A Two-Dimensional Beam-Steering Method to Simultaneously Consider Doppler Centroid and Ground Observation in GEOSAR

Due to Earth's rotation and an elliptical satellite orbit, large Doppler centroids along satellite orbit inevitably occur in geosynchronous Earth orbit synthetic aperture radar (GEOSAR). Nonzero Doppler centroid causes a large range migration, which complicates the data acquisition and design of imaging algorithms. Thus, beam steering is used to decrease the centroid. At the same time, the ground observation of interest is prerequisite for applications. Thus, a unique two-dimensional (2-D) beam-steering method to simultaneously consider the reduction of Doppler centroid and ground observation for the GEOSAR is studied. The minimum-Doppler plane is proposed to minimize the centroid and to guarantee the beams that illuminate the area of interest. Subsequently, to achieve required ground coverage, beam directions determined by the minimum-Doppler plane are slightly adjusted. The method has been validated through the simulation of two types of orbits.