Torsion pendulum facility for ground testing of gravitational sensors for LISA

Abstract

We report here on a torsion pendulum facility for ground-based testing of the Laser Interferometer Space Antenna (LISA) gravitational sensors. We aim to measure weak forces exerted by a capacitive position sensor on a lightweight version of the LISA test mass, suspended from a thin torsion fibre. This facility will permit measurement of the residual, springlike coupling between the test mass and the sensor and characterization of other stray forces relevant to LISA drag-free control. The expected force sensitivity of the proposed torsion pendulum is limited by the intrinsic thermal noise at ≈3 × 10−13 N Hz−1/2 at 1 mHz. We briefly describe the design and implementation of the apparatus, its expected performance and preliminary experimental data.