Simultaneous determination of Earth orientation parameters and station coordinates from combination of results of different observation techniques

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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Geodetic VLBI Analysis at the National Geographic Institute of Spain

Proceedings ◽

10.3390/proceedings2019019002 ◽

2019 ◽

Vol 19 (1) ◽

pp. 2

Author(s):

Víctor Puente ◽

Esther Azcue ◽

Susana García-Espada ◽

Yaiza Gómez-Espada

Keyword(s):

Earth Orientation Parameters ◽

Technical Aspects ◽

National Geographic ◽

Earth Orientation ◽

Geodetic Vlbi ◽

Software Packages ◽

Station Coordinates ◽

Set Up ◽

Orientation Parameters ◽

Troposphere Delays

National Geographic Institute of Spain has a strong background concerning technical aspects of geodetic VLBI. As a step forward in this field, a VLBI analysis team has been set up and tests with different software packages have been carried out. In this sense, two VLBI software packages have been used for experimentation activities in order to compare and validate IGE capability to produce accurate and consistent geodetic products, specifically Earth Orientation Parameters, station coordinates and troposphere delays. The purpose of this contribution is to present the results of these analyses, including some tests to use GNSS-based troposphere delay in VLBI processing and the study of gravitational deformation in Yebes radiotelescope.

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Unconstrained Estimation of VLBI Global Observing System Station Coordinates

Advances in Geosciences ◽

10.5194/adgeo-55-23-2021 ◽

2021 ◽

Vol 55 ◽

pp. 23-31

Author(s):

Markus Mikschi ◽

Johannes Böhm ◽

Matthias Schartner

Keyword(s):

Reference Frame ◽

Terrestrial Reference Frame ◽

Baseline Length ◽

Radio Telescopes ◽

Earth Orientation Parameters ◽

The Earth ◽

Station Coordinates ◽

International Vlbi Service ◽

Orientation Parameters

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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Combination of GNSS and VLBI data for consistent estimation of Earth Orientation Parameters

10.5194/egusphere-egu2020-4722 ◽

2020 ◽

Author(s):

Lisa Lengert ◽

Hendrik Hellmers ◽

Claudia Flohrer ◽

Daniela Thaller ◽

Alexander Kehm

Keyword(s):

Normal Equation ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

Starting Point ◽

Station Coordinates ◽

Space Geodetic Techniques ◽

Vlbi Data ◽

Gnss Data ◽

The Impact ◽

Orientation Parameters

We present the current activities of the Federal Agency for Cartography and Geodesy (BKG) towards a combined processing of VLBI and GNSS data.&#160; The main goal of the combined analyses of the two different space-geodetic techniques is the improvement of the consistency between the techniques through common parameters, as Earth Orientation Parameters (EOPs), but also station coordinates and tropospheric parameters through local ties and atmospheric ties, respectively.The combination of GNSS data with VLBI 24-hour sessions and VLBI Intensive sessions is studied in detail w.r.t. EOPs to exploit he combination benefit to its maximum extend. We analyse the impact of the combination on the technique-specific parameters (e.g. dUT1), but also on common parameters (e.g. LOD, polar motion, station coordinates). When using GNSS data in combination with VLBI Intensive sessions, we can demonstrate an accuracy improvement of the dUT1 time series.We also study the combination of troposphere parameters, focusing first on the validation of the technique-specific troposphere parameters at VLBI-GNSS co-located sites and on the modelling of the corresponding atmospheric ties.BKGs primary interest is the combination of GNSS and VLBI data on the observation level. However, the current combination efforts are based on the normal equation level using technique-specific SINEX files as a starting point.

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Determination of the extragalactic-planetary frame tie from Earth orientation parameters

Chinese Science Bulletin ◽

10.1007/bf02882470 ◽

1997 ◽

Vol 42 (4) ◽

pp. 315-318

Author(s):

Jinsong Ping ◽

Jinling Li ◽

Wenjing Jin ◽

Zhihan Qian

Keyword(s):

Earth Orientation Parameters ◽

Earth Orientation ◽

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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Determination of the Long Period Nutation Terms from Optical Astrometry and VLBI Data

International Astronomical Union Colloquium ◽

10.1017/s0252921100061777 ◽

2000 ◽

Vol 178 ◽

pp. 607-612

Author(s):

P. Yaya ◽

C. Bizouard ◽

C. Ron

Keyword(s):

Linear Trend ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

Long Period ◽

The Earth ◽

Vlbi Data ◽

Orientation Parameters

AbstractA 100-year long optical astrometric series of the Earth Orientation Parameters produced by a Czech team (Vondrák et al., 1998) has been analysed in order to determine components of nutation. Our interest is mostly focused on the long periodic terms: 18.6-year term, 9.3-year term and linear trend, still correlated in VLBI series which cover only the last 20 years. A comparison has been made with the corresponding values determined from the VLBI series.

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Baseline-dependent clock offsets in VLBI data analysis

Journal of Geodesy ◽

10.1007/s00190-021-01579-5 ◽

2021 ◽

Vol 95 (12) ◽

Author(s):

Hana Krásná ◽

Frédéric Jaron ◽

Jakob Gruber ◽

Johannes Böhm ◽

Axel Nothnagel

Keyword(s):

Data Analysis ◽

Reference Frames ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

Long Baseline ◽

Station Coordinates ◽

Vlbi Data ◽

Group Delays ◽

The Impact ◽

Orientation Parameters

AbstractThe primary goal of the geodetic Very Long Baseline Interferometry (VLBI) technique is to provide highly accurate terrestrial and celestial reference frames as well as Earth orientation parameters. In compliance with the concept of VLBI, additional parameters reflecting relative offsets and variations of the atomic clocks of the radio telescopes have to be estimated. In addition, reality shows that in many cases significant offsets appear in the observed group delays for individual baselines which have to be compensated for by estimating so-called baseline-dependent clock offsets (BCOs). For the first time, we systematically investigate the impact of BCOs to stress their importance for all kinds of VLBI data analyses. For our investigations, we concentrate on analyzing data from both legacy networks of the CONT17 campaign. Various aspects of BCOs including their impact on the estimates of geodetically important parameters, such as station coordinates and Earth orientation parameters, are investigated. In addition, some of the theory behind the BCO determination, e.g., the impact of changing the reference clock in the observing network on the BCO estimate is introduced together with the relationship between BCOs and triangle delay closures. In conclusion, missing channels, and here in particular at S band, affecting the ionospheric delay calibration, are identified to be the dominant cause for the occurrence of significant BCOs in VLBI data analysis.

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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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