Comparison of multiconjugate adaptive optics configurations and control algorithms for the Gemini South 8-m telescope

Abstract

This paper focuses on two main categories of the multiconjugate adaptive optics (MCAO) parameter space for performance optimization: the geometrical configuration of guide stars and deformable mirrors (DMs), and the wavefront reconstructors. From the first category it is shown how, for a fixed reconstructor and imaging wavelength, the performance metrics with a few important exceptions improve with an increasing number of (1) DMs, (2) actuators per DM and (3) guide stars. The metrics are seen to degrade with (1) an increasing field of compensation and (2) DM conjugation altitude mismatch with the significant turbulent atmospheric layers. In the second category, this study also compares the performance with a fixed MCAO configuration using the least- square estimator (LSE) and the maximum a posteriori estimator (MAP) for wavefront reconstruction. The MAP is shown to perform significantly better than the LSE at low or intermediate signal-to-noise ratios (SNRs), and somewhat better even in the absence of noise due to its a priori knowledge of the phase statistics.