Abstract:The MOtion COmpensation (MOCO) of Light Of Sight (LOS) error is very important in low-frequency Ultra Wide-Band Synthetic Aperture Radar (UWB SAR). In this paper, the second-order MOCO is studied which compensate the range-variant component of LOS error. In second-order MOCO, the assumption that there is no effect of range-variant LOS error on the Range Cell Migration Correction (RCMC) is supposed, which is not satisfied in UWB SAR. This paper analyzes the application of the second-order MOCO in low-frequency UWB SAR. Three methods which can be applied to compensate the range-variant LOS error are presented. First method implements the second-order MOCO after RCMC, second method implements it before RCMC, and the last method implements it in sub-band which is split along range direction. The three methods are compared and analyzed in this paper. Finally, the effectiveness of theoretical analysis is validated with simulation and real low-frequency UWB SAR data.