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ESRL/PSD Seminar Series

PSD Flash Seminars:Remote sensing using GNSS bistatic radar of opportunity

Valery Zavorotny
NOAA/ESRL PSD Climate Physics Branch


In the past decade there has been considerable interest in using signals of opportunity such as those from Global Navigation Satellite Systems for remote sensing of ocean, land, snow and ice. GNSS-reflected signals, after being received and processed by the airborne or space-borne receiver, are available as delay correlation waveforms or as delay-Doppler maps. These bistatic signals collected from the ocean surface can be used for altimetric or wind-scatterometric purposes complimenting traditional monostatic radar techniques. Similarly, information about soil moisture, snow depth and vegetation can be inferred from GNSS reflected signals.

Even signals routinely recorded by GPS receivers installed to measure crustal deformation for geophysical studies can be used for remote sensing of soil moisture, snow and vegetation in the vicinity of their antennas. This technique exploits interference of direct and reflected signals causing the composite signal, observed using signal-to-noise ratio (SNR) data, to undulate with time while the GPS satellite ascends or descends at relatively low elevation angles. The existing research has shown that GNSS reflectometry has the potential to be a low-cost, wide-coverage technique for studying Earth’s environmental processes.

In the first part of the talk a short overview will be presented to above applications of GNSS reflectometry, whereas in the second part the measurements of ocean surface roughness, wind speed and direction will be covered considering both aircraft and orbital receiving systems. Results of wind speed and wind direction retrievals using delay-Doppler maps processed from the data collected by the GPS software receiver onboard the NOAA Gulfstream-IV jet aircraft will be discussed. Finally, an overview of the planned Cyclone Global Navigation Satellite System (CYGNSS) mission will be given.

Tuesday, June 24
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