Rough-Surface Polarimetry in Companion SAR Missions
Lorenzo Ianninia, Davide Comiteb, Nazzareno Pierdiccab, Paco López‐Dekkera
- aDepartment of Geoscience and Remote Sensing, Delft University of Technology, Delft, The Netherlands
- bDepartment of Information Engineering, Electronics and Telecommunications, Sapienza Università di Roma, Rome, Italy
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Abstract
Bistatic scattering from rough surfaces is typically approached through the analysis of the scattered field in the conventional H and V polarization basis, which coincides with the zenith and azimuth unit vectors in a spherical reference frame. This study delves into the impacts of different choices of the transmit and receive linear basis on the performance and design of a synthetic aperture radar (SAR) mission receive-only companion. This article formalizes the rotation of the scattered wave orientation at the antenna axes of the companion with respect to the transmitted one and introduces a novel set of linear polarizations, named principal polarizations, in transmit and receive, deemed more suited to represent the scattering mechanisms of rough surfaces. Such a set is defined by the polarization bases that maximize the radar cross section. It is shown that the theoretical estimates from the proposed geometrical framework provide a good agreement with analytical and numerical simulations, performed considering state-of-the-art numerical solutions. In addition, this article promotes the hypothesis that a bistatic radar configuration, defined through the conventional H and V linear basis, presents a strong similarity, from a target information retrieval standpoint, to a monostatic compact <inline-formula> <tex-math notation="LaTeX">$\varphi $ </tex-math></inline-formula>-pol mode, i.e., with the transmission of a linear polarization rotated by an angle <inline-formula> <tex-math notation="LaTeX">$\varphi $ </tex-math></inline-formula>. The rotation <inline-formula> <tex-math notation="LaTeX">$\varphi $ </tex-math></inline-formula> varies over the swath and as a function of satellite separation. For baselines of 250–300 km, such as those envisioned by the European Space Agency (ESA) Harmony Earth Explorer candidate, and for steep incidence angles, an equivalent <inline-formula> <tex-math notation="LaTeX">$\pi /8$ </tex-math></inline-formula>-pol can be achieved for rough surfaces.