Two-aperture measurements for GEO-feeder adaptive optics pre-compensation optimization.

We present a method to estimate the pre-compensation phase of ground-to-geostationary orbit (GEO) optical links based on downlink phase and log-amplitude measurements from two ground apertures. This method allows us to reduce the point-ahead anisoplanatism that currently limits the telecom performance of GEO-feeder links. It is shown to reduce the anisoplanatic phase variance by 50%, hence improving the statistics of the coupled flux aboard the satellite. It also outperforms the one-aperture estimation method for very severe atmospheric conditions. Besides, only low-resolution amplitude measurements are required on the second aperture to reach the performance of the novel estimator.