Contribution to the global VGOS network by potential sites in South America

Abstract

Very-long-baseline interferometry (VLBI) networks have historically lacked enough antennas to densify the southern hemisphere adequately. This situation not only impacts directly the realization of the Celestial Reference System but also the determination of the Earth Orientation Parameters (EOP). In the last years, a significant step in the modernization of the VLBI infrastructure has been taken with the VLBI Global Observing System (VGOS). However, the distribution of VGOS antennas is still far from being homogeneous. In this work, we used the software VieSched++ for VLBI scheduling to simulate nine new VGOS arrays. These networks, which are more dense in the southern hemisphere and focus on South America, were planned considering existing geodetic sites where a VGOS antenna could be added and new sites where the installation is feasible. We compared the statistical performance of the proposed networks with that of a simulated standard VGOS network and the actual VGOS performance for the last 2 years. A more uniform station distribution does not seem to be associated with better repeatabilities for station coordinates, but the results for EOP and source coordinates improve as expected.