Surrey Satellite Technology (SSTL) and the University of Surrey have used reflected Galileo satellite navigation signals to measure ocean roughness and weather.

The experiment involved SSTL's UK Disaster Monitoring Constellation (DMC) spacecraft, launched in 2003. Using a technique called bistatic radar or "forward scatterometry" the reflectometry experiment on UK-DMC detected the reflected signals transmitted by the SSTL-built GIOVE-A spacecraft, the European Galileo satellite navigation programme's first test spacecraft.

With 20s of captured data from above the Arafura Sea, north of Australia, the reflected signal's shape, once plotted, gave an indication of the sea roughness and weather at that place and time, where the wind speed was around 11.8kt (22km/h).

"This demonstrates the potential offered by Galileo for scientific purposes," says the head of SSTL's global navigation satellite systems team Martin Unwin. "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. An improved measurement system in space could be used to warn mariners of storms and to provide data for global climate change models - potentially even to detect tsunamis," he says.

Reflectometry has advantages because it does not need a special transmitter as the GNSS signals are already being broadcast. The detection system, according to SSTL, is only a modified receiver and an antenna, which could potentially be accommodated on a 10kg (22lb) satellite.

The UK-DMC reflectometry experiment has been used to detect GPS signals reflected off ice and dry land. These measurements could be used as inputs for climate modelling. SSTL is now working on a GNSS reflectometry experiment that would use GPS and Galileo in-service signals in real time to provide accurate weather monitoring.

"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," Unwin says.

Source: Flight International