International VLBI Service for Geodesy and Astrometry

The International VLBI Service for Geodesy and Astrometry (IVS) is a globally operating service that coordinates and performs Very Long Baseline Interferometry (VLBI) activities through its constituent components, supporting geodetic and astrometric work on reference systems and Earth science research. The service consists of over 80 components, which are supported by about 40 organizations in more than 20 countries. It was established in 1999 as a service of the International Association of Geodesy (IAG) and was recognized as a service of the International Astronomical Union (IAU) a year later. The IVS interacts closely with the International Earth Rotation and Reference Systems Service (IERS), which is tasked by IAU and IUGG (International Union of Geodesy and Geophysics) with maintaining the international celestial and terrestrial reference frames (ICRF and ITRF) and providing Earth orientation parameters (EOP) required to study earth orientation variations and to transform between the ICRF and the ITRF. VLBI is one of the most accurate methods used to measure the Earth and its orientation in space. With the help of international networks of radio telescopes compact radio sources (typically quasars) are observed and their signals used to determine the radio source positions, the Earth orientation parameters, and the positions of the radio telescopes. IVS coordinates VLBI observing programs, sets performance standards for VLBI stations, establishes conventions for VLBI data formats and data products, issues recommendations for VLBI data analysis software, sets standards for VLBI analysis documentation, and institutes appropriate VLBI product delivery methods to ensure suitable product quality and timeliness. VLBI data products currently available are the full set of EOP, the TRF, the CRF, and tropospheric parameters. All VLBI data products are archived in IVS Data Centers and are publicly available. The IVS data set extends from 1979. We provide an overview of the status and current activities of the service.