Bistatic reflection of electromagnetic waves from random rough surfaces: Application to the sea surface and snowy-covered^*

Laboratoire IRCCyN (UMR CNRS 6597), Division SETRA, EPUN/IRESTE, Université de Nantes, rue Christian Pauc, La Chantrerie, BP 50609, 44306 Nantes Cedex 3, France

Corresponding author: akhencha@ireste.fr

Received: 11 May 2000
Accepted: 22 January 2001
Published online: 15 April 2001

Abstract

The scattering of waves by random rough surfaces has important applications in remote sensing of oceans and land. The problem of developing a model for rough surfaces is very difficult since, at best, the scattering coefficient σ⁰ is dependent upon (at least) radar frequency, geometrical and physical parameters, incident and observation angles, and polarization. The problem of electromagnetic scattering from a random rough surface is analyzed using the Kirchhoff approximation (stationary phase, scalar approximation), the small perturbation model and the two-scale model. The first major new consideration in this paper is the polarimetric signature calculation as a function of the transmitter location and receiver location for a bistatic radio- link. We calculate the like- and cross-polarized received power directly using the scattering coefficients, without calculating the Mueller matrix. Next, the study of the regions of validity of the Kirchhoff and small-perturbation rough surface scattering models (in the bistatic case) is presented. Comparisons between the numerical calculations and the models are made for various of the surface height rms and correlation length both normalized to the incident wave number (denoted by σ and L, respectively). By using these two parameters to form a two-dimensional space, the approximate regions of validity are then established. The second major new consideration is the development of a theoretical two-scale model describing bistatic reflectivity as well as the numerical results computed for the bistatic radar cross-section from rough surfaces especially from the sea and snow-covered surfaces. The results are used to show the Brewster angle effect on near-grazing angle scattering.