Gravity gradiometer for measuring diagonal components of the gradient tensor

摘要

Disclosed is a system for measuring a gravity gradient tensor. The system comprises of: a gravity gradient sensor (40) with a pair of transversely arranged masses (41, 42) for use in a gravity gradiometer for measuring components of a gravity gradient tensor; a calibration sensor for sensing, at room temperature prior to cryogenic operation of the gravity gradiometer, whether one of the pair of masses associated with the calibration sensor is balanced; and an adjusting mechanism for adjusting the balance of the masses at room temperature prior to cryogenic operation of the gravity gradiometer. The calibration sensor comprises a resonant circuit having an inductor, and a capacitor which has a first plate formed by a surface of one of the masses and a second plate spaced from that surface of one of the masses; and an oscillator for receiving a signal from the resonant circuit and for producing an output signal indicative of the spacing between the first plate and the second plate. In use the calibration sensor produces a signal indicative of the balance of the one of the pair of masses associated with the calibration sensor.