Our goal is to develop a fully bistatic scattering model from Signals of Opportunity (linearly and circularly polarized incident waves) for vegetated terrains. Advancement of coherent radar scattering model from monostatic to fully bistatic creates the opportunity to exploit measurements of scattered fields from vegetated landscapes in arbitrary directions, as might be available from signals-of-opportunity such as GNSS/GPS or MilComSat reflected signals.
The three major scattering contributions considered in this model are: 1- direct ground bistatic scattering, 2- vegetation volume (branches) bistatic scattering, and 3- scattering due to interaction between ground and overlaying vegetation layer, which includes trunk-ground and branch-ground bistatic scattering. Fig. 1 shows the bistatic scattering model with all the scattering mechanisms, in which G, B, BG, and TG are denoted as Ground, Branch, Branch-Ground, and Trunk-Ground contributions, respectively. Sensitivity analysis with respect to soil moisture content and VWC shows that sensitivity to VWC is highly reduced in the bistatic (specular) direction, whereas sensitivity to soil moisture is preserved. This finding has potential for more accurate soil moisture retrievals regardless of the amount of VWC.
Figure 1: Single species bistatic scattering model with major scattering mechanisms (G, B, and (BG&TG))