Abstract
The spacetime around Earth is a good environment in order to perform tests of gravitational theories. According to Einstein’s view of gravitational phenomena, the Earth mass-energy content curves the surrounding spacetime in a peculiar way. This (relatively) quiet dynamical environment enables a good reconstruction of geodetic satellites (test masses) orbit, provided that high-quality tracking data are available. This is the case of the LAGEOS satellites, built and launched mainly for geodetic and geodynamical purposes, but equally good for fundamental physics studies. A review of these studies is presented, focusing on data, models, and analysis strategies. Some recent and less recent results are presented. All of them indicate general relativity theory as a very good description of gravitational phenomena, at least in the studied environment.
Highlights
The general theory of relativity by Albert Einstein is nowadays the most precise description of the gravitational dynamics we have at our disposal
The values can be seen in the fourth column of Table 1: given a typical satellite laser ranging (SLR) Normal Point precision of ≃1 mm, we can notice that the Schwarzschild signal is well above the noise, while the gravitomagnetic one is barely above it
While in general geodetic and geophysical problems often the majority of model parameters are estimated, in the analyses only few of them were estimated, namely, those most directly related to the particular orbit of the satellites; the other parameters were selected as consider parameters, that is, ones which are already known with sufficient accuracy from other sources
Summary
The general theory of relativity by Albert Einstein is nowadays the most precise description of the gravitational dynamics we have at our disposal. The LAGEOS are target for laser pulses sent from ground stations, used to calculate their instantaneous distance (range); the outstanding precision of this tracking technique, named satellite laser ranging (SLR), allows a precise determination of their orbits This can be done with dedicated procedures and a fine modelling of their dynamics. It is possible to exploit the same data to perform fundamental physics tests, by comparing the (measured and reconstructed) orbit with the ones predicted by several, competing, gravitational theories This very simple objective requires a number of steps to be performed, which will be described in the following. This is especially true since the sought for signals often lie several orders of magnitude below the “competitive” signals
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