Earth Level Research Articles

Mean Earth'S Equipotential Surface From Topex/Poseidon Altimetry

The geopotential value of W 0 = (62 636 855.611 ± 0.008) m 2 s −2 which specifies the equipotential surface fitting the mean ocean surface best, was obtained from four years (1993 - 1996) of TOPEX/POSEIDON altimeter data (AVISO, 1995). The altimeter calibration error limits the actual accuracy of W 0 to about (0.2 - 0.5) m 2 s −2 (2 - 5) cm. The same accuracy limits also apply to the corresponding semimajor axis of the mean Earth's level ellipsoid a = 6 378 136.72 m (mean tide system), a = 6 378 136.62 m (zero tide system), a = 6 378 136.59 m (tide-free). The variations in the yearly mean values of the geopotential did not exceed ±0.025 m 2 s −2 (±2.5 mm).

The Martian Nonhydrostatic Components of Moment-of-Inertia

The author puts forward the proposal in this paper that all the terrestrial planets (Venus, the Earth, and Mars) as well as the Moon deviate from hydrostatic equilibrium to some degree. The Earth's level of deviation of these four celestial bodies is minimum, and that of Mars is maximum. Moreover, the author estimates Martian nonhydrostatic components of the principal moments-of-inertia using five models for the interior of Mars. Comparison with other terrestrial planets shows that setting the range of mean moment-of-inertia ratio, I/MR2, in 0.345 ~ 0.355for Mars is reasonable.

Mean equatorial gravity derived from various geopotential models

Mean equatorial gravity\(\bar g_e \) has been computed from geopotential models GEM-10C, GEM-7, GEM-T1, GEM-T2, GEM-T3, JGM-1, JGM-2, JGM-3 and OSU91A and compared to the normal equatorial gravity, γe=978 032·699 × 10−5 m s−2, computed from four given parameters defining the Earth's level ellipsoid. In all models ge>γe.