Testing the local spacetime dynamics by heliospheric radiocommunication methods

H.-J Fahr,M Siewert

doi:10.5194/angeo-26-727-2008

Abstract

Abstract. According to general relativistic theories, cosmological spacetime is dynamic. This prediction is in excellent agreement with the huge majority of astronomical observations on large cosmic scales, especially the observations of cosmological redshifts of distant galaxies. However, on scales of heliospheric distances, verifications of general relativistic effects are based on Schwarzschild metric tests or kinetical corrections, such as the perihelion motion of Mercury, photon deflection at the Sun and gravitational photon redshifts in central gravity fields. As we will show in this paper, there is, however, a chance to detect new cosmologically relevant features on heliospheric scales by careful study of photon propagations in the local spacetime metrics, based on red- or blueshifts as a clear, but up to now overlooked, signature of the local spacetime dynamics. Thus, we propose the challenging possibility of carrying out experiments of cosmological relevance by simply using high-precision radio tracking of heliospheric spaceprobes, as already practised in cases like Pioneer-10/11, Galileo and Ulysses.

Highlights

When radiotracking distant spaceprobes from Earth, one may sooner or later ask the fundamental question, how the freely propagating radiophotons used to trace these objects, as well as the motion of these objects themselves, are affected by the dynamical metrical properties of spacetime that they cross on their geodetics
As we will show in this paper, there is, a chance to detect new cosmologically relevant features on heliospheric scales by careful study of photon propagations in the local spacetime metrics, based on red- or blueshifts as a clear, but up to now overlooked, signature of the local spacetime dynamics
Another test of the general relativistic perturbation of local space is measuring the Lense-Thirring effect, for which an experimental method has been proposed by Ciufolini (1986) and observationally carried out by Bertotti et al (1987) who analysed lunar-LASER-ranging data to observe the geodetic lunar perigee precession and found this precession velocity to be within an accuracy of 10% to the predicted value of 19.2 ms/year (Mueller et al, 1991)

Summary

Introduction

When radiotracking distant spaceprobes from Earth, one may sooner or later ask the fundamental question, how the freely propagating radiophotons used to trace these objects, as well as the motion of these objects themselves, are affected by the dynamical metrical properties of spacetime that they cross on their geodetics. Despite an increasing number of successful general relativistic tests in the solar system, at least one unknown parameter remains in the model Up to these days, no satisfying connection exists between the global cosmological Robertson-Walker metric describing the expanding universe and gravitationally bound, inhomogeneous systems, such as the solar system. No satisfying connection exists between the global cosmological Robertson-Walker metric describing the expanding universe and gravitationally bound, inhomogeneous systems, such as the solar system This must provoke the question what kind of frequency shift photons experience on intermediate scales, i.e. scales small with respect to cosmic scales, but large with respect to Schwarzschild scales associated with pointlike masses. Siewert: Testing the local spacetime dynamics by heliospheric radiocommunication methods central masses where cosmological effects start to contribute, it is quite possible that additional, previously unmodeled frequency shifts emerge in the solar system. We derive this modified spacetime evolution on local scales

A sketch of modified spacetime evolutions on local scales

Frequency shifts of freely propagating photons

Findings

Conclusions