Modeling and Simulation of GNSS-R Signals with Ocean Currents

In recent years, with the development of Global Navigation Satellite System (GNSS), GNSS reflectometry (GNSS-R) has become a new method in the field of remote sensing. And the simulation of the GNSS-R research is very important. The simulation of GNSS-R signals mostly uses wind-driven wave spectrum, which ignoring other factors in the real ocean environment, such as the currents. Therefore, this paper proposes a method for modeling GNSS-R signal with considering currents. The influence of currents on the wave spectrum is simulated, and the wave spectrum model of the wind and currents is established. The Kirchhoff approximation-geometric optics is used to calculate the composite scattering coefficient. Finally, with the newly built model, the delay waveform (DW) and the Delay-Doppler maps (DDM) obtained from the simulation in the space-borne scene are analyzed. The results show that ocean currents of different speeds and directions have different effects on the simulation of GNSS reflected signals. The simulation results of the proposed model have good consistency with the theoretical waveform, and the correlation coefficient between DWs is raised to 0.9999. It is proved that the proposed model of GNSS-R signals considering the influence of currents is feasible and effective. And it made the simulated reflected signal more realistic.