Scientists look to GPS as a tool to measure ocean currents from space

The technology developed by the NOC scientists uses GPS signals as a parameter to measure ocean surface heights. The team uses GNSS-Reflectometry, a technology that measures the reflection of satellite-based navigation signals, including GPS, off an object. GNSS-R data previously has been used to measure wind speed, but in this project, the scientists are using these GPS reflections to measure sea surface height. “We are really encouraged by our results since it demonstrates for the first time that we are able to map the overall sea surface height from space using the GPS-reflections technique,” said NOC scientist Dr. Paolo Cipollini.

Currently, ocean surface height is measured from space using radar altimeters. Though accurate, there are not enough satellite altimeters in orbit to be able to measure at a scale below 100km. GNSS-Reflectometry receivers can measure changes on this small scale, providing a significant benefit over existing satellite altimeters. GNSS-Reflectometry receivers also can be connected a constellation, potentially providing scientists with a thirty-fold improvement in the amount of data gathered.

Several of these GNSS satellite transmitters are already in orbit and others can be deployed quickly and affordably as the technology matures. Later this year, NASA plans to launch a constellation of GNSS-Reflectometry receivers as part of the NASA CYGNSS mission. The team hopes to improve the technology, moving it beyond surface height and eventually using it to map currents by measuring the slopes currents cause on the ocean’s surface. The project is a joint collaboration between the NOC, the University of Michigan and the Jet Propulsion Laboratory. A summary of the results was published recently in the journal Geophysical Research Letters.

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