Towards a Dynamic Absolute Gravity System

Abstract

We present results from a first stage prototype dynamic absolute gravity system. In contrast to relative instruments which measure differential force, absolute instruments directly measure the gravity field by tracking a freely falling object in an evacuated chamber using a laser interferometer. The measurement method is based on precise standards of time and distance providing an absolutely calibrated system that neither drifts nor tares. Traditionally absolute gravimeters have been used only in static applications. Because these types of instruments provide an absolute value rather than a measured difference, it is desirable to investigate the feasibility of acquiring absolute data from a moving platform. The static absolute gravity instruments use a long period isolation device to remove ground and environmental noise from the interferometer, We present here a prototype system that uses an external sensor rather than an isolation device to record the motion of the fixed interferometer, and incorporates these data directly into the equation of motion to determine the absolute value of gravity, Results indicate the strap-down system shows promise for gravity acquisition from a moving platform and may eventually be superior in terms of price and performance with current spring-based measurement systems. This has important implications in terms of field portable static absolute gravity systems and lays the foundation for absolute gravity acquisition in dynamic environments.