Review of On-orbit State Estimation of Space Targets with Radar Imagery

Space target state estimation aims to obtain a target’s on-orbit attitude, structure, movement, and other parameters accurately. This process helps observers analyze the target action intention, check for potential fault threats, and predict the development of on-orbit situations and is the core technology in the field of space situation awareness. Currently, the estimation of the on-orbit state of space targets mainly relies on external observations from high-performance sensors, such as radars, paralleled by the emergence of a series of representative methods. This paper briefly introduces the development status of inverse synthetic-aperture radar used for space target monitoring at home and abroad. Then, several representative methods, including data feature matching, three-dimensional (3D) imaging reconstruction, and multi-look fusion estimation, are introduced. The data feature-matching technology performs well when the priori target 3D model and scene conditions are given. The state estimation with 3D geometric reconstruction has the potential for fine description of the target, but high-level observation conditions are required. Finally, the future development trend of this direction is forecasted.