The first on-sky demonstration of intensity-based angular phase estimation.

High data-rate ground-to-satellite optical links require adaptive optics (AO) pre-compensation to mitigate uplink turbulence. Current systems rely on downlink-based correction, limited by phase anisoplanatism due to the point-ahead angle (PAA), which can cause long and deep signal attenuations onboard the satellite. We previously proposed a model-based estimator using downlink phase and intensity and turbulence statistical priors to optimize the pre-compensation phase at PAA. Here, we report the first on-sky demonstration of this method: by observing close visual binary stars (30 μrad) in the visible with an open-loop Shack-Hartmann sensor, we demonstrate up to 28% reduction in anisoplanatic tip errors compared to phase-only estimation, in agreement with theory.