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A Solar System Survey of Forced Librations in LongitudeForced librations are periodic rotational rate variations due to gravitational interactions with an orbital partner. We have developed an analytic theory capable of calculating expected amplitudes of forced librations for nonresonant rotators as well as for bodies existing in a spin-orbit resonance. The theory has been applied to 34 solar system bodies, including terrestrial planets, planetary satellites, and the asteroid Eros. Parameters governing libration amplitude are the body s orbital eccentricity, moment difference, and the ratio of its spin rate to its orbital rate. In each case the largest libration amplitude is associated with the forcing frequency 2 (p - 1) n, where n is the orbital mean motion and p is the spin/orbit rate ratio. This dominant frequency is simply semidiurnal as seen from the position of the torquing body. The maximum libration angular amplitude is 1.3 x 10(exp -2) radians for Thebe, and the maximum mean equatorial displacement is 1.4 km for Mimas.
Document ID
20060010023
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Cornstock, Robert L.
(Scripps Institution of Oceanography La Jolla, CA, United States)
Bills, Bruce G.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 23, 2013
Publication Date
September 3, 2003
Publication Information
Publication: Journal of Geophysical Research
Volume: 108
Issue: E9
Subject Category
Geophysics
Funding Number(s)
CONTRACT_GRANT: NRA 00-OSS-01
CONTRACT_GRANT: NAG5-11682
Distribution Limits
Public
Copyright
Other

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