A GRAVITATIONAL REFERENCE SENSOR FOR ADVANCED DRAG-FREE SATELLITES

LISA and the next generation of space-based laser interferometers require gravitational reference sensors (GRS) to provide distance measurements with picometer precision. To meet this goal, we describe a stand-alone GRS structure that has high sensitivity and easy integration with a satellite. The stand-alone GRS integrates balanced optical probing of the proof-mass position in its housing, and provides a correlated reference surface to an independent external interferometer. The use of optical sensing allows for a large gap between the proof-mass and housing, which is the best way to reduce many proof-mass disturbances.