A Michelson interferometer system for testing the stability of a piezo-electric actuator intended for use in space

The Laser Interferometer Space Antenna (LISA) experiment will search for gravitational waves generated by cataclysmic events far back in astronomical history. LISA is an interferometer formed by three spacecraft positioned five million km apart, and to observe gravitational waves, it must monitor test mass positions with picometre level resolution. One of the numerous technological challenges is to identify an actuator with appropriate accuracy, precision and stability for positioning of the optical fibres used to deliver LISA's laser sources. We have developed a Michelson interferometer system to determine the temporal and thermal stability of candidate actuators, with an emphasis on characterisation in the milliHertz frequency range required for gravitational wave detection in space. This paper describes the interferometer data logging and calibration and presents preliminary results in the form of a "noise spectrum" generated from the small perturbation of a nominally static mirror. The maximum displacement of the mirror was ∼50 nm with sub-Hz noise levels of 0.1-1 nmHz. This is within the LISA noise specification, and confirms that the apparatus is stable enough for the characterisation of the actuator. © 2007 IOP Publishing Ltd