Surface bistatic scattering coefficient by means the facet model radar altimetry application

The necessity of studying the bistatic scattering coefficient was affirmed recently in the ambit of an ESA project: PARIS ("Passive Reflectometry And Interferometric System"). This project aims at obtaining important information about ocean state, by using as transmitters some sources of opportunity, instead in reception a constellation of small receiving satellites is assumed: this concept can be regarded as a multistatic altimetry. In order to built a software simulator it\´s necessary to develop an accurate model for representing the Earth\´s surface. The electromagnetic model that we have used to evaluate the scattered field consists of representing a portion of rough surface with a set of facets, each of them can be considered as a transmitting antenna and its illumination function is provided by the transmitter. The total scattered field can be evaluated as the coherent sum of the fields re-radiated by each facet. In this paper, in order to evaluate the goodness of the facet model, we have compared the bistatic scattering coefficient obtained using this approach with the analytical Kirchhoff models such as geometric optics and physics one.