Analytical description of physical librations of saturnian coorbital satellites Janus and Epimetheus

作者：Robutel Philippe^*; Rambaux Nicolas; Castillo Rogez Julie

来源：Icarus, 2011, 211(1): 758-769.

DOI：10.1016/j.icarus.2010.09.014

• Celestial mechanics
• Resonances, Spin-orbit
• Rotational dynamics
• Satellites, Shapes
• Saturn, Satellites

Janus and Epimetheus are famously known for their distinctive horseshoe-shaped orbits resulting from a 1:1 orbital resonance. Every 4 years these two satellites swap their orbits by a few tens of kilometers as a result of their close encounter. Recently Tiscareno et al. (Tiscareno, M.S., Thomas, P.C., Burns, J.A. [2009]. Icarus 204, 254-261) have proposed a model of rotation based on images from the Cassini orbiter. These authors inferred the amplitude of rotational librational motion in longitude at the orbital period by fitting a shape model to Cassini ISS images. By a quasi-periodic approximation of the orbital motion, we describe how the orbital swap impacts the rotation of the satellites. To that purpose, we have developed a formalism based on quasi-periodic series with long- and short-period librations. In this framework, the amplitude of the libration at the orbital period is found proportional to a term accounting for the orbital swap. We checked the analytical quasi-periodic development by performing a numerical simulation and find both results in good agreement. To complete this study, the results obtained for the short-period librations are studied with the help of an adiabatic-like approach.

• 出版日期2011-1