Assessing Control Robustness of CubeSat Propulsion Systems for (99942) Apophis Proximity Operations

The exploration of minor celestial bodies is gaining increasing attention due to its scientific relevance, engineering challenges, and implications for planetary defense. Simultaneously, the use of miniaturized platforms such as Cube-Sats is expanding due to their lower development, qualification, and launch costs. Their cost-effectiveness enables higher-risk operations, making them well suited for proximity missions around minor bodies. The RAMSES mission embodies these two concepts, with the mothercraft RAMSES set to reach (99942) Apophis and conduct in-depth studies during its close encounter. The mission will deploy two 6U CubeSats, RCS-1 and RCS-2, to characterize the asteroid. The dynamical environment in proximity of asteroids is highly uncertain, with perturbations playing a significant role. Therefore, robust orbital and attitude guidance and control strategies are essential for ensuring mission success under varying conditions. To address this challenge, this study presents a 6-DoF guidance and control simulation framework for proximity operations along hyperbolic trajectories near minor bodies, with a specific focus on (99942) Apophis. An optimization algorithm is developed to integrate attitude dynamics with trajectory design while accounting for the performance and technological constraints of CubeSat propulsion systems. This approach evaluates the feasibility of employing miniaturized propulsion technologies in a minor body environment. The analysis explores 4 different propulsion technologies, namely bipropellant, monopropellant, cold gas, and resistojet, and 10 orbital distances to determine the feasibility of flying hyperbolic arcs. Based on the proposed methodology, the results indicate that a minimum thrust of 8 mN is required to enable such trajectories. Additionally, key performance metrics, including observation time, firing time, propellant consumption, and pointing accuracy, are analyzed. The values and trends of these parameters are presented as functions of thrust level and orbital distance.