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CRIRES User Manual

   Doc.  Number:   ESO-254264
   Doc.  Version:   P109.4
   Issued  on:

2021-12-01

Page:

24 of 99

Document Classification: ESO Internal Use [Confidential for Non-ESO Staff]

3.2.3.1   Gas cells
The   CRIRES   science   cases   also   demand   specialized,   highly   accurate   wavelength
calibration   techniques.   Therefore,   another   part   of   the   upgrade   is   concerned   with   the
installation  of  novel  IR  absorption  gas  cells with  multi-species  gas fillings (NH

3

,

13

CH

4

, C

2

H

2

).

These gases provide a set of densely distributed absorption lines imprinted on the stellar
spectra in the

H

- and

K

-bands (see Figure 17). Note that the pipeline will not calculate the

wavelength solution based on the gas cell data;; this is left to the experienced user.

Figure 17: Absorption line spectrum of the new short gas cell (SGC) in the H and K bands
(top) and the N

2

O gas cell in the L and M bands (bottom). The FTS scan of both cells is

provided on the CRIRES webpages under 'Tools'.

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Содержание CRIRES

Страница 1: ...748 Garching bei M nchen www eso org Programme Directorate of Operations DOO Project WP Cryogenic IR echelle Spectrometer CRIRES CRIRES User Manual Document Number ESO 254264 Document Version P109 4 D...

Страница 2: ...eneric offsets differential tracking and spectro astrometry major revision concerning observing limits and overheads implementation of results from Comm4 4 5 7 2 Characterization of polarimetry mode u...

Страница 3: ...metrology concept 15 3 2 THE WARM PART 16 3 2 1 The Adaptive Optic System MACAO 16 3 2 2 MACAO Hardware Description 20 3 2 3 The New Calibration Unit 22 3 2 4 The Spectro Polarimetry Unit SPU 27 4 INS...

Страница 4: ...nt details 65 6 3 6 Differential Tracking parameters 65 6 3 7 Spectro Polarimetry 66 6 4 SCIENCE TEMPLATES 66 6 4 1 Exposure Time details 67 6 4 2 Nodding details 68 6 4 3 Generic offsets details 69 6...

Страница 5: ...settings 1 2 Definitions Acronyms and Abbreviations Throughout this document we will use the terms CRIRES and oCRIRES to refer to CRIRES after and before the upgrade respectively However it should be...

Страница 6: ...ts crires html Both Service and Visitor mode Observation Blocks OBs should be prepared with the latest version of the Phase 2 web based preparation tool p2 available at https www eso org sci observing...

Страница 7: ...l can be found at http www eso org observing dfo quality 1 4 Contact Information In case of specific questions related to proposal preparation Service Mode observations and the use of the pipeline do...

Страница 8: ...summary of the new and main instrument parameters is given below Min spectral resolving power 40 000 and 80 0001 Wavelength coverage 0 95 5 3 m YJHKLM bands RV precision 20 m s by using the Short Gas...

Страница 9: ...of the central wavelength resulting in low observing efficiency for many scientific programmes requiring a broad spectral coverage The CRIRES upgrade project CRIRES has transformed this VLT instrument...

Страница 10: ...m s 1 Since M dwarfs and brown dwarfs have low effective temperatures radiating most of their energy in the IR 1 0 2 5 m a high resolution IR spectrograph is therefore ideal for following up low mass...

Страница 11: ...to the IR 2 For cool objects most of the flux is in the IR so there is also a gain due to the increased signal to noise ratio 3 In order to disentangle Zeeman broadening from other broadening effects...

Страница 12: ...he light on the spectrograph s entrance slit Further details of the AO system can be found in Section 3 2 1 of this manual CRIRES can be used without adaptive optics in which case the AO module just a...

Страница 13: ...nal CRIRES instrument Figure 4 Top view of the new CRIRES fore optics assembly Figure 4 shows that the beam from the f 15 focus at the new entrance slit A is collimated by a parabolic mirror B and arr...

Страница 14: ...etectors To accommodate the echelle spectral format a larger field was required to cover up to ten orders per band with a slit length of 10 arcseconds Figure 6 presents a comparison between the oCRIRE...

Страница 15: ...3 m diameter 1 m high vessel Including its support structure the total weight of the instrument is 6 2 t spread between 2 t for the warm part or AO system and 4 2 t for the cold part The optics inside...

Страница 16: ...tal applied correction in the cross dispersion direction The metrology can be activated or deactivated in the acquisition and observing templates When it is enabled during the acquisition the metrolog...

Страница 17: ...dential for Non ESO Staff Figure 8 The upgraded CRIRES warm part assembly with etalon system calibration slide AO system and de rotator mechanism Figure 9 PSF without left and with right MACAO correct...

Страница 18: ...10 The wavefront sensor WFS measures WF distortions which are processed by a real time computer RTC The RTC controls a deformable mirror DM to compensate the WF distortions The DM is a continuous thi...

Страница 19: ...actuators behind the DM and the rate at which WF errors can be measured processed and corrected the server loop bandwidth The performance of an AO system is also linked to the observing conditions Th...

Страница 20: ...Figure 12 Assembly of the deformable mirror DM and tip tilt mount TTM left and of the gimbal mount right Figure 13 The optical path of the wavefront sensor box 3 2 2 MACAO Hardware Description The MA...

Страница 21: ...tially implemented in the wavefront analyzer Extraction of the reference star beam field selector Projection of the reference star image on the membrane mirror imaging lens Scan of the intra and extra...

Страница 22: ...e to the APD cabinet mounted on the instrument The APD counts are recorded by the APD counter module synchronously with the membrane signal The front end assembly of the fiber bundle is shown in Figur...

Страница 23: ...the light path by a carriage stage place just before the derotator mirror see Figure 16 i The new polarimetry unit ii a gas cell either for wavelength calibrations when used with the halogen lamp whi...

Страница 24: ...of novel IR absorption gas cells with multi species gas fillings NH3 13 CH4 C2H2 These gases provide a set of densely distributed absorption lines imprinted on the stellar spectra in the H and K bands...

Страница 25: ...erference Each of these fringes serves as a reference marker to tackle the wavelength calibration For this purpose a continuum light source with a feature free flat broadband spectrum is coupled to a...

Страница 26: ...s Atmospheric lines Wavelength calibration Sky L M band where the lamps have few lines and continuum Halogen lamp Flat Fields YJHKLM Integrating Sphere Extended spectrum black body temperature 3000 31...

Страница 27: ...CRIRES calibration carriage see Figure 16 The polarization unit includes two circular polarisation beam splitters for YJ and HK bands and two beam splitter for YJ and HK bands combined with an achroma...

Страница 28: ...epeatability is of the order of 10 px 4 2 AO performance The performance achieved by the MACAO system of CRIRES has been evaluated by laboratory simulations comparing two cases i in closed loop with g...

Страница 29: ...h cases the exposure times were the same however in closed loop a flux level being about 1 8 times higher was attained than in the open loop observations Figure 22 Improved throughput thanks to the us...

Страница 30: ...ction is still obtained with stars as faint as R 14 mag under very good seeing conditions while moderate image quality improvement may be seen with stars as faint as R 15 mag under excellent condition...

Страница 31: ...l will lead to detector persistence that require a couple of minutes to decay to the extent that it does not affect subsequent exposures anymore Note that the parameter NDIT should not be confused wit...

Страница 32: ...ciency 2000nm 93 98 95 Read out noise e RMS MinDIT 1 427s 11 12 12 DIT 50s interpolation between the upper and lower value accordingly to selected DIT DIT 50s 6 6 6 Saturation ADU px 37000 37000 37000...

Страница 33: ...see Figure 25 and Figure 26 Figure 25 Correction for non linearity effects implemented by the pipeline The correction factor from the polynomial fits pixel by pixel evaluated at certain ADU levels and...

Страница 34: ...f 0 degrees in the SKY derotator mode North is up and East towards the left The un vignetted FoV usable for target acquisition and guiding is 22 8 x 30 8 The centre of the usable FoV and of the slit i...

Страница 35: ...ral density filter in K The SV is sufficiently sensitive that any emitting point source for which one aims to obtain a spectrum should be seen on the SV image In AO mode stars of H 15 are easily detec...

Страница 36: ...PU respectively for circular and linear polarimetry Figure 28 Measurements of the throughput of the Spectro Polarimetry Unit SPU Figure 29 The Stokes V polarization is shown for the star Gamma Equ H 4...

Страница 37: ...er IR spectrometer SPIROU working in the same spectral region and equipped with an SPU unit was done using the spectro polarimetric standard star Gamma Equ The polarisation signal was compared in Y to...

Страница 38: ...ings offered with oCRIRES the upgraded CRIRES provides a list of fixed wavelength settings to the users All settings are handled by the Data Reduction Software DRS No free settings are offered Figure...

Страница 39: ...t illumination is considered These regions are dominated by telluric lines and are not of general interest for most science cases Table 4 Approximate spectral coverage achieved within different photom...

Страница 40: ...55 1198 13 1199 08 1224 77 1225 74 1252 56 1253 59 1281 74 1282 74 1312 19 1313 26 1344 15 1345 23 H1559 1682 63 1682 97 1735 50 1737 42 H1567 1744 20 1745 84 H1575 1753 20 1754 28 Figure 32 Left Flat...

Страница 41: ...done by using different methods For an accuracy corresponding to 5 pixels the start and end wavelengths and the derived dispersion for each detector is sufficient In most wavelength settings both emi...

Страница 42: ...h slit width being either 0 2 or 0 4 arcsec The appearance of a spectrum on the science detectors mosaic is shown in Figure 34 The pixel scale of the science detector is 59 milli arcsec A slit width o...

Страница 43: ...ng to a RV drift of 200 m s 1 following metrology alignment than it was without metrology 0 05 px over 30 min RV drift 50 m s 1 For this reason we recommend making use of the telluric absorption lines...

Страница 44: ...Doc Version P109 4 Issued on 2021 12 01 Page 44 of 99 Document Classification ESO Internal Use Confidential for Non ESO Staff Figure 35 Total observed throughput in 4 different settings Results are f...

Страница 45: ...time which includes instrument and telescope overheads see 5 6 Observing constraints set see 5 3 consisting of Turbulence Category Precipitable Water Vapour PWV Moon phase Sky transparency and Airmass...

Страница 46: ...S NoAO observations the TCs are defined using the percentiles of the seeing distribution as listed in Table 7 Table 7 Turbulence categories for CRIRES NoAO mode Turbulence Category 10 20 30 50 70 85 1...

Страница 47: ...int in p1 and p2 For observation in the YJH bands 2000 nm any PWV value below 5 mm requires a justification in the proposal For observations in the K band 2000 2500 nm we recommend setting the PWV con...

Страница 48: ...ued on 2021 12 01 Page 48 of 99 Document Classification ESO Internal Use Confidential for Non ESO Staff Figure 36 Atmospheric transmission from 900 5500nm computed by PCLnWin HITRAN for Paranal atmosp...

Страница 49: ...sued on 2021 12 01 Page 49 of 99 Document Classification ESO Internal Use Confidential for Non ESO Staff Figure 37 PWV sensitive atmospheric transmission from 900 5500nm computed with RFM HITRAN for P...

Страница 50: ...n PWV absorption produced by the CRIRES ETC 5 3 4 Lunar Illumination The Moon illumination i e Fraction of Lunar Illumination FLI is defined as the fraction of the lunar disk illuminated at local Chil...

Страница 51: ...ons with AO stars fainter than R 10 Photometric conditions should be only requested for observations requiring accurate flux calibration of the spectra 5 4 Observing Strategy 5 4 1 Background removal...

Страница 52: ...cularly important for CRIRES observations as the detectors suffer from a relatively large number of bad pixels In addition the spatial extent of a spectrum is at most a few pixels in nominal condition...

Страница 53: ...mass difference of less than 0 2 Usually either hot stars or solar analogues should be used as telluric standards The observations of the science and telluric standard star are typically taken consecu...

Страница 54: ...put flux can be specified as surface brightness If the Emission line option is chosen it corresponds either to the total line flux for a point source or to the surface brightness for an extended sourc...

Страница 55: ...instrument setup is defined in terms of setting i e Y1029 see Table 19 column 1 and grating orders For observations below 1400 nm mind the wavelength regions of the optical ghosts on the detector see...

Страница 56: ...ion time which is given by the total exposure time on target i e open shutter time plus the overheads The estimated overheads related to both telescope and instrument are listed in the following table...

Страница 57: ...512 4s An alternative way to easily calculate the overhead is to create a CRIRES mock OB by using p2demo available at https www eso org p2demo Under the CRIRES programme ID 60 A 9253 K the folder name...

Страница 58: ...so org sci observing phase2 html CRIRES news http www eso org sci facilities paranal instruments crires news html Service Mode SM http www eso org sci observing phase2 SMGuidelines html Visitor Mode V...

Страница 59: ...endar airmass html Visitors should bear in mind that in case of strong wind it may happen that the telescope cannot be pointed at their main targets For this reason it is strongly recommended to prepa...

Страница 60: ...mode the telescope moves then to the AO NGS specified by the user Once the AO NGS is centred on the MACAO field selector the AO loop is closed 3 The telescope moves to the SVGS which is then acquired...

Страница 61: ...e specified directly in the ephemerids PAF file 6 8 6 3 2 Optional Telescope Guide Star VLT GS details In the following we describe all parameters present in the acquisition templates that the user is...

Страница 62: ...other words TEL TARG OFFSETALPHA and TEL TARG OFFSETDELTA are positive if the SVGS is located to the East and North of the target Note that during the OB execution the SVGS must be kept always within...

Страница 63: ...SF SEQ NGS MAG refers to the magnitude of the NGS in the R passband See 4 2 1 3 for the allowed range AO guide stars FWHM arcsec TSF SEQ NGS FWHM gives the FWHM of the NGS in arcsec used to optimize t...

Страница 64: ...e left unchanged at 00 00 00 000 RA DEC offset between the target and SV guide star must be left unchanged at 0 If target AO NGS SVGS then Target AO Guide Star must be set to yes SV Guide Star AO Star...

Страница 65: ...ld be used for point sources as it reduces slit loss introduced by differential refraction This is particularly important when SV guiding is done in one band e g in K and the observations in another o...

Страница 66: ...sures are possible and the sky signal is removed from the object spectrum by subtracting two exposures taken at different slit positions On the other hand when the target is an extended object nodding...

Страница 67: ...DIT to such a value so that the detector counts remain well below the saturation limit but at the same time the number of detector read outs NDIT x exposures is kept as low as possible Otherwise the s...

Страница 68: ...width TSF SEQ JITTER WIDTH refers to the small offset added to each nodding offset see 5 4 1 2 It helps correct for bad detector pixels SEQ JITTER WIDTH gives the width of the jitter box in arcsecond...

Страница 69: ...then the sequence will be capped when reaching SEQ NOFF Lists of offsets in RA DEC or X Y TSF SEQ OFFSET1 LIST SEQ OFFSET2 LIST refer to the list of offsets being in arcseconds At the first position t...

Страница 70: ...SV detector for the given parameters for the case of DETECTOR coordinate offsets Offsets in X are perpendicular to the slit while offsets in Y are always parallel to the slit All motions are made in d...

Страница 71: ...and the AO NGS For this reason the CRIRES_spec_obs_SpectroAstrometry template cannot be used with differential tracking List of position angles TSF INS DROT POSANG LIST is the list of position angles...

Страница 72: ...OSANG 0 Polarimeter rotation angle TSF INS ROT POSANG sets the initial reference angle on the sky for linear polarization Stokes Q and U this can be useful when observing extended objects This value i...

Страница 73: ...RES follows the standard astronomical offset conventions and definitions Position angles PAs are measured from 0 to 360 degrees North corresponds to a PA of 0 degrees East to a PA of 90 degrees All of...

Страница 74: ...ctro photometric standard star or telluric observations Any OB for either a telluric or a spectro photometric standard star must consist of an acquisition template see Table 10 and of the calibration...

Страница 75: ...nchanged for flat fielding The maximum flux parameter is used to automatically calculate the appropriate DIT given the requested NDIT 6 6 3 Wavelength calibration template The reproducibility of the w...

Страница 76: ...s it allows to individually set the flux level of the FPET following the UNE Number of cleaning darks TSF SEQ NCD if set 0 then the specified number of cleaning darks will be taken with the goal to re...

Страница 77: ...In the p2 Constraint Set tab users need to define the suitable observing conditions for the OB execution We remind here that users are not allowed to define the OB constraint set more stringent than w...

Страница 78: ...cuted within a specific time window On the other hand in VM the ephemeris should cover the assigned time night The ephemeris files are ASCII files compatible with the VLT parameter file PAF format and...

Страница 79: ...posures will be taken through the 0 2 or 0 4 slit In the YJHKL bands the daily calibrations are always taken with metrology Table 17 lists the regular standard calibration typically taken in the morni...

Страница 80: ...027 954 469 964 367 970 921 981 276 987 946 998 782 1005 572 1016 919 1023 833 1035 720 1042 762 1055 221 1062 397 1075 463 1082 777 1096 487 1103 946 954 912 961 050 971 371 977 616 988 402 994 757...

Страница 81: ...1518 984 1550 547 1561 179 1594 869 1605 765 1641 760 1652 978 1691 468 1703 015 1744 251 1756 147 1441 764 1451 115 1479 728 1489 326 1519 730 1529 589 1561 937 1572 071 1606 549 1616 973 1653 768 1...

Страница 82: ...3178 534 3344 379 3365 421 3553 261 3575 622 3789 923 3813 777 4060 288 4085 850 2861 977 2878 942 3012 584 3030 445 3179 904 3198 760 3366 874 3386 842 3577 168 3598 387 3815 429 3838 066 4087 622 4...

Страница 83: ...760 5202 785 5233 663 3599 884 3619 935 3839 916 3861 307 4114 210 4137 133 4430 656 4455 347 4799 765 4826 520 5235 856 5265 049 16 15 14 13 12 11 M4368 4368 182 3512 986 3536 332 3747 211 3772 117 4...

Страница 84: ...efault P2 label SEQ NGS ISTARGET T F T Target AO Guide Star SEQ NGS ALPHA 0 RA of AO guide star SEQ NGS DELTA 0 DEC of AO guide star SEQ NGS COLOR 1 5 0 AO guide star B R color value SEQ NGS FWHM 0 10...

Страница 85: ...0 0 0 0 Position angle INS SLIT1 NAME w_0 2 w_0 4 w_0 2 Entrance slit width INS WLEN CWLEN See Table 19 Standard wavelength setting TEL TARG ALPHA NODEFAULT Right Ascension TEL TARG DELTA NODEFAULT De...

Страница 86: ...DEC offset between target and SV guidestar INS OPTI1 NAME FREE GAS_N20 GAS_SGC FREE Optional gas cell INS DROT MODE SKY ELEV NODEFAULT Derotator Mode INS DROT POSANG 0 0 360 0 0 0 Position angle INS S...

Страница 87: ...de of the AO guide star SEQ SVGS HMAG 5 20 H band magnitude of the SV Guide Star Reference star tracking table file Name of PAF file Ephemeris file of reference object Target tracking table file Name...

Страница 88: ...o mechanical positioning via metrology Recommended yes SEQ SVGS HMAG 5 20 H band magnitude of the SV Guide Star Reference star tracking table file Name of PAF file Ephemeris file of reference object T...

Страница 89: ...ed Parameter Range default P2 label SEQ NGS ISTARGET T F T Target AO Guide Star SEQ NGS ALPHA 0 RA of AO guide star SEQ NGS DELTA 0 DEC of AO guide star SEQ NGS COLOR 1 5 0 AO guide star B R color val...

Страница 90: ...ide star INS POL TYPE V Q U V Polarization Stokes parameter INS SLIT1 NAME w_0 2 w_0 4 w_0 2 Entrance slit width INS WLEN CWLEN See Table 19 Standard wavelength setting TEL TARG ALPHA NODEFAULT Right...

Страница 91: ...ing to user defined position angles pattern CRIRES_pol_obs_AutoNodOnSlit AO assisted spectro polarimetry performed by nodding along the slit CRIRES_spec_obs_AutoNodOnSlit To be specified Parameter Ran...

Страница 92: ...EFAULT List of offsets in RA or X SEQ OFFSET2 LIST NODEFAULT List of offsets in DEC or Y INS METROLOGY ST T F F Improve opto mechanical positioning via metrology INS OPTI1 NAME FREE GAS_N20 GAS_SGC Ga...

Страница 93: ...n value SEQ NOD DELAY 0 0 10 0 6 Nodding delay in seconds SEQ RETURN T F T Return to origin SEQ FLUX TOLERANC 0 01 0 10 0 05 Flux Tolerance Fixed values DPR CATG SCIENCE Data product category DPR TECH...

Страница 94: ...ic star CRIRES_pol_cal_AutoNodOnSlit attached standard star for polarimetry CRIRES_spec_cal_Wave wavelength calibration CRIRES_pol_cal_Wave wavelength calibration with the polarimeter inserted CRIRES_...

Страница 95: ...1 NDIT 1 1000 1 NDIT SEQ NEXPO 1 100 10 Number of exposures per nodding position SEQ NABCYCLES 0 100 1 Number of nodding cycles INS METROLOGY ST T F F Improve opto mechanical positioning via metrology...

Страница 96: ...rt gas cell optional INS DECKER POS Dek13 Dek24 Open Open Decker Position Open for spectroscopy INS SLIT1 NAME w_0 2 w_0 4 w_0 2 Entrance slit width INS WLEN CWLEN See Table 19 Reference wavelength Hi...

Страница 97: ...UM Data product technique DPR TYPE OBJECT Data product type CRIRES_spec_cal_LampFlats To be specified Parameter Range default Label DET1 NDIT 1 1000 1 NDIT SEQ NEXPO 1 100 1 Number of exposures SEQ MA...

Страница 98: ...be specified Parameter Range default Label DET1 DIT 1 4 900 NODEFAULT DIT DET1 NDIT 1 1000 1 NDIT SEQ NEXPO 1 100 Number of exposures INS OPTI1 NAME FREE GAS_SGC GAS_N20 FREE Gas cell INS SLIT1 NAME w...

Страница 99: ...RES The DRS follows ESO standards for data reduction pipelines and uses the usual tools for execution It calibrates the detector properties and characterizes the location of the spectral orders on the...

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