Enhancing Close-Proximity Small-Body Missions: The Role of Spacecraft Autonomy

Exploration of small bodies is advancing, yet missions operating in close proximity to these bodies encounter substantial challenges such as environmental uncertainties, communication delays, and high costs. Autonomy provides real-time decision-making solutions and is increasingly integrated into resource-limited platforms such as CubeSats, enabling riskier yet cost-effective operations. This study uses the Multi-Spacecraft Concept and Autonomy Tool (MuSCAT) simulator to model a 6U spacecraft operating in proximity of various bodies with different shapes and physical parameters: (99942) Apophis, (101955) Bennu, 67P/Churyumov-Gerasimenko, and (433) Eros. The focus is on attitude and orbital estimation and control. Simulated star trackers, sun sensors, and inertial measurement unit data support attitude estimation, while reaction wheels and microthrusters handle attitude control, including desaturation. Landmark-based optical navigation aids orbit determination, and a chemical thruster is used for orbital control. A 20-day quasi-terminator polar orbit is simulated for each body, considering 15 orbital distances, 3 thrusting error levels, and 2 event-based control strategies. The study identifies a one-day interval between trajectory correction maneuvers as a practical autonomy threshold. Monte Carlo simulations assess autonomy requirements, mission cost, and reaction wheel desaturation frequency. Results show that autonomy is crucial near smaller, less massive bodies but unnecessary for larger ones, while small thrust errors have minimal impact on trajectory evolution.