Second-order motion compensation in bistatic airborne SAR based on a geometrical approach

Common efficient SAR processing algorithms are based on nominal operational conditions. Unfortunately, due to atmospheric turbulences and maneuvering errors, these conditions are often violated in real SAR systems. Hence, a crucial problem in most airborne SAR systems is the compensation of motion errors; if not corrected, the image quality will considerably degrade. A first-order motion compensation (MoCo) technique was developed at our institute, based on a precise knowledge of the position and the velocity of the transmitter and the receiver. The problem arose while proceeding with our processing algorithm, since the reconstructed image was better focused but not completely focused. Our paper proposes a second-order MoCo technique that will considerably improve the reconstruction of the SAR image. While the first-order MoCo considered the range and azimuth times, the second-order MoCo approximation will consider the frequencies. Experiments with different sets of bistatic airborne SAR data are performed based on this solution, and some promising results are given.