Position sensors for LISA drag-free control

The extreme level of isolation from stray forces required for LISA makes the development of 'drag-free control' technologies essential to the mission. We report here on the progress in the development of a capacitive, six degree-of-freedom, position sensor designed to meet the required low levels of position read-out noise (1 nm Hz −1/2 ) and stray force noise (3 × 10 −15 N Hz −1/2 ) across the LISA bandwidth of 0.1 mHz to 0.1 Hz. In this paper we briefly discuss sensor design and expected performance before presenting preliminary noise measurements made with a prototype sensor.