High-order coronagraphic phase diversity: demonstration of COFFEE on SPHERE.

1. High-order coronagraphic phase diversity: demonstration of COFFEE on SPHERE. B.Paul1,2, J-F Sauvage1, L. Mugnier1, K. Dohlen2, D. Mouillet3, T. Fusco1,2 , J.-L. Beuzit3, M. Ferrari2, M. N’Diaye4 1 Onera, DOTA/HRA 2 Laboratoire d’Astrophysique de Marseille 3 Institut de Planétologie et d'Astrophysique de Grenoble 4 Space Telescope Science Institute 1

2. Outline • Context: high-contrast imaging • Principle of COFFEE • COFFEE's optimization & performance evaluation • Application to the SPHERE instrument

3. Context: XAO for high-contrast imaging High contrast needs for exoplanet imaging Today: Angular separations from 0.1 to arcsec (a few /D to 100 /D) Contrast up to 106 - 107 Observation made from the ground (turbulence) Tomorrow: Angular separations below 0.1 arcsec Contrast up to 109 - 1010 (Earth like planets) Ground / space observations Limitation: Light residuals in final focal plane created by quasi-static aberrations (Non Common Path Aberrations) Solution : focal plane wavefront sensing with the scientific detector

4. COFFEE : phase diversity using coronagraphic images (1/2) Detector Pupil plane • Coronagraphic imaging system • Coronagraphic focal plane mask • Downstream aberrations (ϕd) Diversity phase (ϕdiv) Upstream aberrations (ϕu) i(ϕu, ϕd) i(ϕu+ϕdiv, ϕd) Image formation model One image: not enough data + Two images: OK • Coronagraphic phase diversity: • Uses only two images to estimate the aberrations upstream of the coronagraph • Rely on a coronagraphic image formation model: ic (ϕu, ϕd)= Model(ϕu, ϕd) 4

5. COFFEE : phase diversity using coronagraphic images (2/2) COFFEE: COronagraphic Focal-plane wave-Front Estimator for Exoplanet detection Estimation of aberrations upstream (ϕu) and downstream (ϕd) of the coronagraph by criterion J minimization Definition of a maximum a posteriori criterion: « Maximum Likelihood »: Distance experimental images / computed images Regularization metrics: A priori information on the parameters J.-F. Sauvage, L. Mugnier, B. Paul et R. Villecroze, Coronagraphic phase diversity: a simple focal plane sensor for high-contrast imaging, Optics Letter, Dec. 2012

6. COFFEE's optimization (1/3) AO4ELT3 2013 SPIE 2012 • Adaptation to any coronagraphic device • Model : perfect coronagraph model • Model mismatch • Application to the apodized Roddier & Roddier coronagraph only • Model : electric field propagation • No model mismatch • Can be adapted to any coronagraphic focal plane mask M (ALC, FQPM, VPM…) • Estimation of high-order aberrations • Aberration estimation: Zernike modes • Estimation of low-order aberrations only • Strong aliasing error • Aberration estimation: pixel map • Estimation of high-order aberration • Reduction of the aliasing error 100 parameters > 3.103 parameters B. Paul, J.-F. Sauvage et L. M. Mugnier, Coronagraphic phase diversity: performance study and laboratory demonstration, A&A, April 2013

7. COFFEE's optimization (2/3) : performance evaluation Aberration estimation: simulation • Coronagraph: ALC (4,52 λ/D); Lyot Stop = 100% • WFEup = 50 nm ; WFEdown = 20 nm (λ = 1589 nm, monochromatic images) • Incoming flux: 1e9 photons ; detector noise: σe-= 1 e-; photon noise • No residual turbulence idiv ifoc up up Image computation Simulation COFFEE: aberration estimation Estimation Image computation εrec= 1.71 nm RMS

8. COFFEE’s optimization(3/3) : NCPA compensation Pseudo-closed loop: simulation • Coronagraph: ALC; Lyot Stop = 96% • WFEup = 50 nm ; WFEdown = 20 nm (λ = 1589 nm, monochromatic images) • DM: 41x41 actuators • Incoming flux: 1e9 photons ; detector noise: σe-= 1 e-; photon noise • No residual turbulence Contrast 10-0 10-1 No compensation No compensation 10-2 10-3 10-4 10-5 After NCPA compensation After NCPA compensation 10-6 10-7

9. COFFEE : validation on SPHERE (1/5) Calibration Point-Source, H band Exp. images XAO system, 41 act, 1200Hz Coronagraph ALC (incl. Apodizer) COFFEE Dead actuator IRDIS imager, H2 band, ALC Stop COFFEE : Rec. images • Coronagraph : ALC (dM = 4.5 λ/D) • Coronagraphic images : IRDIS • Diversity phase : AO loop 9

10. COFFEE : validation on SPHERE (2/5) • Low order aberration estimation : Zernike modes • Wavelength : 1589 nm • Coronagraph : APO1 / ALC2 • Lyot Stop : Stop ALC (96% entrance pupil + 15% central obstruction) Coronagraphic image computed by COFFEE IRDIS Estimated aberration Defocus Astigmatism 10

11. COFFEE : validation on SPHERE (3/5) • High order aberration estimation : poke • Wavelength : 1589 nm • Coronagraph : APO1 / ALC2 • Lyot Stop : Stop ALC (96% entrance pupil + 15% central obstruction) Introduced poke Estimated poke

12. COFFEE : validation on SPHERE (4/5) Pseudo – closed loop process COFFEE Acquisition of two images ifoc, idiv From u, computation off correction slopes Closed loop on initial reference slopes Measurment of u and d Modification of reference slopes • Wavelength : 1589 nm • Coronagraph : apodized Lyot coronagraph (dM = 4.5 λ/D) • Lyot Stop : Stop ALC (96% entrance pupil + 15% central obstruction) • Gain = 0.5

13. COFFEE : validation on SPHERE (5/5) First validation of the compensation process: Contrast No compensation 10-4 10-5 After NCPA compensation (5 iterations) 10-6 Energy decrease Contrast : gain x2 – x5 Energy increase

14. Conclusion & Perspectives COFFEE : application of the phase diversity to coronagraphic images • COFFEE’s optimization: • Estimation of a pixel-wise map • New imaging model: Adaptation to any coronagraphic mask M • Application to SPHERE : • Estimation of introduced aberration • First experimental validation of the compensation process • Perspectives • COFFEE: full validation of iterative process on SPHERE • Combination with ZELDA for a SPHERE upgrade (K. Dohlen talk, Thu. 14h) • Ultimate extinction • Creation of a dark hole on the detector • Impact of a segmented mirror => refined cophasing

15. …. Thanks for your attention !