On Thursday Europe launched into orbit the most massive telecommunications satellite ever built on the continent. Managed by the European Space Agency and commercial operator Inmarsat, the 6.6-tonne Alphasat will relay data between different spots on the globe — using radio waves in the already crowded L-band frequency range. But it will also test out a laser communication device that could give a boost to space communications.
One piece of experimental equipment will broadcast at the higher and underused frequencies in the Q/V band. Higher frequencies encode more information, increasing the bandwidth available for transmissions. Sending such signals to the ground has been technically challenging because they are more easily disturbed by the atmosphere.
A second device will shoot and detect beams of laser light that have even higher frequencies and can carry even more information. Other satellites equipped with such terminals will be able to send information from low-Earth orbit up to Alphasat, which will relay the data to the ground from its high geosynchronous orbit. This will be the first step towards a network of laser-relay satellites intended to handle data from a planned fleet of European Earth-observing satellites.
An advanced star tracker particularly resistant to radiation will help these communications systems to aim their messages. Like a mariner out on the sea, it observes the stars to help the craft orient itself properly.
The Ariane 5 rocket that carried Alphasat also put into orbit INSAT-3D. This satellite will provide weather forecasting services to India.