Calibration of a superconducting gravimeter: a comparison between the mass attraction method and the use of FG5 absolute gravity measurements

The Superconducting Gravimeter GWR T015 is recording continuously in a laboratory of ENEA (Italian National Institute for Energy Development) at Brasimone site, in the Apennines between Bologna and Florence (Italy). The gravimeter is routinely calibrated by means of a moving mass system with a precision of about 0,3%. In October 1997 a comparison campaign between the absolute gravimeter FG5- 206 of EOST (Ecole et Observatoire des Sciences de la Terre) of Strasbourg and the Superconducting Gravimeter (SC) itself has been performed, in order to verify and to improve the precision of the calibration factor of the SC gravimeter. The seismic noise due to the Umbria-Marche swarm earthquakes didn\\\\\\\'t affect the measurements, and the result of the comparison campaign agrees with the mass system at a level of 0.06%. The calibration constant of the SC gravimeter has been improved by a factor 2.5.