Dario Modenini, University of Bologna; Giacomo Curzi, University of Bologna; Alfredo Locarini, Alma Mater Studiorum – University of Bologna; Paolo Tortora, University of Bologna; Stefano Cicalò, Space Dynamics Services s.r.l.; Alessia Bertolucci, Space Dynamics Services s.r.l.; Francesca Guerra, Space Dynamics Services s.r.l.; Mauro Cardone, Agenzia Spaziale Italiana
Keywords: Autonomous operations, Collision Avoidance, Risk Assessment, Orbit determination, GNSS, Galileo
Abstract:
Space-based solutions are generating growing interest in service providers (internet, imaging, surveillance, etc.), thanks to a cheaper access to space. One of the overall effects is an expected dramatic increase in the space traffic to be handled. Parts of the larger Space Traffic Management discipline, Conjunction Assessment (CA), Risk Analysis (RA) and Collision Avoidance (COLA) are crucial to ensure a safe operational environment but are becoming increasingly heavy tasks to be performed with the current approach.
In this context, project ABACO, funded by the Italian Space Agency, proposes the operational and physical architecture of an onboard-satellite subsystem able to mitigate the ground workload to yield a paradigm shift in the current CARA and COLA processes. The overall project goal is the manufacturing of a TRL 4 prototype of ABACO tested in laboratory environment, which will offer a useful step towards an automatic Space Traffic Management. The motivation behind ABACO project stems from the following two observations.
A major concern in RA and COLA is the “freshness” of the data upon which the maneuver-vs-non-maneuver decision is based. Moving the RA onboard, one guarantees that high-quality quasi-real time data are used for estimating and propagating the spacecraft trajectories, thus limiting unnecessary COLA maneuvers. This responds effectively to the need for autonomous operations of future spacecraft, where the source data for RA are not provided solely by the ground tracking radars, but possibly also from other sources e.g., onboard GNSS, onboard optical tracking, onboard access to third-party SSA databases.
The second point concerns traffic coordination. ABACO keeps the ground as the traffic manager for events when both objects involved are active. In that case in fact, ABACO must cope with other collision avoidance approaches and ground is the place where all operators can interact, therefore, a good place where the most appropriate/fair decision can be made about which spacecraft has the right to maneuver. Still, ABACO ultimately decide if the maneuver is to be executed or not. For safety reasons however, a human can always overwrite the ABACO process discarding events under consideration, provided that a communication slot with the spacecraft is available.
ABACO implements the above points by proposing an architecture that: i) produces a safe, usable risk metric with the help of an accurate GNSS based, quasi-real time orbit and covariance estimation and prediction, ii) interfaces with an autonomous ground software for gathering initial Space Situational Awareness data and coordination of maneuvers. The flow of operation is as follows: ABACO accepts Conjunction Data Messages (CDMs) generated from ground to trigger an autonomous onboard risk analysis. If coordination is needed, a first trial avoidance maneuver is sent to ground for traffic coordination by a (possibly autonomous) referee service. The referee communicates to ABACO if it has been assigned for a maneuver slot or not. At this point, ABACO continue updating the data for RA from any available source (CDMs included) and has full authority to wait up to the most convenient time to decide for a maneuver, balancing maneuver efficiency against quality of data.
From a hardware point of view, ABACO features a navigation unit, devoted to the autonomous orbit determination and prediction for the hosting spacecraft, plus a collision avoidance unit, which provides risk assessment and mitigation functionalities, such as the computation of evasive orbital maneuvers and evaluation of secondary conjunctions.
Date of Conference: September 19-22, 2023
Track: Conjunction/RPO