MERCURY: LIBRATION, GRAVITATIONAL FIELD AND ITS VARIATIONS

C of its gravitational field are periodic (with period of orbital motion in 87.97 days) and are characterized by the big amplitude of the order 5x10 -8 that in a few orders bigger than corresponding tidal variations of the geopotential coefficients. Librations of Mercury in longitude have been studied on the base of plane model about the motion of non-spherical celestial body with a liquid core in a central gravitational field. For accepted in the paper models of Mercury the amplitudes of periodic librations were evaluated. Due to influence of solar gravitational moments the Mercury angular velocity is varied on 0.03 %. A phenomenon of non- perturbance of Mercury rotation in vicinity of pericenter of orbit has been established. In period about 15 days the angular velocity of Mercury saves almost the permanent value. 2. Mercury models. Here we will consider this planet as ellipsoidal unchangeable body with some model values of the main parameters of its gravitational field 2 J and 22 C and others