An important step towards reliable optical communication between ground and space is the characterization and understanding of atmospheric conditions -even when being at one place and performing links into one direction, but at different times. Within this paper the analysis of five years of optical links from a laser terminal on a geostationary satellite (TDP1-LCT on Alphasat) to ground (T-AOGS at Tenerife) is shown. The data, in total 40.2 h of reliable measurements extracted from 516 performed links, are spread over several times of the year and almost all times of day. For one of the main parameters describing the atmosphere (the Fried Parameter r0) a clear characteristic over the day is validated. For the up-link the influence of different transmitted beam divergence angles on the link budget in terms of mean power and fade statistic is shown. A short outlook on upcoming changes within the TDP-1 software and the T-AOGS functionality is given.

After more than 3 years of operational experiences with the Transportable Adaptive Optical Ground Station (T-AOGS) it is not any more the question whether optical communication through atmosphere is possible for Geo to ground applications. It is important to understand the performance of optical communication under different atmosphericconditions and which the key parameters are to improve simplicity, robustness and availability of optical bi-directional satellite to ground links (SGL). We report within this paper on the characterization of the atmospheric channel for ground to GEO optical communication without adaptive optics correction in the uplink. Besides the telemetry data of the space segment and the T-AOGS, also a special measurement campaign was carried out using the 1m telescope of the ESA-OGS in parallel. An outlook for further analysis and activities is given.

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