Strategies for Monitoring of Assets in Geosynchronous Orbit (GEO) Using Space-Based Sub-THz Inverse Synthetic Aperture Radar (ISAR)

This article is concerned with the investigation and analysis of a new operational and technical capability to assess geosynchronous orbit (GEO) satellites from spaceborne platforms using extremely high-frequency radar operating at sub-THz frequencies. The concept of close monitoring and highly detailed imagery of GEO assets from all aspects, including those unattainable from the Earth, is developed based on the analysis of two proposed orbital deployment scenarios. Accounting for orbital perturbation factors during an extended period of time, the ability to build multiaspect ISAR imagery of the asset during single and multiple encounters is demonstrated, based on the mutual attitudes of the asset and the radar platform. A linearized model of the encounter geometry is presented and the approach to generate a sequence of ISAR image frames according to the geometry of the proposed scenarios is detailed. The simulation of ISAR frames at two frequency bands, centered at 75 and 300 GHz produced in a developed metaheuristic simulator, graphical electromagnetic ISAR simulator for sub-THz (GEIST), is demonstrated, to highlight the transition of scattering mechanisms and the change in visibility of particular features. Attitude-agnostic frame-to-frame image alignment and linear feature extraction using the Hough transform are then demonstrated on a sequence of simulated images.