Remote sensing of soil moisture using P-band signals of opportunity (SoOp): Initial results

Initial results from the first airborne campaign to evaluate P-band reflectometry for soil moisture remote sensing are presented. P-band radiation has a penetration depth of 10-20 cm, compared to around 5 cm for L-band. This offers the possibility of measuring Root-Zone Soil Moisture (RZSM), a capability that does not presently exist in spaceborne remote sensing. Signals of Opportunity Airborne Demonstrator (SoOp-AD) is a brassboard P-band reflectometry demonstration instrument, developed under the NASA Instrument Incubator Program (IIP-13). Soil reflectivity is estimated from the cross-correlation of direct and reflected signals from a geostationary communication satellite. SoOp-AD will demonstrate key technological advancements on the roadmap to a spaceborne instrument, including an FPGA-based correlator array and “smart antenna” null-steering in the post-processing stage. The first airborne tests of SoOp-AD were conducted around the ARS Micronet in Little Washita, OK. Initial results confirm the assumption of coherent scattering, show the water-land transition over Lake Ellsworth, and present reasonable values for reflectivity over the instrumented area.