The Simulating Analysis and Validation of Soil Moisture Retrieval Using S-Band Radar

There are several optical and radar small satellites in HJ constellation which is developed in China,and they will be launched gradually since the end of 2007.In the constellation,HJ-1C is planned to be launched in 2008,on which an S-Band SAR is loaded.The S-Band SAR will work at 3.2GHz,VV-polarization and incidence angle range is 25°~47°.Backscattering coefficient retrieved by radar is very sensitive to soil moisture,because soil dielectric constant has a strong influence on backscatter coefficient,and soil moisture content is a determined factor to soil moisture.Because the number of influencing factors is larger than the number of observations,inversion become an "ill" problem,the result is that conventional physical model can not be used to obtain the model inputs directly.So,physical model must be simplified for acquiring an input from the model output.Following this method,based on the configuration parameters of HJ-1C and SAR sensor,soil moisture change retrieval method is studied using AIEM(Advanced Integral Equation Model) simulation data in this paper.Firstly,the applicability of traditional method(based on Simple Scattering Model) for soil moisture change retrieval using single-polarization SAR data is analyzed at S-Band(totally four bands data is checked,namely,Ku-band,C-band,S-band and L-band),the result shows the method is applicable at S-band,ever has better outcome than using C-band data.Then,a comparison is performed when using different soil moisture parameter as input in the method,the result shows the best result achieved when vertical-polarization amplitude is used.Finally,the validation is done using simulated data,the result shows that almost 80% of the data has an error less than 5%.The result of this paper will benefit to the quick-application of HJ data after its launched.