On the implications of the Galactic aberration in proper motions for the Celestial Reference Frame

During the last few years, much attention has been paid to the astrometric implications of the galactic aberration in proper motions (GA). This effect causes systematic errors in astrometric measurements at a mu as level. Some authors consider it so serious that it requires redefinition of the Celestial Reference Frame (CRF). We argue that such attention to the GA is exaggerated too much. It is just a small astrometric correction that must be taken into account during highly accurate astrometric and geodetic data processing. The accuracy of this correction depends on the accuracy of the Galactic rotation parameters and, for most applications, on the accuracy of the rotation matrix between Galactic and equatorial systems. Our analysis has shown that our current knowledge of these two factors is sufficient to compute the correction of the GA with an accuracy better than 10 per cent. The remaining effect at the level of a few tenths mu as yr(-1) is negligible nowadays. Another consequence of introducing the GA correction is the necessity to return to classical astrometric modelling of the extragalactic radio source position -derived by very-long-baseline interferometry (VLBI) - by the linear trend model. Changing the current paradigm of the VLBI-derived CRF, based on the assumption of zero motion of radio sources, to classical one leads to bias in the radio source positions of up to several tens of mu as for a catalogue at epoch J2000.0.