  Geodetic Very Long Baseline Interferometry (VLBI) data are capable of
measuring the light deflection caused by the gravitational field of the Sun and
large planets with high accuracy. The parameter $\gamma$ of the parametrized
Post-Newtonian (PPN) formalism estimated using observations of reference radio
sources near the Sun should be equal to unity in the general relativity. We
have run several VLBI experiments tracking reference radio sources from 1 to 3
degrees from the Sun. The best formal accuracy of the parameter $\gamma$
achieved in the single-session mode is less than 0.01 percent, or better than
the formal accuracy obtained with a global solution included all available
observations at arbitrary elongation from the Sun. We are planning more
experiments starting from 2020 using better observing conditions near the
minimum of the Solar activity cycle.

Instrumentation and Methods for Astrophysics