ESTIMATION OF OCEAN WAVE SPECTRA USING 2-ANTENNA SAR SYSTEMS

Data from Synthetic Aperture Radar (SAR) systems can be used to estimate ocean wave directional spectra, but the method is limited by nonlinearities associated with the velocity bunching mechanism and by the azimuth falloff effect, which reduces the range of azimuth wavelengths that can be observed. The theoretical analysis presented in this communication suggests that the use of two or more receive antennas, spaced in the along-track direction, may reduce these limitations. Specifially, the band of useable azimuth wavenumbers is shifted by an amount proportional to the antenna spacing, so that a broader range of wavenumbers can be covered by combining the spectrum obtained from the two-antenna signals with the conventional image spectrum. The angular dependence of the velocity modulation mechanism is also modified to include purely range-traveling waves in the two-antenna case.