Spin Estimation and 3-D Geometry Reconstruction Using Multiperspective Space-Borne Sub-THz Interferometric Inverse Synthetic Aperture Radar

Sub-terahertz (sub-THz) radar enables high-resolution and highly detailed imaging of space objects, offering substantial advantages for space domain awareness (SDA). Accurate estimation of spin motion and three-dimensional (3D) geometry of non-cooperative space targets is essential for SDA tasks such as target characterization, autonomous rendezvous and proximity operation (RPO), and debris removal. Interferometric ISAR (InISAR), which generates 3D images in the form of point clouds, can also resolve the effective rotation vector—defined as the component of the total rotation vector perpendicular to the line of sight (LOS). This component is critical for 2D image scaling and for enhancing understanding of the imaging projection plane (IPP). However, the component along the LOS remains unknown, which limits the ability to fully exploit multi-perspective ISAR imaging to characterize targets. In this paper, a novel spin estimation framework is proposed based on multi-perspective InISAR, which leverages viewing angle diversity during on-orbit observation to resolve the total rotation vector of space targets. The proposed method performs InISAR imaging and the estimation of the effective rotation vector for each perspective, followed by the combination of effective rotation vectors to determine the total rotation vector as a unified least-squares solution. The framework requires no prior 3D model and achieves robust spin estimation. Both simulation experiments using sub-THz radar parameters and laboratory validation using W-band radar are carried out to verify the effectiveness of the proposed method, demonstrating its potential for future SDA and on-orbit servicing applications.