63 research outputs found
Liquid actuated gravity experiments
We describe a new actuation technique for gravity experiments based on a
liquid field mass. The Characterizing idea is to modulate the gravity force
acting on a test mass by controlling the level of a liquid in a suitable
container. This allows to obtain a periodical gravity force without moving
parts (except the liquid level) close to the TM. We describe in detail the most
relevant aspects of the liquid actuator and discuss how it can be used in
gravity experiments. In particular we analyse an application to test the
inverse square law in the mm to cm distance region
A quasi-complete mechanical model for a double torsion pendulum
We present a dynamical model for the double torsion pendulum nicknamed PETER,
where one torsion pendulum hangs in cascade, but off-axis, from the other. The
dynamics of interest in these devices lies around the torsional resonance, that
is at very low frequencies (mHz). However, we find that, in order to properly
describe the forced motion of the pendulums, also other modes must be
considered, namely swinging and bouncing oscillations of the two suspended
masses, that resonate at higher frequencies (Hz). Although the system has
obviously 6+6 Degrees of Freedom, we find that 8 are sufficient for an accurate
description of the observed motion. This model produces reliable estimates of
the response to generic external disturbances and actuating forces or torques.
In particular, we compute the effect of seismic floor motion (tilt noise) on
the low frequency part of the signal spectra and show that it properly accounts
for most of the measured low frequency noise.Comment: 15 pages, 6 figure
Dark gravitomagnetism with LISA and gravitational waves space detectors
We present here the proposal to use the LISA interferometer for detecting the gravito-
magnetic field due to the rotation of the Milky Way, including the contribution given by
the dark matter halo. The galactic signal would be superposed to the gravitomagnetic
field of the Sun. The technique to be used is based on the asymmetric propagation of
light along the closed contour of the space interferometer (Sagnac-like approach). Both
principle and practical aspects of the proposed experiment are discussed. The strategy
for disentangling the sought for signal from the kinematic terms due to proper rotation
and orbital motion is based on the time modulation of the time of flight asymmetry.
Such modulation will be originated by the annual oscillation of the plane of the interfer-
ometer with respect to the galactic plane. Also the effect of the gravitomagnetic field on
the polarization of the electromagnetic signals is presented as an in principle detectable
phenomenon
Testing gravitation with satellite laser ranging and the LARASE experiment
The International Laser Ranging Service (ILRS) provides range measurements of pas- sive satellites around the Earth through the powerful Satellite Laser Ranging (SLR) technique. These very precise measurements of the distance between an on-ground laser station and a satellite equipped with cube corner retro-reflectors (CCRs) make possible precise tests and measurements in fundamental physics and, in particular, in gravitational physics. The LAGEOS (NASA 1976) and LAGEOS II (NASA/ASI 1992) satellites are outstanding examples of very good test particles because of their very low area-to-mass ratio as well as the high quality of their tracking data and, consequently, of the precise orbit determination (POD) we can obtain after a refined modeling of their orbit. The aim of our research program LARASE (LAser RAnged Satellites Experi- ment) is to go a step further in testing gravitation in the field of Earth by means of the joint analysis of the orbits of the two LAGEOS satellites together with that of the most recently launched LARES (ASI, 2012) satellite. Therefore, our work falls in the so-called weak field and slow motion (WFSM) limit of Einstein’s general relativity (GR) where, in terms of Newtonian physics, relativistic effects appear as two new fields to be added to the classical gravitational field: the gravitoelectric and the gravitomagnetic fields. A fundamental ingredient to reach such a goal is to provide high-quality updated models for the perturbing non-gravitational perturbations (NGP) acting on the surface of these satellites. In fact, regardless of their minimization thanks to a smaller value for the area-to-mass ratio, the subtle and complex to model perturbing effects of the NGP play a crucial role in the POD of the considered satellites, especially in the case of the thermal thrust effects. A large amount of SLR data of LAGEOS and LAGEOS II has been worked out using a set of dedicated models for the satellite dynamics and the related post-fit residuals have been analyzed. A parallel work was performed with LARES, although at a preliminary stage. Our recent work on the orbit modeling and on the data analysis of the orbit of such satellites is presented and discussed
A 1% Measurement of the gravitomagnetic field of the earth with laser-tracked satellites
A new measurement of the gravitomagnetic field of the Earth is presented. The measurement has been obtained through the careful evaluation of the Lense-Thirring (LT) precession on the combined orbits of three passive geodetic satellites, LAGEOS, LAGEOS II, and LARES, tracked by the Satellite Laser Ranging (SLR) technique. This general relativity precession, also known as frame-dragging, is a manifestation of spacetime curvature generated by mass-currents, a peculiarity of Einstein’s theory of gravitation. The measurement stands out, compared to previous measurements in the same context, for its precision (≃7.4×10−3, at a 95% confidence level) and accuracy (≃16×10−3), i.e., for a reliable and robust evaluation of the systematic sources of error due to both gravitational and non-gravitational perturbations. To achieve this measurement, we have largely exploited the results of the GRACE (Gravity Recovery And Climate Experiment) mission in order to significantly improve the description of the Earth’s gravitational field, also modeling its dependence on time. In this way, we strongly reduced the systematic errors due to the uncertainty in the knowledge of the Earth even zonal harmonics and, at the same time, avoided a possible bias of the final result and, consequently, of the precision of the measurement, linked to a non-reliable handling of the unmodeled and mismodeled periodic effects
Testing general relativity vs. alternative theories of gravitation with the SaToR-G experiment
Enhanced Lightweight Design : First Results of the FP7 Project ENLIGHT
© 2016 The Authors. Published by Elsevier B.V. The European Green Vehicle project ENLIGHT aims to advance highly innovative lightweight material technologies for application in structural vehicle parts of future volume produced Electric Vehicles (EVs) along four axes: performance, manufacturability, cost effectiveness and lifecycle footprint. The main target is to develop viable and sustainable solutions for medium production volume up to 50.000 EVs destined to reach the market in the next 8-12 years. The specific objectives of the ENLIGHT project are on holistic and integrated conceptual design and manufacturing concerning how the technologies and materials addressed can be combined into a representative medium-volume EV. The solutions will be demonstrated in five modules: a front module and central floor module, a front door, a sub-frame and suspension system as well as a cross-car beam. In this paper, a summary of the major results obtained up to the 3rd project year will be presented. ispartof: pages:1031-1040 ispartof: Transportation Research Procedia vol:14 pages:1031-1040 ispartof: 6th Transport Research Arena TRA2016 location:Warsaw, Poland date:18 Apr - 21 Apr 2016 status: publishe
Optimizing the Earth-LISA "rendez-vous"
We present a general survey of heliocentric LISA orbits, hoping it might help
in the exercise of rescoping the mission. We try to semi-analytically optimize
the orbital parameters in order to minimize the disturbances coming from the
Earth-LISA interaction. In a set of numerical simulations we include
nonautonomous perturbations and provide an estimate of Doppler shift and
breathing as a function of the trailing angle.Comment: 18 pages, 16 figures. Submitted on CQ
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