ASTRONOMICAL ADAPTIVE OPTICS .1. MODAL CONTROL OPTIMIZATION

The value of adaptive optics (AO) for astronomy no longer needs to be demonstrated. To match the extreme requirements of astronomy in terms of resolution and sensitivity requires us to optimize an AO system to a great variety of situations. In particular, this paper addresses the case of low flux levels and shows that the final image quality can be improved by adapting the spatial and temporal correction performance of the AO system. The wavefront is considered as a weighted sum of spa tial modes. Each mode has an individual behavior characterized by its signal to noise ratio and correlation time. Taking this into account l eads us to attribute a specific, optimized correction bandwidth to eac h mode. To apply this optimization method to a practical use of adapti ve optics, one proposes a scheme where all the required inputs are col lected by the AO system itself. The method becomes entirely independen t of theoretical assumptions about the turbulence.