Measuring the LISA test mass magnetic properties with a torsion pendulum

Achieving the low frequency LISA sensitivity requires that the test masses acting as the interferometer end mirrors are free-falling with an unprecedented small degree of deviation. Magnetic disturbances, originating in the interaction of the test mass with the environmental magnetic field, can significantly deteriorate the LISA performance and can be parametrized through the test mass remnant dipole moment (m) over right arrow (r) and the magnetic susceptibility chi. While the LISA test flight precursor LTP will investigate these effects during the preliminary phases of the mission, the very stringent requirements on the test mass magnetic cleanliness make ground-based characterization of its magnetic properties paramount. We propose a torsion pendulum technique to accurately measure on the ground the magnetic properties of the LISA/LTP test masses.FORCE NOISE.