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Abstract
The potential of Advanced Synthetic Aperture Radar (ASAR) for the retrieval of surface soil moisture over bare soils was evaluated for several ASAR acquisition configurations: (1) one date/single channel (one incidence and one polarization); (2) one date/two channels (one incidence and two polarizations); (3) two dates/two channels (two incidences and one polarization); and (4) two dates/four channels (two incidences and two polarizations). The retrieval of soil moisture from backscattering measurements is discussed, using empirical inversion approaches. When compared with the results obtained with a single polarization (HH or HV), the use of two polarizations (HH and HV) does not enable a significant improvement in estimating soil moisture. For the best estimates of soil moisture, ASAR data should be acquired at both low and high incidence angles. ASAR proves to be a good remote sensing tool for measuring surface soil moisture, with accuracy for the retrieved soil moisture that can reach 3.5% (RMSE).
Acknowledgments
This work was supported by BRGM (the French Geological Survey), CNES (Centre National des Etudes Spatiales), and two national programmes: PNTS (the French national remote sensing programme) and PNRH (the French national hydrology programme). The authors wish to thank ESA (the European Space Agency) for kindly providing the ASAR images under Project No. 351 ENVISAT/ASAR. The SPOT images were obtained at special rates through the ISIS programme of the CNES (Centre National d'Etudes Spatiales). The authors also thank Olivier Cerdan, Ary Bruand, Steven Hosford, and Odile Duval for their logistic support during the field campaigns.