Dynamics of Satellites in Binary Near-Earth Asteroid Systems: A Study Based on Radar Observations

In the past 15 years, three previously unrecognized sub-populations ofnear-Earth asteroids (NEAs) have been discovered. About 15% of NEAsare binaries, at least 10% of NEAs are contact binaries, and dozensof asteroid pairs have been identified. Numerous science questionshave arisen about the formation and evolution processes of thesesystems and about the inter-relationships between these groups.Addressing these questions informs us about a wide range of importantsolar system processes that shape small bodies and planetesimals.Here I have chosen to focus on providing one of the most completecharacterizations of a binary system among all known asteroidbinaries, and on studying the spin-orbit interactions in this and 8additional binary systems. One hypothesis that has not been fullyexplored is the possibility of chaotic rotation of asteroid satellitesand the impact that such a state has on the evolution of the binarysystems. I examine this problem as well as the possibility ofdetecting librational motions in synchronous satellites. Because theArecibo and Goldstone radar systems enable superb characterizations ofbinaries and NEAs in general, this dissertation makes abundant use ofradar data. Radar observations provide images of asteroids atdecameter resolution, and these images can be inverted to determinethe 3D shapes of the components, which are essential to properly modelthe system dynamics. Radar data also enable precise determination ofthe mutual orbit, which is another crucial ingredient. In the firsttwo chapters of the dissertation, I describe the observations andphysical characterizations of asteroid 2000~ET70 and binary asteroid2000 DP107. The characterization of 2000 DP107 includes size, shape,spin, mass, and density of each component, making this binary one ofthe best-characterized asteroid binary to date. In the last chapterof the dissertation, I describe a computationally efficientfourth-order numerical integrator that I used to investigate thecoupled spin and orbital dynamics of the satellites of NEAs. The speedof the integrator enabled multi-year timescale simulations of 9well-characterized binary near-Earth asteroids. The numericalsimulations illuminate a range of rotational regimes for asteroidsatellites and the conditions under which the various regimes prevail.One of the rotational regimes is chaotic, and I find that thisrotation state can substantially delay the radiative evolution ofbinary systems