Multilook images of ocean waves by synthetic aperture radars

A property of multilook processing of synthetic aperture radar (SAR) data is that a time lapse exists between subapertures, so that they contain information about a scattering surface at different times. Reported here is a theoretical study on the images of dynamic ocean waves processed by this technique. It is shown that due to the time lapse the subimages of a moving ocean wave differ in position depending on the look number and the wave phase velocity. Such images cannot be enhanced by the incoherent addition so much as those of stationary surfaces. The difference in image position can be corrected by defocusing the azimuth reference signal by the same amount as for the correction of defocusing induced by the wave motion. Discussions are presented on the correction of image positions and on the effect of defocusing. The property of the time lapse could be applied to estimating not only the phase velocity of ocean waves but also temporal changes in general scattering surfaces.