Effects of the ground surface on polarimetric features of broadband radar scattering from subsurface metallic objects

Throughout the world, the problem of buried unexploded ordnance (UXO) poses an enormous, persistent, and expensive problem. While UXO generally consis ts of sizable bodies of ferrous metal and can therefore be detected, with c urrent technology it is extremely difficult to distinguish them reliably fr om typically widespread pieces of clutter. Thus the problem is one of subsu rface discrimination. Our previous modeling work on scattering of ground pe netrating radar (GPR) from metallic objects surrounded by an infinite soil- like medium has suggested the utility of a number of key discriminants in b roadband fully polarimetric sensing. In particular, resonance structure, in duced field rotatation and ellipticity, and bistatic observation of scatter ed signals were shown to offer key information about target shape and size. Here we investigate the effects on signature features of the proximity of a ground surface to the targets for the common case of shallow burial (<1 m ). Overall, our analyses suggest that the key discriminants seen in scatter ing in an infinite medium survive the complex interactions with the ground surface. In some instances, these revealing signatures appear to be strengt hened by the presence of a nearby surface. Multiposition backscatter also a llows fundamental inferences about target elongation and symmetry when thos e cannot be obtained from single position viewing.