Sudhakar Prasad (University of New Mexico)
Keywords: BRDF, CASSPI Model
Abstract:
Passive solar illumination of a space object gives rise, in general, to both specular reflections and diffuse scattering which a ground-based imaging system would observe as spatially localized glints and spatially generalized brightness patterns, respectively. The glints have nontrivial polarimetric signatures but their spectral signatures are typically only slightly modified versions of the solar spectrum, while the diffuse, generalized scattering is essentially unpolarized and spatially uniform over a pure material but carries spectral signatures that are characteristic of the surface material content. The spatial shape and extension of a glint about a point at which the surface normal of the underlying smooth mean surface bisects the solar angle in the solar illumination plane are determined directly by the degree of roughness of the underlying mean smooth surface. By contrast, the diffuse scattering is largely independent of the angle of incidence of sunlight locally at a surface point, with a uniform spectral signature. It is this dichotomy of features between specular and diffuse scattering in the spectral-polarimetric data that can permit one to recover rather robustly the three-dimensional (3D) shape, pose, and spectral signature of a solar-reflecting surface from its spatial-spectral-polarimetric brightness data. Indeed, for a smooth mean surface made of a pure material that can be characterized via a low-dimensional parametric shape model and thus permits a highly sparse mathematical description, the recovery of these surface attributes as well as its roughness can be obtained well even from compressive spectral-polarimetric image data obtained using a focal-plane spatial code. Such data can be obtained from systems like the Coded-Aperture Snapshot Spectral Polarimetric Imager (CASSPI) [1].
Date of Conference: September 10-13, 2013
Track: Poster