Precision Accelerometers for Gravity Gradient Measurements

An accelerometer, based on a microwave sapphire resonator, is under development for application in a compact gravity gradiometer. This gravity gradiometer potentially can be used in space gradiometry, precision navigation, and geodesy. The principle of operation of the accelerometer is based on measurements of classical springproof-mass displacements, which are converted to phase shifts in the output signal of a sapphire microwave resonator transducer. A prototype accelerometer has demonstrated a figure of merit sensitivity [Q(djldx)] of 3.9 X 10 MHz/{tm. With a proof mass of 4500 g and a cantilevered beryllium-copper spring having a spring constant of about 60,000 N/m, this result corresponds to the detection of micro-g accelerations for low-frequency «1 Hz) components of the acceleration vector by means of a precision frequency reference source.