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We present the results of tests that demonstrate the functionality and performance of the test-mass discharge system for LISA and LISA Pathfinder. In space, the LISA and LISA Pathfinder test-masses will accumulate charge from energetic charged particles. Using the photoelectric effect, a system of ultra-violet (UV) illumination will discharge the test masses. Testing of this UV discharge system, integrated with the LISA Pathfinder engineering model sensor in the torsion pendulum facility at the University of Trento has shown that: isolated test-masses can be charged positively or negatively using UV light; the rate of charging can be measured and is proportional to the UV power; the test-mass charge can be continuously held near zero with a combination of light illuminating the test mass and the surrounding sensor housing, without introducing excess force noise above the pendulum detection limit. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A four mass torsion pendulum facility for testing of the LISA GRS is under development in Trento. With a LISA-like test mass suspended off-axis with respect to the pendulum fiber, the facility allows for a direct measurement of surface force disturbances arising in the GRS. We present here results with a prototype pendulum integrated with very large-gap sensors, which allows an estimate of the intrinsic pendulum noise floor in the absence of sensor related force noise. The apparatus has shown a torque noise near to its mechanical thermal noise limit, and would allow to place upper limits on GRS related disturbances with a best sensitivity of [formula] at 1mHz, a factor 50 from the LISA goal. Also, we discuss the characterization of the gravity gradient noise, one environmental noise source that could limit the apparatus performances, and report on the status of development of the facility. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]