Free librations of the moon determined by an analysis of laser range measurements

摘要: Among the lunar laser range measurements obtained during past six years at McDonald Observatory, those available cover period August 1969-November 1974, being 1377 normal observations made on three Apollo reflectors and that of Lunokhod II. The fit these data led to a rms residual 55 cm. In this study, large number parameters have been resolved, including geocentric coordinates telescope, selenocentric each reflectors, as well orbital elements Moon. addition, interest has directed more specially towards study rotational motion Moon particularly problem its free librations. performed resolutions give evidence modes oscillations. determined amplitudes arise 1″.7 in longitude 0″.5 8″.7 latitude, with respective periods 2.9 years, 27.3 days 75 years. connection parameters, fittings also most part gravitational field: moment inertia parametersβ andγ, third degree harmonics. These new results should now permit research implications oscillations effects, concerning impact history properties internal structure. On basis here, one can already estimate an order magnitude for theQ dissipation coefficient comparable from seismic studies