Three-Dimensional High-Resolution Space-Borne ISAR Imaging With Compact Antenna Configuration for Large Rotational Angle
Rui Gong, Ling Wang, Daiyin Zhu
Abstract
Space Situation Awareness (SSA) has gained much more attention in the last decades due to the increasing of the number of spacecrafts in space, which provides powerful space surveillance and hence ensure the safe flight of spacecrafts. Inverse Synthetic Aperture Radar (ISAR) is an effective tool for uncooperative target recognition and has been widely used in ground-based SSA systems. Due to the increasing usage of small spacecrafts in the missions and similar appearance of most spacecrafts, the high-resolution imaging is more highly needed for reliable spacecraft recognition than before, which is also desired by the component-level recognition. Furthermore, the Three-Dimensional (3D) image reconstruction of spacecrafts is much helpful to evaluate the structures due to the addition of the third-dimension information and hence become a much promising tool for deep target analysis. This article proposes a high-resolution spaceborne 3D ISAR imaging method with less requirement on the antenna configuration and high computational efficiency. Firstly, dedicated processing is designed to get high azimuthal resolution using large target-to-radar rotational angle accumulation. We address associated issues including the Migration Through Resolution Cell (MTRC) phenomenon and the high-order azimuthal phase modulation leading to defocusing of the resultant spacecraft images. Secondly, with the generated high resolution Two-Dimensional (2D) images, we use dual-antenna interferometric processing to acquire the 3D coordinates. To get precise coordinates of scatterers in both vertical and horizontal directions, the cross-range scaling technique is used. Finally, interferometric processing is used for locating the targets' height coordinates. Simulation results indicate that the presented method can provide 3D images of spacecrafts of higher resolution with simple system structure than the traditional Interferometric ISAR (InISAR) image methods.