On the incidence angle dependence of synthetic aperture radar co-polarisation sea surface signature

In this study, the behaviour of co-polarisation sea surface signature is analysed with respect to L-band airborne synthetic aperture radar incidence angle under low-to-moderate sea state. The sensitivity of polarised and unpolarised backscattering component to changes in incidence angles is investigated. When dealing with the polarised part, the scattering behaviour of horizontal, vertical and circular polarisations are considered while the normalised pedestal height is evaluated as estimator of the amount of unpolarised power scattered off sea surface. Experimental results suggest that: 1) deviation from Bragg scattering occurs at lower and higher incidence angles; 2) backscattering at vertical polarisation keeps constant while backscattering at horizontal (circular) polarisation decreases (increases) with incidence angle; 3) the pedestal height of the co-polarisation sea surface signature remarkably increases when the incidence angle increases, with the largest variation observed at lower angles of incidence.