Scattering from Surfaces with Different Roughness Scales: Analysis and Interpretation

This paper discusses several approaches to scattering from slightly rough» very rough, composite, and rough spherical surfaces. Average incoherent scattering cross sections for slightly rough surfaces are obtained using a perturbation technique for a perfect conductor, and for a surface material which is homogeneous (with variable permeability, \Lr, as well as permittivity, «r)« The results, correct to the first order, include polarization dependence, and particular solutions with curves are presented for the vertical, horizontal, and circular states. They are compared with measured data. The scattering process for this class of surfaces is interpreted physically. Three optics techniques yielding results for very rough surface scattering cross sections are presented, and it is shown that they all give the same solution for Gaussian surfaces. Both homogeneous and perfectly conducting surface materials are treated, and polarization dependence is preserved. The restrictions under which the solutions are valid are enumerated. The physical interpretations of the scattering mechanism for this class of surfaces are discussed and shed valuable insight on the process. Curves are shown for backscattering, employing two probability models. Surfaces consisting of both very rough and slightly rough structures together, termed conoposite surfaces, are analyzed, and an heuristic physical derivation of their scattering cross section is presented. Curves for backscattering cross section are shown, and comparison with measured results confirms the validity of this approach. Average backscattering cross sections for rough spherical surfaces are presented. Both the coherent and incoherent cross sections are given for slightly and very rough spheres. These results have application to planetary surface radar scatter and to passive satellite communications. The large volume of published material on the subject is reviewed. The first two parts dealing with slightly rough and very rough surfaces, rather than retrace detailed mathematical derivations available elsewhere, attempt to accomplish five goals: (i) to compare the various analyses already available, (ii) to elucidate xplicitly the approximations involved in each approach, (iii) to explain and interpret the physical process behind the mathematics producing the scattering, (iv) to present meaningful