Accurate analysis method of background ionosphere effects on Geosynchronous SAR focusing

The background ionosphere time variance within the extremely long integration time of Geosynchronous Synthetic Aperture Radar (GEO SAR) needs to be considered for GEO SAR focusing. Meanwhile, because of the curved trajectory and the very complex geometry relationship between satellite motion and earth rotation, the traditional analysis method of background ionosphere on LEO SAR imaging will no longer suitable in GEO SAR. In this paper, a GEO SAR signal model is proposed to describe the effects of total electron content (TEC) variance within the long integration time. Then, a GEO SAR signal two-dimensional spectrum under the effects of background ionosphere is derived for the first time. The GEO SAR defocusing phase errors are derived analytically. At last, the US Total Electron Content (US-TEC) data are used and the focusing results are presented, verifying the analysis.