MultiView phase corrections at low frequencies for precise astrometry

Abstract

We present a multi-calibrator solution, i.e. MultiView, to achieve accurate astrometry on the level of the thermal noise at low VLBI frequencies dominated by ionospheric residuals. We demonstrate on L-band VLBA observations how MultiView provides superior astrometry to conventional phase referencing techniques (Rioja et al. 2017). We also introduce a new trial method to detect antenna based systematic errors in the observations (Orosz et al. 2017}. All presented methods and results are based on our recent papers (Orosz et al. 2017; Rioja et al. 2017).