Atmospheric compensation over a 2.3 km propagation path with a multi-conjugate (piston-MEMS/modal DM) adaptive system

We discuss the expansion of wavefront distortion compensation based on stochastic parallel gradient descent (SPGD) optimization to the control of several wavefront correctors. We describe then a SPGD adaptive optics system that uses a low-order deformable mirror with modal control and a high-resolution (either 132 or 320 control channels) piston-type MEMS mirror. The system was installed at a 2.3km near-horizontal propagation and used for atmospheric compensation experiments. Results obtained for different system configurations are presented.