Europe's Galileo signals used for ocean remote sensing in space

Nov 23, 2007

Surrey Satellite Technology Ltd and the University of Surrey have succeeded in detecting a weakly reflected Galileo signal off the ocean surface using the GPS Reflectometry Experiment on one of SSTL’s small satellites, UK-DMC. The reflection was received off the North coast of Australia on 4th November 2007, and the shape of the reflection gives an indication of the ocean roughness, and hence the weather at that place and time (where the wind speed was around 22 km/h, or 14 mph).

The GPS Reflectometry Experiment was carried into space on the British remote sensing satellite UK-DMC launched in 2003. The experiment was a pioneering demonstration that GPS reflections could be used as a means to determining the roughness of the ocean, using a method called ‘bistatic radar’ or ‘forward scatterometry’. Unlike other radar remote sensing techniques, no transmitter is required as GPS satellites are already broadcasting predictable signals to the Earth 24 hours a day. A satellite dedicated to GPS reflectometry would only therefore need to carry a modified GPS receiver and an antenna, which could potentially be accommodated on a tiny 10 kg satellite platform at a low cost.

GIOVE-A, the first Galileo demonstration satellite, also coincidentally built by SSTL was commissioned by the European Space Agency and has been transmitting prototype Galileo signals since its launch in December 2005. While 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 from a short 20 second data collection by a PhD student at the University of Surrey, Philip Jales.

Dr Martin Unwin, head of the GNSS/GPS team in SSTL, commented: "This is an important achievement in the field of remote sensing, and shows the potential offered by Galileo for scientific purposes. Signals from Galileo in conjunction with those from GPS, and the Russian and Chinese systems, Glonass and Compass, can all be used as part of a new tool for ocean sensing. A constellation of small satellites could be deployed at a low cost to take measurements over the oceans where there are large gaps in forecast knowledge at present.

More navigation satellites mean more measurements, and some 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 such as this could be used to warn mariners of storms, and as an input towards global climate change models, and potentially even to detect Tsunamis."

The UK-DMC Reflectometry Experiment has also previously been used to detect GPS signals reflected off ice and, surprisingly, off dry land. The value of these measurements has yet to be fully explored, but they may be used as inputs for climate modelling.

A future revision of the experiment, the ‘GNSS Reflectometry Instrument’ is now being designed at Surrey with a view to a 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. "The sooner Galileo is up and transmitting the better," said Dr Unwin.

Source: University of Surrey

Explore further: Researchers use NASA and other data to look into the heart of a solar storm

add to favorites email to friend print save as pdf

Related Stories

Airlines on alert as eruption begins in Iceland

6 hours ago

Iceland's Bardarbunga volcano burst forth with a small eruption Saturday under the ice of Europe's largest glacier, scientists said, prompting the country to close airspace over the area.

Two Galileo satellites lose their way

9 hours ago

Two European Galileo satellites launched as part of a navigation system designed to rival GPS have failed to locate their intended orbit, launch firm Arianespace said Saturday.

Volcanic eruption begins under Iceland glacier

9 hours ago

Iceland's Bardarbunga volcano began erupting Saturday under the country's largest glacier after a week of seismic activity rattled the area with thousands of earthquakes, the country's Meteorological Office ...

Recommended for you

Informing NASA's Asteroid Initiative: A citizen forum

15 hours ago

In its history, the Earth has been repeatedly struck by asteroids, large chunks of rock from space that can cause considerable damage in a collision. Can we—or should we—try to protect Earth from potentially ...

Image: Rosetta's comet looms

21 hours ago

Wow! Rosetta is getting ever-closer to its target comet by the day. This navigation camera shot from Aug. 23 shows that the spacecraft is so close to Comet 67P/Churyumov-Gerasimenko that it's difficult to ...

A salty, martian meteorite offers clues to habitability

22 hours ago

Life as we know it requires energy of some sort to survive and thrive. For plants, that source of energy is the Sun. But there are some microbes that can survive using energy from chemical reactions. Some ...

User comments : 0