Femto-Newton level testing of free-fall on-ground
Abstract
The concept that particles in free-fall define geodesic reference frames is at the foundation of General Relativity. Free-falling test-masses are crucial to all experiments aimed at directly measuring curvature caused by celestial bodies, like gravitational waves observatories, and to those probing the limits of General Relativity and alternative theories of gravitation. Among those experiments, the Laser Interferometric Space Antenna -LISA -will be the first high sensitivity gravitational wave observatory in space. It aims to observe gravitational waves emitted from galactic and cosmological sources in the frequency range from 0.1 mHz to 0.1 Hz. To meet its scientific goals, LISA requires that the deviation from perfect free-fall be lower than roughly 3 × 10-15 m s-2 Hz-1/2 in the measurement frequency band. This is several orders of magnitude below that achieved by other free-fall experiments. To prove the feasibility of this level of free-fall, a technology demonstration mission, LISA Pathfinder, with goals relaxed by roughly and order of magnitude, is planned and will be launched in 2012. On-ground testing is however essential for the validation of the physical models of the known force disturbances, for the identification of as yet unknown disturbance sources, and for the development of the technology needed for achieving the desired free-fall quality. Torsion pen-dulums are the device of choice for testing surface force disturbances. We have already demon-strated that surface forces acting on the test mass are consistent with the LISA Pathfinder goals. We will report on recent efforts to push the torsion pendulum sensitivity beyond the femto-Newton level, and on interesting results obtained so far in preparation for LISA Pathfinder.
- Publication:
-
38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.3742N