The Self-Coherent Camera : a focal plane sensor for EPICS ?

¹ LESIA, Observatoire de Paris, CNRS, Université Pierre et Marie Curie Paris 6 and Université Denis Diderot Paris7 – 5, place Jules Janssen, 92195 Meudon, France.
² Groupement d’Intérêt Scientifique Partenariat Haute Résolution Angulaire Sol Espace (PHASE) between ONERA, Observatoire de Paris, CNRS and Université Denis Diderot Paris 7

^a e-mail: pierre.baudoz@obspm.fr

Abstract

In the framework of the European Extremely Large Telescope, EPICS is an ambitious instrument devoted to the direct detection and the characterization of extrasolar planets. Since the performance of such an instrument is limited by wavefront errors, the use of extreme Adaptive Optic (AO) systems is mandatory. Studies for future planet finder instruments such as SPHERE/VLT or GPI/GEMINI show that a strong limitation of the performance of a planet finder is the differential aberrations that are not measured by the wavefront sensor, which is physically separated from the common optics by a beam splitter. We propose here to efficiently estimate these aberrations by directly measuring the wavefront errors in the final science image. To do so, we propose to couple the foreseen extreme AO system at high speed of EPICS with a low speed Self-Coherent Camera (SCC) which can measure directly the differential aberrations at the final science focal plane. The SCC which is based on the principle of light coherence estimates the wavefront errors by spatially encoding the speckles with fringes in the final image. After recalling the principle of the SCC, we present simulation results of the SCC performance in the context of EPICS.