Sparse Matrix Methods for Wavefront Reconstruction Revisited

This paper contains a review of sparse matrix methods for open-loop wavefront estimation in astronomical adaptive optics systems with a large number of degrees of freedom. We address shortcomings of existing sparse methods for multiconjugate adaptive optics and propose some alternative approaches. We also review certain closed-loop control schemes, dubbed pseudo open-loop control (POLC), that make use of open-loop linear algebra, and we propose an extension of POLC that makes use of knowledge of atmospheric dynamics to carry out predictive estimation in closed loop