  Geodetic Very Long Baseline Interferometry (VLBI) measures the group delay in
the barycentric reference frame. As the Earth is orbiting around the Solar
system barycentre with the velocity $V$ of 30 km/s, VLBI proves to be a handy
tool to detect the subtle effects of the special and general relativity theory
with a magnitude of $(V/\textrm{c})^2$. The theoretical correction for the
second order terms reaches up to 300~ps, and it is implemented in the geodetic
VLBI group delay model. The total contribution of the second order terms splits
into two effects - the variation of the Earth scale, and the deflection of the
apparent position of the radio source. The Robertson-Mansouri-Sexl (RMS)
generalization of the Lorenz transformation is used for many modern tests of
the special relativity theory. We develop an alteration of the RMS formalism to
probe the Lorenz invariance with the geodetic VLBI data. The kinematic approach
implies three parameters (as a function of the moving reference frame velocity)
and the standard Einstein synchronisation. A generalised relativistic model of
geodetic VLBI data includes all three parameters that could be estimated.
Though, since the modern laboratory Michelson-Morley and Kennedy-Thorndike
experiments are more accurate than VLBI technique, the presented equations may
be used to test the VLBI group delay model itself.
