Three-Dimensional High-Resolution Space-Borne ISAR Imaging With Compact Antenna Configuration for Large Rotational Angle

Space situation awareness (SSA) has gained much more attention in the last decades due to the increasing number of spacecraft in space, which provides powerful space surveillance, and hence, ensures the safe flight of spacecraft. 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 spacecraft in missions and the similar appearance of most spacecraft, 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 3-D image reconstruction of spacecraft is very helpful in evaluating the structures due to the addition of the 3-D information, and hence, has become a very promising tool for deep target analysis. This article proposes a high-resolution spaceborne 3-D ISAR imaging method with fewer requirements on the antenna configuration and high computational efficiency. First, 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 phenomenon and the high-order azimuthal phase modulation leading to defocusing of the resultant spacecraft images. Second, with the generated high-resolution 2-D images, we use dual-antenna interferometric processing to acquire the 3-D 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 3-D images of spacecraft of higher resolution with a simple system structure than the traditional interferometric ISAR image methods.