Near-Earth Asteroid Satellite Spins Under Spin-Orbit Coupling

TL;DR

This paper introduces a high-order numerical method to simulate the coupled spin and orbital dynamics of binary and triple near-Earth asteroid systems, revealing chaotic spin states and their implications for asteroid evolution.

Contribution

A fourth-order integrator for simulating coupled spin-orbit dynamics of rigid bodies with arbitrary mass distributions in asteroid systems.

Findings

Chaotic spin states are prevalent in asynchronous satellites.

Libration amplitudes can be significant even for moderately elongated satellites.

Chaotic regions influence binary asteroid evolution and observational interpretations.

Abstract

We develop a fourth-order numerical integrator to simulate the coupled spin and orbital motions of two rigid bodies having arbitrary mass distributions under the influence of their mutual gravitational potential. We simulate the dynamics of components in well-characterized binary and triple near-Earth asteroid systems and use surface of section plots to map the possible spin configurations of the satellites. For asynchronous satellites, the analysis reveals large regions of phase space where the spin state of the satellite is chaotic. For synchronous satellites, we show that libration amplitudes can reach detectable values even for moderately elongated shapes. The presence of chaotic regions in the phase space has important consequences for the evolution of binary asteroids. It may substantially increase spin synchronization timescales, explain the observed fraction of asynchronous binaries, delay BYORP-type evolution, and extend the lifetime of binaries. The variations in spin rate due to large librations also affect the analysis and interpretation of lightcurve and radar observations.