The main porpouse of G-GranSasso-DS has been to define in detail the guidelines and principal specifications for an experiment to measure the earth gravitomagnetism with 1% of accuracy. Lageos and Gravity Probe B have measured this quantity with 10% and 19% of accuracy; Lares, which has been launched at the beginning of March 2012, will improve the measurement going down to 1-2% of accuracy. The proposed experiment is very different from the other since it is earth based and uses the light as a probe. The proposed experiment is based on the use of ring-lasers, top precision sensors to measure angular velocity.
Our group has built a prototype ringlaser, G-Pisa; which has been used to measure tilt of the ground, near the suspension of mirrors, in the central part of the Virgo interferometric antenna, during the last scientific runs. G-Pisa is an absolute angular velocity sensor, able to work for months without interruption with sensitivity in the nrad / s / sqrt (Hz). After writing the Design Study, this group has moved to Group 2, where the experiment continues as G-GranSasso-RD. Our Design Study has been published in Phys. Rev. D.