Environmental stability of MEMS gravimeters.

Wee-g is a new gravimeter that utilises a micro-electromechanical system (MEMS) sensor. The use of MEMS-based sensors has benefits as a new gravimetry technology because the low cost of the base material silicon and accessibility of manufacturing facilities will enable increased availability of gravimeters. However, the challenge of working with silicon for a gravimetry device is its thermal sensitivity, which affects the Young's Modulus of the material. In the context of Wee-g's sensor design, when the flexures that support the proof mass become softer because of temperature changes, under gravity the proof mass change position. Changes to the ambient pressure can also result in changes to the proof mass position. Wee-g has a thermal control system that effectively controls the temperature at the sensor to within 1mK, but field observations indicate that large changes to ambient environmental conditions can be coupled to the sensor output. Here we present the results of environmental stability tests conducted on a Wee-g field prototype with implications for its performance in field environments that vary in temperature and pressure significantly.