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Proceedings Paper

Experimental validation of the high-order coronagraphic phase diversity (COFFEE) on the SPHERE system
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Paper Abstract

The final performance of current and future instruments dedicated to exoplanet detection and characterization (such as SPHERE on the VLT, GPI on Gemini North or future instruments on the E-ELT) is limited by intensity residuals in the scientific image plane, which originate in uncorrected optical aberrations. After correction of the atmospheric turbulence, the main contribution to these residuals comes from the quasi-static aberrations introduced upstream of the coronagraph. In order to measure and compensate for these aberrations, we propose a dedicated focal-plane sensor called COFFEE (for COronagraphic Focal-plane wave-Front Estimation for Exoplanet detection), which consists in an extension of conventional phase diversity to a coronagraphic system: aberrations both upstream and downstream of the coronagraph are estimated using two coronagraphic focal-plane images, recorded from the scientific camera itself, without any differential aberration. This communication gathers COFFEE’s improvements: the phase estimation is performed on a pixel-wise map coupled with a dedicated regularization metric. This allows COFFEE to estimate very high order aberrations, making possible to estimate and compensate for quasi-static aberrations with nanometric precision, leading to an optimization of the contrast on the scientific detector in the whole AO corrected area. Besides, COFFEE has been modified so that it can be used with any coronagraphic focal plane mask. Lastly, we use COFFEE to measure and correct the wavefront on the SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) instrument during its integration phase: COFFEE’s estimation is used to compensate for the quasi-static aberrations upstream of the coronagraph, leading to a contrast improvement on the scientific camera.

Paper Details

Date Published: 26 September 2013
PDF: 10 pages
Proc. SPIE 8864, Techniques and Instrumentation for Detection of Exoplanets VI, 88640D (26 September 2013); doi: 10.1117/12.2023651
Show Author Affiliations
Baptiste Paul, ONERA (France)
Lab. d'Astrophysique de Marseille, Univ. Aix-Marseille (France)
Groupement d'intérêt scientifique PHASE (France)
Jean-François Sauvage, ONERA (France)
IPAG, CNRS, Univ. Joseph Fourier (France)
Groupement d'intérêt scientifique PHASE (France)
Laurent M. Mugnier, ONERA (France)
Groupement d'intérêt scientifique PHASE (France)
Kjetil Dohlen, Lab. d'Astrophysique de Marseille, CNRS, Univ. Aix-Marseille (France)
Groupement d'intérêt scientifique PHASE (France)
David Mouillet, IPAG, CNRS, Univ. Joseph Fourier (France)
Groupement d'intérêt scientifique PHASE (France)
Thierry Fusco, ONERA (France)
Lab. d'Astrophysique de Marseille, Univ. Aix-Marseille (France)
Groupement d'intérêt scientifique PHASE (France)
Jean-Luc Beuzit, IPAG, CNRS, Univ. Joseph Fourier (France)
Groupement d'intérêt scientifique PHASE (France)
Mamadou N'Diaye, Space Telescope Science Institute (United States)
Groupement d'intérêt scientifique PHASE (France)
Marc Ferrari, Lab. d'Astrophysique de Marseille, CNRS, Univ. Aix-Marseille (France)
Groupement d'intérêt scientifique PHASE (France)


Published in SPIE Proceedings Vol. 8864:
Techniques and Instrumentation for Detection of Exoplanets VI
Stuart Shaklan, Editor(s)

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