First analyses of the new iOSG-type Superconducting Gravimeters at the J9 Gravimetric Observatory of Strasbourg and at the Low Noise Underground Laboratory of Rustrel, France

Today the instrumental performance of the cryogenic gravity instruments has been further improved by the development of a new generation of superconducting gravimeter (SG): the so-called iOSG which is a superconducting gravimeter designed for observatory purpose with a heavier sphere than previous SGs. A special SG prototype (called OSG-056), with sensor properties intermediate between the compact SG and iOSG, has already been recorded since 2009 at the Black Forest Observatory (BFO, Germany) with promising results in terms of sensitivity. An additional iOSG (iOSG-024) has been installed at the LSSB low background noise underground research laboratory in Rustrel (France), funded thanks to the EQUIPEX MIGA (Matter wave-laser based Interferometer Gravitation Antenna) project and is operational since July 2015.

A new iOSG (iOSG-023) similar to the one operating at the LSBB was installed at the J9 Gravimetric Observatory of Strasbourg and has been recorded since February 2016 in parallel to the old compact SG C026. The iOSG-023 was funded by the EQUIPEX RESIF-CORE (French seismological and geodetic network: the core implementation).

We present the performances of these newly installed instruments in terms of noise levels in the seismic (in the millihertz frequency range) and sub-seismic (below 1 mHz) bands using a standardized procedure based on the computation of the residual power spectral densities over a quiet time period. First tidal analyses and calibration results are also presented.