The first ever data link between satellites has been established using a laser beam as the signal carrier.
On board the European Space Agency's (ESA's) Artemis satellite is the Silex system, which provides an optical data transmission link with the French National Centre of Space Studies' Earth observation satellite, Spot 4, which also has a Silex terminal.
The silex system was designed and built by Astrium, a European space company.
Through the laser link, images from Spot 4 can be transmitted to the image processing centre at Spot Image in Toulouse, France, via Artemis at a rate of 50Mbit/s. This is possible whenever the two satellites are in line of sight. This reduces the time between taking the picture and delivery to the centre, as Spot 4 previously stored images in its memory until it could dump them to a ground station.