Estimation of Uncompensated Trajectory Deviations and Image Refocusing for High-Resolution SAR

The accuracy of trajectory measurements is one of the crucial factors in high-resolution SAR imaging. Common navigation systems often do not fulfill the requirements that results in significant image quality degradation. In the paper, a new autofocus algorithm for the reconstruction of the SAR platform trajectory deviations is proposed. The approach is based on the estimation of the Doppler rate errors on a sequence of short-time intervals. The method is capable of estimation of time-varying and range-dependent phase error functions. The key steps of the developed technique are illustrated. The method is demonstrated on experimental data obtained with an X-band airborne SAR system.