NEXT year, European Space Agency engineers will aim a 60-kilowatt laser at a small spacecraft orbiting the Moon. But they won鈥檛 be trying to destroy it. The laser will be testing a new light-based communication system designed to gather far more information from space probes than is possible now.
There is a pressing need for better communication with space probes. As imaging systems improve, the flood of data they generate is starting to overwhelm the low capacity radio signals that are supposed to beam data back to Earth. Organisations like NASA鈥檚 Deep Space Network 鈥� an earthbound collection of vast radio dishes that keep in touch with faraway spacecraft 鈥� are demanding ever more bandwidth. One solution is to use the same near-infrared frequencies used in optical fibre telecoms systems, potentially providing up to 100 times the capacity of today鈥檚 deep space radio links.
ESA recently tested laser communications between orbiting satellites, but this will be the first time a link has spanned the 400,000 kilometres from Earth to a fast-moving spacecraft in lunar orbit. The SMART-1 probe, due to be launched in August this year, will carry cameras to record infrared, visible light and X-rays from the Moon鈥檚 surface.
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For SMART-1鈥檚 Laser Link experiment, an infrared mapping camera will be pointed at a laser at a ground station on the Canary Islands, back on Earth. ESA says the precision required to aim the camera will be 鈥渓ike hitting a penny from a mile away鈥�.
鈥淲e鈥檒l only test the optical connection,鈥� says Bernard Foing, a scientist at ESTEC, ESA鈥檚 research centre in Noordwijk, the Netherlands. 鈥淲e are not going to transmit any data, although we may try some Morse code.鈥� The results will be used to assess blurring and weakening of the beam by Earth鈥檚 atmosphere.
A laser-based network would require probes to have dishes that could aim a narrow laser beam precisely enough to hit receivers back on Earth. Existing telescopes could act as receivers, and by switching from one to another the network could avoid interruption caused by cloud cover problems or the Earth鈥檚 rotation.
