computing euclid psfs - cosmostat · 2016-11-07 · computing euclid psfs • what is a typical psf...
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ComputingEuclidPSFs• WhatisatypicalPSFforEuclidmission?• OpticalPSF
– Typicaldeviationfromthenominalopticaldesign– Spatially,temporallyandwavelengthdependent
• Detectorcharacteristics– Intra-pixelresponsefunction(IPQE)– Chargediffusion(detectorPSF)– Chargetransferinefficiency(CTI)– Brighter-fatter
• AOCS(attitudeandorbitalcontrolsystem)– Temporalvariationofthetelescopepointing
• CapturethePSFcomplexity:– Spatialvariations– Wavelengthvariation– Temporalvariation(medium– hourtolongscale– days/months)
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Korsch telescope,dichroicandinstruments
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VIS
NISP
AirbusDefense&Space (CodeV)
• Amonte-carlo toleranced telescopemodelNo.69(95%ofthesystemswillhaveabetterWFErms) chosenbyAirbusDefenseandSpaceamongseveralmonte-carlomodelsmadewithCodeVraytracing– Manufacturingerror:alignment,tilt(parameters)– Remainingdeviationafterpolishing(2Dimages)– Afterlaunchvibration(parameters)– Afterthermalcooldown(2Dimages)– Alignmentandfocusreadjustment(compensator)
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Airbus(CodeV)toCEA-IAP(Zemax)• ConversionfromCodeVmodelfiletoaZemax inputfile(SamuelRonayette)– Conversionusingthetoolseq2zmx.exeprovidedbyZemax– Checkandcorrectforerrorsoftheconversion.– Makeonlyone2DMSEimageforeachopticalsurfacebyinterpolating,addingandfittingpolynomials.
– InputtheMSEimagesinZemax.
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M1asanexample
Anexampleof2Dresidualimagesafterpolynomialssurfacesubtraction
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M1thermal4nmrms
M1mounting2nmrms
FOM1thermal1.6nmrms
ComputeaPSFinZemax
• Twomethods:FFTversusHuygens
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WFMandFouriersolutionfromLanceMiller
(Oldmodelbutstillvalidforinternalcomparisons)
Huygenscomputationistooslow(tensofmn)!
WhyHuygens?• FFTinZemax cannotsimulate
anonorthogonal detectorplaneaccurately.
VISangleofchiefray is~10deg.
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PSFfactorypipeline:fromPSFtoWFM• WhysimulateWFMinsteadofPSFs:
– WFMhavefinitesize– WFMareeasytoscaleinwavelength(VISachromatic)– WFMareeasiertointerpolate
• Pipelineschema:Gridproduction/gridinterpolation
ZEMAX WFMFinegrid
HF/BFdecomposition
Zernicke coeffsFinegrid
WFM-HFmapsFinegrid
ForpositionX,Yinterpolation
Zernicke coeffsAtX,Y
WFM-HFmapsAtX,Y
Fourier PSF
SLOW(Zemax licences)
SLOW(butmassiveParallelpossible)
OnLINUXcomputerfarms
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PSFfactory:WFMgridspecs• HowgoodmustbetheWFMtogetPSFwithinrequirements(refisHuygens):• Thepupilmustbedetailedenoughtocontainallinformations.• Keyparameteristhesampling.Highestfrequencyarethespider sharpedges.• Analysis showthata4096x4096sampling isrequiredfora1e-5accuracyinellipt.• Ifedgesmoothingisappliedinthemask,asamplingof1028px isequallygood.• ZemaxSimulationwithoutobstruction tobefittedwithorthogonalpolynomials.
• HowgoodmustbethegridofWFMtogetPSFwithintherequirements:• ThegridmustsampletheFPAwellenoughtocapturethespatialvariations• Analysis showthatthePSFellfromWFMisstableto1e-4with3arcsec.• Interpolationwillbeneededtogodownto1e-5• Thefinalgridis700x800WFMoverthefullVISFPA
PSFstabilitywithin1e-4(2.7arsec) 3monthson2Zemax machines
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PSFfactorypipeline:interpolation
WFMdecomposition:low/Highfrequencies• Lowfrequencies :Zernikepolynomials to56th order(800x800x56 table)• Highfrequencies :HFpixelmaps(pupil size):800x800maps:2.2TB.• Zernikefitsaredone inZEMAX,HFareWFMresidual afterZernikesubtraction.• Doneonlyonceforagrid.
WFMreconstruction:low/Highfrequencies• LowFreq :bilinearinterpolationofeachZernikecoefficient(4clothest gridpoints)• HighFreq :bilinear interpolationofeachpixeloftheHFmaps(4clothest)• Obscuration addedfollowingaanalyticmodelwiththeFPAposition• Doneforeachstar/galaxyposition• Pythoncode,easilytorunonclusters(30son1core/WFMmap)
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PSFfactory:WFMtoPSF– affineDFT (L.Miller)
WFMtoPSFisaFouriertransform:WhynotFFT?• FFTlinks theimagesamplingtothepupil size(hugepaddingneeded)• FFTcannotcopewithnonorthogonaldetectorplane
LanceMiller developedaDFTcode(discret Fouriertransform):affineDFT• Usercanselectthepsf sampling• VerygoodaccuracycomparedtoHuygens(1e-5inellipticity)
Itisslow…100sona32coremachinefora512pxPSF.
Butitispossibletorunitoncomputerfarms(unlikeZemax)
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PSFfactory:wavelengthinterpolation(L.Miller)• SimulatethePSFforacoloredobject• Thebandpass isVERYlarge:450um.Factorof2from!• Bruteforce:slicetheSEDoftheobjectinnslices, compute
thenPSF,applyweightandstack.• Numberifslicesrequiredtoconvergeonellipticity (1e-5)is
around100slices(100affineDFT runsperobject!!).
• Onesolution:interpolation• DifficulttointerpolatethePSF(varyingsize,noboundaries)• GotoFourierspace,interpolate,weight,stack,backtoreal
space.• Only20PSFsareneededtointerpolateto100with1e-5
accuracy.
affineDFT 20PSFs
Fourier
100fftPSF
ColoredPSF
Fourier- 1
Interpolation
weight,stack
1fftPSF
SolarPSFMonowl PSFFromPerdereau andBoucaud
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Othercontributions:DetectorPSF
DetectorPSF(NiemiandKitching):• Chargesspreadinthesubstrateinneighbouringpixel• NotBrighter– Fatter(butdetPSF(flux)containssome)• Simulatedasa2DGaussianconvolution (analytical /empirical
formulaefrommeasurements)• Dependsoncolorandflux• FWHM:around8um– 0.6px – 0.06arcsec
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Othercontributions:AOCSPSF
AOCSPSF(Astrium data):• ThePSF ismodified bythepointingmovementsofthespacecraft.• Thalessent100realizationoftimeseries(700s, onpoint/s)• Method:
– Convertpointings anglestoFPApositions– Fit2Dgaussians parametersovertheFPApositions– 5th orderpolynomial fit(betterthan1e-6)
• Finalsigmaaround0.11px• NotconstantovertheFPA(smallvariation)
(becauseoftherotationaroundthepointingaxis)
Somevalidationtest:ECinternal
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WFMreconstructionatgridpoint:• Checkthatthedecomposition /reconstructiondoesnotalterthePSF.• ComputetheWFMatagridpositionusingthepipeline(LF/BF)• ComparewiththeoriginalPSF• Smallresidualtilt(doesnotaffectthePSFshapebuttheposition)• Underinvestigation.
WFMinterpolation:• InterpolateaWFM/PSFaroundapointofthegrid• ComparewiththecentralWFM/PSF• Verygoodaccuracy(below1e-5finalvariation)• Realinterpolationisonsmallerscale->evenbetterresults. • UsegreenWFMtointerpolateat
theredPSF position• CompareredtointerpolatedPSF
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Somemorevalidationtest:Perdereau /Boucaud
PSFstatistics:• 40x40grid,mono-wl• Ellipticity,FWHM,EE,
positions• VariationsovertheFPA
AnissueregardingthevariationsofthepositionsofthereconstructedPSFswasfound.WeinvestigateifitisthesameproblemthantheresidualtiltofthePSFsreconstruction
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ComparisonwithAstrium PSFs
PSFsfromAstrium :• PSFsat9referencegridpositions(F1toF9).• Monochromatic(800nm)• Highfrequencymapsincluded• FromtheoriginalCodeV opticalmodel
ComparewithourPSFs(ZEMAX)• Wefindsomedescrepancies webelievecomefromtheHF
transcriptionfromCodeV toZEMAX• Firstissueidentified:indexationofZernicke polynomialsin
ZEMAX(with/withoutgridsag)• Otherissuesarebeinganalysed now.
• WebelievethatwecapturedtheLowFreq correctly.(TBC)• ProgressinbeingmadeontheHFcontribution.
Productsuptonow(opticalPSFs)
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Sensibilityanalysis :• WFMwithlowandhighfrequencyMSE• PSFsgeneratedbyvaryingeachopticalelement position/angle• Monochromatic(800nm)• LanceMillerWFMmodeling
Phasediversity:• Onlylowfrequencymechanical surfaceerror(MSE)• PSFsandwavefrontswithdefocus(21M2offsets:-200to200um)• 9positions+8aroundonecorner• UsedforWFMreconstruction
PSFstatisticalanalysis :• WFMwithlowandhighfrequencyMSE• 40*40positions,LF+HF,solarSED
PSFsforOU-SHE(F.Courbin)• OnlyZernikepolynomialscomponentofWFM• 12000PSFs(x4forthedithers)• LFonly• Firstditherisreadytobereleased(opticalPSFonly)
Zernicke polynomial:• CompletegridofZernikepolynomials
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Todo list…Production:• PSFsforOU-SHE(remaining3dithers)
– AddAOCSanddetectorcontributions
Modelvalidation:• SolvetheissueswiththeHFdiscrepancywithAstrium PSFs• WriteafullreportonthePSFfactorytestsandvalidation• Adddichroiccontribution
• MigratethecodetotheSDCsECinfrastructure