Abstract
Within the framework of the relativity experiment of the ESA/JAXA BepiColombo mission to Mercury, which was launched at the end of 2018, we describe how a test of alternative theories of gravity, including torsion can be set up. Following March et al. (2011), the effects of a non-vanishing spacetime torsion have been parameterized by three torsion parameters, t1, t2, and t3. These parameters can be estimated within a global least squares fit, together with a number of parameters of interest, such as post-Newtonian parameters γ and β, and the orbits of Mercury and the Earth. The simulations have been performed by means of the ORBIT14 orbit determination software, which was developed by the Celestial Mechanics Group of the University of Pisa for the analysis of the BepiColombo radio science experiment. We claim that the torsion parameters can be determined by means of the relativity experiment of BepiColombo at the level of some parts in 10−4, which is a significant result for constraining gravitational theories that allow spacetime torsion.
Highlights
Available experimental findings concerning gravitational interaction indicate that the Einstein’sGeneral Theory of Relativity (GR) is presently the most suitable theory of gravitation
We denote “reference simulation” as the case in which the solution is computed in the standard reference scenario that is described in Section 4.1, which consists in estimating the state vectors of Mercury and the Earth-Moon barycenter (EMB) at the central epoch of the mission (6 plus six parameters) and the relativity parameters, for a total of 21 parameters
We have shown how to account for a possible non-vanishing spacetime torsion in the framework of the Mercury Orbiter Radio science Experiment (MORE) relativity experiment
Summary
Available experimental findings concerning gravitational interaction indicate that the Einstein’sGeneral Theory of Relativity (GR) is presently the most suitable theory of gravitation. Because GR was originally formulated as a theory involving mass distribution at macroscopic level, it is desirable to consider suitable generalizations of GR that include micro-physical processes, which could possibly induce macroscopic effects, to be constrained, in turn, by experiments (cfr., e.g., the discussion in [1]). Because spin averages out at macroscopic level, GR considers that the dynamical behavior of a macroscopic distribution of mass can be described by the energy-momentum tensor of matter alone, which is coupled to the metric gμν of a Riemann spacetime. At the microscopic level, the spin angular momentum plays a role in the dynamics, it must be coupled in some way to spacetime. This fact leads to the formulation of a more general spacetime, the four-dimensional
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