Orbit dynamics in the vicinity of contact binary asteroid

A contact binary asteroid is an asteroid consisting of two lobes that are in contact. In this study, the two lobes are approximated by an ellipsoid and a sphere, respectively, with two free system parameters: the mass ratio μ between the two components and the gravitational-centripetal acceleration ratio k of the asteroid. The situations for k > 1, k = 1, k < 1 are studied. Firstly, by applying the zero-velocity surfaces, the equilibrium points (EPs) and their linear stabilities are identified as functions of μ and κ. Then, based on the physical parameters of the 1996 HW1 system, the stable, unstable and center manifolds associated with the EPs of this specific system are identified, for understanding the motion in the vicinity of the EPs and the patterns of escape and capture trajectories. Thirdly, with the approximate analytical initial condition, numerical iteration and continuation methods, the planar (Lyapunov) and vertical orbits are determined. Their linear stabilities are evaluated through eigenvalues of the monodromy matrix of the linearized system, and their potential for mission orbits are discussed. Finally, the planar prograde and retrograde periodic orbits is investigated over large regions around the system. The influence of the parameter κ on the velocity and stability of these orbits is also explored by numerical simulations.