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

TL;DR

This study developed a ground-based telescope system to measure laser light aberration from the geostationary satellite ARTEMIS, observing atmospheric refraction and aberration effects consistent with relativity during satellite laser communication experiments.

Contribution

It provides the first direct measurements of laser aberration from a geostationary satellite through thin clouds, confirming theoretical predictions.

Findings

Observed laser beam splitting along declination and right ascension.

Detected atmospheric refraction effects on laser beam.

Confirmed relativistic aberration of light from a moving satellite.

Abstract

A precise ground based telescope system was developed for laser communication experiments with the geostationary satellite ARTEMIS of ESA. Precise tracking of the satellite was realized by using time resolved coordinates of the satellite. During the experiments, the time propagation of laser signal from the satellite and the point-ahead angle for the laser beam were calculated. Some laser experiments though thin clouds were performed. A splitting of some images of the laser beam from the satellite along declination and right ascension coordinates of telescope could be observed through thin clouds. The splitting along the declination coordinate may be interpreted as refraction in the atmosphere. The splitting along the right ascension coordinate is equivalent to the calculated point-ahead angle for the satellite. We find out that a small part of laser beam was observed ahead of the velocity vector in the point where the satellite would be after the laser light from the satellite reaches the telescope. These results are in accordance with the theory of relativity for aberration of light during transition from immovable to movable coordinate systems. We directly observed laser light aberration as result of moving of satellite with angular velocity close to Earth rotation.