ISAAC User Manual VLT MAN ESO 14100 0841 13 gene
126. s the frequency of the pickup noise and n is an integer number Additionally it will be possible to remove the pickup noise at the reduction stage see http www eso org sci facilities paranal instruments isaac doc drg html drg html Even with exposures as long as 900s the performance of MR spectroscopy between the OH lines in the J or H bands is readout noise limited It is therefore advisable to integrate for the longest possible time but the very high density of hot pixels and cosmic rays can seriously limit the data quality if the integrations are too long These bad pixels and cosmic rays are better removed when combining a large number of images The best compromise between data integrity and readout noise is difficult to find and somehow depends on the program It is advised to choose DITs of 10 15 minutes in J H and K band below 2 2 jum medium resolution spectroscopy and smaller values above 2 2 um in K band medium resolution spectroscopy If the total duration of the observation is short i e one single OB lasting less than one hour it is advisable to reduce the DIT to say 5 minutes or so and increase the number of exposures and telescope positions at which data is obtained This will make it easier to properly reject bad pixels If on the other hand the total duration of the observation is long i e several OBs each lasting 1 hr or so then it is advisable to increase the exposure time to 10 15 minutes Then by combini
127. se that if it perpendicular to the slit only half the integration time will be spent on target The parameters dealing with chopping and nodding are e Integration time minutes This parameter allows one to define the total integra tion time excluding overheads See section 6 2 for how to compute the overheads The DIT NDIT and the number of chop and nod cycles will be determined automatically e Chop Throw arcsec This is the chopping throw in arcsec it is limited to the 10 30 arcsec range However we strongly recommend that users limit the throw to 20 arcseconds or less e ChopNod PARA of PERP to Slit Either PARA if chopping is done along the slit or PERP if perpendicular to it Nodding will always be done parallel to the chopping The first exposure is done without initially offsetting the telescope The first image A is a chopped subtracted image the second image B is taken with the telescope offset in the opposite direction to the chop etc Users of the LWS3 LR mode are requested to set the central wavelength to one of the following values 3 55 or 4 75 ym Other values are not supported by the calibration plan see section 10 If the parameter Return to Origin 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 Table 54 Parameters of ISAACLW_spec_obs_AutoChopNod P2PP label Keyword Default Description Jitter Box Width SE
128. sible to do accurate wavelength calibration with the arc spectra Although we do provide an arc that is taken with the grating in third order the telluric features should prove to be more accurate 5 6 Chopping For LW broad band imaging and LW LR spectroscopy chopping is the only offered mode For other LW instrument setups the user can choose not to use chopping The basic characteristics and definitions of chopping are e The chopping throw is the distance between the two beams The maximum chop throw is 30 arcsec e The chopping angle can be defined with reference to the SKY or to the DETECTOR see appendix A 3 e Guiding can be achieved on both beams provided that the throw is approximately less than 20 arcseconds which corresponds to the field of view of the guide probe If the throw is greater than this guiding will be performed on only the central ON beam This will result in significantly poorer image quality in the OFF beam Thus we generally recommend that the chopping throw be kept to 20 arc seconds or less e The chopping frequency is automatically defined in the templates and is based on the instrument mode in use It typically varies between 0 1 and 0 5 Hz e Chopping is always associated with nodding in the opposite direction of the chop The nodding frequency is also automatically defined in the templates to give optimum per formance for each instrument mode e The detector acquisition system is synchronised in a t
129. slit showing two slit defects Table 5 ISAAC slits Slit width arcsec Slit Height arcsec 0 3 120 0 6 120 0 8 12011 1 0 120 1 5 120 2 0 120 Ul Defects on the slit limit the usable length to 90 arcsec resolution in the LR and MR modes The order is automatically set by the templates and the user only needs to define the central wavelength of the observations 2 4 Polarimetric Mode ISAAC offers SW imaging polarimetry in the Hawaii arm A Wollaston prism in one of the two filter wheels splits the incoming parallel beam into two beams which are perpendicularly polarised The beams are separated by 21 arcseconds Thus 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 24 arc seconds 20 arc seconds respectively is inserted at the focal plane Thus in a single exposure at least half the field will be missing so three exposures with telescope offsets in between are required to image one field see Section A 7 5 for more details The Wollaston prism is not achromatic so the exact separation between the two beams is a function of wavelength In J the separation is 22 5 arcseconds while in Ks the separation is 21 arcseconds The beam separation is also a function of position from the top to the bottom ISAAC User Manual VLT MAN ESO 14100 0841 7 Table 6 Wavelength range orde
130. t has its own GUI which allows one to access all instrument parameters Figure 5 shows the ISAAC OS GUI The users only use templates to control the instrument and therefore have no direct interaction with OS However the OS GUI is useful for the visitors as a status display panel displaying all information from instrument detector and telescope ISAAC OS TYPE UNDEFINED INS_USER SYSTEM File Options Commands Tools Status Imaging Catg Type Tech E Expo File Exp Id 67 Exposure Count Down STATE SUBSTATE ISAAC SW CALIB II SKY FLAT IMAGE jitterTest_0011 00 z 00 00 ON LI N E Expo Name New Data 10 000 l DLE Instrument Mode Info jittertest_0011 ExposureTime Phase Inactive Requestor swi m WCS W Seq Naming 12 R 5 W Archive Header RTD Detector Hawaiisci02 ICS ONLINE IDLE SIMULATION DCS ONLINE IDLE SIMULATION TCS ONLINE Idle Functions Calibration Mirror Arm Window Chopping Preset Offsets NO TCS Chopping Telescope offset M Combined slit_0 3_tilted 3 Chopping ON OFF OFF Aab opoe OFFSET e E Throw x o y Jo OFFSET slit_1_tilted PupilObj Wavelength Pos Angle gt XY offset via RTD al closed Number of chop cycles mask L2 Order Number of cycles to skip Rotator offset 357 OFFSET Chop frequency Hz M2
131. tal 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 1 minute per telescope position rule means here that both DIT x NDIT for the OBJECT positions plus overheads and DITx NDIT for the SKY positions plus overheads shall each exceed one minute of time ISAAC User Manual VLT MAN ESO 14100 0841 63 ISAACSW_img_obs FixedSkyUOf set N Sky positions E Sky offset Alpha feo Pp o A pP A H E Template Parameters gt gt ER Number of AB or BA cycles 3 Jitter box width 30 Sky offset Alpha 200 Sky offset Delta 170 Rotate pupil F Jitter box Object positions Figure 12 Illustration of the ISAACSW_img_obs_FixedSky0ffset template The black dots in the central square represent the position of a star which was originally at the centre of the field The other square represents the mean position of the SKY frames ISAAC User Manual VLT MAN ESO 14100 0841 64 A 7 4 ISAACSW_img obs GenericOffset This template is for imaging and has the flexibility to do any sequence of telescope offsets either in detector or sky coordinates Table 40 Parameters of ISAACSW_img obs_GenericOffset P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs Observation Category SEQ CATG SCIENCE Observation category science or preimaging Number of Exposures SEQ NEXPO Number of e
132. tant Narrow Band Filters on each filter wheel E g NB_2 09 on filter wheel 1 and NB_2 17 on filter wheel 2 Important note when the bright object in the field of view is not the target to centre on slit the target may become too faint to see due to the use of the Narrow Band Filter s In this case see Sec 5 3 offsets from a reference star should be used 5 4 3 LW Imaging and Spectroscopy For NB_3 21 and NB 3 28 non chopping observations the maximum brightness is L 5 Users who wish to observe brighter stars in these filters should use chopping For LW spectroscopy objects brighter than 4th magnitude should be acquired with the NB filters 5 5 Night Flat fields and arcs Due to non reproducibility effects involving the grating and the slit there are usually slight differences between flats and arcs taken at different times As flats and arcs are taken the day after the observations this can limit the accuracy at which spectroscopic data can be flat fielded and wavelength calibrated To circumvent this special templates have been created to allow flat fields or arcs to be taken at the end of the spectroscopic templates without moving the grating or slit wheel ISAACLW_spec_cal_NightCalib for LW ISAACSW_spec_cal_NightCalib for SW If used these templates must be attached at the end of each spectroscopic template They are not autonomous they must not be used on their own It is believed that the flat field non reproducibility p
133. templates produce a data cube for each nod position which contains the two half cycle frames For the narrow band 3 21 and 3 28 um filters non chopping observations can also be used The imaging mode for NB_3 21 and NB_3 28 non chopping observations is LWI3 8 2 Recommended DITs and NDITs For observations that use chopping DIT and NDIT are not parameters they are automatically set by the templates and depend on the filter For observations without chopping the optimal DIT values are given in Table 24 NDIT should be set so that the total exposure at any one position is one minute Table 24 LW detector settings for imaging Mode and filter DIT seconds LWI3 3 21 um filter 0 35 to 0 7 LWI3 3 28 um filter 0 35 to 0 5 8 3 Calibration Plan Supported calibrations are e Sky flats taken at three different airmasses in all filters used during a night e Zero points of the night in the L and M_NB filters whenever they are used at night These zero points aim to provide photometric calibration to an accuracy of 10 Users requiring higher accuracy should provide OBs that will be executed either immediately before or after their observations In this case the time spent doing these observations will be charged to the user Narrow band filter zero points are not supported by the calibration plan and should be explicitly requested and prepared by the users e Dark frames for any DIT and readout mode used at night are take
134. ter wheel 1 INS FILT3 NAME LW Filter wheel 1 LW Filter wheel 2 INS FILT4 NAME LW Filter wheel 2 Table 51 Parameters of ISAACLW_img_acq MoveToSlitNoChop P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of DITs Alpha offset arcsec TEL TARG OFFSETALPHA 10 RA offset arcsec Delta offset arcsec TEL TARG OFFSETDELTA 10 DEC offset arsec Angle on Sky deg TEL ROT OFFANGLE 0 Position angle DDD TTT Preset Telescope SEQ PRESET T Preset telescope Alpha offset from Ref Star SEQ REF OFFSETALPHA 0 Offset from Ref Star arcsec Delta offset from Ref Star SEQ REF OFFSETDELTA 0 Offset from Ref Star arcsec LW Filter wheel 1 INS FILT3 NAME LW Filter wheel 1 LW Filter wheel 2 INS FILT4 NAME z LW Filter wheel 2 Slit INS SLIT Slit e g slit_1 field of view of 1 arcmin if the acquisition filter is either L or narrow band M Therefore acquisitions involving objects separated by more than 1 arcmin should be acquired with either the narrow band LW or the SW filters This template does not use chopping It should not be used to acquire targets if the subsequent LW spectroscopic template uses chopping This template is functionally identical to the ISAACSW_img_acq_MoveToS1lit template so users should refer to Sec A 6 5 for details ISAAC User Manual VLT MAN ESO 14100 0841 79 A 10 Aladdin Observation and Calibration Templates With Chop ping
135. the slit losses and or accurate flux calibration we recommend that you explicitly ask in your README file that the telluric standard is observed also with the 2 slit or in slit less mode Alternatively if the broad band magnitudes of the object are known the absolute flux calibra tion can be derived by convolving the measured spectrum with the broad band filter curves In this case the IR magnitude of the standard is irrelevant only the spectral type is important This works at Low Resolution but not at Medium Resolution where the spectral coverage is smaller than the filter bandwidth Locating spectra Because ISAAC uses two different optical paths in imaging and spectroscopy the formats in imaging and spectroscopy are different E g if an object is along the slit at pixel Ying its position along the slit in spectroscopy is Y spec Note for instance that the vertical axis is flipped between imaging and spectroscopy The relationship Y spe function Y img is calibrated and maintained by ESO http www eso org observing dfo quality ISAAC qc qc_IS_startrace htm1 At the end of each acquisition see appendix A the image that is displayed on the RTD which usually consists of a moderately deep sky subtracted image is dumped to disk The locations of the slits are accurately known so it is always possible to know exactly what was observed from the acquisition images For faint objects it is not always easy to locate the spectrum
136. tical This angle is totally transparent to the user The Y axis between images and spectra is flipped See figure 8 for illustrations of the orientation convention A 3 Chopping conventions and definitions Chop Throw arcsec This is the throw of the chopping in arcsec The formal allowed range is 10 30 arcseconds however we strongly recommend that the throw is kept to 20 arcseconds or less If the chop throw is between 20 and 30 arcsec guiding is only possible on one beam leading to a deterioration of the image quality due to intermittent loss of AO corrections Chop Position Angle This is the chopping position angle in degrees If the Chop Angle Coordinate is set to SKY then the chopping will be in sky coordinates The convention is that 0 degree will result in chopping to the South i e the OFF beam will be to the South of the ON beam negative and positive images respectively on the acquisition images and that the angle of the chop is defined from North to West The ISAAC User Manual VLT MAN ESO 14100 0841 50 y y A Slit m 1024 1024 Slit 1024 1024 _ E AN li E Pd y T N N Xx w I 1 1 1 1 a b Figure 8 Orientation convention for images including acquisition images a Field orien tation on detector at 0 rotation angle on sky b Field orientation at 30 rotation angle on sky The slit position is overlaid In spectra the Y axis is flipped The
137. tion as in the science template 12 3 Pipeline Burst and FastJitter observations produce data cubes that are not pipeline supported How ever the same recipes that process standard darks and twilight flats can also deal with the windowed frames While the FastJitter data come in cubes where each layer is an actual image and can be copied and then handled as such in the case of the Burst mode it is necessary to first reconstruct the images This technique is not supported by the ISAAC pipeline Table 26 Hardware windowing characteristic in Burst and FastJitter mode Burst mode FastJitter mode Window Size pxs StartX StartY pxs Field of View min DIT ms max NDIT min DIT ms max NDIT 32x32 497 4 7x4 7 3 2 16000 12 32000 64x64 481 9 5x9 5 6 4 15990 12 15990 128x128 449 19x19 14 3995 14 3995 256x256 385 38x38 37 995 37 995 512x512 257 75x75 106 245 106 245 ISAAC User Manual VLT MAN ESO 14100 0841 47 Table 27 Burst mode technical info Note that the reported execution times are just indicative and may vary depending on the net connection Window Size pxs 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 32x32 64x64 64x64 64x64 64x64 64x64 64x64 64x64 DIT ms 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 4 0 4 5 5 0 5 0 5 0 5 0 5 0 5 0 NDIT N Frames
138. tion in the entire field it is recommended that the target is placed on or close to this pixel Otherwise the target may move behind the mask after the field is rotated Service Mode users should make it clear where they wish their target to be placed Table 36 Parameters of ISAACSW_img_acq Polarimetry P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of DITs Alpha offset arcsec TEL TARG OFFSETALPHA 10 RA offset arcsec Delta offset arcsec TEL TARG OFFSETDELTA 10 DEC offset arsec Angle on Sky deg TEL ROT OFFANGLE 0 Position angle DDD TTT Preset Telescope SEQ PRESET T Preset telescope SW Filter wheel 1 INS FILT1 NAME Filter wheel 1 SW Filter wheel 2 INS FILT2 NAME Filter wheel 2 ISAAC User Manual VLT MAN ESO 14100 0841 58 ISAAC img obs_AutoJitter a angle on the sky 30 E N Jitter box width Isaac field of view 1 1 1024 1024 Template Parameters Number of exposures 8 Jitter box width 30 x Figure 10 Illustration of the ISAACSW_img_obs_AutoJitter template The black dots repre sent the position of a star which was originally at the centre of the field A 7 Hawaii Imaging Templates All Hawaii Imaging templates use the SWI1 mode except the ISAACSW_img_acq_ Polarimetry template which uses the SWP1 mode For more information see section 7 A 7 1 ISAACSW_img obs_AutoJitter This template offsets the telesc
139. tions It allows windowing of the detector which is recommended in case of very bright target thus very short DIT values We suggest to set always DIT minimum DIT see Table 26 for the minimum DIT values which correspond to each windowing and to select a DIT NDIT combination such that their product is 0 5 1 sec We also suggest to set the same detector windowing and the same filters combination as in the following science template thus to minimise the number of instrument setups and therefore the overheads In all cases the instrument set up should be carefully checked and selected on the basis of the target magnitude A 9 7 ISAACLW_img_acq MoveToSlitNoChop The template presets the telescope and allows the operator to interactively centre objects into the selected slit The instrument mode for this template is LWI3 which is not offered for L and NB_M imaging Consequently the detector may have to be windowed down to a ISAAC User Manual VLT MAN ESO 14100 0841 78 Table 50 Parameters of ISAACLW_img_acq_FastPhot P2PP label Keyword Default Description DIT DET DIT Detector Integration Time secs NDIT DET NDIT Number of DITs WINX DET WIN NX 1024 number of columns WINY DET WIN NY 1024 number of lines STARTY DET WIN STARTX 1 first column of window STARTY DET WIN STARTY 1 first row of window Angle on Sky deg TEL ROT OFFANGLE 0 Position angle DDD TTT Preset Telescope SEQ PRESET T Preset telescope LW Fil
140. tor Integration Time secs NDIT DET NDIT Number of DITs Alpha offset arcsec TEL TARG OFFSETALPHA 10 RA offset arcsec Delta offset arcsec TEL TARG OFFSETDELTA 10 DEC offset arcsec Angle on Sky deg TEL ROT OFFANGLE 0 Position angle DDD TTT Preset Telescope SEQ PRESET E Preset telescope SW Filter wheel 1 INS FILT1 NAME Filter wheel 1 SW Filter wheel 2 INS FILT2 NAME Filter wheel 2 59 ISAAC User Manual VLT MAN ESO 14100 0841 56 A 6 5 ISAACSW_img_acq MoveToSlit All SW spectroscopy OBs must make use of this template for target acquisition The only exception is for RRM observations for which ISAACSW_img_acq MoveToSlitrrm see Section A 6 6 must be used instead See also section 5 3 and 5 4 for more specific information regarding slit acquisition This template is very similar to the ISAACSW_img_acq MoveToPixel template A drawing of the selected slit is displayed on the RTD and is superimposed on the image of the field The centring of the target or reference objects is then done interactively with the tool described in appendix A 6 4 In most cases users will use the option to move the selected object to the centre of the slit It is recommended to set DIT and NDIT such that the exposure time DIT x NDIT gt 20 to average out atmospheric variations and to ensure good target centring on the slit The template also allows one to place two objects into the slit without the requirement of calculating the position
141. ts would guarantee that the objects go straight into the slit It is mandatory to useeither of the acquisition templates ISAACSW_img_acq_MoveToSlit or ISAACSW_img_acq_MoveToSlitrrm for all SW spectroscopic OBs and to use the same slit in both the acquisition and observing templates It is recommended to use at least 20s of exposure time for the acquisition DIT x NDIT to average over the seeing motion and thus allow a correct centring of the target The templates provide interactive tools to rotate the field and or make telescope offsets to centre objects into the selected slit which is overlaid on the RTD It can also be used to place two objects in the slit without having to precompute the position angle Service mode users requiring the rotation angle to be found in this way should make this clear in the finding chart and README and identify which stars to use OBs for which target acquisition cannot be completed within a few minutes of time will not be executed Acquisition can be done either on the target itself or on reference targets The object used for acquisition has to be brighter than approximately 17 18th magnitude in the IR when acquisition is done with the near IR Broad Band filters J H or Ks Exceptions will be tolerated for moving targets and special situations to be evaluated on a case by case basis When the science target is fainter than the above quoted magnitude the procedure for ac quisition should rely on reference ob
142. ubsequent LW imaging observations that use chopping This template presets the telescope and allows the operator to interactively centre the field In visitor mode the interactive part of the template will be executed by the instrument operator under the supervision of the visiting astronomer In service mode it is mandatory that the users send detailed information for target acquisition The chopping parameters to be defined are ISAAC User Manual VLT MAN ESO 14100 0841 75 e Chop Throw arcsec This is the throw of the chopping in arcsec it is limited to the 10 30 arcsec range A chop throw of lt 20 arcsec is recommended e Number of Chop Cycles This is the number of chop cycles to be averaged in the acquisition system preprocessor The higher the value the better the detection limit but the longer the acquisition time One chop cycle will typically last between 2 to 10 seconds depending on chopping frequency The minimum number of chop cycles is 1 This parameter may be adjusted by the operation staff at execution time if the object is too faint e Chop Position Angle See section A 2 e Chop Angle Coordinate Either SKY or DETECTOR After completion of the preset the instrument and detector are set The observer is then prompted to define an offset This is simply done by drawing an arrow on the screen with the left hand button of the mouse If the offset is accepted the telescope offsets by the desired amount F
143. ut noise of the detector and not by the shot noise from the sky continuum Longer integration times are possible but lead to very poor cosmetics hot pixels and cosmic rays see Section 9 3 3 Imaging Jitter Because of the high sky brightness in the IR its rapid variability detector cosmetics and detector instabilities accurate sky subtraction is essential and this requires special attention and procedures The standard practice is to resort to the jitter technique also called shift and add and all ISAAC SW and some LW imaging templates make use of it When the field is uncrowded sky frames can be estimated from the object frames themselves In practice a running sky is built from the 5 frames that were taken immediately before and after the frame from which the sky is being estimated All sky subtracted frames are then co added with adequate shifts to form the final image When the field is crowded or the object extended i e covering a large fraction of the array the sky has to be sampled away from the object resulting in a loss of efficiency for the observations which can amount to 50 of the time if the sky has to be sampled as frequently as the object In this case all the object and sky positions are jittered between themselves A more detailed explanation can be found http www eso org projects dfs papers jitter99 ISAAC User Manual VLT MAN ESO 14100 0841 12 Chopping This technique is rese
144. ve Unfortunately hot stars do contain some features usually lines of hydrogen and helium that can be difficult to remove If the region around the hydrogen and helium lines are of interest then one can also observe a late type star which should have weak hydrogen and helium lines This star is then used to correct for the helium and hydrogen absorption in the spectrum of the hot star Some hot stars also have emission lines or are in dusty regions These stars should be avoided The V I colour of the star can be used as an indicator of dust For stars hotter than AO it should be negative And lastly hot stars tend to lie near the galactic plane so there may be situations where there are no nearby hot stars Solar analogs for the purpose of removing telluric features are stars with spectral type GOV to G4V These standards have many absorption lines in the IR particularly in the J band The features can be removed by dividing by the solar spectrum that has been degraded to the resolution of the observations This can be a bit tricky with ISAAC as the spectral resolution is variable In addition to hot stars and solar analogs IR astronomers have used other stellar types as telluric standards For example F dwarfs are commonly used We would like users to think carefully about which star is best for their program Although the observatory will automatically observe a telluric standard for service programs we cannot guarantee that we will
145. ve the same pixel scale and maximum FoV However in Burst and FastJitter modes the detector can be hardware windowed to FoV as small as 4 7x4 7 arcsec i e 32x32 pixels In spectroscopy M1 is retracted and light is diverted by M2 onto the 3 mirror collimator M3 M4 and M5 Light then reaches the grating in Littrow mode and is reflected back to M6 via the 3 mirror collimator An intermediate spectrum is formed on M6 which is conjugated with the slit plane The rest of the optical path is identical to the imaging path 2 2 Imaging Modes The characteristics of the imaging modes are summarised in table 1 and they are described in greater detail in Sections 7 8 and 12 The filters available in SWI1 LWI3 and LWI4 modes are listed in tables 2 and 3 Note that the filter central wavelengths are field dependent this is a general characteristic of filters due to the variation of the incidence angle on the filter across the field of view The effect is 0 3 of the central wavelength in some NB filters in K which represents a significant fraction of the bandwidth of these filters 2 2 1 Comparison of JHK imaging in Hawaii and Aladdin arms Due to technical problems in P69 it was necessary to transfer some SW observations to the Aladdin arm Although the technical problems are now fixed we decided to keep and offer the possibility of JHK imaging with the Aladdin arm Note however that we have little experience with JHK Aladdin observations
146. ves the telescope alternatively between object and sky positions The object positions of the telescope are randomly distributed around the object initial telescope position and within a box whose dimensions are set by the parameter Jitter Box Width in arcsec The minimum value for this parameter is 10 arcsec The sky positions are also randomly distributed around a fixed offset position defined by the parameters Sky Offset in Alpha and Sky Offset in Delta from the original object telescope position The box dimensions of the random sky positions are set by the parameter Jitter Box Width i e the sky exposures are distributed in a box offset from the initial telescope position Table 39 Parameters of ISAACSW_img obs_FixedSky0ffset P2PP label Keyword Def Description DIT DET DIT Detector Integration Time secs Observation Category SEQ CATG SCIENCE Observation category science or preimaging Jitter Box Width SEQ JITTER WIDTH Random offset box width arcsec Return to Origin SEQ RETURN T Return to Origin Sky Offset in Alpha SEQ SKYOFFSET ALPHA Sky Offset in Alpha arcsec Sky Offset in Delta SEQ SKYOFFSET DELTA Sky Offset in Delta arcsec Rotate Pupil SEQ ROTPUPIL T Pupil rotation compensation Number of AB or BA cycles SEQ NABCYCLES Number of AB or BA cycles NDIT for the OBJECT positions SEQ NDIT OBJECT NDIT used on OBJECT positions NDIT for the
147. xposures List of NDIT SEQ NDIT LIST NDIT List Return to Origin SEQ RETURN T Return to Origin Flag Obs Type 0 or S SEQ OBSTYPE LIST Observation type list S or O List of offsets X or RA SEQ OFFSET1 LIST T X or RA offset list arcsec List of offsets Y or DEC SEQ OFFSET2 LIST 7 Y or DEC offset list arcsec Offset Coordinates SEQ OFFSET COORDS SKY or DETECTOR coordinates SW Filter wheel 1 INS FILT1 NAME Filter wheel 1 SW Filter wheel 2 INS FILT2 NAME Filter wheel 2 Figure 13 and 14 illustrate what the template does ISAACSW_img_obs_GenericOffset 1024 1024 Position angle on the Sky 30 A E N Template Parameters Obs Type 0 List of Offsets in Xor RA 0 75075007 50 List of Offsets in Y or DEC 0 0 45 0 45 45 0 45 Number of exposures 8 Offset Coordinates DETECTOR ISAAC field of view 1 1 Figure 13 Illustration of the ISAACSW_img_obs_GenericOffset template The black dots represent the position of a star which was originally at the centre of the field In this example Offset Coordinates is set to DETECTOR and the stars not the telescope are moved in X and Y according to the list of offsets Telescope offsets are defined as lists with the parameters List of offsets X or RA and List of offsets Y or DEC The offsets are relative to the previous position in RA and DEC or in X and Y depending on the Offset Coordinates parameter and they are defined in arcsec Additionally
148. y are in Garching for service observations Visitors can save the pipeline reduced data for themselves Pipeline reduced data are not part of the data package they receive at the end of their run The old ISAAC pipeline which was based on the eclipse library can still be downloaded from http www eso org sci software eclipse but is no longer supported The new ISAAC Pipeline is based on esorex see http www eso org sci software cpl esorex html for more information and can be downloaded from http www eso org sci software pipelines A manual for this pipeline is available at the same direction ISAAC User Manual VLT MAN ESO 14100 0841 28 Table 13 Aladdin Templates cookbook Action Template s to use Acquisition Simple telescope preset ISAACLW_img_acq Preset Preset telescope and central field with chopping ISAACLW_img_acq MoveToPixel Preset telescope and central field without chopping ISAACLW_img_acq MoveToPixNoChop Preset telescope and central field without chopping and without AO ISAACLW_img_acq FastPhot Preset telescope and central object s in slit with chopping ISAACLW_img_acq MoveToSlit Preset telescope and central object s in slit without chopping ISAACLW_img_acq_MoveToS1itNoChop Imaging Imaging with chopping and nodding ISAACLW_img_obs_AutoChopNod Imaging without chopping J Block H Ks and ISAACLW_img_obs_AutoJitter narrow band imaging below 3 5 um ISAACLW_img_obs_Auto

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