1.Aerospace Information Research Institute， Chinese Academy of Sciences；2.School of Electronic ， Electrical and Communication Engineering， University of Chinese Academy of Sciences
Abstract： High-resolution lunar synthetic aperture radar (SAR) imaging is constrained by limited navigation accuracy and incomplete prior topographic information, which makes motion errors and terrain errors prone to coupling and thus causes image defocusing. To address this problem, and based on an analysis of the tracking capability of the deep-space measurement and control network, this paper focuses on lunar orbital SAR establishes an imaging geometry and error propagation model that combines orbit measurement data with a lunar digital elevation model (DEM). This model is used to quantitatively characterize the impact and tolerance of velocity errors and height errors on the imaging phase. On this basis, a two-dimensional space-variant error correction method is proposed. First, an equivalent velocity is estimated by an image-entropy-minimization autofocus criterion; then, DEM-based subaperture terrain phase compensation is applied to suppress the residual space-variant phase. Simulation data processing produces point-target and distributed-target images under injected velocity and height errors, demonstrating the effectiveness of the proposed two-dimensional space-variant error correction procedure and its ability to mitigate motion–terrain coupled errors. Furthermore, compared with uncorrected results, the proposed method clearly improves the peak sidelobe ratio and integrated sidelobe ratio of point targets, while the image entropy in representative distributed-target regions is effectively reduced by 0.116, 0.154, and 0.203 bit in the L-, Ku-, and Ka-band cases, respectively.
