A double torsion pendulum with two cascade soft degrees of freedom

Year: 2012

Authors: Marconi L., Stanga R., Bassan M.

Autors Affiliation: Università degli Studi di Firenze, INFN Firenze, Italy; Università di Roma Tor Vergata, INFN Roma 2, Italy

Abstract: We report on a double torsion pendulum, where motion along two degrees of freedom (DoFs) is almost free. The Test Mass (TM) is enclosed in a replica of the LISA-Pathfinder electrostatic readout and actuation system. This apparatus is designed to perform extensive ground testing of undesired effects such as leakage of the readout noise from one DoF to another, or actuation cross talks with closed feedback loop. Such investigation is relevant to the noise budget of LISA and LISA-Pathfinder missions, as the TM will be sensitive to weak forces along all 6 degrees of freedom (DoFs). The instrument being developed in Firenze is capable of measuring the forces and stiffnesses acting simultaneously along the 2 soft DoFs. We have completed an upgrade of the apparatus to a definitive configuration and we report on both advances in the commissioning tests and on measurements of residual charge, with the first DoF released.

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KeyWords: Budget control; Data handling; Gravitational effects; Gravity waves; Information analysis; Mechanics; Pendulums; Relativity; Space probes; Torsional stress, Actuation systems; Closed feedback loop; Commissioning test; Degrees of freedom (DoFs); LISA Pathfinder; Measurements of; Residual charge; Two degrees of freedom, Degrees of freedom (mechanics)