Closed-form Polarimetric Two-Scale Model for sea scattering evaluation

Among the methods to compute scattering from rough surfaces, the Two-Scale Model (TSM) is a good compromise between range of validity and accuracy on one hand, and efficiency on the other hand. In fact, its range of validity is the union of those of the Geometrical Optics (GO) and of the small perturbation method (SPM). On the other hand, if one is interested only in copolarized normalized radar cross section, a combination of the analytical closed form expressions of GO and SPM can be used, so that high efficiency is obtained. However, if a fully polarimetric analysis of the scattering must be performed, a numerical integration is needed, which strongly reduces the efficiency. Recently, some of the authors of this work developed an approximated closed-form expression of such an integral, and then of the fully polarimetric version of TSM, that was named Polarimetric TSM (PTSM). However, this expression was only obtained for statistically isotropic rough surfaces and in the backscattering configuration. In this work we present the rationale for the extension to anisotropic roughness and to the bistatic configuration, aimed at evaluating scattering from the sea surface. Results are shown for anisotropic surfaces in the backscattering case and for isotropic surfaces in the bistatic scattering case. They can be usefully employed in sea state monitoring via microwave remote sensing systems.