Testing of General Relativity with Geodetic VLBI

TL;DR

This study uses geodetic VLBI to measure the Sun's gravitational light deflection, refining the estimate of the parameter 'gamma' in General Relativity to within 0.06% and examining systematic deviations related to the Sun's angular position.

Contribution

The paper presents a new analysis of VLBI data near the Sun that isolates the parameter 'gamma' from elongation angle effects, improving the precision of tests of General Relativity.

Findings

'gamma' is close to unity with 0.06% precision

Systematic deviations depend on angular elongation from the Sun

Short and long baseline data show statistical inconsistencies

Abstract

The geodetic VLBI technique is capable of measuring the Sun's gravity light deflection from distant radio sources around the whole sky. This light deflection is equivalent to the conventional gravitational delay used for the reduction of geodetic VLBI data. While numerous tests based on a global set of VLBI data have shown that the parameter 'gamma' of the post-Newtonian approximation is equal to unity with a precision of about 0.02 percent, more detailed analysis reveals some systematic deviations depending on the angular elongation from the Sun. In this paper a limited set of VLBI observations near the Sun were adjusted to obtain the estimate of the parameter 'gamma' free of the elongation angle impact. The parameter 'gamma' is still found to be close to unity with precision of 0.06 percent, two subsets of VLBI data measured at short and long baselines produce some statistical inconsistency.