The self-coherent camera-phasing sensor : from numerical simulations to early experiments

Abstract

Extremely Large Telescopes (ELTs) are the next technological step when considering astrophysical observation. They will provide unprecedented angular resolution, thus improving the imaging capability and hopefully allow the imaging of the first Earth-like exoplanet. For technological and mechanical reasons, the primary mirror of these instruments will have to be segmented. To reach the image quality needed for the most demanding observational programs, the segments must be kept aligned below tens of nm RMS. The development of cophasing technics is of prime importance for the next generation of space- and ground-based segmented telescopes. We propose to describe in this paper a new focal plane cophasing sensor that exploits the scientific image of a coronagraphic instrument to retrieve simultaneously piston and tip-tilt misalignments. It is based on the self- coherent camera (SCC) principle and provides a non-invasive system and an efficient phasing sensor from the image domain. Numerical simulations have successfully demonstrated the proper functioning of this system and its algorithms. Along this, work to implement and test the self-coherent camera - phasing sensor (SCC-PS) is currently ongoing and a first look at the cophasing stage of the Segmented Pupil Experiment for Exoplanet Detection (SPEED) will be proposed.