A Novel Spaceborne ISAR Imaging Method for Space Targets Based on HOSVPC

Compared with ground-based radar, spaceborne inverse synthetic aperture radar (SBISAR) has advantages in space situational awareness. Since the motion of the target relative to the radar is complex and nonuniform, high-order spatial variant phase (SVP) can be induced, resulting in a defocused image. Due to the unknown spatial distribution of scatterers, the correction of high-order SVP is a hard task. In this letter, a novel SBISAR imaging method for space targets based on high-order SVP compensation (HOSVPC) is proposed. First, the geometric model for SBISAR imaging of space targets is established, and the slant range model is derived. The specific form of the high-order SVP is derived, which is modeled as the sum of the range term and the velocity term. Second, to correct the high-order SVP, an orbit parameter estimation method and the HOSVPC algorithm are proposed. The range term is compensated first using the orbit parameters, the velocity term is then corrected using nonuniform resampling, and the first-order term of the range term is finally compensated back. Finally, a well-focused ISAR image is obtained through cross-range compression. Scatterer simulation and electromagnetic simulation results demonstrate the effectiveness of the proposed algorithm.