The national network of permanent gravimeters is one of the Résif’s specific actions.
The set of permanent Résif gravimeters consists of superconducting (also called cryogenic) gravimeters.
- A superconducting gravimeter that has continuously measured the temporal variations of gravity on the historical site of the Gravimetric Observatory of Strasbourg (fort J9) since October 1987. Currently, the instrument is a GWR iOSG #23 model which was installed in February 2016 thanks to the support of Résif. It is monitored by the Ecole et observatoire des sciences de la Terre (Eost).
- The iGrav #2 instrument was installed on the Larzac plateauin May 2011. It is managed by the OSU Oreme (Observatoire de recherche méditerranéen de l’environnement). This instrument’s main objective is to determine water storage variations in a karstic system in combination with other geophysical measurements.
- The Laboratoire National de Métrologie et d’Essais (LNE) site in Trappes has been equipped with iGrav #5 since February 2013, as part of the Kibble balance project (formerly watt balance). The latter project allows the Planck constant to be determined via the conversion between mechanical and electrical power and has been used in the new definition of the kilogram since 2018. It is managed by the Paris Observatory.
- The iOSG #24 GWR gravimeter was installed at the Low Noise Subterranean Laboratory (LSBB) in Rustrel in October 2015 as part of the Equipex Miga, whose main objective is to construct an atomic interferometer to observe the Earth’s gravitational field and provide a new tool to detect gravitational waves.
These different instruments are part of the International Geodynamics and Earth Tide Service (Igets, http://igets.u-strasbg.fr) the objective of which is the measurement, archiving and distribution of long time series of superconducting gravimeters, inclinometers and extensometers, etc. Eost hosts the central office of Igets and, as an Analysis Centre, produces level 2 data (data pre-processed to allow tidal analyses) and level 3 data (residues after geophysical corrections).
The article on the evolution of gravimetry services in Resif’s Newsletter n°16 (June 2019 – French)
Domain : Gravimetry
Instrumentation : Permanent
Steering : Ecole et observatoire des sciences de la Terre, Eost (Strasbourg)
Supervisor and contact : Jean-Paul Boy, Eost
Members : Observatoire de Paris Meudon (OBSPM), Oreme, LSBB
The iOSG superconducting gravimeter of the Strasbourg Gravity Observatory © Nolwenn Portier, Eost. To know more about it