Research relative to the development of a cryogenic microwave cavity gradiometer for orbital use

Technical approaches to increase the sensitivity of a non-cryogenic gradiometer toward the goal of 0.001 EU/square root of Hz, with solutions that have the potential of achieving an even more ambitious threshold, such as 0.0001 EU/square root of Hz are discussed. This goal can be achieved with a gradiometer design in which the proof masses are each suspended from two small arms, the torsion of which is directly related to the displacement of the sensing element. A negative-spring action, aimed at reducing the resonance frequency, is provided in this design by means of an external electrostatic field. This configuration of the instrument is also suitable for use in a tensorial arrangement.