In June 2006, optical downlinks from a LEO satellite to a ground station in Oberpfaffenhofen (20 km south-west from Munich) have been performed. For the first time on European grounds, an optical LEO downlink has been established. KIODO is the result of a cooperation between JAXA (Japanese Aerospace eXploration Agency) who operated the satellite, and DLR who operated the ground station. DLR developed a transportable ground station capable of performing various optical free-space communication experiments. A near-infrared laser beam with a footprint of a few meters and modulated by a 50-Mbit/s signal was received in the ground station by a 40-cm telescope. One of the challenges in optical satellite communications is the high accuracy of the laser pointing. Five out of eight trials could be performed successfully while the other three were hindered by cloud blockage. The aim of this successful experiment also was to measure the optical communication channel between satellite and ground station, and to investigate the impact of the atmosphere on the transmission. For future tests, data rates shall be extended to the gigabit area.
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