Terahertz ISAR Imaging with Non-Rigid Vibration Compensation and Sidelobe Suppression of Space Targets

Terahertz (THz) inverse synthetic aperture radar (ISAR) imaging of space target has the advantage of high resolution and all-day capability for spatial situational awareness (SSA). However, compared with microwave ISAR imaging, micro vibrations of radar platform and target can cause images defocusing and quality degradation in THz band. Commonly, the existing algorithms considered vibration as simple harmonic motion in rigid body, and estimated the vibration parameters for phase error compensation. Nevertheless, these methods are dependent on the prominent points and cannot focus on the complex non-rigid vibration of the space target. Aiming at these problems, an ISAR imaging framework that can be leveraged for complex non-rigid vibration compensation is proposed. First, a compressed sensing (CS) model is established to compensate for the vibration phase error in ISAR imaging. Then, the alternating direction method of multipliers (ADMM) is employed to optimize the CS model. Subsequently, considering that strong scattering points of space targets will cover up the weak scattering information in ISAR images, a sidelobe suppression constraint is appended. Thus, the weak scattering information is retained while removing the sidelobe and noise. It is worth mentioning that the ISAR imaging algorithm is derived to a two dimension (2-D) matrix form to reduce memory usage and to improve computational efficiency. Finally, simulated and measured data are utilized to verify the superiority of the proposed algorithm, and proves the potential of ISAR imaging for practical space targets.