LEO-to-ground low elevation optical communication: optimization of an adaptive optics design robust to scintillation

To maximize the duration of optical downlinks with Low-Earth Orbit satellites, it is crucial to ensure the coupling in the ground terminal even at low elevations. Adaptive optics systems are designed to correct the wavefront deformation induced by the atmospheric turbulence. However, at low elevations, amplitude fluctuations (or scintillation) are challenging this correction. Here we propose an AO system design robust to scintillation, with a focus on the wavefront sensor subsystem: from the wavefront analysis with a Shack-Hartmann Wavefront Sensor to the reconstruction. We then present a simulation of the whole AO system robust to strong perturbations and scintillation which shows remarkable results in terms of coupling efficiency in a single mode fiber. Finally the gain in performance is interpreted thanks to a detailed AO error budget.