Validity study of rough surface scattering models

The limits of accuracy for rough surface models is largely uncertain. Previous numerical studies using the method of moments (MoM) have given broad assessments of the reliability of physical and geometrical optics, the small perturbation method, and other models. Improvements in digital computers allow a dense sampling of points from a chosen parameter space to give more accurate results than previously possible. RMS errors are shown for physical optics (PO), geometrical optics (GO), small perturbation method (SPM), iterated physical optics (ITPO), Monte Carlo physical optics (MCPO), and the small slope approximation (SSA) for power law surfaces. The models investigated show a wide range of regions of validity. Among all models, the ITPO method shows the best correlation to the truth values of the MoM calculations. However, stochastic models require significantly less computation time. Among the stochastic models, the third-order SSA models show the best overall agreement with the truth values. Unlike past studies, this study shows that the regions of validity for the PO and SPM are not disjoint. Instead, for the parameter space used, PO is always at least as accurate as SPM.