Computer Aided Ballistic Orbit Classification Around Small Bodies
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Computer Aided Ballistic Orbit Classification Around Small Bodies Benjamin F. Villac1 Alex J. Pini3
· Rodney L. Anderson2 ·
© American Astronautical Society 2016
Abstract Orbital dynamics around small bodies are as varied as the shapes and dynamical states of these bodies. While various classes of orbits have been analyzed in detail, the global overview of relevant ballistic orbits at particular bodies is not easily computed or organized. Yet, correctly categorizing these orbits will ease their future use in the overall trajectory design process. This paper overviews methods that have been used to organize orbits, focusing on periodic orbits in particular, and introduces new methods based on clustering approaches. Keywords Trajectory design · Periodic orbits · Clustering · Data mining · Asteroid missions
Introduction Past and present missions to small bodies, such as the NEAR Shoemaker, Hayabusa and OSIRIS-REx missions, have used a multi-stage approach to methodically characterize the target asteroids before approaching their vicinity with more confidence [1–3]. This strategy addresses the large uncertainty in the close-proximity dynamical environment prior to the first encounter. In each phase, the dominant forces driving the dynamics change, and various models need to be selected in the trajectory design
Benjamin F. Villac
[email protected] 1
Pr. Systems Engineer, a.i.solutions, Inc., 4500 Forbes Blvd., Suite 300, Lanham, MD 20706, USA
2
Technologist, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, M/S 301-121, Pasadena, CA 91109, USA
3
Systems Engineer, a.i.solutions, Inc., NASA GSFC, B28 N278, Greenbelt, MD 20771, USA
J of Astronaut Sci
process. For example, far from an asteroid, simplified dynamical models (ranging from linearized dynamics to averaging methods) can be used to provide a global overview of the dynamics with sufficient accuracy [4]. As data are gathered and better approximations of the gravitational field are obtained, the spacecraft is transferred to regions closer to the body, where the non-uniform gravity and rotational state of the small body must be considered. In this phase, the orbital dynamics can be chaotic and present non-intuitive regimes of motion, which present both challenges in operating an actual spacecraft and opportunities to develop new mission concepts [5, 6]. While past and current missions have used active control (either low-thrust in the case of the DAWN spacecraft [7] or closed-loop control for final descent to the surface and touch-down events), the study of ballistic orbits near these primitive bodies is also expected to support the development of innovative mission concepts, such as automated long-term exploration or navigation beacons, small probe swarms with limited control authority, or simply the selection of relevant orbits for particular scientific observations. In particular, several classes of ballistic orbits have been analyzed in detail (e.g., terminator, ecliptic, or libration point orbits)
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