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A precise ground based telescope system was developed for laser communicationexperiments with the geostationary satellite ARTEMIS of ESA. Precise trackingof the satellite was realized by using time resolved coordinates of thesatellite. During the experiments, the time propagation of laser signal fromthe satellite and the point-ahead angle for the laser beam were calculated.Some laser experiments though thin clouds were performed. A splitting of someimages of the laser beam from the satellite along declination and rightascension coordinates of telescope could be observed through thin clouds. Thesplitting along the declination coordinate may be interpreted as refraction inthe atmosphere. The splitting along the right ascension coordinate isequivalent to the calculated point-ahead angle for the satellite. We find outthat a small part of laser beam was observed ahead of the velocity vector inthe point where the satellite would be after the laser light from the satellitereaches the telescope. These results are in accordance with the theory ofrelativity for aberration of light during transition from immovable to movablecoordinate systems. We directly observed laser light aberration as result ofmoving of satellite with angular velocity close to Earth rotation.

Direct measurements of laser light aberration from the ARTEMIS geostationary satellite through thin clouds