Imaging Shadows with Sub-THz ISAR for Space-Borne Targets

Sub-THz (200 GHz - 700 GHz) Radar has been shown to provide superior imaging capabilities using Inverse Synthetic Aperture Radar (ISAR) for target recognition, identifying the state of an object in the space domain from a space-based sensor. Higher frequencies provide inherently larger bandwidths which achieves a much finer range resolution, higher sensitivity to surface textures which allows fine details of the object to be resolved, as well as shorter integration times for refined cross-range resolutions. Man-made Resident Space Objects (RSO) have a number of deployables (e.g. antennas, robotic arms, probes), which can aid identification of the mission and intent of the RSO, yet they might be very difficult to image due to their low reflectivity towards the observer. Instead, if the shadow cast by the deployable onto the body of the object can be resolved within the image it can serve as a descriptor of such a deployable and therefore inform the observer about the mission and/or state of the object. The capability of resolving shadows in ISAR processing at 300 GHz is presented.