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F. Varadi (UCLA), S. Musotto (UCLA and Univ. of Padova, Italy), W. Moore, G. Schubert (UCLA)
The dynamics of synchronous rotation and physical librations are revisited in order to establish a general framework applicable to a variety of problems. The orientation matrix of the body is decomposed around the equilibrium state into perfectly synchronous rotation and deviation. The normal modes of the linearized equations are computed in the case of a circular satellite orbit, yielding both the periods and the eigenspaces of three librations. Libration in longitude decouples from the other two, vertical modes. First, there is a fast vertical mode, with a period very close to the average rotational period. It corresponds to tilting the body around a horizontal axis while retaining nearly principal-axis rotation. In the inertial frame, this mode appears as nutation and free precession. The other, a slow vertical mode, is the free wobble. The effects of orbital inclination are investigated from the point of view of Cassini states. Orbital eccentricity has a surprisingly large effect on physical librations due to an interaction between free precession and wobble. A perturbation theory is outlined to explain the nature of the interaction.
The author(s) of this abstract have provided an email address for comments about the abstract: varadi@ucla.edu
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.