Underground Sagnac gyroscope with sub-prad/s rotation rate sensitivity: Toward general relativity tests on Earth

Measuring in a single location on Earth its angular rotation rate with respect to the celestial frame, with a sensitivity enabling access to the tiny Lense-Thirring effect, is an extremely challenging task. GINGERINO is a large frame ring laser gyroscope, operating as free running and unattended inside the underground laboratory of the Gran Sasso, Italy. The main geodetic signals, i.e., annual and Chandler wobbles, daily polar motion, and length of the day, are recovered from GINGERINO data using standard linear regression methods, demonstrating a sensitivity approaching tens of frad/s, therefore close to the requirements for Earth-based Lense-Thirring and Lorentz violation tests.