Measurement of the Solar Gravitational Deflection of Radio Waves using Geodetic Very-Long-Baseline Interferometry Data, 1979 1999

We used very-long-baseline interferometry (VLBI) to measure the deflection by the Sun of radio waves emanating from distant compact radio sources. This bending is characterized in the parametrized post-Newtonian formalism by γ, which is unity in general relativity. Using a large geodetic VLBI data set, we obtained γ=0.9998₃±0.0004₅ (estimated standard error). We found no systematic biases from our analysis of subgroups of data.