Dynamical measurements of the gravitational quadrupole coupling to experimental test masses

This paper reports and discusses the first experimental results obtained using a novel dynamical method for measuring the inertial imbalance -I/I of three reference test masses. Good agreement between experiment and theory is found, and a measurement precision for -I/I of better than one part in 104 is demonstrated. The measured values of -I/I can be converted with high sensitivity into gravitational quadrupolar coupling, e.g. for assessing masses intended for use in equivalence principle experiments. Some future developments for quantifying systematic error are discussed, in order to convert the current level of precision into measurement accuracy.