A full-polarization GNSS-R Delay-Doppler-Map (DDM) simulator for bare soil freeze/thaw process detection

The soil freeze/thaw processes have a significant impact on the surface energy and moisture balance, which play a key role in ecosystem diversity and productivity. The air-/space-borne Global Navigation Satellite System (GNSS)-Reflectometry (GNSS-R) is a bistatic radar with receiving power as the Delay Doppler Map (DDM), which may monitor soil freeze/thaw processes. However, the scattering mechanism of monitoring soil freeze/thaw processes by GNSS-R DDM is not clear. In this paper, it is the first time to simulate full-polarization GNSS-R Delay-Doppler-Map (DDM) for bare soil freeze/thaw process, not only the linear polarization but also the circular polarizations. As the bare soil freeze/thaw process occurs, the corresponding DDM variations are able to present by this simulator. Other geophysical parameters, such as soil moisture and surface roughness, are also two important parameters affecting the final GNSS-R receiver power and their effects on DDM are also presented by the simulator. This simulator can be a potentially efficient tool for data analysis and interoperation of GNSS-R received power as well as the in situ experimental design.