SEASAT sees the winds with SAR

The original justification for the inclusion of an L-band synthetic aperture radar on Seasat was for the measurement of ocean surface wave spectra. Indeed, the initial research on ocean wave measurement from Seasat evolved to the point where SAR imagery from the subsequent ERS-1, ERS-2, and ENVISAT satellite SARs are routinely combined with wave model estimates to produce ocean surface wave spectra. The scatterometer on Seasat was the primary means of measuring ocean surface wind speed direction. Nonetheless, patterns of SAR-measured normalized radar cross section clearly showed spatial structures associated with variations in wind speed and direction. In the last five years, it has become more apparent that SAR imagery can be used to make high spatial resolution estimates of wind speed. In this paper, we trace the evolution of SAR wind speed measurement capabilities from Seasat to the present.