The Transition From Weak to Strong Diffuse Radar Bistatic Scattering From Rough Ocean Surface

Many of the currently used models of scattering from a rough ocean surface are designed for the regime of strong diffuse scattering that takes place at large Rayleigh parameter <inline-formula> <tex-math notation="LaTeX">$\it R_{a}$ </tex-math></inline-formula>. Using them for the case of weak, or even moderate diffuse scattering that is characterized by <inline-formula> <tex-math notation="LaTeX">$\it R_{a} \lesssim 1$ </tex-math></inline-formula> would lead to an incorrect result. At the same time, for practical applications, it is important to describe the transition from partially coherent scattering to completely noncoherent, strong diffuse scattering in terms of the bistatic radar cross section <inline-formula> <tex-math notation="LaTeX">$\sigma _{0}$ </tex-math></inline-formula>. This situation may occur for scattering of global navigation satellite system (GNSS) signals or other signals of opportunity from a rough ocean surface under weak winds, or from ice. In this paper, we obtain an expression for <inline-formula> <tex-math notation="LaTeX">$\sigma _{0}$ </tex-math></inline-formula> for the case of weak-to-moderate diffuse scattering using a formulation based on the small slope approximation of the first order. For a reasonable range of <inline-formula> <tex-math notation="LaTeX">$\it R_{a}$ </tex-math></inline-formula>, calculations can be quickly performed using standard desktop computers. We demonstrate results of such calculations for bistatic radar scattering for <inline-formula> <tex-math notation="LaTeX">$L$ </tex-math></inline-formula>-band at low-to-moderate <inline-formula> <tex-math notation="LaTeX">$\it R_{a}$ </tex-math></inline-formula> and its transition to <inline-formula> <tex-math notation="LaTeX">$\sigma _{0}$ </tex-math></inline-formula> at large values of <inline-formula> <tex-math notation="LaTeX">$\it R_{a}$ </tex-math></inline-formula>.