Accurate slant range model and focusing method in geosynchronous SAR

Geosynchronous (GEO) SAR is a radar satellite running in the inclinational geosynchronous orbit (36000km). During the long signal propagation delay time, the relative motion between satellite and target cannot be ignored. In this paper, the two-way slant range is analytically obtained from vector derivation. Meanwhile, it is found that the image formation must consider the non-uniform velocity in a long synthetic aperture time, and therefore, based on the derived slant range and the instantaneous velocity of satellite, a modified back projection algorithm is put forward to overcome the error of the “stop-and-go” error as well as the effects of the non-uniform satellite velocity. Simulation results validate the correctness of the improved imaging algorithm.