1 High-order coronagraphic phase diversity: demonstration of COFFEE on SPHERE. B.Paul 1,2, J-F Sauvage 1, L. Mugnier 1, K. Dohlen 2, D. Mouillet 3, T. Fusco 1,2, J.-L. Beuzit 3, M. Ferrari 2, M. N’Diaye 4 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

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

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  Observation made from the ground (turbulence)  Tomorrow:  Angular separations below 0.1 arcsec  Contrast up to (Earth like planets)  Ground / space observations 3 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 Upstream aberrations ( ϕ u ) i( ϕ u, ϕ d ) i( ϕ u + ϕ div, ϕ d ) Diversity phase ( ϕ div ) COFFEE : phase diversity using coronagraphic images (1/2) Coronagraphic imaging system  Coronagraphic focal plane mask  Downstream aberrations ( ϕ d ) + One image: not enough data Two images: OK Image formation model Coronagraphic phase diversity:  Uses only two images to estimate the aberrations upstream of the coronagraph  Rely on a coronagraphic image formation model: i c ( ϕ u, ϕ d ) = Model( ϕ u, ϕ d ) Pupil plane Detector

COFFEE : phase diversity using coronagraphic images (2/2) COFFEE: COronagraphic Focal-plane wave-Front Estimator for Exoplanet detection Estimation of aberrations upstream ( ϕ u ) and downstream ( ϕ d ) of the coronagraph by criterion J minimization « 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 Definition of a maximum a posteriori criterion:

Aberration estimation: pixel map Estimation of high-order aberration Reduction of the aliasing error Aberration estimation: Zernike modes  Estimation of low-order aberrations only  Strong aliasing error Model : electric field propagation No model mismatch Can be adapted to any coronagraphic focal plane mask M (ALC, FQPM, VPM…) COFFEE's optimization (1/3)  Adaptation to any coronagraphic device 6  Estimation of high-order aberrations Model : perfect coronagraph model  Model mismatch  Application to the apodized Roddier & Roddier coronagraph only 100 parameters > parameters SPIE 2012 AO4ELT B. Paul, J.-F. Sauvage et L. M. Mugnier, Coronagraphic phase diversity: performance study and laboratory demonstration, A&A, April 2013

COFFEE's optimization (2/3) : performance evaluation Aberration estimation: simulation  Coronagraph: ALC (4,52 λ/D); Lyot Stop = 100%  WFE up = 50 nm ; WFE down = 20 nm (λ = 1589 nm, monochromatic images)  Incoming flux: 1e9 photons ; detector noise: σ e- = 1 e-; photon noise  No residual turbulence  up i foc i div ε rec = 1.71 nm RMS Simulation Estimation Image computation  up COFFEE: aberration estimation Image computation

Pseudo-closed loop: simulation  Coronagraph: ALC; Lyot Stop = 96%  WFE up = 50 nm ; WFE down = 20 nm (λ = 1589 nm, monochromatic images)  DM: 41x41 actuators  Incoming flux: 1e9 photons ; detector noise: σ e- = 1 e-; photon noise  No residual turbulence No compensation After NCPA compensation 8 COFFEE’s optimization(3/3) : NCPA compensation No compensation After NCPA compensation Contrast

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

Defocus Astigmatism IRDIS Coronagraphic image computed by COFFEE Estimated aberration 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) 10

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

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

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

 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 Conclusion & Perspectives 14 COFFEE : application of the phase diversity to coronagraphic images 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 !