Improved VLBI measurement of the solar system acceleration

Aims. We propose new estimates of the secular aberration drift, which is mainly caused by the rotation of the solar system about the Galactic center, based on up-to-date VLBI observations and improved method of outlier elimination. Methods. We fitted degree-2 vector spherical harmonics to the extragalactic radio source proper motion field derived from geodetic VLBI observations during 1979-2013. We paid particular attention to the outlier elimination procedure that removes outliers from (i) radio source coordinate time series and (ii) the proper motion sample. Results. We obtain more accurate values of the Solar system acceleration than in our previous paper. The acceleration vector is oriented towards the Galactic center within similar to 7 degrees. The component perpendicular to the Galactic plane is statistically insignificant. We show that an insufficient cleaning of the data set can lead to strong variations in the dipole amplitude and orientation, and hence to statistically biased results.