ИСТИНА

The report provides an overview of the use of compact extragalactic radio sources to build the celestial reference frames. Decades of observations have revealed a systematic (unrecoverable by increasing sample) error component in measurements of coordinates of quasars. It is explained by the structure of radio sources, and can be taken into account when changing the measurement model. Further improvement in the accuracy of observations with assuming the existence of apparent motion now allows to explore very subtle kinematic effects, for example, the absolute acceleration of the Sun moving in the Galaxy.