Recent experiments in Ocean remote sensing with bistatic radar using Navigation Satellite Signals

This paper will present results from a recent airborne campaign to collect and anayze reflected Global Navigation Satellite System (GNSS-R) signals. The objective of this experiment was to test the GNSS Instrument for Multistatic and Occulatation Sensing (GISMOS) and provide additional data for comparison of GNSS-R sea roughness retrievals with in situ measurements. Raw sampled data from the direct GPS signal (using a conventional navigation antenna) and the reflected signal (both right and left-hand circularly polarized nadir antennas) were recorded at both the L1 (1575.42 MHz) and L2 (1227.6 MHz) frequencies. These signals were post-processed using a software-defined radio. Low cost consumer gaming processors were reprogrammed to efficiently generate Delay-Doppler maps (DDMs). A scattering model was then fit to these DDMs in order to estimate the upwind and cross-wind slope variances and the principal axis direction. Initial results suggest a sensitivity to wind direction.