Inverse Synthetic Aperture Radar Imaging of Reentry Target Under the Strong Interference of Plasma Sheath

Abstract

Accurate inverse synthetic aperture radar (ISAR) imaging of a reentry target is severely challenged by the plasma sheath formed around the vehicle surface. In such environments, the plasma sheath acts not only as a lossy dispersive medium but also as a distributed parasitic scatterer with a nonuniform velocity field, which introduces additional Doppler components and distorts the 1-D range profiles (ODRPs) after pulse compression. This article investigates the fundamental failure mechanism of conventional envelope-based ISAR motion compensation methods under plasma sheath interference. Furthermore, this article reveals the intrinsic limitation of dechirped signals for ISAR imaging under plasma sheath interference and clarifies the necessity of employing intermediate-frequency (IF) direct-sampled signals. To overcome this limitation, a coherent motion compensation (CMC) framework is proposed for sheath-contaminated radar echoes. The proposed method is validated using both a simplified scatterer model and a multiphysics simulation framework combining Fluent-based plasma-flow modeling and FEKO-based electromagnetic scattering analysis. Results demonstrate that the proposed approach effectively suppresses the impact of sheath-induced parasitic echoes and produces well-focused ISAR images under severe plasma sheath interference.