Proceedings of the International Astronomical Union

Contributed Papers

Radio interferometric tests of general relativity

E. B. Fomalonta1 and S. Kopeikina2

a1 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA email:

a2 Dept. of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA email:


Since VLBI techniques produce a microarcsecond positional accuracy of celestial objects, tests of GR using radio sources as probes of a gravitational field have been made. We present the results from two recent tests using the VLBA: in 2005, the measurement of the classical solar deflection; and in 2002, the measurement of the retarded gravitational deflection associated with Jupiter. The deflection experiment measured γ to an accuracy of 3 × 10−4; the Jupiter experiment measured the retarded term to 20% accuracy. The controversy over the interpretation of the retarded term is summarized.


  • gravitation;
  • techniques: interferometric;
  • astrometry