Galileo signal reflections used for monitoring waves and weather at sea

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1 Press Release Monday 26 th November 2007 Galileo signal reflections used for monitoring waves and weather at sea 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, demonstrating 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 Dr Martin Unwin, head of the Global Navigation Satellite Systems (GNSS) / GPS team at SSTL explained: This is an important achievement in remote sensing and 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. 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. In early November, 20 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 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).

2 Dr Unwin continued: 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 GPS Reflectometry is of great interest to engineers and scientists as a cost effective means of remote sensing. Firstly, 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 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. The UK-DMC Reflectometry Experiment has also previously been used to detect GPS signals reflected off ice and, surprisingly, 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 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.

3 Fig 1 (a) Fig 1(b)

4 Fig 2 Figure 1: Galileo signals detected by the UK-DMC satellite GPS Reflectometry Experiment on 4th November 2007 a) GIOVE-A signal received directly (before reflection). b) GIOVE-A signal received after reflection off the Arafura Sea near the north coast of Australia. The signal is spread out in delay and in Doppler shift by the roughness of the ocean caused by 14 mph (22 km/h) winds. Figure 2: Illustration of satellite collecting GPS reflectometry measurements over the ocean and ice as a new means of remote sensing Surrey Satellite Technology Ltd (SSTL) develops innovative technologies to change the economics of space, delivering cost effective satellite missions within rapid timescales. The Company is a world leader in the design, manufacture and operation of high performance small satellites with experience gained over more than 25 years and 27 missions launched. SSTL employs 250 staff working on LEO, GEO and interplanetary missions, turnkey satellite platforms and space-proven satellite subsystems and optical systems. The Company also provides know-how transfer and training programmes and consultancy services, and performs studies for ESA, NASA and commercial customers related to platform design, mission analysis and planning.

5 Based in Guildford, UK, SSTL is owned by the University of Surrey (85%), SSTL staff (5%), and SpaceX of the USA (10%). Notes to editor: Supporting figures can be downloaded from the online press room. These can be previewed in the printable pdf version of this press release, that can be downloaded from the SSTL online press room : SSTL Contact: Audrey Nice, Surrey Satellite Technology Limited Tel: +44 (0) a.nice@sstl.co.uk Press Contact: Robin Wolstenholme, Ballard Communications Management (BCM) Tel: +44 (0) r.wolstenholme@ballard.co.uk