Polarimetric Characterization of Unresolved Space Objects

Abstract

This paper introduces a new remote sensing technique based on polarimetric detection principles, aimed at enhancing the identification, characterization, and discrimination of unresolved space objects like amorphous silicon, polysilicon, Mylar, and Kapton. Some of the polarimetric measurements performed at different angles of incidence (object angular rotations) such as diattenuation, depolarization and retardance matrices of these space objects are presented using backscattered polarimetric signals obtained with a polarimetric system (test bed). The depolarization index profile with changing angle of incidence for these samples is approximated by an inverted Gaussian function. Depolarization is minimum for specular reflection and increases asymptotically in a Gaussian fashion as the angles of incidence and scatter increase. Parameters of the Gaussian profiles fitted to the depolarization data are used to compare samples. The results show that the shape of depolarization profile for one object (Mylar) is almost flat, whereas the other three objects (amorphous silicon, polysilicon, and Kapton) show depolarizing trend with increasing angle of incidence. Additionally, the fractal properties of these objects using the backscattered polarimetric signals obtained with the polarimetric system is compared. The fractal dimension of the backscattered polarimetric signals is obtained for two different experimental geometries, copolarized and cross-polarized geometry, for two different object angular rotations using multiresolution box-counting technique. The results confirms that the fractal dimension of the cross-polarized signals are greater than that for copolarized signals of all objects and increases as the angular rotation of the object increases.