Tutorial review of synthetic-aperture radar /SAR/ with applications to imaging of the ocean surface

This review paper shows how an airborne (or spaceborne) synthetic-aperture radar (SAR) - comprising a pulsed microwave transmitter, antenna, and a phase-coherent receiver - can produce high-resolution two-dimensional images of radar-mapped areas. A major feature is that the antenna beam is typically at right angles to the velocity vector. The discussion covers the synthetic aperture, relevant range and cross-range (azimuth) ambiguities, signal processing, phase errors, mapping rate, SNR, radar image of ocean waves, and radar-frequency dependence for a fixed resolution. High resolution in range is obtained using wideband transmitted pulses, and high resolution in azimuth is achieved by signal processing the coherent phase history of target-reflected signals collected for the integration time period. SAR images of ocean waves are reported which correlate well with optical photographs and visual observations. A SAR is expected to measure the directional spectra of oceanic waves.