Ku- and C-band SAR for discriminating agricultural crop and soil conditions

[Departement_IRSTEA]GT [TR1_IRSTEA]51 - METHODO / GEOSYSTEMESInternational audienceA method is proposed to estimate both green leaf area index (GLAI) and soil moisture (hv), based on radar measurements at the Ku-band (14.85 GHz) and C-band (5.35 GHz) frequencies. The Ku-band backscatter at large incidence angles was found to be independant of soil moisture conditions and could be used alone to estimate GLAI. Then, the Ku-band estimate of GLAI could be used with a measurement of C-band backscatter in a canopy radiative transfer model to isolate the value of hv. This concept was demonstrated with a set of Ku- and C-band synthetic aperture radar (SAR) backscatter data acquired over agricultural fields in Arizona. The demonstration showed promise for operational application of the method, though several limitations were identified. Since both Ku- and C-band o° are sensitive to soil roughness or row direction. This limitation may be less serious for farm management applications since crop type and cultivation practices are generally well known and can be taken into consideration. Another limitation of the use of Ku- and C-band o° is the appparent saturation of Ku-band signal with increasing GLAI. Operational implementation of this approach will require dual-frequency sensors aboard an aircraft or orbiting satellite