Modeling and Processing of Two-Dimensional Spatial-Variant Geosynchronous SAR Data

Imaging of spatial-variant geosynchronous synthetic aperture radar (GEO SAR) in the L band with long integration time is discussed. To compensate for spatial variances in both range and azimuth directions, a new algorithm based on improved omega-K ( $\Omega {\rm K}$ ) and three-time azimuth chirp scaling (3ACS) is proposed. First, the integration time and the slant range model were analyzed. Second, the two-dimensional (2-D) spectrum was used for range cell migration correction (RCMC), secondary range compression (SRC), and azimuth compression, and the influences of spatial variances on each term were considered. Third, the improved $\Omega {\rm K}$ was used to compensate for the range variance, and 3ACS was used to compensate for the azimuth variance. The scope of 2-D focusing in high-resolution GEO SAR imaging was clearly enlarged. Finally, the performance of the algorithm was demonstrated using simulations based on a spaceborne radar advance simulator (SBRAS).