Using the BDS-R Signal for Soil Moisture Estimation

BeiDou Navigation Satellite System Reflectometry (BDS-R) is an emerging area of BeiDou (BD) applications that use reflected signals in microwave remote sensing. Soil moisture (SM) estimation by using the BD GEO signals are more favorable than the GPS signals, since the fixed elevation angle, the fixed height of orbit, the fixed satellite coverage. In this study, the principle of SM measuring by BDS-R is described. First the signal-to-noise ratio (SNR) data of BD directed and reflected signals are collected though the right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) antenna, then the SNR data is extracted and the reflection coefficient is computed, at last, the variance of the reflection coefficient is calculated and the empirical model between in situ SM and the variance is established. One month of experimental data are collected at BaoXie, WuHan, and analyzed for further inversion. Experimental results show that the variance of reflection coefficient increases when SM increases and decreases when SM decreases. We can conclude that using BDS-R to retrieve SM is feasible, which will expand the application field of the BD system.