Physical Modelling of Instruments

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Physical Modelling of Instruments. Activities in ESOs Instrumentation Division. Florian Kerber, Paul Bristow. Our Partners. INS, TEC, DMD, LPO, Instrument Teams (CRIRES, X-shooter ) Space Telescope European Coordinating Facility (ST-ECF) M.R. Rosa Atomic Spectroscopy Group (NIST) - PowerPoint PPT Presentation


<ul><li><p>Physical Modelling of Instruments Activities in ESOs Instrumentation DivisionFlorian Kerber, Paul Bristow</p></li><li><p>Our PartnersINS, TEC, DMD, LPO, Instrument Teams (CRIRES, X-shooter )Space Telescope European Coordinating Facility (ST-ECF)M.R. RosaAtomic Spectroscopy Group (NIST)J. Reader, G. Nave, C.J. SansonettiCHARMS (NASA, Goddard SFC)D.B. Leviton, B.J. Frey</p></li><li><p>OutlineInstrument Modelling - ConceptInstrument Modelling - BasicsInstrument Modelling - Details Input for the ModelDiscussion</p></li><li><p>Building &amp; Operating an InstrumentScience RequirementsOptical Design (code V, Zemax) Engineering ExpertiseTesting and Commissioning</p><p>Operation and Data FlowCalibration of InstrumentScientific Data and Archive</p></li><li><p>From Concept to ApplicationM. Rosa: Predictive calibration strategies: The FOS as a case study (1995)P. Ballester, M. Rosa: Modeling echelle spectrographs (A&amp;AS 126, 563, 1997) P. Ballester, M. Rosa: Instrument Modelling in Observational Astronomy (ADASS XIII, 2004) Bristow, Kerber, Rosa: four papers in HST Calibration Workshop, 2006UVES, SINFONI, FOS, STIS, VLTI, ETC</p></li><li><p>Physical ModelOptical Model (Ray trace)High quality Input DataSimulated DataClose loop between Model and ObservationsOptimizer Tool (Simulated Annealing)</p></li><li><p>STIS-CE Lamp Project Pt-Ne atlas, Reader et al. (1990) done for GHRSSTIS uses Pt/Cr-Ne lampImpact of the Cr lines strongest in the NUV List of &gt; 5000 lines accurate to &lt; 1/1000 nm</p><p>Echelle, c 251.3 nm # of lines: Pt-Ne 258 # of lines: Pt-Ne 258 vs Pt/Cr-Ne 1612</p></li><li><p>STIS</p></li><li><p>Standard: =(3.3 1.9)STIS Model: =(0.6 1.7)STIS Science Demo Case: Result 1 pixel10-4 nm</p></li><li><p>Traditional Wavelength CalibrationData collected for known wavelength source (lamp or sky):Match observed features to wavelengths of known featuresFit detector location against wavelength =&gt; polynomial dispersion solution</p></li><li><p>Physical Model ApproachEssentially same input as the polynomial:x,y location on detectorEntrance slit position (ps) &amp; wavelength ()Require that the model maps: for all observed features.</p></li><li><p>CRIRES950 - 5000 nmResolution / 100,000ZnSe pre-disperser prismEchelle 31.6 lines/mm4 x Aladdin III 1k x1k InSb arrayCommissioning June 06</p></li><li><p>Model Kernel</p></li><li><p>Model KernelSpeedStreamlined (simplistic) descriptionFast - suitable for multiple realisationsSpectrograph (CRIRES - cold part only)Tips and tilts of principal componentsDispersive behaviour of prism and gratingDetector layoutThis is not a full optical model</p></li><li><p>Operating Modes (foreseen)General optimisation (calibration scientist, offline)Grating &amp; prism optimisation (automatic)Data reduction (pipeline)Data simulation (interactive, offline)</p></li><li><p>Operating Modes (foreseen)General optimisation (calibration scientist, offline)Grating &amp; prism optimisation (automatic)Data reduction (pipeline)Data simulation (interactive, offline)</p></li><li><p>Operating Modes (foreseen)General optimisation (calibration scientist, offline)Grating &amp; prism optimisation (automatic)Data reduction (pipeline)Data simulation (interactive, offline)</p></li><li><p>Operating Modes (foreseen)General optimisation (calibration scientist, offline)Grating &amp; prism optimisation (automatic)Data reduction (pipeline)Data simulation (interactive, offline)</p></li><li><p>Simulated Stellar Spectrum</p></li><li><p>Optimisation StrategyTake limits from design and constructionOne order/mode - rich spectraOptimise detector layoutMultiple order/modes (detector layout fixed)Optimise all except prism/gratingAll order/modes (all parameters fixed except prism/grating)Optimise prism/grating settings for each mode</p></li><li><p>Near IR Wavelength Standards12701290 nmTh-ArNeKr</p></li><li><p>Th-Ar lamp:Visible and Near IREstablished standard source in VisualPalmer &amp; Engleman (1983) 278 - 1000 nmFEROS, FLAMES, HARPS, UVES, Xshooter Cryogenic High Resolution Echelle Spectrometer (CRIRES) at VLT950 - 5000 nm, Resolution ~100,000Project to establish wavelength standards (NIST)UV/VIS/IR 2 m Fourier Transform Spectrometer (FTS)</p></li><li><p>Measurements with FTS at ESO</p></li><li><p>Spectrum - Operating Current</p></li><li><p>Th-Ar in the near IR: Summary&gt; 2000 lines as wavelength standards in the range 900 - 4500 nm </p><p>insight into the properties of Th-Ar lamps, variation of the spectral output/continuum as a function of current </p><p>Th-Ar hollow cathode lamps - a standard source for wavelength calibration for near IR astronomy </p></li><li><p>CRIRES pre-disperser prism - ZnSen(,T)</p><p>from CHARMS, (GSFC, NASA)Leviton &amp; Frey, 2004</p></li><li><p>ZnSe Prism: Temperature 73 - 77 KMeasured line shiftsPhysical ModelTh-Ar line listn(,T) &amp; dn/dT of ZnSeWavelength [nm]11241138</p></li><li><p>Location of Th-Ar lines - Temperature</p></li><li><p>Conclusions - Physical ModelPreserve know how about instrumentReplace empirical wavelength calibration High quality input data is essentialPredictive powerSupport instrument developmentassess expected performancereduce riskCalibration data is still required!</p></li><li><p>Conclusions - Physical ModelThe resulting calibration is predictive and expected to be more preciseThe process of optimising the model is somewhat more complex than fitting a polynomialUnderstanding of physical properties and their changesCRIRES will be the first ESO instrument to utilise this approach to calibration</p></li></ul>