VISIR Operational Manual
Contents
1. 8 5um and generate the Telluric OB see Fig 11 Y Telluric Standard 60 A 9234 A Paranal Science Operations Ho VISIR_spec_acq_MoveToSlit VISIR spectroscopy acquisition templa yw VISIR_spec_cal_LRAutoChopNod VISIR_spec_obs_LMHRAutoChopNe H Y DPR hy CATG CALIB Y TECH SPECTRUM CHOPNOD TYPE STD 7 INS Y FILT2 NAME OPEN Y GRAT1 WLEN 8 5 Y MODE SPC py RESOL LR SOURCE SKY Hy SEQ ka CHOPNOD DIR PARALLEL Y NODTIME 0 Y RETURN T y TIME 180 ps WEATHER G JITTER WIDTH 0 y TEL pp CHOP POSANG 0 CHOP THROW 8 Figure 11 A typical SPC Telluric OB case 2 you need a telluric that is within 0 2 airmass difference from a science target with a high airmass In such case boxes Target LST and Std Obs LST need to respectively report VISIR Operational Manual VLT MAN ESO 14300 5129 12 the expected LST at half the execution time of the science OB and the LST at the time the Telluric will be actually observed This time the Delta airmass of the Telluric candidates is estimated with respect to the science target airmass and all in a way so as to select a Telluric within 0 2 difference 5 Organizing the VISIR working space 5 1 RTDs There are 2 RTDs e the IRDCS real time display Fig 3 basically allows you to monitor the sky background in real time to do so chose the DIT option in DATA It is convenient to open the STAT2. and how to classify any SPC IMG OB based on the weather constraints VISIR Operational Manual VLT MAN ESO 14300 5129 19 8 Summary of Typical SM OB Execution If you have reached this point then you are able to do the following e identify the necessary info regarding the requested VISIR service mode SPC IMG setup e g IMG Filter Q2 and SF 0 075 or SPC LR 04 slit width A 12 8um e identify the necessary calibrators whether STD or Telluric for the service mode OBs e generate specific OBs to execute the calibrators IMG STD OBs are chosen from the OT while Telluric are generated from the stdsopMain tool e execute the calibrator OBs at Zenith acquire the STD Telluric star and most impor tantly decide the best weather flag G F P S to keep the background below 6 000 ADU e derive an initial sensitivity at Zenith for the SPC IMG calibrator e iterate if necessary different weather flags to reach the best possible lowest in Jansky value sensitivity that is below the reference values e start the science SM OB with exactly the same weather flag decided on the STD Telluric taken at Zenith e acquire the target with any weather flag because this does not compromise the fact that the science template has exactly the same weather flag decided on the STD Telluric taken at Zenith e Again for ALL IMG service mode OBs take STD at zenith decide weather flag and check the achievable sensisitivity execute
3. e g B3 and B5 lt 200 lt Magn Range Vmag lt fioo Target Airm E Delta Airm dx 0 05 Catalogue Selection Cohen Jy Search gt gt lt lt 411 2 282 702 179 0 05 20 14 05 42 27 42 KOIII 2 09 999 122 806 126 587 86 205 35 947 5 738 1 494 1 093 0 049 0 43 35 37 17 59 11 77 KOIII S 99 999 1151 419 1187 021 808 380 337 077 53 810 14 012 1 093 0 049 23 10 21 53 45 14 48 16 K1III S 99 999 164 244 198 181 136 239 57 712 9 095 2 496 1 069 0 025 0 23 04 39 15 56 33 20 MOIII E 99 999 81 182 113 591 83 826 36 284 5 783 1 625 1 066 0 022 22 06 06 88 39 32 36 07 K3III a 99 999 207 686 247 010 175 990 75 404 11 355 3 093 1 060 0 016 Instrument Setup Spec Mode LR Instrument VISIR 2 S Slit Position 1 00 Wavelength 8 4 Figure 10 The stdsopMain window used to select a proper Telluric at a given airmass differ ence from a given target at Zenith So in this case you would enter the local Sideral time in the Right Ascension box and chose a particular Declination e g 40 00 if you have wind coming from the North case 1 you need a simple telluric at Zenith In such case boxes Std Obs LST and Target LST can be both set to the local Sideral time Set the Delta airmass to 0 05 0 1 select the Cohen Jy from the Catalogue Selection and press Search Chose the star with the lowest airmass difference insert the correct setup e g LR slit width 1 00
4. 8 4 IF 0 0250 0 0200 0 0160 0 0125 J12 2 4 IF 0 0250 0 0200 0 0160 0 0125 Q1 2 IF 0 0125 0 0100 0 0080 0 0080 Q2 2 IF 0 0125 0 0100 0 0080 0 0080 Q3 2 IF 0 0400 0 0250 0 0200 0 0160 Table 1 The DIT s as hardcoded for each filter in the 0127 FoV as a function of the weather flag VISIR Operational Manual VLT MAN ESO 14300 5129 filters Chopping Period s FoV Good Fair Poor Sad PAH1 4 SF 0 0200 0 0160 0 0125 0 0100 SIC 4 SF 0 0250 0 0200 0 0160 0 0125 All 4 SF 0 0625 0 0500 0 0400 0 0250 SIV 1 4 SF 0 0100 0 0080 0 0080 0 0080 SIV 4 SF 0 0400 0 0250 0 0200 0 0160 SIV 2 4 SF 0 0160 0 0125 0 0100 0 0080 PAH2 1 4 SF 0 0125 0 0100 0 0080 0 0080 PAH2 4 SF 0 0100 0 0080 0 0080 0 0080 PAH2 2 4 SF 0 0125 0 0100 0 0080 0 0080 NEII 1 4 SF 0 0200 0 0160 0 0125 0 0100 NEII 4 SF 0 0250 0 0200 0 0160 0 0125 NEII 2 4 SF 0 0200 0 0160 0 0125 0 0100 B8 7 4 SF 0 0500 0 0400 0 0250 0 0200 B9 7 4 SF 0 0400 0 0250 0 0200 0 0160 B10 7 4 SF 0 0400 0 0250 0 0200 0 0160 B11 7 4 SF 0 0625 0 0500 0 0400 0 0250 B12 4 4 SF 0 0400 0 0250 0 0200 0 0160 J7 9 4 SF 0 0800 0 0625 0 0500 0 0400 J8 9 4 SF 0 0125 0 0100 0 0080 0 0080 J9 8 4 SF 0 0625 0 0500 0 0400 0 0250 J12 2 4 SF 0 0625 0 0500 0 04
5. Cik File Readout Mode Imager_syncABAB Seq File 5C IRACE SEQ Imager_sync_se Acq Proc vidiracoABRE Load Detector Configuration e Search Path INS BOOT w INTROOT wv VLTROOT Y VLTDATA w TCLTK_ROOT w MODULE OTHER Tee Voltages Root Directory kag Sub Directory DET Save Returned Path Absolute Relative Speed Filter Ir azi def gf o Directories Files ROOT SYSTEM MISC IRACE DET Imager_VISIR dcf Imager_VISIR_SUN dcf Spectro_VISIR_SUN dcf ntinuous Mode nter Reset H AAA Hl Selection fdata VISIR INS_ROOT SYSTEM MISC IRACE DET Spectro_VISIR dcf oK Filter Cancel Help Figure 23 Switching from the IMG to SPC detector during day time e Diaphram wheel This is the first piece that intersects the entering light It is a wheel holding either a mirror masks e g pinhole or grid array masks The mirrors MOA MOB and MOC when deployed all direct the light to the SPC detector Whereas if you want to use the IMAGER detector you should either SF or IF also VLF e Filter wheel here you can chose any filter and the light passes through e TMA three mirror anastigmatic the easiest way is to imagine this as an objective wheel or a lens It allows to get rid of chromatic aberrations e The light has finally reached the IMAGER detector So to get the star simulator working you need to clear the way of the light so as it reaches the IMAGER detector with
6. image Since this acquisition template is used only by Astronomers you should always take this image and once again if the target is bright enough you should be able to identify the target However it may be that the target is faint and you are unable to identify it even in the first image obtained with the SPC detector In such cases you simply trust the fact that the target has been centered in the IMG detector and should be centered in the SPC detector Lastly the only reason why Astronomer use this complicated acquisition template is because the IMG detector is more sensitive and it is easier to identify fainter targets 7 VISIR service mode OBs classification In principle once you have derived the sensitivity from the calibrator you should be already able to classify the science OB This is because the 2 criteria used to classify the service mode OBs are sensitivities and image quality 7 1 Image Quality Remember that MIR observations would almost always provide diffraction limited images in the N and Q band That is if the optical seeing on the guide probe is somewhere around 078 VISIR will deliver images with FWHM around 0 4 and below So when we say that image quality is one of 2 parameters to classify any service mode OB we mean check the shape of the reduced science images if you are doing a IMG program or the STD Telluric during acquisition if you are doing a SPC program If there are no particular e
7. script that actually excludes these lines and provides the so called in 75 best value To run this script from GASGA NO e select the reduced telluric standard star file usually displayed in red e g r VISIR 2010 10 25T04 55 04 tpl A01 0000 fits e With the right mouse button or in the menu Selected files select Run e Make sure you are in diska home astro3 scripts and chose VISIR SPC sens sh e This script calls an IDL batch procedure which displays see Fig 8 the sensitivity as a function of wavelength as given in the selected files The Y axis scale ranges from 0 to twice the reference announced sensitivity for the given setting for the current period This reference announced sensitivity is indicated by a dashed horizontal line at the middle of each graph The procedure also selects the 75 best sensitivity points and shows their mean sensitivity e Use this 75 best sensitivity as your measurred sensitivity for that particular setup File Selected files Tools Help Z E BEE File Displaying 421 files Unfiltered gt l 083 A 0930 VIMOS 555555555 E 086 E 0242 VISIR UNKNOWN gt Gj 086 8 0479 VISIR UNKNOWN gt l 086 8 0774 ISAAC id 386 A 0566 A ISAAC gt El 386 A 0566 ISAAC gt mg 60 A 9021 ISAAC gt E 60 A 9050 VIMOS 555555555 mJ 60 A 92344 VISIR UNKNOWN B 200145820 Telluric Standard El VISIR_SPCIMG El visir_spcimc_ fits El visir_sPCIMG_SLITTEST298_0001 fit
8. telescope i e both emit in the MIR window see Sec 9 4 So MIR detector are quite hard to manufacture given the huge number of incident photons e g 10 photons s Consequently the typical exposure time DIT is very short less than a second So it is quite a challenge to observe in the MIR window from ground based telescopes it is too easy to do it from space MIR atmosphere transmission at Paranal 1 2 1 0 0 8 0 6 Transmission 0 4 0 2 0 0 ME 5 10 15 20 5 30 Wavelength um Figure 1 MIR atmospheric transmission at Paranal VISIR Operational Manual VLT MAN ESO 14300 5129 2 2 Basic MIR concepts 2 1 Chopping and Nodding Given the intrinsic difficulties in ground based MIR observations and to overcome the high background problem smart astronomers invented the so called Chopping Nodding technique see Fig 2 Unless you are observing a very very bright target e g STANDARD star you will NOT see your target unless the Choppining Nodding technique is employed It is very simple e Chopping in nodding position 1 the secondary mirror chops or moves at a certain frequency e g 0 25 Hz or 4 seconds period from ON target to OFF target The max imum allowed movement is 30 0 The difference of these 2 images allows us to cancel most of the undesired background yet the target is NOT visible e Chopping in nodding position 2 the telescope itself is moved slightly OFF ta
9. the SM science OB and most importantly if the STD taken is Zenith has A air mass gt 0 2 with respect to the science target then take a second STD this time having A air mass lt 0 2 So the first STD is to derive sensitivity weather flag while the second STD if necessary is taken for the flux calibration at that particular airmass e For ALL SPC LR we apply the same strategy for the IMG service mode OBs That is if the Telluric taken is zanith has A air mass gt 0 2 with respect to the science target then take a second Telluric this time having A air mass lt 0 2 e For SPC MR SPC HR SPC HRz the observatory provides only the Telluric taken at Zenith for the sensitivity and it is the user s responsibility to provide his flux calibrators e Check the image quality of the IMG pipeline reduced images and the SPC acquistion images investigate the presence of possible elongation and keep in mind that VISIR provides diffraction limit images hence the seeing cosntraints are almost always re spected e If the STD Telluric sensitivity taken at Zenith are below the reference Jansky values the image quality is acceptable then you can classify the OB according to the table reporting sensitivity limits vs weather constraints Table 3 Do not forget the A air mass lt 0 2 constraints and provide a STD Telluric when the IMG amp SPC LR targets are observed at high airmass VISIR Operational Manual VLT MAN ESO 14300 5129 Th
10. whereto actually monitor the background level is to execute a STD Telluric OB just before your science OB and measure the background in the STD Telluric acquisition images Depending on weather detector temperature location on the array the levels are variable For the observations levels should ideally be kept at values lower than 6 000 ADUs and almost never above 10 000 ADUs to avoid the striping feature Note that the background level increases with airmass at a rate so far measured only for PAH1 of about 1 000 ADUs per 0 1 increase in airmass In spectroscopy make a cut along the dispersion direction values should not exceed 3 000 ADUs in particular if the sky emission lines fall on bad pixels in the lower left corner In imaging with the spectroscopic detector values as large as 15 000 ADUs can happen but the detector is then not on the linearity curve any more better change filter NEI 21 EI IRDCS_ATD Real Time Display 1 0 03 43 01 Ble View Graphics Real time Test Figure 3 The IRDC real time display Always chose DIT to monitor the background level and put the statistical box away from bad pixels regions Unlike other instruments where you can easily edit the DIT increase it or decrease it to do so with VISIR you are bound to use only well specified DIT NDIT that were estimated during the commissioning phase and are now hardcoded These fixed DITs are referred to as weather flag rangi
11. 00 0 0250 Q1 2 SF 0 0400 0 0250 0 0200 0 0160 Q2 2 SF 0 0400 0 0250 0 0200 0 0160 Q3 2 SF 0 0125 0 0100 0 0080 0 0080 Table 2 Same as in Table 1 but for the 0 075 FoV VISIR Operational Manual VLT MAN ESO 14300 5129 6 from FAIR to POOR and so on If changing the weather flag does not help and the target is still un visible try increasing the EXPOSURE TIME e g 60 to 180 seconds If still not visible and background level is safely below 6 000 ADU then the USER has made some mistake Abort the OB start another program and send a ticket to USD 3 VISIR Observing Requirements 3 1 OB Setup Info When observing in the MIR there are two things to keep in mind e All VISIR science SPC IMG data must be calibrated with a STD or a Telluric within 2 hours and 0 2 Airmass difference with respect to the science OB e There are NO VISIR daily calibrations only daily monitoring of the detector hence if you do not calibrate the OB with a STD Telluric in exactly the same setup right before or after the science OB then the science data are useless E OB Report PSF_ref_0_II_after 0B Id 495925 386 C 0111 4 SM VISIR Cal Req Standard calibrations User Com Has to be observed after PDS66_Q_II arget HD137627 RA 15 31 41 451 Dec 69 28 58 866 Eq 12000 User Com SIV filter ObsDesc PSF_ref_0_II_after ISIR_img_acq_MoveToPixel Relative Chop Nod Di PERPENDICULAR Total inte
12. 000 5000 Nell 12 81 12 18 gel us e NelI 2 13 04 15 22 TE e rid Q1 17 65 50 120 HRx Nill 18 24 8000 Q2 18 72 50 80 HRx SIII 18 71 4000 mi hs d SE pene Q3 19 50 100 160 4 Sensitivity from STD Telluric stars So the sensitivity is usually measured on a set of standard stars e g the Cohen STDs It is defined as the limiting flux of a point source detected with a signal to noise ratio S N of 10 in one hour of on source integration 4 1 IMG Sensitivity Figure 7 shows the command line used to extract the Measured Sensitivity MS during the night So e Go to astro3Qwesoft3 and change directory to VISIR test Then run the command in brief RES WEN SLIT Figure 7 Extracting the IMG SPC sensitivity during the night VISIR sensit V3 2010 10 24 The output is shown Fig 7 VISIR Operational Manual VLT MAN ESO 14300 5129 9 e You can fully trust the IMG derived sensitivities The script does the comparison be tween the measured and reference sensitivity c f Fig 6 and as a function of the user s constraints PHO CLR THN THK see Section 7 4 it concludes the correct OB classification A B C e Very soon the procedure VISIR sensit V3 amp VISIR log V3 currently found in VISIR test will be the default procedure and can run anywhere from astro3Q wgsoff3 4 2 SPC sensitivity As for the SPC sensitivities the derived values can be altered increased by the sky lines So you can run a GASGANO
13. 14300 5129 1 1 Introduction Please refer to the User manual for specific VISIR issue This document is intended only for operational purposes and driving of the instrument First of all remember that VISIR is the most stable and coolest instrument on Paranal So relax and enjoy its operations VISIR is a unique instrument It performs as i an IMAGER in two mid infrared windows 8 13ym and 16 25ym and ii as a SPECTROMETER in Low Medium High resolution in long slit mode and High resolution in cross dispersed mode The imager has 2 offerred spatial field of views pixel sizes i 0 075 and ii 07127 designated as Small and Intermediate Field SF IF The respective Field of View FoV is 19 2 x 1972 and 32 5 x 3275 The offerred SPC slits have width of 10 0775 and 074 Observing in the MIR window allows us to study stars of course but most importantly the dust and gas that can surround a star a galaxy or a black hole Figure 1 shows how the atmosphere is transparent in two atmospheric windows the N and Q bands Observations in Q band are more sensitive to the water vapor in the atmosphere Hence whenever observing in this window a constant monitoring of the atmosphere H20 content is required see Section 9 1 The major dis advantage of observing in the N and Q window is that sky background level is extremely high with respect to the objects we want to observe This high background comes from both the atmosphere and the
14. 300 5129 25 e Applying a lower current to the ECU 7 5 to 5 5 Ampere in order to avoid sautration 9 4 Wein s displacement law Wein s law is very useful in illustrating what who emits in the MIR window and therefore besides the atmosphere contributes to the MIR backgournd Indeed a consequence of this law is that the wavelength A at which the intensity of the radiation is maximum Amax is only a function of the black body temperature b Amax T where Amax is the peak wavelength T is the absolute temperature of the blackbody and b is the Wien s displacement constant For our purposes b can be expressed in nanometer Inm 107 um or lum 1000nm being b 2897768 5 nm K Thus the Ama at which a human body emit is a function of its temperature 27 C 300 K or 80 6 F and thereby Amax A A 9659nm H Vum i e right in the N band Similarly assuming that the temperature of telescope components M1 M2 etc are kept at 10 C 283 K or 50 F then Amax SB Soe K 10239nm 10 2um
15. C blind offset 0 0 Rotator on Sky PA 0 0 Get Guide Star from CATALOGUE Guide star RA 0 Guide star DEC 0 Chopping Position An O Chopping Amplitude 8 Imager Filter PAH2 Acquisition Filter NEII_2 Spectrometer Slit Ty LONG Spectrometer Slit Wi 0 40 ISIR_spec_obs_HRAutoChopNod Relative Chop Nod Di PARALLEL Random Jitter Width 0 otal integration ti 1620 Chopping Position An O Chopping Amplitude 8 Spectrometer Filter Spectrometer Wavelen 12 810 ConSet No Name Seeing 0 8 Sky transparency Clear ir mass 5 0 Fractional lunar illumination 1 0 Moon angular distance 215 ime Intervals 1970 01 01T00 00 00 2009 08 11T20 00 00 Figure 5 Basic info for a SPC science OB the very basic parameters you will need to fully calibrate VISIR Data A typical breakdown of an IMG OB is presented in Fig 4 So ignoring the acquisition VISIR img acq Move ToPixel template specifics the setup for the science VISIR img obs AutoChopNod template are Imager pixel scale 0 075 and Imager Filter Q2 On the other hand a typical SPC OB breakdown Fig 5 shows the acquisition VISIR spc acq ImgMove ToPizel template and the setup for the science VISIR spc obs HRAutoChopNod Thus it is clear that the setup is Resolution HR and SPC A 12 810um Reminder the available resolutions are Low Medium High and High cross dispersed LR MD HR and HRx respectively 3 2 IMG amp SPC Calibrators Now that you know the setup of the sci
16. EUROPEAN SOUTHERN OBSERVATORY ES Organisation Europ ene pour des Recherches Astronomiques dans H misph re Austral Q Europ ische Organisation f r astronomische Forschung in der s dlichen Hemisph re ESO European Southern Observatory Karl Schwarzschild Str 2 D 85748 Garching bei M nchen Very Large Telescope Paranal Science Operations VISIR Operational Manual Doc No VLT MAN ESO 14300 5129 Issue 88 Date 31 11 2010 Y Momany US dE HEEN Date Signature A Kaufer o Cs eee a eh oy ee ee ee ee ee Date Signature Released EE ehe eked eae ees Pha bee tat Munae es Date Signature VISIR Operational Manual VLT MAN ESO 14300 5129 This page was intentionally left blank VISIR Operational Manual VLT MAN ESO 14300 5129 ill Change Record Issue Rev Date Section Parag affected Reason Initiation Documents Remarks 1 0 31 11 10 creation First release v1 0 edited by Y Momany VISIR Operational Manual VLT MAN ESO 14300 5129 Contents 1 Introduction 2 Basic MIR concepts St A lt a sac pando POR Sw E Er ee RES 22 Background level corria ARA AA 3 VISIR Observing Requirements ol DESIDIA ida rea as a A a ES 32 IMG amp 5PC Calibrators decena eR OE OR Re OR RE ES 4 Sensitivity from STD Telluric stars Al ii a eh a ee ee a aog eo eee SE os OS ee BE e oa de OP UPR eg ge ww EME OEE ME CREE OBE eR Sa eG os 43 eege the STO Tele score ee ad es Dr CIO
17. ISTICS box from the VIEW option Use the statistical box on a relevant region e g in the middle of the detector array and away from bad pixels regions Also you should click in order on the 3 buttons next to Z z That will swope the X direction swope the Y direction and rotate the image At the end the largest masked region of bad pixels should be on the lower right part of the detector Only now you have North up and East to the left on this RTD e the VISIR RTD basically displays the reduced images regardless if it is during SCIENCE or ACQUISITION On this RTD you will be asked to move the target to a precise pixel or put the target in the center of the slit This RTD has history of freezing not refreshing automatically every now and then and the only way to avoid it is by NOT performing anything on it except for picking object and centering the target If the viRTD does not refresh close the window from the File menu and re start it again left button and select VISIR RTD from the RTD menu From DETDATA check the name of the last obtained image and load it from the File menu 5 2 The OS 99 99 of the time you operate VISIR you will remain in the BOB workspace having to monitor only BOB and the OS Figure 12 shows the OS status while CHOPPING is working The OS is very simple but at the same time provides all the necessary info you need So the IMAGER section displays the used pixel scale in this example 0 127 IF t
18. LW Slit cu_0 16 0 40 arcsec Resolution MR Longslit Central Wavelength 12 91 micron Detector Temp 7 29 K Telescope Chop Status CHOPPING STOP CHOPPING Chop Frequency Cer Jta Chop Throw 8 arcsec Chop Posang C o legt Last Sync at 2010 10 25704 04 40 000000 Figure 12 The OS while CHOPPING is operating 6 Starting the Observation Put VISIR ON LINE and from the Telescope menu enable the TCS Fetch the OB from BoB and execute 6 1 IMG Acquisition e VISIR IMG ACQ PRESET this is the simplest acquisition mode and requires no in teraction from the NA or TiO The telescope does the preset according to the input coordinates and one assumes that the target is in VISIR field of view Next observation blocks y SN1987A_N 2 086 D 0192 A UNKNOWN HY VISIR_img_acq_Preset VISIR imaging preset template TEL SEQ PRESET T INS E MODE IMG SOURCE SKY Figure 13 The IMG simple preset template e VISIR IMG ACQ MoveToPixel this template requires Fig 14 that the TiO NA cen ters the target STD or any target in general in a specific pixel If the SKY level is acceptable and the target is visible in the VISIR RTD a pop up window will ask you if the centering of the target is correct VISIR Operational Manual VLT MAN ESO 14300 5129 Figure 14 The VISIR IMG ACQ MoveToPixel template Now if you are observing a STD star from the observatory queues you will be as
19. anel and in tma put PUPILIM and press setup c f Fig 20 This should allow you to see the Pupil Image and recognize the M2 spider and M3 tower Also visible would be the M3 mirror brought to 90degrees and the small mirrors imprint around the M1 Check what does the over sizing mean e Save the image and give it a clear name e g PUPIL IMG PAH1 IF fits e Now switch to the SPC detector and set it up as in Fig 21 e In the DCS workspace you need to switch from the IMG to the SPC detector To do this select Config Load detector config and select Spetro VISIR dcf see Fig 23 e Now select Manual Configuration and load one of the Spetro readout e g the first e Now the last thing you need to do is to let the light go the SPC detector by selecting diaph MOA in the imager sub panel inn the ICS workspace e You should be able to see the Pupil image on the SPC detector by now save it 9 3 The Monochromator First of all let us follow the light path as it passes through the Extended Calibration Unit UCU all the way to the instrument After it passes the ECU the light will encounter the following VISIR Operational Manual VLT MAN ESO 14300 5129 23 Infrared Acquisition Module File Config Online Param State ONLINE Operation Mode NORMAL Chip Name DRS_SiAs_256x256 Sub State IDLE Detector Configuration Imager_VISIR Volt File 3 Manual Configuration
20. ans obd Thanks to modifications by Jared O and Pedro M the X Y Z are now hard coded and all you need to do is to set the minimum and maximum A the filter and the pixel scale You can also lower the exposure time down to 10 seconds Point source movements in Y and Z directions Extended source Y movement only flat folding mirror SS M3 The focal plane is inside the cryostat chopper Extended blackbody Offner SS M2 and SS M1 mirrors j 1 i Mono 77250 R 500 1000 pin hole 2 off axis parabolic mirrors reimager Figure 25 Schematic view of the star simulator VISIR ICS Control wvisir Ha State ONLINE idle Op mode NORMAL LCU oK Spectrometer Imager Star Simulator m irl ONLINE OFF j OFF VISIR 3 chma Lommel OFF OFF ICS chop omg OPEN OPEN Control 1 Soure ONLINE 118 000 47200 mm jme 3 beam ONLINE 3 000 1200 mm 3 J point ONLINE 15 000 12000 mm 22 000 m eeneg ONLINE 12 900 11098 um fag 4 exts ms Ers N ontine OFF OFF T 20 20 20 Open issues e The absolute calibration of the A vs encoder position is still poorly characterized i e we still do not know its stability level Hence the transmission curve of certain filters needs constant monitoring to infer the stability of the calibration VISIR Operational Manual VLT MAN ESO 14
21. ence OB that you want to execute you must chose a calibrator for it before you start it The reason for this is simple to execute calibrate and classify a VISIR IMG SPC OB you need to know the achieved VISIR sensitivity at that particular time of the night If the sensitivity is good or below certain reference values see Fig 6 then you can A PRIORI know if you i should execute the OB and ii are able to classify it as A or B So although we spend quite some time taking STDs and Tellurics a NA or TiO can avoid wasting VLT time because he she knows if the OB is feasible or not and if feasible he she knows already if it is to be classified A or B VISIR Operational Manual VLT MAN ESO 14300 5129 Figure 6 Left The median SPC sensitivities used as reference for classification of VISIR SPC service mode observations Right the same but for IMG Mode Spectral A median sensitivity mJy 100h ege 5 IMG Filter Central A median sensitivity SF IF MR 7 4 8 0 1000 mJy 100h MR 8 0 9 4 200 Sc KEE a PAH1 8 59 5 8 MR 19 9 20 3 2000 ArIII 8 99 6 70 T tea an pa SIV 1 9 82 30 60 HR ee 17 03 10000 SIV 10 49 8 13 HRx AT 8 HRx Srel 5000 SIV 2 10 77 9 20 HRx SIV 10 51 4000 PAH2 1125 6 9 HRx Coll 10 52 4000 HRx wie SE 11 57 2000 SiC 11 85 7 18 HRx CIV 11 76 3000 PAH2 2 11 88 7 15 HRx H2 2 12 27 1500 HRx moan Set 12 47 2000 Nell 1 12 27 12 20 HRx Nell 12 81 2
22. et Pick the target and click on slit center and chose move and continue if you are confident that everything went fine Otherwise chose move and repeat Once done you will be asked if you want to take the through slit image Skip this step if you are doing a STD Observatory star DO NOT skip this step if you are centering a target for a service mode OB because it is the only way for the Astronomer to actually believe that his her target was properly centered VISIR Operational Manual VLT MAN ESO 14300 5129 17 e VISIR SPC ACQ IMGMoveToPizel this acquisition template is not easy because it uses the IMG and not the SPC detector to center the target in the slit drawing In this case the pop up window will only allow you to pick the target and it will independently move it to the slit center Once this is done then the setup will change and the SPC detector is employed ATTENTION during this step you will see that the slit drawing changed from VER TICAL to HORIZONTAL and that the target seems OUTSIDE of the slit center Do NOT worry because this is basically the old reduced image obtained on the IMG detector that has the slit drawing of the SPC detector So wait until the new image has been obtained If the target is bright enough then it will appear about 077 to right of the slit center but perfectly within the slit width You can now offset the target to fall exactly in the center Once done you will be asked for the through slit
23. gration ti 30 RA blind offset 0 0 DEC blind offset 0 0 Rotator on Sky PA 0 0 Get Guide Star from SETUPFILE Guide star RA 15 32 25 367 Guide star DEC 69 27 26 720 Chopping Position An O Chopping Amplitude 8 Imager Filter SIY Imager pixel scale 0 075 ISIR_img_obs_AutoChopNod Observation Category SCIENCE Relative Chop Nod Di PERPENDICULAR Random Jitter Width 1 0 Total integration ti 620 Chopping Position An O Chopping Amplitude 8 Imager Filter Q2 Imager pixel scale 0 075 ConSet PSF_ref_0_II_after Seeing 1 0 Sky transparency Clear ir mass E Fractional lunar illumination 1 0 Moon angular distance 2 25 ime Intervals 2011 03 02T07 34 00 2011 03 31T23 59 00 FindingCharts finding_chart_PSF_ref jpg Figure 4 Basic info for an IMG science OB Hence it follows that you must know the exact setup for the science OB So from the Ob serving Tool OT username 0 passwd OHS4xxxx or the SMTS VISIR A B C select an OB From the Reports menu select ObsBlockBreakdown and Selected This provides you with VISIR Operational Manual VLT MAN ESO 14300 5129 7 E OB Report LkCal5 2 0B Id 389284 084 C 0211 4 SM VISIR User Com Execute contiguously with calibration OB CAL_LkCal5 2 arget LkCal5 RA 04 39 17 790 Dec 22 21 03 400 Eq 12000 User Com 2 5 ObsDesc No Name ISIR_spec_acq_ImgMoveToSlit Relative Chop Nod Di PARALLEL Total integration ti 330 RA blind offset 0 0 DE
24. he filter and the IMG detector temperature should be between 5 9 lt T lt 6 1 The SPECTROMETER section reports the employed filter the slit width in mm and arcsec respectively the resolution MR in this case the central A 12 91ym and lastly the SPC detector temperature should be between 7 2 lt T lt 7 4 The Telescope section reports that the M2 was actually chopping with a Chopping position angle of zero degrees a chopping throw of 8 0 and a frequency of 0 1 Hz These last 3 values change as a function of the employed filters SPC IMG and user defined requirements chopping throw and chopping position angle Lastly if it happens that you abort a running exposure it is good that you press ABORT and STOP EXTENSION SYNCHRONIZATION VISIR Operational Manual VLT MAN ESO 14300 5129 13 PI Vis Control wvisir OOOO File Options Engineering Telescope Instrument Help Instrument State omme Mode see os IR DCS ICS TCS PLC State ONLINE ONLINE ONLINE ONLINE W Substate serue IDE O ae mE E Access Norman NORMAL NORMAL E Exposure Status mme INTEGRATING DIT 0 6250 sec NDIT E Exposure 90 00 sec 73 sec END ABORT Filename VISIR_SPC_CAL298_0001 fits Last Sync at 2010 10 25704 04 40 00 STOP EXT SYNC Imager Scale MOA 0 127 arcsecipix Filter PAHI Detector Temp 5 99 K Spectrometer Filter N_
25. ified C must repeat 7 4 Sky transparency PHO CLR THN THK constraints have a completely different meaning when observing in MIR with VISIR These do not necessarily relate to the photometric stability and sensitivity in the mid infrared MIR photometric stability of any given night can only be obtained by comparing the conversion factors for a given filter over the night This is why it is recommended to always include the PAH1 and PAH2 filters whenever you observe a STD star So if you are lucky and observing with VISIR for few hours then you can compare the conversion factors of e g PAH1 over the night and conclude something on the night photometric stability So the bottom line of VISIR service mode OB classification comes to Table 3 For example a PHO constraint in IMG mode using PAH1 with the SF pixel size is respected if VISIR provides a sensitivity equal or below 8 milli Jansky mJy in PAH1 Once again the cur rent version of the sensitivity script see Section 4 tells you which PHO CLR THN THK are satisfied given the measured sensitivity that you obtained constraint classification A B C PHOT MS lt AS MS lt AS 20 MS gt AS 20 CLR MS lt AS 20 MS lt AS 30 MS gt AS 30 THN MS lt AS 30 MS lt AS 50 MS gt AS 50 THK MS lt AS 50 MS lt AS 100 Table 3 The measured sensitivity MS as compared to the Announced sensitivity AS
26. igure Interface Errors Help eit e Mi Bs JES E el OBs ot gt bob gt INS ID VISIR 1 60 Next observation blocks 3 y HD198048_12 9_IF 60 A 9234 A UNKNOWN gt WISIR_img_acq_MoveToPixel VISIR imaging acquisition template HY VISIR_img_cal_AutoChopNod VISIR_img_obs_AutoChopNod VISI INS FILT1 NAME PAH1 PFOV 0 127 MODE IMG SOURCE SKY SEQ CHOPNOD DIR PERPENDICULAR JITTER WIDTH 0 TIME 120 NODTIME 0 RETURN T WEATHER G TEL E CHOP POSANG 0 CHOP THROW 10 DPR CATG CALIB TECH IMAGE CHOPNOD TYPE STD Eh eg A EE E Soasi KAT m ei Template log messages Be 1 Start Reset status Figure 9 A typical STD IMG OB Once the STD is acquired select the filters that are requested by the Astronomer plus the PAH1 and PAH2 filters Make sure to take note of the correct weather flag that you decide best 4 3 2 SPC SPC From the DETDATA xterm give the command line stdsop Main This will open a window like that in Fig 10 Once again we estimate the sensitivity for any particular SPC setup VISIR Operational Manual VLT MAN ESO 14300 5129 11 stdsopMain Qwvisir E File Std Options Hely Standard Star Observation Preparation Standard Star Search Right Ascen 22 00 Declination 40 00 Epoch Ir TargetLST 22 30 Std Obs LST 23 05 lt SpecType
27. is page was intentionally left blank 20 VISIR Operational Manual VLT MAN ESO 14300 5129 21 9 Miscellaneous 9 1 Atmosphere Water Vapor content Whenever possible and especially during variable weather conditions while observing with VISIR the OB SkySpectrum_ MR_ BurstMode to be fetched BOB should be executed to take a MR sky spectrum It is relatively very short and takes about 1 minute This OB measure the water vapor WV content of the atmosphere and is usually referred to as Precipitable Water Vapor PWV The execution is very simple on astro3 wgsoff3 and from any directory give the command line H2Qcalc_last Once completed this procedure will show the results of the fit see Fig 19 Please report the measured PWV which has been extrapolated to an airmass of 1 0 in the night report the example reports a value of 2 26 If you are interested in the PWV of a given night then the command line is A20calc YYYY MM DD VISIR GEN TEC BURSTDDD_ NNNN fits where YY YY MM DD is the date at the beginning of the night and VISIR_GEN_TEC_ BURSTDDD_NNNN fits is the name of the file just produced Best fit Water Column PWV 2 26 0 43 mm T rerepa T 10 Print Al Date of Measurement 2010 1025T0 09 34 2059 Print Marked E e 04 ADU s pix Flux 1 00e 19 5 Wavelength micron Figure 19 An example of the estimate water vapor content PWV as measured by the H2Ocalc_ last scri
28. ked to move the star to the center of a green box Pick the star click to slit center and chose to move and continue or move and repeat The major issue you need to worry about is that the final position DOES NOT overlap with any of the masked bad pixels regions check the dark regions in Fig 15 So if you are dealing with a STD star you can move the star even outside of the designed box the pipeline will find the star anyways e Next observation blocks y HD198048_12 9_IF 60 4 9234 A UNKNOWN y VISIR_img_acq_MoveToPixel VISIR imaging acquisition template 7 INS ra FILT1 NAME BAH Le PFOV 0 127 ra MODE IMG SOURCE SKY y SEQ ra CHOPNOD DIR PERPENDICULAR 2 TIME 60 ro NODTIME 0 PRESET T WEATHER G ra TEL DPR ra CATG ACQUISITION r TECH IMAGE CHOPNOD JITTER 2 TYPE OBJECT gt VISIR_img_cal_AutoChopNod VISIR_img_obs_AutoChopNod VISIF gt VISIR_img_cal_AutoChopNod VISIR_img_obs_AutoChopNod VISIF j gt VISIR_img_cal_AutoChopNod VISIR_img_obs_AutoChopNod VISIF L gt VISIR_img_cal_AutoChopNod VISIR_img_obs_AutoChopNod VISIF virtd Real Time Display 1 20 Hal 14 Figure 15 STD MoveToPixel template After centering the star in the green box it is better that you move the STD star away from the bad pixel region On the other hand if a SCIENCE IMG OB uses VISIR IMG ACQ MoveToPixel then most likely you need
29. longations then conclude the image quality was ok 7 2 Sensitivity As explained in Section 4 sensitivity is a value you estimate from a known calibrator star and when compared with reference values known as Announced sensitivities you can infer if VISIR is delivering good quality science products at that particular moment in the night Now since the MIR sky is quickly variable all you need to check once you have the sensitivity value is to make sure that e For IMG that the photometric standard star is observed very close in time to the service VISIR Operational Manual VLT MAN ESO 14300 5129 18 mode OB that is the STD OB must be observed within 2 hours having a AAirmass of lt 0 2 In other words the STD OB done either before or after the science OB e the setup of the STD OB plus the weather flag is exactly the same of the science OB Now coming from optical observing background one might ask what about the Moon and sky transparency constraint Well 7 3 Moon Constraint Moon constraints FLI and distance are usually irrelevant in the mid infrared They are not taken into account for the classification of the OB it is always OK except if the Active Optics AO is affected by the moonlight leading to a degradation of the image quality Telescope guiding and active optics can however under certain circumstances be compromised for moon distances lt 30 In cases the observations are compromised they will be class
30. ng from GOOD FAIR POOR and SAD So DIT weather flag and going from G to S means lowering the DIT see Table 1 By default all STD Telluric and science OBs have weather flag set to GOOD Now if the reduced image in the VISIR RTD DOES NOT show your target and you see that the background was higher than 6 000 ADUs then abort the OB and change the weather flag from GOOD to FAIR Preset False Re start the OB check the background If needed go VISIR Operational Manual VLT MAN ESO 14300 5129 4 filters Chopping Period s FoV Good Fair Poor Sad PAH1 4 IF 0 0625 0 0500 0 0400 0 0250 SIC 4 IF 0 0100 0 0080 0 0080 0 0080 All 4 IF 0 0200 0 0160 0 0125 0 0100 SIV 1 4 IF 0 0250 0 0200 0 0160 0 0125 SIV 4 IF 0 0160 0 0125 0 0100 0 0080 SIV 2 4 IF 0 0500 0 0400 0 0250 0 0200 PAH2 1 4 IF 99999 0 0400 0 0250 0 0200 PAH2 4 IF 0 0400 0 0250 0 0200 0 0160 PAH2 2 4 IF 0 0400 0 0250 0 0200 0 0160 NEII 1 4 IF 0 0625 0 0500 0 0400 0 0250 NEII 4 IF 0 0800 0 0625 0 0500 0 0400 NEII 2 4 IF 0 0625 0 0500 0 0400 0 0250 B8 7 4 IF 0 0250 0 0200 0 0160 0 0125 B9 7 4 IF 0 0125 0 0100 0 0080 0 0080 B10 7 4 IF 0 0125 0 0100 0 0080 0 0080 B11 7 4 IF 0 0250 0 0200 0 0160 0 0125 B12 4 4 IF 0 0200 0 0160 0 0125 0 0100 J7 9 4 IF 0 0250 0 0200 0 0160 0 0125 J8 9 4 IF 0 0400 0 0250 0 0200 0 0160 J9
31. o a el dro o es a RA OR L2 aia AA A 5 Organizing the VISIR working space SL RIDS savoir 6 RES GE EG AE ey EAE E Bok eo BH a ee TO ee eh ee Grek oe On Ge a ee Ge Io ew Oe ew ES 6 Starting the Observation 6 1 IMG Acquisition cord eee OE RR eR OE BR OS OS GA So coea eh ee eM OER ORO EE a 7 VISIR service mode OBs classification Pi Tee ee a r oS oa o eS a a eee eS Coe POI so corea He eer eR ee EH EEE EES RHE REE RO E oee Bh ae ERE wR EER EH REDS HEH SE HSE SAS TA ai IA Summary of Typical SM OB Execution Miscellaneous 9 1 Atmosphere Water Vapor content 9 2 Taking a Pupil Image with IMG SPC detector Oo The Monochromat t ss o w A eg de RK eR Ae ERM a E 94A Weis displacement bw iascc o bebe es bebe ew A ee eS lv NDS 12 12 12 13 13 16 17 17 17 18 18 19 VISIR Operational Manual VLT MAN ESO 14300 5129 List of acronyms BLIP BOB DIT FWHM ICS IR IRACE MIR OB P2PP PSF S N UT VISIR TCS TMA WCU Background limited performance Broker of observation blocks Detector integration time Full width at half maximum Instrument control software Infrared Infrared array control electronics Mid infrared Observing block Phase 2 proposal preparation Point spread function Signal to noise ratio Unit telescope VLT imager and spectrometer for the mid infrared Telescope control system Three mirrors anastigmatic Warm calibration unit VISIR Operational Manual VLT MAN ESO
32. pt 9 2 Taking a Pupil Image with IMG SPC detector e First of all use a normal IF STD star OB and make sure to put the star in the center of the detector X Y 128 128 Abort the OB al VISIR ICS Control wvisir LI Tool Spectrometer Imager Star Simulator m Fita Joer NE Pan 972 Fam VISIR m NLINE 24 p ICS m tma ONLINE PUPILIM 720 PUPILIM Control Figure 20 Setting the IMG detector to take the PUPIL image An indication that the collimated path is not well aligned VISIR Operational Manual VLT MAN ESO 14300 5129 22 VISIR ICS Control wvisir JJ i CU Maintenance Tools Std Options Help Spectrometer Imager Star Simulator 4 Focu ONDINE 10 0 Jao deg ang VISIR y fi1ts ONLINE NEII_2 320 MEIS ICS J etal ONLINE OPEN 248 CLOSED Control reso ONLINE PUPILIM 60 PUPILIM ae ome MIRROR 0 MIRROR_ 4 gaimr ONLINE IMAGING 0 IMAGING slit ONLINE OPEN 192 OPEN scan JINS cRATi N ontine E NONE Figure 21 Setting the SPC detector to take the PUPIL image Figure 22 Example of the Pupil image of the IMG detector obtained with PAH1 on October 3 1 2010 Visible are the M3 tower open to allow the VISIR observations and the M2 spider e In the ICS workspace select the imager sub p
33. rget and again the secondary mirror chops back and forth ON and OFF the target e The difference between the results of the Chopping in position 1 and 2 unveils the target e This perpendicular chopping nodding technique mainly used for IMAGING hereafter IMG delivers 2 positive and 2 negative detections of the target These are separated by the so called chopping throw typically 8 0 The parallel chopping nodding technique used for both IMG and SPECTROSCOPY hereafter SPC delivers one positive and 2 negatives In such case the positive detection is basically the sum of 2 positives Staring images Staring images Achopper position A chopper position Chopped images Nodding A beam Nodding B beam chopping and nodding registration technique of observation Chopped nodded image Final Image zoomed He2 10 blue compact galaxy Figure 2 Illustration of the chopping and nodding technique VISIR Operational Manual VLT MAN ESO 14300 5129 3 2 2 Background level There are 2 cases for which the chopping nodding technique would fail delivering showing a target The most obvious is that the target is very faint The second case however involves a wrong handling by the NA or TiO of the background level i e the detector is saturated The background level is best monitored via the IRDCS real time display Fig 3 when dis playing individual DIT single frames This is the howto do it The
34. s r VISIR 2010 10 25T04 04 5 VIS El visir_sPcIMG H VISIR_SPCIMG_SLITTEST298_0006 fits Br visiR 2010 10 25T07 07 15 141_tpI A01_0000 fits Select application to run k le BRE p Look In C scripts TO D ViSIR SPC_sens sh C Newrolder E wem sPc_sens sh me 1 0000 fits lt unknown orig name gt SPC_PHOT_TAE D visir fuxsh D visir_ttuxsh de find Jia Load Filter a Filter Auto Display vm pt erh D wsir_spc_extr sh Value PZ Ve F 2010 10 25107 10 47 0 5 i FileName VISIR SPC_extr sh Files of Type An Files EN ISO ESO VLT 13 VISIR INS TROWE OBJECT RA er STD 04 14 00 37 Las 17 42 9 Figure 8 Extracting the 75 best SPC sensitivity during the night VISIR Operational Manual VLT MAN ESO 14300 5129 10 4 3 Choosing the STD Telluric 4 3 1 IMG IMG from the OT chose the VISIR Photom STD TOP NEW queue and after ordering it in Right Ascension chose the closest in terms of airmass STD to the Local Sideral Time This is because we measure sensitivity at Zenith or very close to it Make sure to select the correct FOV SF or IF corresponding to your science OB Fetch the OB and execute it Figure 9 shows the case of HD198048 selected in the IF 0127 mode The reported 12 9 is the flux value of that STD star in Jansky BOB Broker for Observation Blocks bob_ins wvisir File Conf
35. to put the target in the center of the detector However please check the README of that OB and check that the employed chopping throw would not put the other negatives positives outside of the Field of view Figure 16 shows the case of a perpendicular CHOPPING NODDING technique applied on a STD star The star was offsetted from the green box in a way to avoid the close bad pixels regions and at the same time keep all 4 negative positive beams within the FOV VISIR Operational Manual VLT MAN ESO 14300 5129 15 Figure 16 The same STD star moved outside of the green box but in a way to keep the 4 beams within the FoV Figure 17 Example of a MoveToPixel acqsuition of a science target that had a 45 chopping position angle keeping the 2 negative beams within the detector VISIR Operational Manual VLT MAN ESO 14300 5129 16 6 2 SPC Acquisition E Virtd Real Time Display 1 20 HE Telescope Offset Pick Object Figure 18 The MoveToPixel SPC template before and after NA TiO centering intervention The vertical strips are due to the brightness of the target hitting some hot pixels e VISIR SPC ACQ MoveToSlit this is the simplest acquisition mode for SPC On the VISIR RTD you will hopefully identify the target check the above instructions and see that it is not in the center of the slit drawing see Fig 18 The pop up window is already asking you if you want to offset or rotate to center the targ
36. your favorite pixel scale Here follows the procedure to derive a filter transmission curve e First you need to center the MIR source in the detector and basically play with SOURCE and BEAM to adjust its X Y position Later you need to adjust POINT which is the Z axis focusing of the light So first of all you need to set the instrument by hand and once you have found these values then you can run the OB for the filter transmission curve e Chosing the IMG detector put DCS to loaded and from config load the detector config and chose Imager VISIR dcf Put DCS back online e change NDIT to something like 200 and NDIT to 0 02 and put VISIR ONLINE e chose the desired pixel scale SF IF e Switch the IR lamp ON VISIR Operational Manual VLT MAN ESO 14300 5129 24 m entrance window polen vi Ee O EN Es diaphragm Mi F eso focal plane ai F cold stop x a Diaphragm A wl OEP hy _ y 7 a se y YA 4 a emeng bake i pret V it a m o ste 0 L gt Image Detector TMA optics filter lt O dd M1 Figure 24 The optical path to the imager and a hand drawn one e play with X Y Z values until you have the correct values for the centering Keep a note of these values e g for Nell 118 05 8 35 22 870 For the time being to derive the filter transmission curve it is enough to run the OB VISIR img tec FiltTr
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