ANALYSIS OF EFFECTS OF TIME VARIANT TROPOSPHERE ON GEOSYNCHRONOUS SAR IMAGING

The tropospheric time variance within the ultra-long integration time of Geosynchronous Synthetic Aperture Radar (GEO SAR) needs to be considered for imaging. Meanwhile, because of the curved trajectory and the very complex geometry relationship between the target position and the satellite, the traditional analysis method of troposphere on low earth orbit (LEO) SAR imaging will no longer be suitable in GEO SAR. In this paper, GEO SAR signal phase errors induced by the time variation of troposphere is obtained. Then, a GEO SAR signal's two-dimension frequency spectrum under the effects of the troposphere is derived for the first time. The GEO SAR 2-D image shift and image defocusing phase errors are derived analytically. At last, the atmospheric refractivity profile (ARP) data provided by the Chinese meteorological satellite FengYun-3 (FY-3) are used and the focusing results are presented to verify the aforementioned analysis.