[G07-5] GGOS observations: VLBI

[G07-5-01] The VLBI Global Observing System and its link to GGOS

^○Axel Nothnagel¹, Dirk Behrend², Hayo Hase³, Arthur Niell⁴, Bill Petrachenko⁵, Gino Tuccari⁶ (1.University of Bonn, Bonn, Germany, 2.NVI Inc., Greenbelt MD, USA, 3.BKG/AGGO, Wettzell/La Plata, Germany/Argentina, 4.Haystack Observatory, Westford MA, USA, 5.Dominion Radio Observatory, Penticton, Canada, 6.IRA/INAF, Noto, Italy)

The International VLBI Service for Geodesy and Astrometry (IVS) and its infrastructure constitutes one of the fundamental components of GGOS for two main reasons: VLBI is unique in its ability to determine UT1-UTC and the Earth's rotation axis in space (precession/nutation), and it is one of the two techniques to define the scale of the terrestrial reference frame. The latter quantity is tightly connected to the IVS observing network with its precise station coordinates and velocity components. Starting about five years ago, the IVS began implementing the new VGOS concept (VLBI Global Observing System) of fast slewing telescopes enabling a better sampling of the atmosphere and its refraction effects. Experience has been gathered from the on-going developmental sessions, and some preliminary results are available from these measurements. On the other side, the legacy network is still contributing results with very good long term stability. The observational data and the results of the IVS Analysis Centers are kept on openly accessible servers and, thus, form an indispensable contribution to the GGOS project.