Bassan M, Cavalleri A, De Laurentis M, De Marchi F, De Rosa R, Di Fiore L, Dolesi R, Finetti N, Garufi F, Grado A, Hueller M, Marconi L, Milano L, Pucacco G, Stanga R, Visco M, Vitale S, Weber W J
Dipartimento di Fisica, Università di Roma "Tor Vergata," I-00133 Roma, Italy.
INFN-Sezione Roma2, I-00133 Roma, Italy.
Phys Rev Lett. 2016 Feb 5;116(5):051104. doi: 10.1103/PhysRevLett.116.051104.
A torsion pendulum with 2 soft degrees of freedom (DOFs), realized by off-axis cascading two torsion fibers, has been built and operated. This instrument helps characterize the geodesic motion of a test mass for LISA Pathfinder or any other free-fall space mission, providing information on cross talk and other effects that cannot be detected when monitoring a single DOF. We show that it is possible to simultaneously measure both the residual force and the residual torque acting on a quasifree test mass. As an example of the investigations that a double pendulum allows, we report the measurement of the force-to-torque cross talk, i.e., the amount of actuation signal, produced by applying a force on the suspended test mass, that leaks into the rotational DOF, detected by measuring the corresponding (unwanted) torque.
