Alexander Kopaev

Micro-gravity investigations for the LNE watt balance project

We report on a micro-gravity survey of the laboratories where the LNEs watt balance experiment is being conducted, including the characterization of the Scintrex CG-5 relative gravimeter used for this study. The results of the survey are compared with a model of the gravity field generated by the local mass distribution. The ultimate goal is to transfer an absolute measurement of g from one room to another with minimal uncertainty.

Results of the Sixth International Comparison of Absolute Gravimeters, ICAG-2001

Like all the previous International Comparisons of Absolute Gravimeters (ICAGs) the sixth, ICAG-2001, was held at the Bureau International des Poids et Mesures (BIPM). Major improvements in the 2001 campaign were a new measurement strategy using the absolute gravimeters to measure the ties of the gravity network, new sites constructed at the BIPM, improved relative measurements of the ties and gravity gradients, and combined adjustment of the absolute and relative data, realized using new software with a novel data weighting and rejection scheme. The g-values at four sites of the BIPM were measured with an uncertainty of 6 μGal. Good agreement was obtained between the results of the absolute and relative measurements of the ties of the gravity network. The final mean gvalue obtained at the reference site A was 7 μGal less than that obtained in the previous comparison, ICAG-97.

Microgravimetric measurements at the 1994 International Comparison of Absolute Gravimeters

On the occasion of the fourth International Comparison of Absolute Gravimeters carried out at Sevres in 1994 an extensive series of microgravimetric measurements was organized. In total, fifteen LaCoste, four Scintrex CG-3M and one Sodin gravimeter measured, within a small network, vertical gravity gradients and a calibration baseline. The results show that the accuracy for single instruments is in the range of 3 μGal to 5 μGal in gravity difference, for the Scintrex and the LaCoste meters. Data from the series were also used to intercompare different ways of calibrating the gravimeter electrostatic feedback systems. The calibration platform of the Institut fur Angewandte Geodasie, (IFAG), Frankfurt, and the calibration lift of the Observatoire Royal de Belgique (ORB) were installed at Sevres and the results compared with those for the calibration line. This paper gives the first results and a review of the techniques used.

Observations of crustal tide strains in the Elbrus area

Results of observations of tidal strains of the crust in the tectonically active Elbrus area of the Northern Caucasus carried out with the use of the Baksan SSAI laser interferometer strainmeter over the period from 2003 through 2006 are presented. Harmonic analysis is performed with the help of the ETERNA software package. Statistically significant time variations in the amplitudes of the main tidal waves M2 and O1 are revealed. The influence of the topography on tidal strains in the Baksan gorge is estimated at 22% (an increase in the measured strain values). The reduced amplitude factors of the main diurnal (O1) and semidiurnal (M2) waves are underestimated. Numerical modeling of tidal anomalies produced by regional heterogeneous inclusions is performed in a 2-D approximation. The observed anomaly of the M2 wave (12%) is shown to be due to the influence of the main magma-controlling fault associated with the deep magma source of the Elbrus dormant volcano.

Observation of Luni-Solar Tides by the Long Base Laser Interferometer

Results of observations of tidal strains of the crust in the tectonically active region of the Northern Caucasus (the Elbrus mountain area) carried out with the use of the Baksan laser interferometer strainmeter over the period from 2003 through 2006 are presented. Harmonic analysis is performed with the help of the ETERNA software package. Statistically significant time variations in the amplitudes of the main tidal waves M2 and O1 are revealed. The influence of the Baksan canyon topography on tidal strains is estimated at 22% (an increase in the measured strain values). The reduced amplitude factors of the main diurnal O1 and semidiurnal M2 waves are underestimated. Numerical modeling of tidal anomalies produced by regional heterogeneous inclusions is performed in a 2–D approximation. The observed anomaly of the M2 wave (12%) is shown to be due to the influence of the main magmacontrolling fault associated with the deep magma source of the Elbrus dormant volcano.

LINGRAN-100: Laser middle-base interferometric gravitational antenna

The goal of the project is the construction of a wideband gravitational gradiometer based on a laser 100-m Fabry- Perot-Michelson interferometer on free masses in deep rock surroundings. The device is aimed at registering bursts of gravitational radiation with an amplitude of the dimensionless metric variations as small as 10-21 in the frequency range 102 - 103 Hz. The auxiliary purpose is to measure low-frequency variations of the Earth gravity gradients bearing information on the internal dynamics of our planet. The deep under-rock position of the installation inside tunnels of Baksan Neutrino Observatory provides a two-order of magnitude decrease in the geophysical noise level which allows the combination of parallel astrophysical and geophysical studies. For geophysics, the long-based interferometer with hanging mirrors presents a new type of geophysical instrument--an angular gravity gradiometer at low frequencies 10-4 - 10-5 Hz with a resolution of 10-8 - 10-10 rad, which is enough to register weak geodynamical perturbations due to oscillations of the Earth interiors.