Beaconless acquisition for ISL and SGL, summary of 3 years operation in space and on ground

Starting November 2007 and continuing through the present TESAT has been conducting successfully optical inter-satellite communication links utilizing a secondary laser communication payload built by Tesat-Spacecom funded by DLR. Two satellites, TerraSAR-X (TSX), a commercial SAR satellite partially funded by the German Space Agency (DLR) and NFIRE (Near-Field InfraRed Experiment) are equipped with one laser communication payload each. Also optical space-to-ground communication links have been successfully conducted using a compatible ground terminal built by Tesat-Spacecom and the ESA Optical Ground Station on Tenerife. All terminals are using a beaconless spatial acquisition algorithm which was developed for inter-satellite communication links. We present the operational considerations of the beaconless spatial acquisition based on experience gained during 3 years of operation in space and on ground. Included is the impact of atmosphere both, for inter-satellite communication links (low grazing attitude) and space-to-ground links. Furthermore aspects of S/C characteristics and S/C operations centers such as attitude, time, and position knowledge are also covered. Spatial acquisition data gained performing inter-satellite and space-to-ground links is presented.