Inverse synthetic aperture radar range profile compensation of plasma-sheath-enveloped reentry object

Abstract

According to the calculation of electromagnetic (EM) wave transmission, it is found that the EM waves cannot penetrate the high-electron-density areas of plasma enveloping the reentry object, and will be reflected at a certain depth in the plasma sheath to form scattering points. These scattering points will appear in the plasma sheath instead of on the reentry object surface. Because the existence of relative flow velocity between the plasma sheath and the spacecraft surface, the scattering points in plasma sheath characterized with coupled velocities, can cause pulse compression mismatching, which results in the displacement and energy diffusion in one-dimension range profile. When performing inverse synthetic aperture radar (ISAR) imaging on reentry object, the plasma sheath will defocus ISAR images in range dimension. To solve this problem, we deduce the echo model of plasma-sheath-enveloped reentry object. By estimating the coupled velocities, we propose a focusing method to correct the defocus of ISAR image in range dimension to improve the quality of ISAR images. The simulation results suggested that the echoes from different regions of the surface of reentry object had various coupling velocities, and the higher the coupled velocity, the more serious the displacement and energy diffusion in range dimension. Our proposed method can correct the range dimension aberration. Two measurement metrics were used to evaluate the improvement of the focusing method.