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The Sixth International Comparison of Absolute Gravimeters was held from 5 June to 28 August 2001 at the Bureau International des Poids et Mesures (BIPM), Sèvres. Seventeen absolute gravimeters were used to make measurements at five sites of the BIPM gravity network. The vertical gravity gradients at the sites and the ties between them were also measured using seventeen relative gravimeters. For the first time the ties were also measured using absolute gravimeters. Various methods of processing the absolute and relative data were tested to calculate the results. The final results of ICAG-2001 are presented. The acceleration due to gravity at a height of 0.90 m is given as (980 925 701.2 ± 5.5) µGal* and (980 928 018.8 ± 5.5) µGal for sites A and B, respectively,

The Bureau International des Poids et Mesures (BIPM), Sèvres, France, hosted the 7th International Comparison of Absolute Gravimeters (ICAG) and the associated Relative Gravity Campaign (RGC) from August to September 2005.ICAG 2005 was prepared and performed as a metrological pilot study, which aimed:(1) To determine the gravity comparison reference values;(2) To determine the offsets of the absolute gravimeters; and (3) As a pilot study to accumulate experience for the CIPM Key Comparisons.This document presents a complete and extensive review of the technical protocol and data processing procedures. The 1st ICAG-RGC comparison was held at the BIPM in 1980-1981 and since then meetings have been organized every 4 years.In this paper, we present an overview of how the meeting was organized, the conditions of BIPM gravimetric sites, technical specifications, data processing strategy and an analysis of the final results. This 7th ICAG final report supersedes all previously published reports.Readings were obtained from participating instruments, 19 absolute gravimeters and 15 relative gravimeters. Precise levelling measurements were carried out and all measurements were performed on the BIPM micro-gravity network which was specifically designed for the comparison.

The basic equations describing the dynamical effects of the Earth's fluid core (Liouville, Navier-Stokes and elasticity equations) are derived for an ellipsoidal earth model without axial symmetry but with an homogeneous and deformable fluid core and elastic mantle.We develop the balance of moment of momentum up t o the second order and use Love numbers t o describe the inertia tensor's variations. The inertial torque takes into account the ellipticity and the volume change of the liquid core. On the core-mantle boundary we locate dissipative, magnetic and viscous torques. In this way we obtain quite a complete formulation for the Liouville equations.These equations are restricted in order to obtain the usual Chandler and nearly diurnal eigenfrequencies.Then we propose a method for calculating the perturbations of these eigenfrequencies when considering additional terms in the Liouville equations.All these results were obtained by applying the balance of moment of momentum to a fluid-filled ellipsoidal cavity within a rigid shell.This theory, developed for over-simplified earth models, was extended to elastic models with more realistic stratification by Jeffreys & Vicente (1957a, b) and Molodensky (1961); these authors considered a spherical elastic mantle without rotation and very simple core models. Numerical integration has shown the existence of a free period about 3 min shorter than the sidereal day (except for model I1 of Jeffreys & Vicente 1957b), which affects through resonance the amplitude of certain diurnal tidal waves and associated nutations.Shen & Mansinha (1976) have extended Molodensky's theory of harmonic oscillations of any order iz and degree m using a less restricted representation of the core response, and making use of the P(r) stability parameter defined by Pekeris & Accad (1972). Their results are in good agreement with Molodensky's in the case of a neutral stratified core (P(r) = 0).