THE SMALL SLOPE APPROXIMATION REFLECTION COEFFICIENT FOR SCATTERING FROM A PIERSON-MOSKOWITZ SEA-SURFACE

First- and second-order reflection coefficients are presented for the small slope approximation. The first-order reflection coefficient is i dentical to the Kirchhoff, or physical optics, result, and the second- order reflection coefficient reduces to those of perturbation theory a nd the Kirchhoff approximation in the appropriate limits. Numerical re sults are obtained for acoustic or TE-polarized electromagnetic scatte ring from one-dimensional, ''Pierson-Moskowitz'' sea surfaces at low g rating angles. Comparison with exact integral equation results shows t hat the second-order small slope approximation is extremely accurate a nd better than both the perturbation and Kirchhoff methods.