Robust Replanning for Multi-Agent SmallSat Inspection in Failure Scenarios

Future space structures like the proposed Lunar Gateway will require autonomous inspection and maintenance, especially during extended uncrewed periods. Small satellites (SmallSats) offer a low-cost alternative to human extravehicular activities (EVAs) for performing these tasks. However, SmallSats have a high failure rate, particularly with propulsion systems, often causing mission failures. This work is motivated by this failure rate and considers a multi-agent approach to SmallSat inspection as a way of increasing mission success through redundancy. The added risk of the multi-agent approach, namely collision risk during thruster or other system failures, is addressed. We propose a collision-aware path-planning strategy based on the Anytime Dynamic A* (AD*) algorithm, enabling efficient initial path generation and dynamic replanning in response to failures. Implementation considerations like collision-checking in a high-fidelity simulation environment are discussed. The proposed strategy is demonstrated in a case study multi-agent inspection scenario around simulated Lunar Gateway geometry, where one SmallSat experiences a thruster failure, prompting other agents to replan their paths.