Surrey Satellite Technology Ltd. (SSTL) and the University of Surrey have succeeded, for the first time, in capturing a Galileo signal reflected off the ocean surface in orbit. This demonstrates the potential for determining the weather at sea with remote sensing satellites. The pioneering GPS Reflectometry Experiment was launched onboard SSTL’s UK-DMC satellite in 2003 to demonstrate the use of GPS reflections to determine the roughness of the ocean, using a method called “bistatic radar” or “forward scatterometry”. This experiment has now successfully detected a Galileo satellite navigation signal reflected by the ocean’s surface. GIOVE-A, the first Galileo demonstration satellite, also built by SSTL, was commissioned by the European Space Agency and has been transmitting prototype Galileo signals since its launch in December 2005.
In early November 20, seconds of data were captured in orbit above the Arafura Sea, north of Australia, and downloaded to Surrey for processing. While the orbiting experiment on UK-DMC is not optimized for Galileo signals, enough of the reflected signal energy was received to allow the detection and plotting of the weak signal after processing by University of Surrey PhD student, Philip Jales. The shape of the reflection gives an indication of the sea roughness and hence the weather at that place and time, where the wind speed was around 14 mph (22 km/h).
GPS Reflectometry is of great interest to engineers and scientists as a cost effective means of remote sensing. A special transmitter is not required because GPS signals are already broadcast to the Earth 24 hours a day. Also, a satellite dedicated to GPS reflectometry would only need to carry a modified miniaturized GPS/Galileo receiver and an antenna, which could potentially be accommodated on a tiny 10 kg satellite platform at low cost, enabling multiple satellites on a single launch. A future revision of the experiment, the “GNSS Reflectometry Instrument” is now being designed at Surrey with a view to flight on a future satellite mission. It is being designed specifically to receive Galileo signals as well as those from GPS, with the intention of real time processing—Guildford, United Kingdom
