Experimental results of tomographic reconstruction on ONERA laboratory MCAO bench

Abstract

Classic Adaptive Optics (AO) is now a proven technique to correct turbulence for earth based astro- nomical telescopes. But the corrected Field of View (FoV) is however limited by the anisoplanatism e ect. Many concepts of wide field AO systems are now under study, especia lly for ELT's instruments. These systems allow a tomographic reconstruction of the turbulent volume thanks to the use of several WaveFront Sensors (WFS). They can provide for instance a correction in a specific direction (Laser Tomography AO system) with one Deformable Mirror (DM) or in a wide FoV (Multi Conjugate AO system) with several DMs conjugated to di erent altitudes. The performance optimization of such complex systems raises inevitably new questions in terms of calibration and control. We present our current developments on performance optimization of wide field AO system. We show that performance can be significantly improved with tom ographic control based on Linear Quadratic Gaus- sian control, compared to more standard methods. The associated calibration and system modeling strategy is described. The results presented here are the first experime ntal validations of LQG control in closed-loop MCAO and LTAO configurations. These tests have been performed on H OMER bench, recently developed at ONERA and devoted to MCAO and wide field AO laboratory research. Thi s bench implements two deformable mirrors and a wide field Shack-Hartmann WFS.