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Very Long Baseline Interferometry (VLBI) serves as one of the common geodetic methods to define the global reference frames and monitor Earth's orientation variations. The technical upgrade of the VLBI method known as the VLBI Global Observing System (VGOS) includes a critical re-design of the observed frequencies from the dual band mode (S and X band, i.e. 2 GHz and 8 GHz) to observations in a broadband (2 – 14 GHz). Since 2019 the first VGOS experiments are available for the geodetic analysis in free access at the International VLBI service for Geodesy and Astrometry (IVS). Also regional-only subnetworks such as European VLBI stations have succeeded already in VGOS mode. Based on these brand-new observations we review the current geodetic data analysis workflow to build a bridge between geodetic observed delays derived from different bands.

With the VLBI technique radio sources are observed in dedicated time intervals. The most usual length of these observing sessions are 24 and 1-hour long. 24-hour long experiments usually incorporate a global network of stations, and, thus, are the prominent source of a consistent determination of all Earth Orientation Parameters (EOPs), celestial and terrestrial reference frames. The shorter experiments are designed to determine dUT1 parameter only. The number of short or intensive sessions is growing every year. Also some of them involve 3-4 stations in observation programs instead of standard 2-station mode. This leads to a larger number of observations per session, a better coverage of the Earth, and, consequently more accurate dUT1 estimates.All 24-hour and 1-hour sessions since 1984 up to now were re-processed by BKG using the most up-to-date modelling within the parameter estimation. This results in new series of consistently estimated EOPs, station coordinates and troposphere parameters.In this contribution we present our new series and investigate the quality of the obtained geodetic products, especially the EOPs. The work is focused on the consistency between dUT1 parameters derived from 24-hour and 1-hour sessions, respectively. In this study we pinpoint challenges and prospects of the inclusion of 1-hour experiments into the standard analysis of the 24-hour experiments.

Precise measurements of the Earth’s shape, gravity field, and rotation provide critical data for many geoscientific disciplines. In order to obtain reliable data, an accurate, stable, and global reference frame is required. The International Terrestrial Reference Frame, where station positions are modeled linearly, is commonly used throughout the geoscientific community for this purpose. Mass redistribution in the geophysical fluids, namely atmosphere, oceanic, and continental hydrology, cause time dependent variations in station coordinates, and other parameters such as the geocenter coordinates. Tidally-induced loading is described in the IERS Conventions. Models for non-tidal loading are available through the Global Geophysical Fluid Center. An overview of these models is given and comparisons were carried out. Within these comparisons, the best agreement was observed between the two atmospheric models, whereas the biggest discrepancies were found between the hydrology models. The processing setup for the Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR) and Global Navigation Satellite Systems (GNSS) solutions is described, with loading displacement values introduced at the observation level. By using of non-tidal loading models the RMS of the height is reduced for 93% of the GNSS stations, with a max. reduction of 50%. The model impact on the station height in Wettzell derived by GNSS, SLR and VLBI shows a good agreement. In SLR results the Blue-Sky effect is visible. Applying the loading models reduced the seasonal variations visible in the geocenter time series derived by SLR almost completely.

For several years the radio telescope of the Geodetic Observatory Wettzell has participated in the daily one-hour INTENSIVE-sessions (INT), in addition to the 24-hour sessions, in order to determine UT1-UTC. The INT1 sessions are observed together with Kokee Park Geophysical Observatory (Hawaii, USA) and partly with Svetloe (Russia) every weekday and are correlated at Washington Correlator. On Saturday and Sunday, Wettzell is engaged together with Tsukuba (Japan) in the INT2 sessions which are correlated in Japan. On Monday morning INT3 session, which is correlated in Bonn, completes the INTENSIVE observations in the network of Wettzell, Tsukuba and Ny Alesund. For all these INTENSIVE experiments, e-transfer is used to ship the data over standard internet connections to the correlators in near real-time. Wettzell itself routinely uses a fast internet connection at 622 Mbit/sec for these e-transfers. All these efforts reduce the delay times from taking the observations, to correlation, to publishing the final geodetic data product at the primary IVS Data Centers.

In April 2002 the International VLBI Service for Geodesy and Astrometry (IVS) set up the Pilot Project — Tropospheric Parameters, and the Institute of Geodesy and Geophysics (IGG), Vienna, was put in charge of coordinating the project. Seven IVS Analysis Centers have joined the project and regularly submitted their estimates of tropospheric parameters (wet and total zenith delays, horizontal gradients) for all IVS-R1 and IVS-R4 sessions since January 1st, 2002. The individual submissions are combined by a two-step procedure to obtain stable, robust and highly accurate tropospheric parameter time series with one hour resolution. The zenith delays derived by Very Long Baseline Interferometry (VLBI) are compared with those provided by the International GPS Service (IGS). At sites with co-located VLBI and GPS antennas, biases are found between the Global Positioning System (GPS) and VLBI derived zenith delays, although short-term variabilities generally show a good agreement. Possible reasons for these biases are discussed. Additionally, the time series submitted by the individual Analysis Centers are compared to the combined IGS time series for the CONT02 campaign of 15 days of continuous observations in the second half of October 2002.