A numerical procedure for analysis of electromagnetic scattering by a hypersonic cone-like body flying in the near space is presented. First, the fluid dynamics equation is numerically solved to obtain the electron density, colliding frequency, and the air temperature around the body. They are used to calculate the complex relative dielectric constants of the plasma sheath. Then the volume-surface integral equation method is adopted to analyze the scattering properties of the body plus the plasma sheath. The Backscattering Radar Cross-Sections (BRCS) for the body flying at different speeds, attack angles, and elevations are examined. Numerical results show that the BRCS at a frequency higher than 300 MHz is only slightly affected if the speed is smaller than 7 Mach. The BRCS at 1 GHz would be significantly reduced if the speed is greater than 7 Mach and is continuously increased, which can be attributed to the absorption by the lossy plasma sheath. Typically, the BRCS is influenced by 5~10 dBm for a change of attack angle within 0~15 degrees, or for a change of elevation within 30~70 km above the ground.

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In addition to the traditional re-entry warhead and re-entry capsule, more and more hypersonic objects appear in the near space in recent years, such as the X-51, X-37, and so on. Analysis of electromagnetic scattering properties of these objects has important values for identification, recognition, communication and control. Challenging problems to extract their scattering characteristics include at least three aspects: (2) Modeling of plasma sheath due to the hypersonic motion in the thin atmosphere of the near space.(2) Electrically large size of the object itself plus the surrounding non-uniform plasma region. (3) Doppler and micro-Doppler effects caused by the hypersonic translation and possible rations of the object as a whole about an apparent barycenter.In this talk, we will begin with the modeling of the plasma sheath by using computational fluid dynamics software such as the FASTRAN for hypersonic body. With the electron density and atmospheric temperature found by the software, we can calculate the electromagnetic parameters of the plasma region. Then, we will concentrate on analyzing the influences of the plasma sheath on the backscattering cross-sections. A hybrid approach by incorporating the rigorous moment method with the approximate Born iterative method is developed to mitigate the computing cost in solving the matrix equation. The scattering property analyses are performed in the object reference system, and relativity transforms are employed to convert the incident and scattering fields between the lab system and the object system. Finally, extracting methods for the Doppler and micro-Doppler frequencies are introduced, and possible applications of the Doppler and micro-Doppler parameters are discussed.

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