Amplitude and Dilation Compensation of the SAR Altimeter Backscattered Power

Abstract

A new method of forming the synthetic aperture radar altimeter multilook backscattered power waveform is proposed for application over water. The method compensates the waveform for both variations in amplitude and dilation in range, which are caused by the geometry of the observation and the signal processing chain of the instrument. Using Cryosat data collected over the Pacific Ocean and over the Black Sea, the method is used to retrack the geophysical parameters of sea surface height and significant wave height, and the noise level of these retracked parameters is compared with the noise levels of conventionally retracked parameters. It is found that applying amplitude compensation and dilation compensation leads to a reduction in the noise level by up to a factor of 4.0 for sea surface height and 2.5 for significant wave height. The reduction in noise is largest for small significant wave heights. In addition, the waveform is accurately modeled by a single argument function, needing only a scaling and offset to fit the multilook waveform, greatly improving the theoretical description of the waveform dependence on the sea state and instrument parameters.