Numerical Simulations of Roughness Scale Effects on Bistatic Ocean Scattering

The effects of roughness scale on bistatic radar scattering from an ocean surface at L-band are studied using the second order small slope approximation (SSA-II) and the method of moments (MoM). Ocean roughness is represented and varied using different ranges of the KHCC03 spectrum. The criteria of full spectrum truncation are also given. Numerical results are illustrated in fully bistatic configuration at 1.26 GHz. Simulations indicate that short waves with wavenumber larger than 316 rad/m (around 12 wavenumbers of L-band incidence wave) have little effect on ocean scattering. The large-scale waves put more impacts on scattering in the forward directions, especially for large incidence angles. The effects of large-scale roughness on ocean scattering are in general smaller at VV-pol than HH-pol. The bistatic scattering at cross polarizations is less sensitive to the roughness scale as compared to the co-polarizations. For numerical simulations of ocean scattering with incidence angle less than 60°, using small surface profiles with size about 1/6 of those accounting for full spectrum yields results of bistatic scattering coefficients with errors less than 2dB.