High-Resolution ISAR Imaging for Detection of Micro Damages on Spacecraft Thermal Protection System

The thermal protection system (TPS) is an essential component that guarantees the safe flight of high-speed spacecraft. However, the TPS is bound to suffer various level of damages during flight missions, among which the micro damages are difficult to distinguish from optical images. In this paper, we propose a novel approach to detect tiny surface damages of TPS for spacecraft by using inverse synthetic aperture radar (ISAR) imaging. To accomplish this, the procedure consists of three components: electromagnetic scattering simulation, 2-D ISAR imaging, and damage detection and identification. Different types of common TPS surface micro damages such as debonding, cracks, holes, and warpage are simulated. The obtained high-precision 2-D images prominently display the structure and morphology of micro damages. Finally, a relative entropy-based damage detection and identification method is proposed using the established damage characteristics database. The experimental results have demonstrated that by comparing the differences in the statistical characteristics between the damaged and undamaged models, the monitoring and identification of the micro damages can be successfully realized. Overall, the proposed approach offers a promising solution for monitoring the status of TPS in real time and enhancing the safety of high-speed spacecraft during flight missions.