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TechDemoSat-1 (2014)

First use of reflected GPS signals to measure sea-state and generate Delay Doppler Maps on board the satellite, SGR-ReSI instrument, TechDemoSat-1 (2014)

Targeted GPS reflections over Alaska

The SGR-ReSI  instrument on board TechDemoSat-1 has been designed to collect the signals from GPS and other navigation satellites after they have been reflected off the ocean surface and process them on board the satellite into images called Delay Doppler Maps, from which ocean roughness and wind speed measurements at the sea surface can be interpreted.
The technique works in a similar way to existing scatterometric radar from satellites, however it eliminates the need for a transmitter and can process up to four reflections from different GPS satellites simultaneously, presenting an opportunity for collecting more data, more frequently, and over a greater area at a low-cost.
The SGR-ReSI captures the reflected GPS signals and processes the data on board the satellite to be downlinked to a ground station on the next pass and translated into Delay Doppler Maps.
The data from a constellation of satellites carrying the instruments could be used to map all of the Earth’s ocean surface with refreshed data every couple of hours. This would not only be of enormous benefit to the maritime industry, it also offers improvements to weather services and climate research.               
NASA’s 8-satellite “CYGNSS” mission, due for launch in 2016 will use SSTL’s SGR-ReSI to target tropical cyclones and hurricanes.
Delay Doppler maps generated from the SGR-ReSI instrument data

Sea State Payload


TechDemoSat-1 in orbit