Analysis of Effects of Faraday Rotation on Geosynchronous SAR Imaging

Abstract

Faraday rotation (FR) is the rotation of the polarization plane relative to the incident wave under the influence of the ionosphere when the signal passes through the ionosphere, which will affect Geosynchronous Synthetic Aperture Radar (GEO SAR) imaging. Due to the long synthetic aperture time characteristic, the time-freezing model assumption for traditional low earth orbit (LEO) SAR imaging will no longer be suitable for GEO SAR imaging analysis. Therefore, the effects of FR on GEO SAR imaging within the extremely long integration time need to be considered. In this paper, the expression of GEO SAR signal under the effects of FR is deduced, and a quantitative analysis for the amplitude-phase error caused by the FR effect in the integration time is conducted. Then, the results of the influence of FR on the amplitude and azimuth phase of the GEO SAR signal are given by using the measured TEC data. Finally, the global distribution map of FR is drawn, and the spatial distribution characteristics of FR are given.