Surrey Satellite Technology (SSTL) has demonstrated the potential importance of the
troubled Galileo satellite navigation project.
The Univeristy of Surrey-based satellite technology company, which developed the only Galileo satellite in orbit, has demonstrated the potential for determining the weather at sea with remote sensing satellites by capturing a signal from its Giove-A Galileo satellite which was reflected off the ocean surface.
“This demonstrates the potential offered by Galileo for scientific purposes. A constellation of small satellites could be deployed at low cost to take measurements over the oceans where there are large gaps in forecast knowledge at present,” said Dr Martin Unwin, head of the global navigation satellite systems/GPS team at SSTL.
The experiment used GPS reflectometry techniques called bistatic radar or forward scatterometry deployed on SSTL’s UK-DMC satellite launched in 2003. It detected a Galileo satellite navigation signal reflected by the ocean’s surface.
Twenty seconds of data were captured in orbit above the Arafura Sea, north of Australia, and downloaded to Surrey for processing. Whilst the orbiting experiment on UK-DMC is not optimised for Galileo signals, enough of the reflected signal energy was received to allow the detection and plotting of the weak signal.
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).
“Signals from Galileo, in conjunction with GPS and the Russian and Chinese systems, Glonass and Compass, can all be used as part of a new tool for ocean sensing. The future high bandwidth signals transmitted by Galileo, in particular, will enable higher resolution measurements of special interest to scientists, for example, in resolving wave heights,” said Unwin.
The attraction of GPS Reflectometry is that it does not require a special transmitter as GPS signals are being broadcast to the Earth 24 hours a day. Also, a satellite dedicated to GPS reflectometry would only need to carry a modified miniaturised 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.
SSTL is developing a new reflectometry experiment which will receive Galileo signals as well as those from GPS, with the intention of real-time processing.
“The sooner Galileo is up and transmitting the better,” said Dr Unwin.