Improved determination ofγby VLBI

Abstract

Aims. This study revisits the estimate of the post-Newtonian relativistic parameter γ reported previously. We use (i) improved geophysical and astronomical modeling in the analysis software package, and (ii) a higher number of observations, a large part of which come from a relatively small number of VLBA experiments at 8 GHz. Methods. We analyzed more than seven million group delays measured by very long baseline interferometry between August 1979 and August 2010. The parameter γ was least squares fitted to delays as a global parameter over the entire observational time period. Results. The most complete solution of this study yielded γ = 0.99992 ± 0.00012, whereas it was 0.99984 ± 0.00015 in our 2009 paper. The item (i), which is recognized as important for geodesy and reference frame realization, provides estimates of |γ − 1| that are smaller than 10 −4 . As expected, the formal error in γ decreases when additional sessions are processed. In particular, we demonstrate that the inclusion of more than 1.7 million observations from the VLBA (mainly from the RDV and VLBA calibrator survey experiments) in the analysis decreases the formal error in the estimate of γ by about 15% with respect to our previous determination.

Post-Newtonian parametersγandβof scalar-tensor gravity with a general potential

“…These include in particular combined VLBI measurements of γ at elongation angles between 5°and 30° [15] and measurements of γ and β using ephemeris for a large number of celestial bodies in the solar system [16]. One may argue that also the measurements of γ listed above cannot be characterized by a single interaction distance, since the distance between the Sun and the radio signals varies along their path.…”

Use of MESSENGER radioscience data to improve planetary ephemeris and to test general relativity

“…In Table 5, comparisons to least squares estimations of other planetary ephemerides or Moon ephemerides like Pitjeva & Pitjev (2013), Konopliv et al (2011), Müller et al (2008, and Williams et al (2009), as well as estimations deduced from VLBI observations Lambert & Le Poncin-Lafitte (2011), are also given. The most stringent published constraint for the PPN parameter γ has been obtained so far during a dedicated phase of the Cassini mission by Bertotti et al (2003).…”

Was Einstein Right? A Centenary Assessment

“…A 2004 analysis of almost 2 million VLBI observations of 541 radio sources, made by 87 VLBI sites between 1979 and 1999 yielded (1 + γ)/2 = 0.99992 ± 0.00023, or equivalently, γ − 1 = (−1.7 ± 4.5) × 10 −4 [62]. Analyses that incorporated data through 2010 yielded γ − 1 = (−0.8 ± 1.2) × 10 −4 [63]. Analysis of observations made by the Hipparcos optical astrometry satellite yielded a test at the level of 0.3 percent, while the GAIA mission, launched in 2013, is expected to reach the parts per million level.…”