Pre-distortion adaptive optics for optical feeder links: simulations and performance analyses

Optical feeder links offer immense utility in meeting future communication demands—however, atmospheric turbulence limits their performance. This work targets this challenge through analyses of a bidirectional free-space optical communication (FSOC) link that incorporates pre-distortion adaptive optics (AO) between the next-generation optical ground station at the German Aerospace Center (DLR) Oberpfaffenhofen and the laser communications terminal on Alphasat—a satellite in geostationary orbit (GEO). The analyses are performed via end-to-end Monte Carlo simulations that provide realistic performance estimates of the bidirectional FSOC link for a GEO feeder link scenario. We find that applying pre-distortion AO reduces the total uplink losses of the bidirectional FSOC link by up to 10 dB and lessens the scintillation at the GEO satellite by an order of magnitude. Moreover, applying pre-distortion AO eases the link budget requirements needed for maintaining 99.9% link uptime by as much as 20-40 dB, while its use with a laser guide star shows an additional performance improvement of up to 8 dB. These findings demonstrate the desirability and feasibility of utilizing pre-distortion AO for the realization of optical feeder links

Correction of finite spatial and temporal sampling effects in stereo-SCIDAR

Stereo scintillation detection and ranging (S-SCIDAR) is a development of the well-established SCIDAR turbulence profiling technique. An S-SCIDAR instrument has been installed at the focus of one of the 1.8m Auxiliary Telescopes at Paranal observatory since April 2016. We discuss the limitations imposed by the Paranal S-SCIDAR instrument’s finite pixel size and exposure time. We present Monte Carlo simulation results quantifying the errors due to finite spatial and temporal sampling. We have reprocessed the existing S-SCIDAR dataset to compensate for these error sources; we discuss the impact of these corrections on the measured turbulence statistics