Lasers hold promise of faster communications in space

Nature : To be able to transmit more data over ever-longer distances through space, both NASA and the European Space Agency (ESA) are about to launch spacecraft equipped with laser communications systems, which may eventually replace the radio transmission systems currently in use. Lasers, which operate at much higher frequencies than radio waves, offer the possibility of sending gigabits of information every second, compared with the megabits transmitted by radio. On 25 July, the ESA’s Alphasat is scheduled to be launched into a geostationary orbit, where it will act as a relay station between other satellites and Earth. Although it will receive data via laser signals, it will relay the data to Earth via radio waves, which are less vulnerable to Earth’s atmospheric turbulence. Unlike Alphasat, NASA’s Lunar Atmosphere and Dust Environment Explorer, due to go up 5 September, is equipped with an optical system that encodes information by varying the amplitude rather than the frequency of a light wave’s peaks, and so should be able to communicate directly with Earth.