NEAT breadboard system analysis and performance models

Transcription

1 NEAT breadboard system analysis François Hénault, Antoine Crouzier, Fabien Malbet, Pierre Kern, Guillermo Martin, Philippe Feautrier, Eric Staedler, Sylvain Lafrasse, Alain Delboulbé, Jean-Michel Le Duigou, Christophe Cara, Alain Léger a Institut de Planétologie et d Astrophysique de Grenoble, Université Joseph Fourier, CNRS B.P. 53, Grenoble France b Centre National d Etudes Spatiales, 18 Avenue Edouard Belin, Toulouse France c Laboratoire AIM, UMR 7158, CEA-IRFU/CNRS-INSU/Université Paris Diderot, CEA Saclay, Bât 709, Gif-sur-Yvette Cedex, France d Institut d Astrophysique Spatiale (IAS), UMR 8617, Université Paris Sud/CNRS-INSU, Bât , Orsay France Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 1

2 NEAT space instrument Detection of Earth-like extra-solar planets around nearby stars Two free-flying vessels, one for the single-mirror telescope, the other for the focal plane array Relative star positions to be measured within 1 micro-arcsec, corresponding to pixels!! IPAG, CNES, CEA and IAS decided to develop a test bench for demonstrating the feasibility of the extremely ambitious performance Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 2

3 Test bench product tree Designed to simulate the most demanding functions of the space instrument NEAT breadboard Pseudo-Stars Simulator (PSS) Optical Bench Pixels Metrology System (PMS) Detection Unit (DU) QTH Lamp Zerodur Block Laser Source CCD detector Optical Condenser Spherical Mirror Laser Coupler and Splitter Detector Straylight Baffle Neutral Densities Mirror Circular Aperture Phase Modulator Cooling System Liquid Core Fiber Pinholes Mask Optical Switch Polarization Maintaining Fibers Translations and Rotations Stage Optical Enclosure Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 3

4 Test bench - Schematic representation QTH lamp Optical condenser Neutral Densities Liquid optical fiber Pixels metrology system (PMS) ϕ(t) Pinholes mask Diaphragm = 5 mm 2 degs. Spherical mirror Translation & rotation stage CCD plane L = 600 mm Detector straylight baffle Zerodur optical bench NEAT Breadboard (under vacuum) Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 4

5 Test bench General view Inside vacuum enclosure : Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 5

6 Pixels metrology system (PMS) Heart of the instrument, generates set of Young s fringes with temporal phase modulation, sweeping each individual pixel Allows to measure their gains g mn and centroid location (δx mn,δy mn ) 6 different horizontal and vertical baselines thanks to an optical switch and 8 polarizing maintaining fibers Laser HeNe 632 nm Splitter 1 to 2 Thermal probes Shutters Phase modulators Vacuum connector Polarisation maintaining fibres Base1(horizontal) CCD camera Fiber coupler Polarization Optical V- Voltage generator maintaining fibers switch grooves Temperature stabilised box Insulated box Base 2 (vertical) Mirror block Pupil Interference fringes Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 6

7 Analytical performance model - Architecture Metrology radiometric and contrast budgets Pixel dimensions δw mn, δh mn M Metrology photon number N ph Detection noises δi Contrast C Phase noises δφ Metrology and calibration error budget Pixel position δx mn, δy mn Subsystems requirements Pseudo-stars simulator Light source power Pinholes size Optical bench Bench stability Wavefront error Baseline stability Metrology system (PMS) Laser power Laser stability: Intensity, wavelength Phase control accuracy Detection unit (DU) Integration times: Pseudo-stars, metrology Noises (daek, readout ) Crosstalk Pseudo-stars radiometric budget PSF width stability δσ O Pixel Response Function (PRF) width stability δσ m Pixel gain δg mn O Star photon number N ph Detection noises δi Photon noise, RON error budget error δu Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 7

8 Subsystems requirements Metrology radiometric and contrast budgets M Metrology photon number N ph Detection noises δi Contrast C Phase noises δφ Metrology and calibration error budget Type of exposures Pixel dimensions δw mn, δh mn DETECTION UNIT Pixel position δx mn, δy mn Pseudo-stars Metromogy Subsystems requirements Integration time s Single frame frequency Hz Pseudo-stars simulator Pixel gain Single frame time 1.67E E-03 s Light source power Pinholes size Number of frames δg mn CCD width 1.92 mm Optical bench Bench stability Number of pixels along X'-axis 80 Wavefront error Pixel width PSF width 24 Baseline stability stability Quantum efficiency δσ O 0.9 Metrology system (PMS) Full well size Laser power Non linearity 1.00E-03 Laser stability: O Intensity, wavelength Spatial crosstalk 1.00E-02 Pseudo-stars Star photon number N ph Phase control accuracy Digitization radiometric budget Detection noises δi 16 error bits Photon noise, RON budget Detection unit (DU) Dark current ( -10 C) 2853 Integration times: Pseudo-stars, metrology Noises (daek, readout ) Crosstalk micron error δu electrons e - / pixel / s Readout noise (1 khz) e - / pixel Digitization noise factor 4.10E E-06 e - Stray reflections factor (Baffle) Pixel Response Function (PRF) 1.00E-09 width stability δσ m Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 8

9 Metrology error budgets Metrology radiometric and contrast budgets Pixel dimensions δw mn, δh mn M Metrology photon number N ph Detection noises δi Contrast C Phase noises δφ Metrology and calibration error budget Pixel position δx mn, δy mn I V mn mn Subsystems M N requirements Ph gmn BXx' mn + BYy' mn (t) = 1 + Vmn cos 2π + ϕ(t) Pseudo-stars M N simulator λ m L Light source power Pinholes πbxwsize mn πbyh mn C sincard sincard λl λl Optical bench Bench stability Wavefront error Phase and intensity Noises PSF width Baseline stability stability Subsystem Metrology system Name (PMS) Value Unit δσ O Type of noise Pixel gain Laser power Pixel gain δg mn Calibration Errors Laser source Wavelength stability 1.00E-05 δλ/λ Phase noise δφ 1.75E E-07 Laser stability: Fibered system Phase control accuracy 1.00E-05 radians Phase noise δφ 9.21E-16 O 5.28E-05 Intensity, wavelength Fibered system Intensity drift 0.00E+00 Pseudo-stars Intensity Star noise photon δi number 0.00E+00 N ph 0.00E+00 Phase control accuracy Fibered system Intensity noise 2.24E-05 Intensity radiometric budget Detection noise δi noises 1.01E-05 δi error 5.88E-05 Fibered system Straylight (parasitic interferograms) 2.24E-05 Intensity noise Photon δi noise, RON 1.01E-05 budget 5.88E-05 Detection unit (DU) Fibered system Baseline stability micron Phase noise δφ 8.73E E-10 Integration times: Optical bench Bench stability (Z-axis) 0.6 micron Phase noise δφ 1.75E E-08 Pseudo-stars, metrology Detection unit Metrology non linearity 0.00E+00 Intensity noise δi 0.00E E+00 Noises (daek, readout ) Detection unit Shot noise 1.10E+05 photons Intensity noise δi 4.09E E-05 Crosstalk Detection unit Readout noise 2.94 e - / pixel Intensity noise δi 7.77E E-06 Detection unit Digitization noise 6.36E+04 e - Intensity noise δi 2.63E E-05 Detection unit Dark current 2853 e - / pixel / s Intensity noise δi 1.26E E-06 Pixel osition error δu (fraction of pixels) Pixel Response Function (PRF) width stability δσ m RMS Sum 1.51E E-04 Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 9

10 Metrology radiometric and contrast budgets NEAT breadboard system analysis Star position error budget PSF half width (1/e) PRF half width (1/e) Radiometric budget M Metrology photon number N ph Shot noise Detection noises δi Readout noise Metrology and Contrast C Digitization noise calibration Phase noises δφdark current error budget Pseudo-stars characteristics Pixel dimensions 4.39E-05 m δw mn, δh mn 1.20E-05 m 6.54E+04 electrons 1.88E+04 electrons 2.16E+04 electrons 3.04E+04 electrons Pixel position δx mn, δy mn Centroïding Subsystems requirements2 O σ Pixel gain error 1.51E-05 m x' m Im = gm N Ph Exp Erf ( w m/2σ ) 2 m Pixel position error 2.46E-09 Pixel m Pseudo-stars σ simulator gain O σ O Straylight (ghost images) 7.67E-05 Light source power Pinholes M size M Non linearity 7.67E-06 δg Pxel width uncertainty 1 nù mn x' = x' m Im Im PSF width stability 1 nm Optical bench m= 1 m= 1 PRF width stability 1 nm Bench stability Wavefront error PSF width Baseline Star stability centroïd and astrometric stability δσ O Metrology system (PMS) Centroid accuracy error Laser Type power of error Laser stability: (fractional pixels) (micro-arcsec) O Star Intensity, intensity wavelength noise 6.29E-06 Pseudo-stars Star 52 photon number N ph Pixel Phase gain control error accuracy 7.18E-06 radiometric budget Detection 59 noises δi Pixel position error 4.80E Photon noise, RON Detection Straylight unit (ghost (DU) images) 2.95E Integration times: Non linearity 2.95E Pseudo-stars, metrology Pxel Noises width (daek, uncertainty readout ) 8.78E PSF Crosstalk width stability 6.42E Pixel Response PRF width stability 1.81E Function (PRF) width stability RMS positoin sum 6.10E δσ m error budget error δu Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 10

11 Numerical performance model Pixel Response Functions (PRF) (Hyper-Gaussian functions) Metrology Pseudo stars Metrology data: dynamic Young s fringes Pseudo stars data: co-moving stars Dark and flat fields 1 Fringe processing 3 Dark and flat calibration Maps of pixel offsets Pre calibrated pseudo star data Metrology fringes Un-noisy 2 Allan deviations 4 Centroiding Centroid positions versus time Noisy Allan deviations of pixel offsets Standard deviation of distance between centroids 5 Procrustes analysis Un-noisy Pseudo-stars images Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 11 Noisy

12 Comparing models with experimental results Both models in global agreement Unexpected critical error items appearing on the test bench : Parasitic interferograms in laser metrology chain New camera baffle under design, concentrating optics at a later stage Pseudo-stars ghost images of electronic origin Modify electronic circuits or use another CCD Error items not so critical as expected : Pseudo-stars photon noise Metrology laser wavelength stability Zerodur and Invar bench thermal stability Other to be investigated : Laser intensity fluctuations Fringes phase fitting accuracy PRF width instability Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 12

13 Breadboard performance status Performance Required (fractions of pixel) Estimated Pixel position error 5.00E E-04 Star position error 5.00E E-05 Digitization noise 16% Dark current 22% Shot noise 48% Pixel position error Star position error Readout noise 14% Readout noise 2% Shot noise 11% Straylight (parasitic interferograms) 27% Dark current 3% Digitization noise 6% Phase control accuracy 24% Intensity noise 27% PRF width stability 14% Star intensity noise 5% Pixel gain error PSF width 6% stability 5% Pxel width uncertainty 7% Non linearity 2% Straylight (ghost images) 23% Pixel position error 38% Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 13

14 Conclusion The NEAT performance models were very helpful to identify the dominant error sources of the breadboard: Most of are well understood (shot noise, detector noise) Some ones deserving further investigations: parasitic interferograms in metrology beam, pseudo-stars ghost images (electronic crosstalk) In way to be eliminated NEAT space instrument will probably be postponed after year 2020, but its test bench will be pursued for high precision characterization of detectors in situ Future developments: New detector arrays funded by CNES Evolutions of the metrology and astrometric performance models: Detector defocus and tilt stability effects More realistic PSF and PRF shape Influence of opto-mechanical on PSF width stability Ghosts and parasitic interferograms issues Conference Modeling, Systems Engineering, and Project Management for Astronomy VI 14