title: Approaching Free Fall on Two Degrees of Freedom: Simultaneous Measurement of Residual Force and Torque on a Double Torsion Pendulum.
abstract: 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.
authors.affiliation: Dipartimento di Fisica, Università di Roma "Tor Vergata," I-00133 Roma, Italy.|INFN-Sezione Roma2, I-00133 Roma, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Bassan
authors.affiliation: CNR-Istituto di Fotonica e Nanotecnologie, - Fondazione Bruno Kessler, 38123 Povo (TN), Italy.
authors.forename: A
authors.initials: A
authors.lastname: Cavalleri
authors.affiliation: Dipartimento di Fisica, Università di Napoli "Federico II," I-80126 Napoli, Italy.|INFN-Sezione di Napoli, I-80126 Napoli, Italy.
authors.forename: M
authors.initials: M
authors.lastname: De Laurentis
authors.affiliation: Dipartimento di Fisica, Università di Roma "Tor Vergata," I-00133 Roma, Italy.|INFN-Sezione Roma2, I-00133 Roma, Italy.
authors.forename: F
authors.initials: F
authors.lastname: De Marchi
authors.affiliation: Dipartimento di Fisica, Università di Napoli "Federico II," I-80126 Napoli, Italy.|INFN-Sezione di Napoli, I-80126 Napoli, Italy.
authors.forename: R
authors.initials: R
authors.lastname: De Rosa
authors.affiliation: INFN-Sezione di Napoli, I-80126 Napoli, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Di Fiore
authors.affiliation: Dipartimento di Fisica, Università di Trento, I-38050 Povo (TN), Italy.|INFN-TIFPA, 38050 Povo (TN), Italy.
authors.forename: R
authors.initials: R
authors.lastname: Dolesi
authors.affiliation: Dipartimento di Scienze Fisiche e Chimiche, Università degli Studi dell'Aquila, I-67100 l'Aquila, Italy.|INFN-Sezione di Firenze, I-50019 Firenze, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Finetti
authors.affiliation: Dipartimento di Fisica, Università di Napoli "Federico II," I-80126 Napoli, Italy.|INFN-Sezione di Napoli, I-80126 Napoli, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Garufi
authors.affiliation: INFN-Sezione di Napoli, I-80126 Napoli, Italy.|INAF-Osservatorio Astronomico di Capodimonte, I-80126 Napoli, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Grado
authors.affiliation: Dipartimento di Fisica, Università di Trento, I-38050 Povo (TN), Italy.|INFN-TIFPA, 38050 Povo (TN), Italy.
authors.forename: M
authors.initials: M
authors.lastname: Hueller
authors.affiliation: INFN-Sezione di Firenze, I-50019 Firenze, Italy.|Dipartimento di Fisica ed Astronomia, Università degli Studi di Firenze, I-50019 Firenze, Italy.
authors.forename: L
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authors.lastname: Marconi
authors.affiliation: Dipartimento di Fisica, Università di Napoli "Federico II," I-80126 Napoli, Italy.|INFN-Sezione di Napoli, I-80126 Napoli, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Milano
authors.affiliation: Dipartimento di Fisica, Università di Roma "Tor Vergata," I-00133 Roma, Italy.|INFN-Sezione Roma2, I-00133 Roma, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Pucacco
authors.affiliation: INFN-Sezione di Firenze, I-50019 Firenze, Italy.|Dipartimento di Fisica ed Astronomia, Università degli Studi di Firenze, I-50019 Firenze, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Stanga
authors.affiliation: INFN-Sezione Roma2, I-00133 Roma, Italy.|INAF-Istituto di Astrofisica e Planetologia Spaziali, I-00133 Roma, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Visco
authors.affiliation: Dipartimento di Fisica, Università di Trento, I-38050 Povo (TN), Italy.|INFN-TIFPA, 38050 Povo (TN), Italy.
authors.forename: S
authors.initials: S
authors.lastname: Vitale
authors.affiliation: Dipartimento di Fisica, Università di Trento, I-38050 Povo (TN), Italy.|INFN-TIFPA, 38050 Povo (TN), Italy.
authors.forename: W J
authors.initials: WJ
authors.lastname: Weber