Comparative theoretical and experimental study of a Shack-Hartmann and a Phase Diversity SENSOR, for high-precision wavefront sensing dedicated to Space Active Optics
Résumé
The RASCASSE project was commissioned by the french spatial agency (CNES) to study a critical element of the next-generation of Earth-imaging satellites: the wavefront sensor, which is a key subsystem of active optics. The project involved ONERA and Thales Alenia Space (TAS) to study the analyzers, and LAM to design and implement the experiment.At ONERA, we first performed end-to-end simulations of a Shack-Hartmann and a Phase Diversity wavefront sensor on both a point source and extended scenes, with realistic wavefronts supplied by TAS. Then we studied the sensitivity of the sensors and the optimization of their design as a function of several parameters, such as: the strength and the type of aberrations, the image subsampling, the aperture shape, the signal-to-noise ratio, the spectral bandwidth, the type of scene, etc..Finally, we performed experimental measurements on the bench at lam, where both analyzers were run concurrently. The precision we achieved was better than 1 nm rms per measured Zernike mode, for both types of analyzers.
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