Very Large Telescope Paranal Science Operations MIDI
Contents
1. e g 22 54 30 5 for 22 h 54 m 30 5 s Notes e If SEQ ZEROTRACK T the fringes will be tracked around the zero OPD of VLTI MIDI Otherwise the fringes will be tracked at an OPD offset of 50 wm if INS GRIS NAME PRISM and 100 um if INS GRIS NAME GRISM We recommend however to use SEQ ZEROTRACK T The value of SEQ NFRAMES PHOTOMETRY depends on the brightness in N band of the target Let L be the limiting magnitude of the requested mode and telescope type it is recommended to use the following values 2000 for a brightness gt 10 x L 4000 for a a brightness lt 10 x L and gt 2 x L 6000 for a brightness lt 2 x L It is not advised to use systematically the maximum possible number of frames 8000 since it increases the time to take the photometry exposures and the atmospheric trans fer function may change meanwhile biaising the computed visibility In the observation template TEL CHOP POSANG obeys to the same rule as in the acqui sition template Typically a frame lasts 15 ms MIDI Template Manual VLT MAN ESO 15820 3520 8 2 4 3 MIDI starintf_obs_field Keyword name Description Unit format possible values Default value INS FILT NAME Filter used for the ex ArIII N8 7 posure SIV Ni1 3 NeII N8 7 SiC Nband OPEN SEQ NFRINGE SCAN Number of fringes per 12 to 200 12 scan Notes e The actual value of fringes per scan is 200 2 mm scan2. e Acquisition possible with any of the MIDI filters e Fourier mode long scan fringe exposures e Dispersed fringes 0 56 arcsec on sky slit or non dispersed fringes with very long scans field astrometry e Dispersive element either NaCl prism R 30 or KRS5 grism R 230 e Beam combiner either HIGH SENS no photometric channels more sensitive or SCLPHOT photometric channels more accurate e No filter for fringe exposure e Self fringe tracking coherencing at 1 to 2 Hz e Photometry exposures beam A only then beam B only after each fringe exposure in HIGH SENS In SCLPHOT such exposures are taken on a calibrator during the night in order to compute the splitting ratios Hence the number of templates for P82is minimal one template for preset acquisition and fringe search and one template for fringe observation Moreover because of the policy adopted by ESO for observations with MIDI in service mode one calibrated visibility point every hour whatever the correlated magnitude of the science target is and visitor mode one calibrated visibility point every 1 5 hour if the uncorrelated flux is between 1 and 2 Jy at 12 um one calibrated visibility point every hour otherwise the number of keywords to be set by the user is very limited 2 2 The acquisition template According to P2PP rules the first template in an OB must be an acquisition template In the case of MIDI the name of th
3. The software tool used to build OBs is called the P2PP tool It is distributed by ESO and can be installed on the personal computer of the user See http www eso org observing p2pp e Service Mode SM In service mode opposite of the Visitor Mode the observations are carried out by the ESO Paranal Science Operation staff PSO alone Observations can be done at any time during the period depending on the CS given by the user OBs are put into a queue schedule in OT which later send OBs to the instrument e Template A template is a sequence of operations to be executed by the instrument The observa tion software of an instrument dispatches commands written in templates not only to instrument modules that control its motors and the detector but also to the telescopes and VLTI sub systems e Template signature file TSF File which contains template input parameters e Visitor Mode VM The classic observation mode The user is on site to supervise his her program execution 1 6 Modifications for P82 The number of frames for the photometry exposures is now accessible to the user The chopping parameters for photometry have now to be entered also in the observation template for the photometry MIDI Template Manual VLT MAN ESO 15820 3520 3 2 MIDI TEMPLATES 2 1 Observing modes As indicated in the MIDI User Manual the following setup of MIDI will be offered for P82 This setup can be summarized as follows
4. Hence using a guide star with the above conditions allows correction of the science target image Because of the need for background subtraction MIDI requires chopping of the secondary mirrors of the UTs The chopping is used for acquisition exposures to reach beam overlap and later in the observation template for photometry exposures see next Sect 2 3 The user has the possibility to set the off source polar coordinates angle and radius relative to the on source position in the case that an object in the vicinity of the source would appear in the field of view for default of source coordinates biasing the background subtraction The template parameters for the guide star must be set by the user with P2PP see Sect 2 4 1 If no possible guide star exists the acquisition can however be done without Coud guiding but only in the case of the UTs In this case the COU AG GSSOURCE keyword has to be set to NONE Note that in this acquisition mode the data quality strongly depends on the seeing see MIDI PPRS webpage 2 3 The observation template This template is the second and the last one in any MIDI OB description for P82 It is either the normal dispersed fringe template or the field astrometry template Interferograms are recorded in Fourier mode in a fringe exposure In this mode the length of each scan linear OPD modulation over the time is nominally 8x A where A corresponds to the central wavelength
5. eee dee de GE oe HES wo E Glossary a ea ma ea e a s a Ea e A E a a E e e a E A 1 6 Modifications for GC HTC 2 MIDI TEMPLATES ceed PESAN a e oO ee ee de o o ea sl da As ee ee rra a e Re ee Ls Me a ra a a e eg OAL MIDI starinti acq s s ed e se sd dao s E E 2 4 2 MIDI starintf_ obs fringe AEN EN NEE order 2 4 3 MIDI starintf obs feld e e a 2 4 4 Observation description oo a a a List of Abbreviations CS Constraint Set ESO European Southern Observatory LST Local Sidereal Time MACAO Multi Application Curvature wavefront sensor Adaptive Optics MIDI MID infrared Interferometric instrument OB Observation Block OD Observation Description OPC Observation Program Committee OPD Optical Path Difference OT Observation Toolkit PAF PArameter File P2PP Phase 2 Proposal Preparation SM Service Mode STRAP System for Tip tilr removal with Avalanche Photodiodes TSF Template Signature File USD User Support Department UT Unit Telescope VLT Very Large Telescope VLTI Very Large Telescope Interferometer OFF bah e o 0 JOR A WW Ww MIDI Template Manual VLT MAN ESO 15820 3520 1 1 INTRODUCTION 1 1 Scope This document describes the templates for the MIDI mid infrared instrument of the VLT Interferometer Like for all the VLT instruments observations with MIDI are carried out with observation blocks OBs The OBs must be written by the user during Phase 2 preparation with the P2PP tool An OB consists of a set of
6. information and several templates that describe the target acquisition and the observation sequence For some templates the user has to indicate the values of keywords parameters This manual requires the user to already have an insight of MIDI operation as described in the MIDI User Manual that can be downloaded from http www eso org instruments midi manual For the installation of the P2PP tool see http www eso org observing p2pp Note the MIDI specific templates will be downloaded by the P2PP tool For service mode observations it is important to read the MIDI specific service mode instruc tions given on the webpage http www eso org observing p2pp MIDI MIDI P2PP html This page gives suggestions for OB edition with P2PP name constraint set as well as the requirements for the readme file and for the finding charts 1 2 Contact information In case of questions or suggestions related to Phase 2 prepation please contact the ESO User Support Department usd help eso org 1 3 Period of validity of this manual This manual only applies for observations with MIDI in ESO Period 82 starting 1 October 2008 and ending 31 March 2008 1 4 Acknowledgements The Editor of this manual thanks all the members of the ESO VLTI Group Paranal of the ESO Telescope Division Garching and of the ESO Data Management and Operations Division Garching for their input and comments The Editor would also like to than
7. on sky will chop between the target and a position at north of the target If TEL CHOP POSANG 270 east the telescope position on sky will chop between the target and a position at west of the target e The values of SEQ CORR IRFLUX and SEQ UNCORR IRFLUX are used by the software to au tomatically adjust parameters like DIT The value of SEQ UNCORR IRFLUX can be found for example in the IRAS catalog The value of SEQ CORR IRFLUX SEQ UNCORR IRFLUX x visibility can obviously only correspond to a rough estimation since the visibility is what has to be determined by the observation e The value of SEQ HMAG can be approximated from the visual magnitude my and the spectral type of the target using the plot in the MIDI user manual MIDI Template Manual VLT MAN ESO 15820 3520 7 2 4 2 MIDL starintf_ obs fringe Keyword name Description Unit format possible values Default value INS GRIS NAME Dispersive element PRISM PRISM GRISM INS OPT1 NAME Beam combiner HIGH_SENS HIGH_SENS SCI_PHOT SEQ ZEROTRACK Tracking at zero OPD T yes box checked T yes no F no box unchecked SEQ NFRAMES PHOTOMETRY Number of frames in integer lt 8000 4000 each photometry ex posure TEL CHOP POSANG Angle of chopping on degrees 0 sky see note 0 north 90 east TEL CHOP THROW Amplitude of chop arcsec 15 ping on sky COU AG ALPHA Right ascension of HH MM SS SS 0 Coud guide star
8. EUROPEAN SOUTHERN OBSERVATORY ES Organisation Europ ene pour des Recherches Astronomiques dans l H misphere 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 MIDI Template Manual Doc No VLT MAN ESO 15820 3520 Issue 82 Date 30 05 2008 Th Rivinius S Morel Se A Date Signature A Kaufer Approved EE nee ee ae BS ee Pears Date Signature 0 Hainaut Released AN Date Signature MIDI Template Manual VLT MAN ESO 15820 3520 This page was intentionally left blank MIDI Template Manual VLT MAN ESO 15820 3520 111 Change Record Issue Date Section Parag affected Reason Tnitiation Documents Remarks 82 30 May 2008 All P81 version 80 25 May 2007 All P80 version 79 26 November 2006 All P79 version 78 8 June 2006 All P78 version new format 77 8 December 2005 All P77 version 76 31 May 2005 All P76 version Editor Thomas Rivinius S bastien Morel ESO Paranal Science Operations triviniu eso org MIDI Template Manual VLT MAN ESO 15820 3520 Contents EL COD lt tc nat he obs ak ee ee a Se a ee ce ee et ec vet ere ot A Lon be eee eS AA ee ee ee ee A 1 3 Period of validity of this manual 2 2 2 24 5444424264242 4 1 4 Acknowledgements so e cee Pee
9. if SEQ NFRINGE SCAN is larger than 100 100 1 mm scan if SEQ NFRINGE SCAN is between 29 and 100 and is really equal to SEQ NFRINGE SCAN if SEQ NFRINGE SCAN is betwwen 12 and 28 2 4 4 Observation description As mentioned in Sect 2 only one OD is possible It consists of one execution of either the template MIDI starintf_obs_fringe or the template MIDI starintf_obs_field In the OB structure built with P2PP this template must follow the acquisition template MIDI starintf_acq MIDI Template Manual VLT MAN ESO 15820 3520 000
10. is template is MIDI starintf_acq The sequence of this template starts by a preset the target coordinates are sent to the telescopes and the delay lines so they can slew to the position corresponding to the target coordinate at preset time Once the telescopes are tracking and Coud guiding the target should be seen in the FOV of MIDI in imaging mode with a user selected spectral filter To ensure beam interference the images from both beams must be overlapped This is done by several iterations of the sequence exposure star centroid measurement then offsets calculated and sent to the telescope to bring the star image on a reference pixel of the detector It is possible to have as a guide star at the Coud foci an object different from the science target The requirements are e The guide star must be brighter than V 17 MACAO is used for Coud guiding on the UTs V 13 5 on the ATs STRAP is used for Coud guiding MIDI Template Manual VLT MAN ESO 15820 3520 4 e The guide star must be within a radius of 1 arcmin from the science target If the visible magnitude of the guide star is between 12 and 13 5 AT case or between 15 and 17 UT case and if the distance between the target and the guide star is larger than 45 arcsec a warning will be issued It is interesting to notice that the mean isoplanatic angle at Paranal is a little more than 2 arcsec at A 0 6 um This would scale to 1 arcmin at A 10 wm
11. k all the users which have brought comments and suggested corrections of this manual through the ESO User Support Group 1 5 Glossary e Constrain Set CS List of requirements for the conditions of the observation that is given inside an OB OBs are only executed under this set of minimum conditions MIDI Template Manual VLT MAN ESO 15820 3520 2 e Observation Block OB An Observation Block is the smallest schedulable entity for the VLT It consists in a sequence of Templates Usually one Observation Block include one target acquisition and one or several templates for exposures e Observation Description OD A sequence of templates used to specify the observing sequences within one or more OBs e Observation Toolkit OT Tool used to create queues of OBs for later scheduling and possible execution service mode e Proposal Preparation and Submission Phase I The Phase I begins right after the Call for Proposal CfP and ends at the deadline for CfP During this period the potential users are invited to prepare and submit scientific proposals For more information see http www eso org observing proposals index html e Phase 2 Proposal Preparation P2PP Once proposals have been approved by the ESO Observation Program Commitee OPC users are notified and the Phase 2 begins In this phase users are requested to prepare their accepted proposals in the form of OBs and to submit them by Internet in case of service mode
12. of the MIDI spectral window around 10 3 um The interferogram results from the subtraction of the two interferometric channels of MIDI which are 7 phase shifted The number of scans i e interferograms is not set by the user according to the policy of Period 82 see MIDI user manual To compute the raw fringe visibility exposures with one beam only must be taken before and after the fringe exposure These two exposures beam A only then beam B only are called photometry exposures They are performed by the observation template Except for the shutter the instrument optical configuration is exactly the same as the one used for the fringe exposure The off source polar coordinates corresponding to the chopping for photometry exposures are the ones defined by the user in MIDI starintf_acq The observation template recording interferograms by scanning and then performing the two photometry exposures is named MIDI starintf_obs_fringe 2 4 User keywords In the following tables we give for each template the keywords that have to be set by the user with the P2PP tool MIDI Template Manual VLT MAN ESO 15820 3520 5 2 4 1 MIDL starintf_acq Keyword name Description Unit format possible values Default value INS FILT NAME Filter used for acquisi ArIII N8 7 tion SIV N11 3 NeII N8 7 SiC Nband OPEN TEL CHOP POSANG Angle of chopping on degrees 0 sky see note 0 nor
13. set up an underestimated neutral density Also a comment should be added in the OB specifying the magnitude interval of the star e If Coud guiding cannot be used with the science target because it is too faint COU AG GSSOURCE NONE the keyword COU AG GSSOURCE of the corresponding calibrator must also be set at NONE to keep consistency in the observing conditions e Because a part of the MIDI observation software uses the Tcl language which performs a substitution of any expression between brackets and the narrow band filter names containing brackets have to use backslash characters before bracket characters e If no off axis guiding is used COU AG GSSOURCE SCIENCE COU AG ALPHA COU AG DELTA and COU GS MAG can be left at zero e The angle of chopping on sky TEL CHOP POSANG corresponds to the direction on sky where the target is moved when the telescope is in off source position North cor responds to 0 and east to a on the celestial sphere Note that the chopping angle defined by the keyword is the opposite of the position angle defined counter clockwise from north to east on the celestial sphere Hence if TEL CHOP POSANG 0 north the telescope position on sky will chop between the target and a position at south of the target If TEL CHOP POSANG 90 west the telescope position on sky will chop between the target and a position at east of the target If TEL CHOP POSANG 180 south the telescope position
14. th 90 east TEL CHOP THROW Amplitude of chop arcsec 15 ping on sky COU AG ALPHA Right ascension of HH MM SS SS 0 Coud guide star e g 22 54 30 5 for 22 h 54 m 30 5 s COU AG DELTA Declination of Coud DD MM SS SS 0 guide star e g 16 22 45 91 for 16 22 45 91 COU AG GSSOURCE Type of Coud guid SCIENCE no offtarget guiding SCIENCE ing other COU keywords ignored SETUPFILE off target guiding guide star used NONE no Coud guiding used COU GS MAG Visual magnitude of my 12 either the target or its Coud guide star if the target is too faint for Coud guiding DPR CATG Type of target SCIENCE target of scientific SCIENCE interest CALIB calibrator star SEQ UNCORR IRFLUX Uncorrelated flux at Jy 20 12 um SEQ CORR IRFLUX Correlated flux at 12 Jy 15 um SEQ HMAG Magnitude in H band my 2 1 6 um of the target MIDI Template Manual VLT MAN ESO 15820 3520 6 Notes e If you are not using an off axis Coud target you MUST enter as value of COU GS MAG the visual magnitude of your target The minimum allowed magnitude i e maximum flux is 1 0 with the UTs and 1 7 with the ATs e If the target or the off axis guide star is a variable star the magnitude of the star when it is at its maximum of brightness i e the minimum magnitude should be given for COU GS MAG this to prevent the photodiodes of the Coud detectors from being overilluminated for having
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