Testing general relativity with geodetic VLBI

What a single, specially designed experiment can teach us

¹ Geoscience Australia, PO Box 378 Canberra, ACT, 2601 Australia
e-mail: oleg.titov@ga.gov.au
² Department of Geodesy and Geoinformation, Research Group Advanced Geodesy,TU Wien, Gusshausstraße 27-29/E120.4, Wien, 1040 Austria
³ SYRTE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, LNE, Paris, France
⁴ University of Tasmania, Private Bag 37, Hobart, Tasmania, 7001 Australia
⁵ Hartebeesthoek Radio Astronomy Observatory, PO Box 443 Krugersdorp, 1740 South Africa
⁶ Shanghai Astronomical Observatory, 80 Nandan Road, Shanghai, 200030 PR China
⁷ Institute of Applied Astronomy, Kutuzov Embankment, 10, Saint-Petersburg, 191187 Russia
⁸ National Geographic Information Institute, Space Geodetic Observatory, PO Box 30060 Sejong, South Korea
⁹ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109 USA

Received: 21 May 2018
Accepted: 26 June 2018

Abstract

Context. We highlight the capabilities of geodetic VLBI technique to test general relativity in the classical astrometric style, i.e. measuring the deflection of light in the vicinity of the Sun.

Aims. In previous studies, the parameter γ was estimated by global analyses of thousands of geodetic VLBI sessions. Here we estimate γ from a single session where the Sun has approached two strong reference radio sources, 0229+131 and 0235+164, at an elongation angle of 1–3°.

Methods. The AUA020 VLBI session of 1 May 2017 was designed to obtain more than 1000 group delays from the two radio sources. The solar corona effect was effectively calibrated with the dual-frequency observations even at small elongation.

Results. We obtained γ with a greater precision (0.9 × 10⁻⁴) than has been obtained through global analyses of thousands of standard geodetic sessions over decades. Current results demonstrate that the modern VLBI technology is capable of establishing new limits on observational tests of general relativity.