Astronomy VLBA campaign MOJAVE used in geodesy

Abstract

The astronomy VLBA campaign MOJAVE-5 monitors jets in AGN with VLBA experiments. We investigate the dataset bl229 observed at 15 GHz in terms of its suitability for geodetic analysis in order to evaluate the MOJAVE-5 experiments to be a testbed for source structure investigations in geodetic and astrometric VLBI. We show that both geodetic metrics, i.e. the baseline length scatter and wrms of Earth orientation parameters are about a factor of 1.5 greater than from the dedicated geodetic dual-band 2.3/8.6 GHz RV and CN experiments conducted contemporary over the time span from September 2016 to July 2020. We isolate three major differences between the two datasets: a) the scheduling approach, b) treatment of the ionospheric delay, and c) selection of target radio sources. We show that the major factor that causes discrepancies between the baseline length repeatability and the EOP wrms is the more agile schedule of geodetic VLBI experiments that includes more scans at low elevations at shorter time intervals than the astronomical experiments. We conclude that MOJAVE-5 providing the baseline length repeatability under 1 ppb includes very low level of systematic errors which confirms this dataset to be an excellent testbed for investigations of source structure on astrometry and geodesy results in full detail.