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Remote sensing instrumentation onboard missions to asteroids is paramount to address many of the fundamental questions in modern planetary science. Yet in situ surface measurements provide the “ground truth” necessary to validate and enhance the science return of these missions. Nevertheless, because of the dynamical uncertainties associated with the environment near these objects, most missions spend long periods of times stationed afar. Small landers can be used much more daringly, however, and thus have already been identified as valuable assets for in situ exploration. This paper explores the potential for ballistic landing opportunities enabled by the natural dynamics found in binary asteroid systems. The dynamics near a binary asteroid are modeled by means of the circular restricted three-body problem, which provides a reasonable representation of a standard binary system. Natural landing trajectories are then sought that allow for a deployment from the exterior region and touchdown with minimum local-vertical velocity. The results show that, although landing on the main body of the system would require an effective landing system capable to dissipate excess of energy and avoid bouncing off the asteroid, the smaller companion offers the prospect of simple ballistic landing opportunities.

This paper presents a three-dimensional semi-analytical formulation to model the third-body effect on a massless particle in the circular restricted three-body problem dynamical regime. The final expressions are obtained by means of the classical Lagrange planetary equations, by considering as small parameter of the perturbative approach the mass parameter of the system. The variations of the Keplerian orbital elements of the massless particle over one orbital period are computed as a function of the relative phasing between the massless particle and the secondary, and the overall behavior is described in terms of kick maps. Several applications to mission design are introduced, and the accuracy provided by the methodology is discussed on the basis of different initial conditions and physical systems.