Superconducting gravity gradiometer for space and terrestrial applications

Abstract

A three‐axis superconducting gravity gradiometer with a potential sensitivity better than 10⁻³ Eötvös Hz^−1/2 is currently under development for applications in space. Although such a high sensitivity may be needed for only a limited number of terrestrial applications, superconductivity offers many extraordinary effects which can be used to obtain a gravity gradiometer with other characteristics necessary for operation in a hostile moving‐base environment. Utilizing a number of recently devised techniques which rely on certain properties of superconductors, we have produced a design for a sensitive yet rugged gravity gradiometer with a high degree of stability and a common‐mode rejection ratio greater than 10⁹. With a base line of 0.11 m, a sensitivity of 0.1 Eötvös Hz^−1/2 is expected in an environment monitored to a level of 10⁻² m s⁻² Hz^−1/2 for linear vibration and 7×10⁻⁶ rad s⁻¹ Hz^−1/2 for angular vibration. A conventional stabilized platform can be used at this level. The intrinsic noise level, which is two orders of magnitude lower, could be achieved by monitoring the attitude with a superconducting angular accelerometer which is under development. In addition, the new gradiometer design has the versatility of adapting the instrument to different gravity biases by adjusting stored dc currents.