Spacecraft Collision Avoidance System
This activity addresses the growing collision-risk in Low-Earth Orbit by enabling satellites to refine conjunction predictions autonomously, using electro-optical sensors (including star trackers) to collect observations during the final orbits before a potential collision. Relying solely on ground-based tracking introduces significant uncertainties, often resulting in conservative maneuvers, false alarms, wasted propellant, and disruption of normal operations.
Several feasibility and design studies were completed in recent years to validate the concept. Extensive orbital dynamics analyses characterized several features of on-orbit observation opportunities, showing that 70% of potentially colliding objects in LEO pass within 100 km of each other in the orbits before closest approach; however, high angular rates at such distances limit continuous tracking within sensor fields of view. Technology trade-offs identified electro-optical imagers—often the spacecraft’s own star trackers—as the only feasible sensors for such application. Detailed simulations evaluated these sensors across various scenarios, assessing performance against parameters like aperture, pixel scale, and illumination. Simulations show that around 50% of LEO conjunctions offer two good observation windows per orbit at opposite nodes, and another 49% offer at least one, making observation feasible in nearly all cases [2] [3]. Optical apertures of 5 cm reliably detect targets over 1 meter; larger optics yield limited gains compared to added mass. A subset of feasible sensor configurations was further tested for orbit determination. Synthetic imagery from realistic scenarios were processed through astrometric plate-solving and sequential filtering to update the secondary object’s state vector in real time. Case studies showed an order-of-magnitude reduction in positional uncertainty and a corresponding drop in required maneuvers.
References
[1] G. Campiti, G. Brunetti, V. Braun, E. Di Sciascio, and C. Ciminelli, “Orbital Kinematics of Conjuncting Objects and Opportunities for Autonomous Observations,” Acta Astronautica, vol. 208, pp. 355–366, 2023. doi: 10.1016/j.actaastro.2023.04.032. link: https://doi.org/10.1016/j.actaastro.2023.04.032
[2] G. Campiti, G. Brunetti, F. Santoro, M. Reali, R. Vittori, M. N. Armenise, and C. Ciminelli, “Feasibility Assessment of an Autonomous Collision Avoidance System for Satellites,” in Proc. 74th Int. Astronautical Congr., Baku, Azerbaijan, 2–6 Oct. 2023. Available: https://iafastro.directory/iac/archive/browse/IAC-23/A6/7/79827/
[3] G. Campiti, G. Brunetti, and C. Ciminelli, “Detectability of potentially colliding space objects through star trackers onboard at-risk satellites,” Accepted for publication in IEEE Transactions on Aerospace and Electronics Systems, 2025