Adaptive optics for daytime deep-space optical communications

In deep-space optical communications, one particular challenge encountered at the ground receiver side are the wavefront deformations caused by atmospheric turbulence. This gives rise to reduced signal-to-background ratios and signal fades, especially during daytime links. Background rejection is therefore a fundamental requirement for optical links operating in the low-photon-count regime during the day. Both, spectral and spatial filtering subsystems are essential for this application. To this end, we have analyzed several wavefront sensing modalities including: Shack-Hartmann wavefront sensor, holographic wavefront sensing, and wavefront sensorless adaptive optics. The insights gained through simulations were used to drive the design of the laboratory-based demonstrator, which exhibited very similar performance improvements due to high-order correction as in the simulations, despite noise levels of the same magnitude as the signal.