Unconstrained Estimation of VLBI Global Observing System Station Coordinates

Abstract. The International VLBI Service for Geodesy and Astrometry (IVS) is currently setting up a network of smaller and thus faster radio telescopes observing at broader bandwidths for improved determination of geodetic parameters. However, this new VLBI Global Observing System (VGOS) network is not yet strongly linked to the legacy S/X network and the International Terrestrial Reference Frame (ITRF) as only station WESTFORD has ITRF2014 coordinates. In this work, we calculated VGOS station coordinates based on publicly available VGOS sessions until the end of 2019 while defining the geodetic datum by fixing the Earth orientation parameters and the coordinates of the WESTFORD station in an unconstrained adjustment. This set of new coordinates allows the determination of geodetic parameters from the analysis of VGOS sessions, which would otherwise not be possible. As it is the concept of VGOS to use smaller, faster slewing antennas in order to increase the number of observations, shorter estimation intervals for the zenith wet delays and the tropospheric gradients along with different relative constraints were tested and the best performing parametrization, judged by the baseline length repeatability, was used for the estimation of the VGOS station coordinates.

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Testing impact of the strategy of VLBI data analysis on the estimation of Earth Orientation Parameters and station coordinates

Reports on Geodesy and Geoinformatics ◽

10.1515/rgg-2016-0017 ◽

2016 ◽

Vol 101 (1) ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

Agata Wielgosz ◽

Monika Tercjak ◽

Aleksander Brzeziński

Keyword(s):

Reference Frame ◽

Terrestrial Reference Frame ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

Long Baseline ◽

Station Coordinates ◽

Vlbi Data ◽

Weighting Strategy ◽

Orientation Parameters

Abstract Very Long Baseline Interferometry (VLBI) is the only space geodetic technique capable to realise the Celestial Reference Frame and tie it with the Terrestrial Reference Frame. It is also the only technique, which measures all the Earth Orientation Parameters (EOP) on a regular basis, thus the role of VLBI in determination of the universal time, nutation and polar motion and station coordinates is invaluable. Although geodetic VLBI has been providing observations for more than 30 years, there are no clear guidelines how to deal with the stations or baselines having significantly bigger post-fit residuals than the other ones. In our work we compare the common weighting strategy, using squared formal errors, with strategies involving exclusion or down-weighting of stations or baselines. For that purpose we apply the Vienna VLBI Software VieVS with necessary additional procedures. In our analysis we focus on statistical indicators that might be the criterion of excluding or down-weighting the inferior stations or baselines, as well as on the influence of adopted strategy on the EOP and station coordinates estimation. Our analysis shows that in about 99% of 24-hour VLBI sessions there is no need to exclude any data as the down-weighting procedure is sufficiently efficient. Although results presented here do not clearly indicate the best algorithm, they show strengths and weaknesses of the applied methods and point some limitations of automatic analysis of VLBI data. Moreover, it is also shown that the influence of the adopted weighting strategy is not always clearly reflected in the results of analysis.

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A preliminary assessment of the accuracy of the VGOS geodetic products: implications for the terrestrial reference frame and Earth orientation parameters

10.5194/egusphere-egu21-13032 ◽

2021 ◽

Author(s):

Dhiman Mondal ◽

Pedro Elosegui ◽

John Barrett ◽

Brian Corey ◽

Arthur Niell ◽

...

Keyword(s):

Reference Frame ◽

Mixed Mode ◽

Daily Basis ◽

Terrestrial Reference Frame ◽

Preliminary Assessment ◽

Earth Orientation Parameters ◽

Vlbi Observations ◽

International Vlbi Service ◽

Single Baseline ◽

Orientation Parameters

The next-generation VLBI system called VGOS (VLBI Global Observing System) has been designed and built as a significant improvement over the legacy geodetic VLBI system to meet the accuracy and stability goals set by the Global Geodetic Observing System (GGOS). Improved geodetic products are expected as the VGOS technique transitions from demonstration to operational status, which is underway. Since 2019, a network of nine VGOS stations has been observing bi-weekly under the auspices of the International VLBI Service for Geodesy and Astrometry (IVS) to generate standard geodetic products. These products, together with the mixed-mode VLBI observations that tie the VGOS and legacy networks together will be contributions to the next realization of the International Terrestrial Reference Frame (ITRF2020). Moreover, since 2020 a subset of 2 to 4 VGOS stations has also been observing in a VLBI Intensive-like mode to assess the feasibility of Earth rotation (UT1) estimation using VGOS. Intensives are daily legacy VLBI observations that are run on a daily basis using a single baseline between Kokee Park Geophysical Observatory, Hawaii, and Wettzell Observatory, Germany, made with the goal of near-real-time monitoring of UT1. In this presentation, we will describe the VGOS observations, correlation, post-processing, and preliminary geodetic results, including UT1. We will also compare the VGOS estimates to estimates from legacy VLBI, including estimates from mixed-mode observations, to explore the precision and accuracy of the VGOS products.

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Earth Rotation in the Hipparcos Reference Frame

International Astronomical Union Colloquium ◽

10.1017/s0252921100046431 ◽

1997 ◽

Vol 165 ◽

pp. 115-122 ◽

Cited By ~ 1

Author(s):

J. Vondrák ◽

C. Ron ◽

I. Pešek

Keyword(s):

Mathematical Model ◽

Reference Frame ◽

Rheological Parameters ◽

Earth Orientation Parameters ◽

The Earth ◽

Celestial Pole ◽

The Mathematical Model ◽

Orientation Parameters ◽

Celestial Reference Frame

AbstractNew determination of the Earth orientation parameters (EOP), based on optical astrometry observations since the beginning of the century, is now under preparation by the Working group established by Commission 19 of the IAU. The Hipparcos catalog is to define the celestial reference frame in which the new series of EOP are to be described. The novelties of the prepared solution are the higher resolution (5 days) and more parameters estimated from the solution (celestial pole offsets, rheological parameters of the Earth, certain instrumental constants). The mathematical model of the solution is described, and the results based on the observations made with 46 instruments at 29 observatories and a preliminary Hipparcos catalog are presented.

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Contribution of the Vienna Center for VLBI to ITRF2020

10.5194/egusphere-egu21-1088 ◽

2021 ◽

Author(s):

Hana Krásná ◽

David Mayer ◽

Sigrid Böhm

Keyword(s):

Reference Frame ◽

Terrestrial Reference Frame ◽

Normal Equation ◽

Earth Orientation Parameters ◽

International Vlbi Service ◽

Analysis Center ◽

International Terrestrial Reference System ◽

Terrestrial Reference System ◽

The Impact ◽

Orientation Parameters

The next realization of the International Terrestrial Reference System, the ITRF2020, is planned to be released in 2021. Our joint VLBI Analysis Center VIE which runs between TU Wien and BEV is one of eleven IVS (International VLBI Service for Geodesy and Astrometry) analysis centres which provide VLBI input to the ITRF2020. The SINEX files submitted to the IVS Combination Center are produced with the Vienna VLBI and Satellite Software VieVS and contain unconstrained normal equation systems for station position, source coordinates and Earth orientation parameters. In this presentation, we document the included sessions and stations in our submission and introduce the Vienna terrestrial reference frame based on our contribution to the ITRF2020. In particular, we highlight special settings in the Vienna solution and assess the impact on the terrestrial reference frame.

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BKG’s new series of 24-hour and 1-hour VLBI experiments

10.5194/egusphere-egu21-8950 ◽

2021 ◽

Author(s):

Anastasiia Girdiuk ◽

Gerald Engelhardt ◽

Dieter Ullrich ◽

Daniela Thaller ◽

Hendrik Hellmers

Keyword(s):

Reference Frames ◽

Global Network ◽

Time Intervals ◽

Earth Orientation Parameters ◽

Terrestrial Reference Frames ◽

The Earth ◽

Station Coordinates ◽

Orientation Parameters

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.

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The Contribution of the IERS to Astrophysics and Geodynamics

Symposium - International Astronomical Union ◽

10.1017/s0074180900173619 ◽

1993 ◽

Vol 156 ◽

pp. 406-406

Author(s):

M. Feissel ◽

Yaroslav Yatskiv

Keyword(s):

Reference Frame ◽

Global Positioning System ◽

Terrestrial Reference Frame ◽

International Earth Rotation Service ◽

Earth Orientation Parameters ◽

Long Baseline ◽

The Earth ◽

Global Positioning ◽

Orientation Parameters ◽

Celestial Reference Frame

The International Earth Rotation Service (IERS) maintains a celestial reference frame and a terrestrial reference frame based on observations in Very Long Baseline radio Interferometry, Lunar and Satellite Laser Ranging, and Global Positioning System, as well as a time series of the Earth Orientation Parameters in a system that is consistent at the level of 0.001″.

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A Terrestrial Reference System Consistent with WGRS

International Astronomical Union Colloquium ◽

10.1017/s025292110006379x ◽

1991 ◽

Vol 127 ◽

pp. 211-214 ◽

Cited By ~ 2

Author(s):

C. Boucher ◽

Z. Altamimi

Keyword(s):

Reference System ◽

Terrestrial Reference Frame ◽

Reference Systems ◽

International Earth Rotation Service ◽

Earth Orientation Parameters ◽

Terrestrial Reference System ◽

Definition Of ◽

Orientation Parameters ◽

Evolution With Time

AbstractThe IAU and IUGG has jointly established in 1988 an International Earth Rotation Service (IERS) which is in charge of the realization of conventional celestial and terrestrial reference systems, together with the determination of earth orientation parameters which connect them.The theoretical definition of the terrestrial reference system which is realized by IERS through a conventional terrestrial reference frame formed by SLR, LLR, VLBI and GPS stations is presented. In particular its origin, scale, orientation and evolution with time are reviewed, taking into account relativistic and deformation effects.

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The Combined Solution C04 for Earth Orientation Parameters Consistent with International Terrestrial Reference Frame 2005

Geodetic Reference Frames - International Association of Geodesy Symposia ◽

10.1007/978-3-642-00860-3_41 ◽

2009 ◽

pp. 265-270 ◽

Cited By ~ 97

Author(s):

Christian Bizouard ◽

Daniel Gambis

Keyword(s):

Reference Frame ◽

Terrestrial Reference Frame ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

International Terrestrial Reference Frame ◽

Combined Solution ◽

Orientation Parameters

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The use of astronomy VLBA campaign MOJAVE for geodesy

Journal of Geodesy ◽

10.1007/s00190-021-01551-3 ◽

2021 ◽

Vol 95 (9) ◽

Author(s):

Hana Krásná ◽

Leonid Petrov

Keyword(s):

Baseline Length ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

Long Baseline ◽

Station Coordinates ◽

The Difference ◽

Very Long Baseline Array ◽

Orientation Parameters ◽

Source Structure ◽

Selection Of

AbstractWe investigated the suitability of the astronomical 15 GHz Very Long Baseline Array (VLBA) observing program MOJAVE-5 for estimation of geodetic parameters, such as station coordinates and Earth orientation parameters. We processed a concurrent dedicated VLBA geodesy program observed at 2.3 GHz and 8.6 GHz starting on September 2016 through July 2020 as reference dataset. We showed that the baseline length repeatability from MOJAVE-5 experiments is only a factor of 1.5 greater than from the dedicated geodetic dataset and still below 1 ppb. The wrms of the difference of estimated Earth orientation parameters with respect to the reference IERS C04 time series are a factor of 1.3 to 1.8 worse. We isolated three major differences between the datasets in terms of their possible impact on the geodetic results, i.e. the scheduling approach, treatment of the ionospheric delay, and selection of target radio sources. We showed that the major factor causing discrepancies in the estimated geodetic parameters is the different scheduling approach of the datasets. We conclude that systematic errors in MOJAVE-5 dataset are low enough for these data to be used as an excellent testbed for further investigations on the radio source structure effects in geodesy and astrometry.

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Earth Orientation - The Current and Future Situation

Symposium - International Astronomical Union ◽

10.1017/s0074180900228210 ◽

1995 ◽

Vol 166 ◽

pp. 287-291

Author(s):

Dennis D. McCarthy

Keyword(s):

State Of The Art ◽

International Earth Rotation Service ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

Current State ◽

The Earth ◽

Future Situation ◽

Orientation Parameters

Sub-milliarcsecond astrometry often requires an accurate characterization of the orientation of the Earth in a quasi-inertial reference frame. The International Earth Rotation Service (IERS) standards provide the current state of the art in the transformation between celestial and terrestrial reference systems. Improvements in the determination of Earth orientation parameters which describe this transformation continue to be made. Current and future capabilities are given.

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