simulations in the context of sphere exoplanet imaging workshop david mouillet

Simulations in the context of SPHERESimulations in the context of SPHERE

Exoplanet Imaging WorkshopExoplanet Imaging Workshop

David Mouillet David Mouillet Lecture 27 Feb 2012Lecture 27 Feb 2012

Numerous contributors in the simulation work for SPHERE: Kjetil Dohlen, Anthony Boccaletti, Numerous contributors in the simulation work for SPHERE: Kjetil Dohlen, Anthony Boccaletti,

Arthur Vigan, Dino Mesa, Raffaele Gratton, Marcel Carbillet, … Arthur Vigan, Dino Mesa, Raffaele Gratton, Marcel Carbillet, …

SPHERE overall presentationSPHERE overall presentation Many similarities wrt GPI Many similarities wrt GPI (see Lisa’s presentation) in terms (see Lisa’s presentation) in terms

of high level purposes, main components and challenges :of high level purposes, main components and challenges : High order AO, coronagraphs, multi-wavelength differential High order AO, coronagraphs, multi-wavelength differential

imaging, angular differential imaging, budget analysis up to 8-10 imaging, angular differential imaging, budget analysis up to 8-10 target magnitude, …target magnitude, …

With With some significant differencessome significant differences: : Focus: Nasmyth vs Cassegrain (flexures, telescope vs instrument Focus: Nasmyth vs Cassegrain (flexures, telescope vs instrument

WFE)WFE) Wavelength coverage:Wavelength coverage:

A VISIBLE imager with differential polarimetry: ZIMPOL. 500-900 nmA VISIBLE imager with differential polarimetry: ZIMPOL. 500-900 nm Wider NIR simultaneous coverage: 0.95 – 1.65 mic (IFS + diff imager IRDIS, or IFS Wider NIR simultaneous coverage: 0.95 – 1.65 mic (IFS + diff imager IRDIS, or IFS

only)only)

Variable / Differential WFE: Variable / Differential WFE: pupil de-rotator, 2 ADCs: some rotating surfaces (eventhough in a predictible pupil de-rotator, 2 ADCs: some rotating surfaces (eventhough in a predictible

manner)manner) No « CAL » system (NIR tilt/defocus sensor only)No « CAL » system (NIR tilt/defocus sensor only)

High frequency AO correction (41x41 act.)High stability : image / pupil controlVisible – NIR Refraction correctionFoV = 12.5’’40x40 SH-WFS in visible1.2 KHz, RON < 1e-

Pupil apodisation, Focal masks: Lyot, A4Q, ALC. IR-TT sensor for fine entering

Coronagraphic imaging:Dual polarimetry, direct BB + NB. λ = 0.5 – 0.9 µm, λ/2D @ 0.6 µm, FoV = 3.5”

0.95 – 1.35/1.65 µm λ/2D @ 0.95 µm, Spectral resolution: R = 54 / 33FoV = 1.77”

0.95 – 2.32 µm; λ/2D @ 0.95 µm Differential imaging: 2 wavelengths, R~30, FoV = 12.5’’Long Slit spectro: R~50 & 400Differential polarizationNasmyth platform, static bench,

Temperature control, cleanliness control Active vibration control

Beam control (DM, TT, PTT, derotation)Pola controlCalibration

Concept overview

ImplementationImplementationCPICPI

IRDISIRDISIFSIFS

ZIMPOLZIMPOL

ITTMITTM

PTTMPTTM

DMDM

DTTPDTTP

DTTSDTTS

WFSWFS

De-rotatorDe-rotator

VIS ADCVIS ADCNIR ADCNIR ADC

Focus 1Focus 1

Focus 2Focus 2

Focus 3Focus 3

Focus 4Focus 4

NIR coronoNIR corono

VIS coronoVIS corono

HWP2HWP2

HWP1HWP1

Polar CalPolar Cal

IRDISIRDIS

IFSIFS

ZIMPOLZIMPOLCPICPI(structure, (structure,

damping damping

system..)system..)

Calibration Calibration

sourcessources

SPHERE in test environmentSPHERE in test environment

SPHERE small house…

Simulations: risks and Simulations: risks and difficultiesdifficulties

Variety of effects to be taken into account, various Variety of effects to be taken into account, various timescalestimescales

Needed accuracyNeeded accuracy Metric to consider ? Metric to consider ?

Impact on final contrast performance after data Impact on final contrast performance after data reductionreduction

Inter-dependency of various contributors to the Inter-dependency of various contributors to the budgetbudget

Risk: forget an important limitation source, system Risk: forget an important limitation source, system imperfectionimperfection

Risk: in the limit of very bright targets, including only Risk: in the limit of very bright targets, including only well understood defects (also considered in data well understood defects (also considered in data reduction): syndroma of infinite performancereduction): syndroma of infinite performance

separate limitation types: separate limitation types: « noise » contributors derived from « noise » contributors derived from mean image properties and system mean image properties and system properties: stellar halo, detector, properties: stellar halo, detector, background, FFbackground, FF

speckle calibration residualsspeckle calibration residuals

Simulation approachSimulation approach

Requirements for simulation Requirements for simulation ToolsTools

To estimate To estimate mean image profilemean image profile in various conditions in various conditions (AO correction conditions, coronagraphs, filters) (AO correction conditions, coronagraphs, filters) photon photon noise, FF noisenoise, FF noise……

To estimate To estimate sensitivity to WFE dependenciessensitivity to WFE dependencies, , in in particular as a function of wavelength (various sources of particular as a function of wavelength (various sources of chromatism), and time chromatism), and time system specificationssystem specifications

to estimate to estimate long-term speckle pattern evolutionlong-term speckle pattern evolutionDetailed AO loop simulation Detailed AO loop simulation system specification system specification on on stability, noise propagation, control laws, vibration filtering, stability, noise propagation, control laws, vibration filtering, impact of calib errorsimpact of calib errors

IFS internal behaviour IFS internal behaviour system specifications system specifications on cross-on cross-talk, samplings, detector calibration accuracy…talk, samplings, detector calibration accuracy…

Baseline diffraction codeBaseline diffraction code Baseline including: Baseline including:

Fraunhofer propagation through pupil and focal planesFraunhofer propagation through pupil and focal planes

AO-filtered turbulence residuals, based on analytical model: AO-filtered turbulence residuals, based on analytical model: simulation of n independent realization of residualssimulation of n independent realization of residuals

realistic optics wfe in terms of rms and DSPrealistic optics wfe in terms of rms and DSP

various coronagraph typesvarious coronagraph types

WFE: clear distinction between before/after coronagraph, time WFE: clear distinction between before/after coronagraph, time variable, chromaticityvariable, chromaticity

Limitations or effects treated on a case-by-case basisLimitations or effects treated on a case-by-case basis no out-of-pupil WFE in baseline. Fresnel effects only roughly no out-of-pupil WFE in baseline. Fresnel effects only roughly estimated for some of the most sensitive surfaces (PROPER code, estimated for some of the most sensitive surfaces (PROPER code, see J. Krist’s presentation)see J. Krist’s presentation)

Amplitude defects: few test cases but not treated exhaustivelyAmplitude defects: few test cases but not treated exhaustively

Chromatism not treated exhaustively: mainly residual tilt, defocus, Chromatism not treated exhaustively: mainly residual tilt, defocus, diff WFE for IRDIS dual band imagingdiff WFE for IRDIS dual band imaging

Difficulty to handle very different timescales from ms to hrDifficulty to handle very different timescales from ms to hr

Fulfilling the RequirementsFulfilling the Requirements

To estimate To estimate mean image profilemean image profile in various conditions in various conditions (AO correction conditions, coronagraphs, filters) (AO correction conditions, coronagraphs, filters) photon photon noise, FF noisenoise, FF noise……

To estimate To estimate sensitivity to WFE dependenciessensitivity to WFE dependencies, , in in particular as a function of wavelength (various sources of particular as a function of wavelength (various sources of chromatism), and time chromatism), and time system specificationssystem specifications

to estimate to estimate long-term speckle pattern evolutionlong-term speckle pattern evolutionDetailed AO loop simulation Detailed AO loop simulation system specification system specification on on stability, noise propagation, control laws, vibration filtering, stability, noise propagation, control laws, vibration filtering, impact of calib errorsimpact of calib errors

IFS internal behaviour IFS internal behaviour system specifications system specifications on cross-on cross-talk, samplings, detector calibration accuracy…talk, samplings, detector calibration accuracy…


From x,y,From x,y,cubes to simulated detector images:cubes to simulated detector images:Including fraction on lenslets and downstream opticsIncluding fraction on lenslets and downstream optics

Possible detector and calibration defectsPossible detector and calibration defects

Time consuming: can often be restricted to a small part of the Time consuming: can often be restricted to a small part of the imageimage

On operational point of view: definite support to data reduction On operational point of view: definite support to data reduction testingtesting

On Signal/performance point of view:On Signal/performance point of view:Some tests about sensitivity to cross-talkSome tests about sensitivity to cross-talk

Analysis not so easy ; some coupling with image spatial structure, Analysis not so easy ; some coupling with image spatial structure, data extraction algo, and final impact depends also on the temporal data extraction algo, and final impact depends also on the temporal structure (in case of artifact, how wold they smooth down ?)structure (in case of artifact, how wold they smooth down ?)

A point to be precised in very good performance regime (other A point to be precised in very good performance regime (other aspects well handled) and/or if problem in terms of IFS internal aspects well handled) and/or if problem in terms of IFS internal calibration and signal extractioncalibration and signal extraction

IFS internal behaviour IFS internal behaviour IFS internal behaviour IFS internal behaviour


End-2-end simulation from incoming turbulent WFE, through End-2-end simulation from incoming turbulent WFE, through AO signal at each iteration and AO residual estimatesAO signal at each iteration and AO residual estimates

Time consuming: Time consuming: Used for AO loop system analysis and specificationsUsed for AO loop system analysis and specifications

Used to validate simpler analytical tools (based on DSP filtering)Used to validate simpler analytical tools (based on DSP filtering)

NOT used for numerous overall instrument image estimatesNOT used for numerous overall instrument image estimates

Good feedback from tests: Good feedback from tests: good agreement between end-2-end simus and actual loop behaviour. good agreement between end-2-end simus and actual loop behaviour.

Validation of analytical toolValidation of analytical tool

Pending confirmation concerning lowest flux Pending confirmation concerning lowest flux

AO loop detailed study AO loop detailed study AO loop detailed study AO loop detailed study


Simple use of diffraction code, low sensitivity to exact WFE Simple use of diffraction code, low sensitivity to exact WFE values. Main dependencies: values. Main dependencies:

AO correction qualityAO correction quality

CoronagraphCoronagraph

Mean wavelength. (+ also, spectral width if speckle constrast is Mean wavelength. (+ also, spectral width if speckle constrast is concerned)concerned)

combined use with analytical formulae for extrapolation to combined use with analytical formulae for extrapolation to numerous astrophysical cases (star type, distance, numerous astrophysical cases (star type, distance, magnitude, total integraton time, individual detector magnitude, total integraton time, individual detector integration time…) and comparison of various noise sources integration time…) and comparison of various noise sources

Mean Images Mean Images Mean Images Mean Images


Strong support to system specifications, with numerous and Strong support to system specifications, with numerous and coupled system parameters, also depending on signal coupled system parameters, also depending on signal extraction: need for an underlying very schematic approach extraction: need for an underlying very schematic approach for differential imaging: whatever the exact signal extraction for differential imaging: whatever the exact signal extraction algo, we want to minimize algo, we want to minimize

The chromaticity of speckle pattern obtained simultaneouslyThe chromaticity of speckle pattern obtained simultaneously

The image variability over time, with specific attention to two timescales:The image variability over time, with specific attention to two timescales:Minutes : time for companion differential imaging with field rotation (or polarimetric/filter Minutes : time for companion differential imaging with field rotation (or polarimetric/filter switches)switches)

Hour: typical type for deep integration, potential re-calibration of the systemHour: typical type for deep integration, potential re-calibration of the system

Numerous tests made with just simple differences between Numerous tests made with just simple differences between two distinct images: two distinct images:

Not representative to final perfNot representative to final perf

But good estimate to pvarious parameter sensitivityBut good estimate to pvarious parameter sensitivity

Use of baseline diffraction code, in various conditions; Note: Use of baseline diffraction code, in various conditions; Note: AO residuals not critical here. AO residuals not critical here.

Sensitivity to WFE dependencies Sensitivity to WFE dependencies Sensitivity to WFE dependencies Sensitivity to WFE dependencies


Support and typical example for various ADI data reduction: 4 hr Support and typical example for various ADI data reduction: 4 hr continuous observation, crossing meridian, sampled with 144 continuous observation, crossing meridian, sampled with 144 mean images (1 every 100 s). mean images (1 every 100 s).

Use of diffraction code including various timescales and Use of diffraction code including various timescales and variability effects: variability effects:

Approximative representation of turbulence residuals (not sampling AO loop Approximative representation of turbulence residuals (not sampling AO loop iterations): average of 100 independent realization, statistics not fully iterations): average of 100 independent realization, statistics not fully converged but correlated on successive images. converged but correlated on successive images.

Predictible WFE evolution: rotating surfaces, ADC residuals associated to Predictible WFE evolution: rotating surfaces, ADC residuals associated to airmassairmass

Slow random effects: Slow random effects: Turbulence non-stationarity: seeing, windspeedTurbulence non-stationarity: seeing, windspeed

Thermal drifts effects on centering, defocusThermal drifts effects on centering, defocus

Production of x,y,l,t cubes (limited to small number of Production of x,y,l,t cubes (limited to small number of wavelengths up to now…)wavelengths up to now…)

Long-term speckle pattern evolution Long-term speckle pattern evolution Long-term speckle pattern evolution Long-term speckle pattern evolution

Fulfilling the RequirementsFulfilling the RequirementsLong-term speckle pattern evolution Long-term speckle pattern evolution Long-term speckle pattern evolution Long-term speckle pattern evolution

eg: DEC = -45° from Paranal, HA = -2 -> +2 hreg: DEC = -45° from Paranal, HA = -2 -> +2 hrAirmass and Field rotation rateAirmass and Field rotation rate Evolution of pre-coro WFE varEvolution of pre-coro WFE var

Evolution of pre-coro variability between Evolution of pre-coro variability between

successive imagessuccessive images

PSD of difference between WFE: 0 -1PSD of difference between WFE: 0 -1 PSD of difference between WFE: 0 -71PSD of difference between WFE: 0 -71


eg: DEC = -45° from Paranal, HA = -2 -> +2 hreg: DEC = -45° from Paranal, HA = -2 -> +2 hr turbulenceturbulence

r0r0

Wind speedWind speed

Variable de-centeringVariable de-centering

Lessons learntLessons learnt

We have We have the ability to simulate many effects the ability to simulate many effects eventhough some eventhough some care/effort may be involved, and possibly some simplifying tricks (for care/effort may be involved, and possibly some simplifying tricks (for computation time saving)computation time saving)

Eg from very short ot long timescalesEg from very short ot long timescales

Fresnel effects on numerous surfacesFresnel effects on numerous surfaces

Detailed effects internal to IFS…Detailed effects internal to IFS…

A major challenge for system/performance analysis = the A major challenge for system/performance analysis = the number number of parameters involved of parameters involved and combination to signal extraction and combination to signal extraction approachapproach

Strong relation to system/signal: an a priori analysis of defects is needed first Strong relation to system/signal: an a priori analysis of defects is needed first qualitatively => simulations provide the quantitative answerqualitatively => simulations provide the quantitative answer

Single parameter sensitivity analysis in context of a given system paradigm = Single parameter sensitivity analysis in context of a given system paradigm = more robust than multi-parameter investigationmore robust than multi-parameter investigation

Conclusions for a given system may not be extrapolated to another systemConclusions for a given system may not be extrapolated to another system

Major risk for performance prediction = missing significant Major risk for performance prediction = missing significant contributor ?? contributor ??

Risk itemsRisk items risk probably reasonable up to contrast 10 risk probably reasonable up to contrast 10 6-76-7

timescales around minutes at very fine levels (eventhough the timescales around minutes at very fine levels (eventhough the system is specified for this)system is specified for this)

vibrations, turbulence non-stationarityvibrations, turbulence non-stationarity

rotating surfaces, + ADC correctionrotating surfaces, + ADC correction

thermal drifts, slow loops residualsthermal drifts, slow loops residuals

ultimate performance for WFE calibration ? ultimate performance for WFE calibration ? (current assumptions for (current assumptions for simus=quite conservative): simus=quite conservative): margin for improvement and upgradesmargin for improvement and upgrades

Amplitude/Fresnel/chromatic effects, crosstalk effects for Amplitude/Fresnel/chromatic effects, crosstalk effects for contrasts >~10 contrasts >~10 77

Fine detector calibration residuals ?Fine detector calibration residuals ?

+ the unexpected !+ the unexpected !

simulations in the context of sphere exoplanet imaging workshop david mouillet

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