Dynamics and Controls for Binary Asteroids Exploration

Julie Bellerose¹

Over the past few decades, we witnessed a growing interest in studying small bodies of our solar system. A few spacecraft missions have already been sent to small bodies of our solar system. Some studies have indicated that about 16% of the Near-Earth Asteroids may be systems of asteroid pairs, or binary asteroid systems. With the growing interest in asteroid systems in the scientific community, it is fair to assume that a mission will target a binary asteroid system in the near future. In fact, binary systems are interesting as they enable scientific insight into both the geology and dynamics of asteroids.

Operating a spacecraft in such a system is not trivial and there are important challenges in the design and navigation of such a mission. These systems can be thought of as being mini Three Body Problems with primaries that have a non-spherical shape. Despite the low gravity accelerations, the time scale of motion around these systems are on the order of 10s of hours, and motion is strongly perturbed by the system itself and solar effects.

The dynamics and evolution of binary asteroids are first analyzed, as it is necessary to understand this problem to solve the spacecraft orbiter. To properly address such questions, the dynamics of the two celestial bodies themselves need to be characterized. The equilibrium configurations and associated stability give insights on how these binary systems may evolve in time. When perturbations are introduced, the equilibrium states are found to be the minimum energy points of nearby periodic families. These periodic families are characterized and linked to the equilibrium configurations, and general dynamics from unstable to stable configurations is investigated.

Having defined the dynamics of the Two-Body Problem, the dynamics of a spacecraft or particle in the binary asteroid problem can be characterized, accounting for perturbed motion of the primaries, analysis using periodic orbits and libration points, and other methods of astrodynamics. Having a physical shape for the bodies introduces surface constraints and has allowed to generate new ideas for surface exploration vehicles involving their dynamics and control and possible transit trajectories between the two bodies. An innovative mission proposal is developed taking advantage of the unique dynamical environment at binaries to carry out a scientific exploration and characterization mission.

¹PhD Candidate, Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109, juliebel@umich.edu

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