The First Application of Stare Processing to Retrieve Mean Square Slope Using the SGR-ReSI GNSS-R Experiment on TDS-1

The bistatic radar technique of Global Navigation Satellite System-Reflectometry (GNSS-R) is capable of measuring wind and wave parameters using a passive instrument on-board a small satellite platform. In this paper, data from the Space GNSS Receiver-Remote Sensing Instrument (SGR-ReSI) experiment on-board TechDemoSat (TDS-1) are analyzed to perform geophysical parameter retrievals. Stare processing utilizes the high-spatial overlap between successive delay-Doppler maps (DDMs) and the typical Level 1B TDS-1 data product, to achieve multiple looks at the same surface point. The Stare processing approach is detailed as a method to recover the mean square slope (mss) of the scattering surface. This is achieved by fitting a slope probability density function (pdf) to measurements of a surface point over a time series of DDMs. The results of colocations with the global WaveWatch3 (WW3) model are shown. Results show Pearson correlation coefficients of 0.684 between TDS-1 mss and WW3 mss values and 0.742 when compared in dB units. The latter result indicates better correlation for low values of mss with a tail-off in sensitivity for rougher seas. Further work and improvements to the implementation of Stare processing are discussed.