Study about ionospheric effects on Medium-Earth-Orbit SAR Imaging

The Medium-Earth-Orbit Synthetic Aperture Radar (MEOSAR) is one of the most potential next-generation spaceborne SARs for its excellent performance. However, ionospheric effect is one of the most factors for the development of MEOSAR. Many researchers have studied the ionospheric effects on Low-Earth-Orbit SAR (LEOSAR), but there are few papers about ionospheric effects on MEOSAR. So it is very necessary to study ionospheric effects for the development of MEOSAR. In this paper, we established an analysis model for background ionospheric effects on MEOSAR based on the system characteristics of MEOSAR and the spatio-temporal variability of ionosphere firstly. Then we analyzed the effects induced by background ionosphere and its spatio-temporal variability on MEOSAR image quality. According to the results of our analysis, we conclude that the worsening of azimuth resolution, displacement in azimuth and distortion in range image will be serious for MEOSAR. Furthermore, ionospheric effects will become more and more serious with the increase of SAR altitude and the improvement of resolution designed.