Autonomous navigation and guidance for CubeSats to flyby near-Earth asteroids

Recent advancements in CubeSat technology unfold new mission ideas and the possibility to lower the cost of space exploration. Exploiting the natural dynamics around the Sun-Earth barycentric Lagrange points, minimal-ΔV trajectories to flyby asteroids appear which are compatible with current CubeSat propulsive capabilities. Ground operations costs for an interplanetary CubeSat, however, still represent a major challenge towards low-cost missions; hence certain levels of autonomy are desirable. Considering the limited allocation of sensors and actuators in CubeSats, and their limited performance, Monte Carlo simulations are implemented to understand the flyby accuracies that can be achieved through autonomous navigation and guidance. Primary sources of error analyzed in this study include: (1) uncertainties in the departure conditions, (2) errors in the propulsive maneuvers, (3) errors in the observations, and (4) uncertainties in the ephemeris of the target asteroid. An autonomous navigation and guidance strategy is proposed and evaluated, employing observations of the Sun, visible planets and of the target asteroid, and two trajectory correction maneuvers along the trajectory. Flyby accuracies below 100 km are found possible if the mission characteristics are suitable in terms of available ΔV, on-board asteroid visibility time, mission duration, and asteroid ephemeris uncertainty before the mission. Ultimately, this study assesses the readiness level of current CubeSat technology to autonomously flyby near-Earth asteroids, with realistic component specifications and modeling of relevant errors and uncertainties. The effect of the different mission factors on the final flyby accuracies is evaluated, and a feasible autonomous navigation and guidance strategy is proposed in the effort to reduce ground operations and overall mission costs.