A Novel Processing Method for GEO SAR

Geosynchronous synthetic aperture radar (GEO SAR) is more challenging to process than the classical synthetic aperture radar (SAR) because the flight geometry is more complicated and the data is usually non-stationary. Whereas time-domain algorithms can handle general geosynchronous cases, they are very inefficient; therefore, frequency-domain methods are preferred. Several frequency-domain geosynchronous algorithms have been proposed to handle a limited number of geosynchronous cases, but a general algorithm is sought, which can handle cases such as long integration time, large scene, and especially the azimuth shift variation, which is very serious in GEO SAR imaging. In this paper, we proposed a SAR signal and range Doppler (SS-RD) algorithm to handle a more general case of GEO SAR data. The key is to use a spatial-variant (both in azimuth and range) fourth order range equation (SVRE4) to model the non-stationary, and an azimuth-invariant transform (AIT) in SAR signal (SS) domain to handle the azimuth shift variation. Simulations with the space borne radar advance simulator (SBRAS) proved that the SS-RD algorithm can handle GEO SAR data with serious azimuth shift variation.