Updating the Precise Gravity Network at the BIPM

The goal of maintaining an accurate gravity network at the BIPM headquarters is twofold: firstly to support the International Comparison of Absolute Gravimeters (ICAG), and secondly to support the BIPMwatt balance (WB) project, which aims at determining the Planck constant h or realizing a future new definition of the kilogram based on a fixed value of h. In addition the absolute gravitymeasurements, Relative Gravity Campaign (RGC) is organized as part of each ICAG. The BIPM gravity network is characterized by its small size, indoor laboratory conditions, three-dimensional structure, and large number of parallel absolute gravity determinations. Over the last 3 decades, repeated precise horizontal and vertical ties have been measured using relative and absolute gravimeters, and precision leveling has been undertaken regularly to monitor the deformation of the terrain. The ICAG is held every 4 years; the 8th ICAG took place in mid-2009 and for the first time, it was organized as a metrological key comparison as defined by the CIPM MRA. Its results will such constitute a precise and consistent gravity Z. Jiang (*) E.F. Arias L. Tisserand International Bureau of Weights andMeasures (BIPM), Pavillon de Breteuil 92312 SEVRES CEDEX, France e-mail: [email protected] K.U. Kessler-Schulz H.R. Schulz Angewandte Gravimetrie (AG), Rosengarten, Germany V. Palinkas Geodetic Observatory Pecny (GOP), Research Institute of Geodesy, Topography and Cartography, Ondrejov, Czech Republic C. Rothleitner O. Francis University of Luxembourg (UL), Luxembourg, Luxembourg M. Becker (*) Institute of Physical Geodesy, Darmstadt University of Technology (IPGD), Darmstadt, Germany e-mail: [email protected] S. Kenyon et al. (eds.), Geodesy for Planet Earth, International Association of Geodesy Symposia 136, DOI 10.1007/978-3-642-20338-1_32, # Springer-Verlag Berlin Heidelberg 2012 263 reference system in SI units which can be used as the global basis for geodetic and geophysical observations. Additionally, to support the WB project, the network was extended to the BIPM WB laboratory. In this paper, we briefly recall the background of the ICAG/RGC2009 and outline the new characteristics of the updated network, the organization and the performance of the measurements. Finally we present preliminary results from the RGC2009.