Exploration of VGOS station position estimates and the signals within

Over the past decade, the IVS has undertaken enormous efforts to modernize its infrastructure under the VGOS (VLBI global observing system) umbrella in order to meet the objectives set forth by GGOS. Key feature are smaller, faster antennas to facilitate a better sky coverage, equipped with broad-band receivers observing between 2-14 GHz to reach a better signal-to-noise ratio. Another innovation of VGOS are twin telescopes, i.e. two VGOS antennas at the same location, separated only by dozens of meters. Currently three pairs are deployed. And all VGOS antennas, with the exception of a small number, are co-located with a legacy antenna.

The results of the fist years of VGOS observations are unprecedented in their accuracy, especially in regards of the station positions. However, this now unveils previously unknown or unnoticed systematics, signals hidden by the noise, or signals which remained unmodeled as they were considered to small to rise to significance.

In this study, we focus on the station positions of VGOS antennas and their residuals, compare them to their twins, and to the respective legacy antennas. We discuss the impact and origin of until now unseen signals, and explore possible methods to model and/or mitigate them to reach the highest possible accuracy.