Superconducting Gravimeter Data from Walferdange - Level 1

Report (2020)

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy (IAG). IGETS continues the activities of the Global Geodynamics Project ... [more ▼]

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy (IAG). IGETS continues the activities of the Global Geodynamics Project (GGP, 1997-2015) to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. The Walferdange Underground Laboratory for Geodynamics (WULG) is located at the middle of a long labyrinth of galleries which originally have been established for the commercial extraction of gypsum. Exceptional temperature and humidity stability, the absence of water and human perturbations, distance from the ocean and easy access, were some of the motivations for initially choosing this site for instrumentation and Earth tide research. Instruments to measure the micro deformations produced by the tidal forces have been developed and tested in the Laboratory for more than 30 years. Ground deformations and earthquakes are or have been recorded continuously by means of spring gravimeters, vertical and horizontal pendulums, long base water tube tiltmeters, vertical and horizontal strain meters, short period and broad band seismometers. Meteorological parameters (temperature, humidity and atmospheric pressure), as well as radon gas emissions, are also continuously monitored in various locations within the mine. In 2000, the Minister of Research of the Grand-Duchy of Luxembourg decided to establish a new International Reference Station for Intercomparisons of Absolute Gravimeters (ISIAG). The instrumentation to support the project includes a superconducting gravimeter OSG-CT040, an absolute gravimeter FG5X-216, and other ancillary equipment necessary to support research. In January 2002, a first superconducting gravimeter was installed. The instrument was then stopped in March 2003 due to an abnormally large instrumental drift. In December 2003, it was replaced by a brand-new gravimeter with the same name and which continuously operates since that date. Absolute gravity measurements have been performed on a regular time base to calibrate the superconducting gravimeter and to estimate its instrumental drift. Since 2003, the WULG hosted three European Comparisons and one International Comparison of Absolute Gravimeters. It was the first international comparison outside the walls of the BIPM (Bureau International des Poids et Mesures) in Sèvres (France) where it had traditionally been organized for 30 years. [less ▲]

Regional comparison of absolute gravimeters, EURAMET.M.G-K2 key comparison

in Metrologia (2017), 54(1A), 07012

In the framework of the regional EURAMET.M.G-K2 comparison of absolute gravimeters, 17 gravimeters were compared in November 2015. Four gravimeters were from different NMIs and DIs, they were used to link ... [more ▼]

In the framework of the regional EURAMET.M.G-K2 comparison of absolute gravimeters, 17 gravimeters were compared in November 2015. Four gravimeters were from different NMIs and DIs, they were used to link the regional comparison to the CCM.G.K2 by means of linking converter. Combined least-squares adjustments with weighted constraint was used to determine KCRV. Several pilot solutions are presented and compared with the official solution to demonstrate influences of different approaches (e.g. definition of weights and the constraint) on results of the adjustment. In case of the official solution, all the gravimeters are in equivalence with declared uncertainties. == Main text To reach the main text of this paper, click on Final Report [http://www.bipm.org/utils/common/pdf/final_reports/M/G-K2/EURAMET.M.G-K2.pdf] . Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/ [http://kcdb.bipm.org/] . The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA). [less ▲]

The European Comparison of Absolute Gravimeters 2011 (ECAG-2011) in Walferdange, Luxembourg: results and recommendations

in Metrologia (2013), 50(3), 257

We present the results of the third European Comparison of Absolute Gravimeters held in Walferdange, Grand Duchy of Luxembourg, in November 2011. Twenty-two gravimeters from both metrological and non ... [more ▼]

We present the results of the third European Comparison of Absolute Gravimeters held in Walferdange, Grand Duchy of Luxembourg, in November 2011. Twenty-two gravimeters from both metrological and non-metrological institutes are compared. For the first time, corrections for the laser beam diffraction and the self-attraction of the gravimeters are implemented. The gravity observations are also corrected for geophysical gravity changes that occurred during the comparison using the observations of a superconducting gravimeter. We show that these corrections improve the degree of equivalence between the gravimeters. We present the results for two different combinations of data. In the first one, we use only the observations from the metrological institutes. In the second solution, we include all the data from both metrological and non-metrological institutes. Those solutions are then compared with the official result of the comparison published previously and based on the observations of the metrological institutes and the gravity differences at the different sites as measured by non-metrological institutes. Overall, the absolute gravity meters agree with one another with a standard deviation of3.1 µ Gal. Finally, the results of this comparison are linked to previous ones. We conclude with some important recommendations for future comparisons. [less ▲]

Comparison between the Transfer Functions of three Superconducting Gravimeters

in Marées Terrestres Bulletin d'Informations (2011), 147