GNSS-R DELAY-DOPPLER MAPS OF OCEAN SURFACE AT WEAK WINDS

Currently used models for calculation of delay-Doppler maps (DDM) of ocean reflected signals produced by Global Navigation Satellites System (GNSS) frequently rely on the Kirchhoff Approximation in a Geometric Optics limit. These models are usually assume strong diffuse scattering typical for ocean wind-driven waves for moderate and strong winds. These models will produce an incorrect result if to extend them to the case of weak, or even moderate diffuse scattering. To correctly describe DDM under a transition from partially-coherent scattering to completely non-coherent, strong diffuse scattering a more complex formulation of the bistatic radar cross section (BRCS) is needed. Here, the GNSS-R DDMs at weak ocean winds resulted from BRCS obtained with the small slope approximation of the first order (SSA1) are demonstrated, and their behavior is discussed.