Estimation of the acceleration of the solar-system barycenter relative to a system of reference quasars

It is shown that geodetic VLBI observations can be used to estimate the external acceleration of the barycenter of the solar system. This relies on the fact that, in special relativity, the acceleration of the motion of a coordinate origin relative to reference points leads to a drift in the secular aberration, manifest as systematic proper motions of the reference points in the direction of the acceleration vector. The VLBI time-delay equation is modified such that the acceleration vector appears in explicit form. Formulas for a new form of the fundamental VLBI equation and its partial derivative with respect to the acceleration are presented.