Spaceborne Radar for Space Situational Awareness

The space environment around planet Earth comprises a variety of nonhomogeneous and nonstationary fluxes of natural and man-made junk. Such debris may collide at hypervelocity with strategic orbital infrastructure, thus jeopardizing the space economy. For this reason, the European Space Agency (ESA) sustains a strategy to acquire a ?…capability to watch for objects and natural phenomena that could harm satellites in orbit.? Accordingly, large ground-based radars and optical telescopes allow monitoring debris populations with an average size larger than, say 10 cm, up to Low Earth Orbit (LEO) and Geostationary Orbit (GEO respectively. In fact, these assets form fence coverage areas along with a grueling data fusion for orbit estimation while coping with limits related to temporal and spatial observation constraints, atmospheric hindrances, and detection performance (especially with respect to small-size targets). Interestingly, an active space-based debris detection and tracking capability in the microwave region could complement current surveillance assets for an improved Space Situational Awareness (SSA) and, more dauntingly, provide future spacecraft with an early warning capability for direct collision-avoidance maneuvering. Within this framework, the Technology Readiness Level (TRL) of several key enabling technologies in both digital and Radio Frequency (RF) domains, as well as advances in Active Electronically Scanned Array (AESA) antennas, allow contriving imposing onboard processing tasks for bespoke SSA operations and services. Indeed, this Ph.D. work is structured as a Gedankenexperiment to augment SSA by delving into a novel SpaceBorne Radar (SBR) concept inspired by modern and legacy airborne radars. In particular, such an SBR operates as a fully-polarimetric active instrument in the Ka-band to detect and track small-size debris, entailing a scalable Field of View (FoV) which depends on the available transmit peak power (on the order of kilowatts), multichannel diversity, and AESA steering capabilities. This research avenue highlights the benefit of adopting a cognitive-based SBR for future SSA in terms of improved debris orbit determination and time series analysis on Radar Cross Section (RCS) signatures. Moreover, it poses new questions in radar-theory while endorsing further research and development on key space-qualified enabling technologies. Last but not least, an SBR for SSA may support Space Domain Awareness (SDA), thus cueing a potential liaison with the Homeland Protection (HP), since a debris characterized by a low-RCS is ?similar? to a stealth hypervelocity High Value Target (HVT).