Multistatic radar observation of anisotropic bare soil

This study proposes a scattering-based approach to investigate soil moisture estimation over anisotropic bare soil using multistatic radar observations. Two data generation strategies are considered: polarimetric diversity, which uses both co- and cross-polarized measurements at L-band, and frequency diversity, which exploits L- and C-band co-polarized measurements. A novel approach consisting of two steps is proposed: 1) numerical prediction of the normalized radar cross-section using first- and second-order small-slope approximation solutions of the scattering, adopting an anisotropic description of the soil surface; 2) application of a normalized CRLB to benchmark multistatic radar configurations through the worst case performance analysis across all tillage orientations. The investigation demonstrates that both data generation strategies offer remarkable performance (normalized CRLB index < 0.2) in optimized multi-static configurations, with receivers positioned at large baselines (i.e., 100-400 km) relative to the main monostatic SAR. This geometric diversity enables robust parameter de-coupling that significantly outperforms conventional monostatic approaches. A bootstrap analysis reveals that over 80 % of achievable multistatic geometries demonstrate excellent estimation performance, with improvement factors exceeding 60 times relative to monostatic configurations. These findings provide quantitative information for next-generation bistatic SAR missions.