Geosat data give wind speed and wave height



The Navy has released Geosat radar cross section and significant wave height data from the 18-month Geodetic Mission for use by the general public. These data, when combined with data from the Exact Repeat Mission, comprise the most dense global wind speed and wave height data set ever archived. The accuracy of the data when compared with NDBC buoys has been shown [Dobson et al., 1987] to be +/− 1.7 m/s for wind speed and +/− 0.5 m for wave height.

The Geosat altimeter orbits the Earth at an altitude of 800 km and, during the Geodetic Mission, laid down a ground track which precessed about 100 km every 3 days forming a tight mesh over 72 days which was repeated for three consecutive 72-day periods. The primary mission of the instrument was to measure the marine geoid, but it also measured radar cross section (RCS) and significant wave height (SWH). RCS is the return signal backscattered from the ocean surface and is proportional to wind speed. SWH is obtained from the slope of radar-returned pulse. Data are available at a one per second rate with complete global coverage.