Mathematics – Logic
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009dda....40.1305r&link_type=abstract
American Astronomical Society, DDA meeting #40, #13.05; Bulletin of the American Astronomical Society, Vol. 41, p.907
Mathematics
Logic
Scientific paper
The Lunar Laser Ranging experiment has been active since 1969 when Apollo astronauts placed the first retroreflector on the Moon. The data accuracy of a few centimeters, over a time-span of several decades, along with a new numerically integrated ephemeris, DE421, encourages new analysis of the lunar physical librations, and especially the detection of three modes of free physical librations (longitude, latitude, and wobble modes). This analysis was performed by using iteratively a frequency analysis and linear least-squares fit of the wide spectrum of DE421 Moon's physical librations. From this analysis we identified and estimated about 130 terms in the angular series for latitude librations and about 70 terms in the longitude angle and polar coordinates. In this determination, we found the non-negligible amplitude of the three modes of free physical libration. The determined amplitudes become 1.296" in longitude (after correction of two close forcing terms), 0.032" in latitude and 8.196" X 3.312" for the wobble, with the respective periods of 1056.13 days, 8822.88 days (referred to the moving node), and 27257.27 days. The presence of such terms, despite short damping times of 104 to 106 yr, suggests the existence of some source of stimulation acting in geologically recent times.
The research described in this abstract was carried out at the Jet Propulsion Laboratory of the California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Nicolas Rambaux started this research under the Oak Ridge NASA Postdoctoral Program and finished it as an Independent Research Advisor at JPL.
Rambaux Nicolas
Williams James G.
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