Efficient implementation of pseudo open-loop control for adaptive optics on Extremely Large Telescopes

Abstract

Closed-loop adaptive optics systems that use minimum mean square error wavefront reconstruction require the computation of pseudo open-loop wavefront slopes. These techniques incorporate a knowledge of atmospheric statistics that must therefore be represented within the wavefront slope measurements. These pseudo open-loop slopes are computed from the sum of the measured residual slopes and the reconstructed slopes that would be given if the deformablemirror was flat, generally involving the multiplication of an interactionmatrix with actuator demands from the previous time-step. When using dense algebra, this multiplication is computationally expensive for Extremely Large Telescopes, requiring a large memory bandwidth. Here, we show that this requirement can be significantly reduced, maintaining mathematical correctness and significantly reducing system complexity. This therefore reduces the cost of these systems and increases robustness and reliability.N.