Study to Develop Gradiometer Compensation Techniques.

摘要

There are three moving base gravity gradiometers currently under development. The instruments are being develed at the Hughes Research Labs, the Bell Aerospace Corp., and the Charles Stark Draper Lab. The Design goal for each of the sensors is 1 Eotvos Unit (EU). The group includes sensors designed specifically to measure the gravity gradient, as well as sensors which utilize existing accelerometers to provide a gradient estimate. The Hughes and Bell instruments rotate, modulating the information. This rotation transfers the gravity gradient signal to a higher frequency, quieter, portion of the spectrum, and can separate the signal from some sources of instrument bias. The Draper Lab. sensor measures the gradient signal at zero frequency and uses a sophisticated flotation suspension system to isolate the sensing element from errors induced by rotation and jitter. A system of at least three instruments of any one type is required in order to provide a complete gravity gradient tensor estimate. The primary objective of this paper is to define the optimal relative orientations of the three sensors which comprise a minimum gravity gradient measurement system. In addition, the effects of different relative sensor orientations when a fourth, redundant sensor is included, are considered.