Ocean-wave imaging by synthetic-aperture radar: results from the SIR-B experiment in the N.E. Atlantic

Waveheight spectra were extracted from synthetic-aperture radar (SAR) images close to a number of wave-measuring buoys, and the results of radar and in situ measurements were compared as a test of wave-imaging theory. SAR and buoy spectra of waves traveling close to the radar range direction were in good quantitative agreement, with any discrepancies probably attributable to the processing technique. However, SAR estimates of the amplitude of azimuth-traveling waves were very much lower than buoy-derived values. This cannot be accounted for by appealing to nonlinear imaging by the velocity-bunching mechanism, or by velocity smearing, calculating the scene coherence time from the available buoy data. Rather, the scene coherent time must be reduced by a factor of about two, to within the range 0.022-0.027 s. This result highlights a lack of knowledge of scatterer motions and lifetimes on the sea surface