Statistical analysis of SAR wind, wave, and sea ice parameter estimation techniques using complex ERS-2 imagettes

The synthetic aperture radar (SAR) aboard the European remote sensing satellite ERS-2 acquires so called imagettes when operating in wave mode. These are high resolution 10 km x 6 km SAR images taken every 200 km along the orbit over the ocean. These data are operationally processed by the European Space Agency (ESA) to image power spectra (SWA.UWA). In this study the data are processed using the SAR research processor (BSAR) of the German Aerospace Center (DLR) to uncalibrated single look complex (SLC) imagettes. SLC imagettes give the opportunity to derive two looks separated in time by approximately half a second. Using these multilook techniques, newly developed algorithms are applied to derive directional wave spectra, ice parameters, and wind speed with global coverage. The results are compared to buoy measurements, results of the wave model WAM, and the Hasselmann algorithm for SAR wave spectra retrieval. Furthermore the SLC imagettes allow one to study surface features on a global scale ,e.g., statistical distribution of natural slicks, that can effect SAR and scatterometer (SCAT) derived parameters, especially wind. Complex imagettes will be available for the advanced SAR aboard the European satellite ENVISAT and therefore these investigations are an ideal preparation for the planned operational use of ENVISAT imagettes at meteorological centers.