The keynote of the eleventh IVS General Meeting is the improved acuteness with which the new VLBI system is able to observe the system Earth under the theme "VGOS – 20/20 Acuity for VLBI". In 2020 the VGOS (VLBI Global Observing System) network has reached an operationally stable network of expanded geographical extent and it continues to evolve into a truly global network. The high performance of the system is anticipated to provide geodetic and astrometric parameters at improved accuracies and resolutions paving the way for advanced VLBI science and applications.


Session 1: IVS Network Stations and Technical Developments

Conveners: Hayo Hase, Evgeny Nosov, Dirk Behrend
The goals of this decade for the global VLBI network are to provide unprecedented accuracies for geodetic results including station positions and velocities (1 mm and 0.1 mm/yr) and Earth orientation parameters. Therefore, the IVS is introducing the VLBI Global Observing System (VGOS). For the past two decades, the operational products of the IVS have been based on observations made by the legacy S/X network stations which still form the backbone of today’s product generation. In 2019, the evolving VGOS network has matured enough that initial operational products could be derived. It is anticipated that the maturation of the VGOS system and the build-out of the VGOS network will advance in 2020 and subsequent years until VGOS can replace S/X as the production system of the IVS. In this session we seek contributions which demonstrate the efforts of improving the VLBI systems. We request contributions covering aspects on station activities, recent developments, simulations, studies on how to improve the network, status and progress reports for VGOS and legacy systems. The technical developments may cover all signal chain components at the stations (feeds, backends, recording systems) but also reference frequency generation and distribution, timing systems, e-transfer, and RFI excision techniques, among others.

Session 2: Operation and Correlation

Conveners: Chet Ruszczyk, Gino Tuccari, David Hall
This session focuses on the present and near-term future activities at VLBI network stations and correlators. This includes status reports of the legacy stations, VGOS stations, correlators, and mixed-mode observations and other legacy-to-VGOS local ties. In addition, we solicit presentations about issues that relate to improving VLBI data quality product. The near-term future topics could cover presentations about strategies for the transition from the current network to the VGOS network, such as network compatibilities, and investigations of the effect of station and correlation centers conversion to VGOS broadband. Furthermore, we welcome submissions concerning the GGOS project's contributions to local surveys to determine the spatial vectors from the radio telescopes to co-located geodetic instruments.

Session 3: Data Structures, Scheduling and Analysis Strategies

Conveners: John Gipson, Johannes Böhm
IVS Operations Centers are responsible for the scheduling of IVS sessions. IVS Data Centers are responsible for storing and distributing IVS data, and IVS Analysis Centers are responsible for the analysis of IVS sessions, and the production of IVS data products. These functions are interdependent: what happens at one stage of the processing depends on what happens both before and after. In this session, we call for contributions related to the IVS Operations, Data and Analysis Centers' current activities and plans for the future. VLBI data will increase dramatically (a factor of 10-100) in the future because of VGOS. Because of this, we are especially interested in the planned strategies to automate scheduling, data collection, processing and analysis. Presentations related to the comparison and development of analysis strategies are welcomed, as are changes and new strategies that need to be considered due to VGOS and existing or new user requirements.

Session 4: Interpretation of VLBI Results in Geophysics, Geodesy, and Astrometry

Conveners: Chris Dieck, Alet de Witt
The analysis of VLBI observations produces values, time series, and long-term averages & rates of physical parameters. Analysis of particular sessions also produces images of celestial reference frame objects. We seek contributions in topics such as the use of these VLBI products in modeling geophysical fluids from the atmosphere to the core, improvement of the precession-nutation model, investigation of the Earth rotation variations at different time scales (from minutes to decades), inner and outer core nutations, refinement of the terrestrial and celestial reference frames, detection and interpretation of the motions of specific sites and radio sources, atmospheric studies (both the troposphere and the ionosphere), astrophysical investigations, tests of relativity, and other scientific uses of geodetic and astrometric VLBI data and images. Other important topics are the comparison, validation, and combination of VLBI with other space geodetic techniques where special attention is expected to be given to the assessment of the actual accuracy and systematic errors of the VLBI-derived results, and to the errors caused by deficiencies of the models used in data processing. As VGOS operations develop, we are also particularly interested in presentations on the impacts of quasar source structure variability on the ability to meet the precision goals of VGOS and the subsequent implications on the effort required to maintain the celestial reference frame.

Session 5: Extending the Use of VLBI Observations to Frame Ties and Deep Space Exploration

Conveners: James Anderson, Jinling Li
VLBI observations have contributed greatly to astrometric and geodetic studies, including the construction and maintenance of the celestial and terrestrial reference frames (CRF, TRF), as well as the precise determination of the Earth Orientation Parameters (EOP). They also have contributed significantly to geophysical studies such as modeling of tides and the deep Earth structure. Currently efforts are under way to extend the use of VLBI observations to frame ties and deep space exploration. For instance, VLBI observations of satellites could facilitate the determination of reference frame tie parameters allowing to study and remove possible systematic errors of various frames or to improve the reliability and precision of navigation and positioning applications. VLBI observations have already tremendously contributed to the Lunar and Mars exploration efforts both in orbit determination and positioning of deep space probes. VLBI observations of objects of the Gaia frame enables precise frame ties and thus also to improve the determination precision of the EOP. Geophysical and astrophysical studies require contributions from astrometric and geodetic VLBI observations. In this session we seek contributions to extend VLBI observations to frame ties, deep space exploration, demands of astrometric and geodetic VLBI observations to geophysical and astrophysical studies. We also welcome contributions on methodology demonstration, technical verification, and observation practice.