Effect of orbital errors on the geosynchronous circular synthetic aperture radar imaging and interferometric processing

The geosynchronous circular synthetic aperture radar (GEOCSAR) is an innovative SAR system, which can produce high resolution three-dimensional (3D) images and has the potential to provide 3D deformation measurement. With an orbit altitude of approximately 36 000 km, the orbit motion and orbit disturbance effects of GEOCSAR behave differently from those of the conventional spaceborne SAR. In this paper, we analyze the effects of orbit errors on GEOCSAR imaging and interferometric processing. First, we present the GEOCSAR imaging geometry and the orbit errors model based on perturbation analysis. Then, we give the GEOCSAR signal formulation based on imaging geometry, and analyze the effect of the orbit error on the output focused signal. By interferometric processing on the 3D reconstructed images, the relationship between satellite orbit errors and the interferometric phase is deduced. Simulations demonstrate the effects of orbit errors on the GEOCSAR images, interferograms, and the deformations. The conclusions are that the required relative accuracy of orbit estimation should be at centimeter level for GEOCSAR imaging at L-band, and that millimeter-scale accuracy is needed for GEOCSAR interferometric processing.