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

  • Author(s): Naidu, Shantanu
  • Advisor(s): Margot, Jean-Luc
  • et al.
Abstract

In the past 15 years, three previously unrecognized sub-populations of

near-Earth asteroids (NEAs) have been discovered. About 15% of NEAs

are binaries, at least 10% of NEAs are contact binaries, and dozens

of asteroid pairs have been identified. Numerous science questions

have arisen about the formation and evolution processes of these

systems and about the inter-relationships between these groups.

Addressing these questions informs us about a wide range of important

solar system processes that shape small bodies and planetesimals.

Here I have chosen to focus on providing one of the most complete

characterizations of a binary system among all known asteroid

binaries, and on studying the spin-orbit interactions in this and 8

additional binary systems. One hypothesis that has not been fully

explored is the possibility of chaotic rotation of asteroid satellites

and the impact that such a state has on the evolution of the binary

systems. I examine this problem as well as the possibility of

detecting librational motions in synchronous satellites. Because the

Arecibo and Goldstone radar systems enable superb characterizations of

binaries and NEAs in general, this dissertation makes abundant use of

radar data. Radar observations provide images of asteroids at

decameter resolution, and these images can be inverted to determine

the 3D shapes of the components, which are essential to properly model

the system dynamics. Radar data also enable precise determination of

the mutual orbit, which is another crucial ingredient. In the first

two chapters of the dissertation, I describe the observations and

physical characterizations of asteroid 2000~ET70 and binary asteroid

2000 DP107. The characterization of 2000 DP107 includes size, shape,

spin, mass, and density of each component, making this binary one of

the best-characterized asteroid binary to date. In the last chapter

of the dissertation, I describe a computationally efficient

fourth-order numerical integrator that I used to investigate the

coupled spin and orbital dynamics of the satellites of NEAs. The speed

of the integrator enabled multi-year timescale simulations of 9

well-characterized binary near-Earth asteroids. The numerical

simulations illuminate a range of rotational regimes for asteroid

satellites and the conditions under which the various regimes prevail.

One of the rotational regimes is chaotic, and I find that this

rotation state can substantially delay the radiative evolution of

binary systems.

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