Geosynchronous SAR imaging algorithm research

The imaging in geosynchronous synthetic aperture radar (GEO SAR) is more difficult than that of the conventional low earth orbit (LEO) SAR. This paper discusses the problems in GEO SAR imaging, reviews the previous studies, and provides basic solutions to the remaining problems. The two-dimensional space variance of the focusing parameters in the large scene, especially in the squint mode, has not been solved completely, and further improvement for the non-linear chirp scaling method is required. The nearly zero time bandwidth product at some orbital positions of GEO SAR causes the infeasibility of the frequency domain algorithms, and a time domain compensation method can be studied to enlarge the time bandwidth product. Besides, in the long integration time of GEO SAR, the effects of non-ideal factors and the backscattering characteristics variance of the target are quite serious, and the corresponding motion compensation methods require to be studied.