The Physical Librations of the Moon Caused by its Tidal Deformation

Abstract

The Moon, like Earth, is not completely solid, and experiences deformation changes, for example due to the tides, caused by the gravitational pull of the Earth's orbit in a complex and resonant nature of the motion of the Moon. It is shown that these deformations lead to temporary variations of Moon inertia tensor components and consequently to the variations in the movement of the poles of the Moon, as well as to the variations of axial rotation. The indicated variations module is in the order of 10--12 mas (millisecond of arc). There variations are important for the development of the high-precision theory of lunar physical libration, suitable for modern projects for the reclamation of the Moon, in particular the Japanese project ILOM, which contemplates installing the telescope on the lunar surface and determining its orientation accuracy of the order of 1--0.1 msd, as well as the Russian lunar program, providing the launch of five automatic stations to the Moon in 2019--2024