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

2009 ◽  
pp. 265-270 ◽  
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

scholarly journals The First Decade of the IERS

2000 ◽  
Vol 178 ◽  
pp. 201-213 ◽  
Author(s):  
Ivan I. Mueller
Keyword(s):  
Reference Frame ◽  
Reference System ◽  
Terrestrial Reference Frame ◽  
Point Of View ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
Time Space ◽  
International Astronomical ◽  
Celestial Reference System ◽  
Orientation Parameters

AbstractThe International Earth Rotation Service (IERS) was established in 1987 by the International Astronomical Union (IAU) and the International Union of Geodesy and Geophysics (IUGG), and it began operation on 1 January 1988. The primary objectives of the IERS are to serve the astronomical, geodetic and geophysical communities by providing the following: •The International Celestial Reference System (ICRS) and its realization, the International Celestial Reference Frame (ICRF).•The International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF).•Earth orientation parameters required to study Earth orientation variations and to transform between the ICRF and the ITRF.•Geophysical data to interpret time/space variations of the ITRF with respect to the ICRF, i.e., of the Earth orientation parameters, and to model such variations.•Standards, constants and models (i.e., conventions) encouraging international adherence.This presentation primarily covers the first three IERS functions from the operational point of view.

The IDS Contribution to the ITRF2020

2021 ◽  
Author(s):  
Guilhem Moreaux ◽  
Frank Lemoine ◽  
Hugues Capdeville ◽  
Petr Stepanek ◽  
Michiel Otten ◽  
...  
Keyword(s):  
Reference Frame ◽  
Model Error ◽  
Terrestrial Reference Frame ◽  
Primary Objective ◽  
Force Model ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
New Models ◽  
Orientation Parameters ◽  
Improved Methods

<p>In the context of the realization of the next International Terrestrial Reference Frame (ITRF2020), the International DORIS Service (IDS) is involved in the estimation of DORIS station positions/velocities as well as Earth orientation parameters from DORIS data. Thus, the 4 IDS Analysis Centers  have re-analyzed all the DORIS observations from the fifteen DORIS satellites from January 1993 to December 2020.0.</p><p>The primary objective of this study is to analyze the DORIS contribution to ITRF2020 in terms of (1) geocenter and scale solutions; (2) station positions and week-to-week repeatability; (3) Earth orientation parameters; (4) a cumulative position and velocity solution.</p><p>Comparisons with the IDS contribution to ITRF2014 will address the benefits of the new antenna models, new models, including improved methods to handle non-conservative force model error on the Jason satellites, as well as the addition of data (compared to ITRF2014) from the latest DORIS missions (e.g. Jason-3, Sentinel-3A/B) in the IDS combination.</p>

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

2016 ◽  
Vol 101 (1) ◽  
pp. 1-15 ◽  
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.

scholarly journals Unconstrained Estimation of VLBI Global Observing System Station Coordinates

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.

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

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

<p>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.</p>

Contribution of the Vienna Center for VLBI to ITRF2020

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

<p>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.</p>

scholarly journals Indirect linking of the Hipparcos catalog to extragalactic reference frame via Earth orientation parameters

1996 ◽  
Vol 172 ◽  
pp. 491-496
Author(s):  
J. Vondrák
Keyword(s):  
Time Series ◽  
Reference Frame ◽  
Indirect Method ◽  
Reference Frames ◽  
Slow Rotation ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
Vlbi Observations ◽  
Orientation Parameters

The indirect method of linking the Hipparcos reference frame to the frame defined by extragalactic sources is described. To this end, two independent time series of Earth orientation parameters observed by two different techniques with respect to the two reference frames are used: a) Optical astrometry observations (referred to Hipparcos stars), b) VLBI observations (referred to extragalactic objects). The parallel use of both techniques during the last decade enables to determine the orientation of the two reference frames at a fixed epoch and their mutual slow rotation with precision of at least 1mas and 1mas/year, respectively. In order not to raise confusion, the potentiality of the method is demonstrated on the example based on the star catalogues originally used at the participating observatories, not on any of the existing preliminary versions of the Hipparcos catalog.

scholarly journals An Optimum Strategy for Producing Precise GPS Satellite Orbits using Double-Differenced Observations

2018 ◽  
Vol 24 (9) ◽  
pp. 109
Author(s):  
Oday Yaseen Mohamed Zeki Alhamadani
Keyword(s):  
Reference Frame ◽  
Double Difference ◽  
Satellite Orbits ◽  
Special Importance ◽  
Satellite Clock ◽  
Earth Orientation Parameters ◽  
Orbital Parameters ◽  
Earth Orientation ◽  
Gnss Positioning ◽  
Orientation Parameters

Both the double-differenced and zero-differenced GNSS positioning strategies have been widely used by the geodesists for different geodetic applications which are demanded for reliable and precise positions. A closer inspection of the requirements of these two GNSS positioning techniques, the zero-differenced positioning, which is known as Precise Point Positioning (PPP), has gained a special importance due to three main reasons. Firstly, the effective applications of PPP for geodetic purposes and precise applications depend entirely on the availability of the precise satellite products which consist of precise satellite orbital elements, precise satellite clock corrections, and Earth orientation parameters. Secondly, the PPP processing strategy has been employed by the International GNSS Service (IGS) and IGS analysis centers to evaluate their products in terms of homogeneity and precision over a long period of time. Thirdly, the precise positions, which are determined using PPP technique, and are referenced directly to the geodetic reference frame of the satellite orbital parameters. Thus, the definition of the geodetic datum of the site coordinates using different strategies plays an enormous role in the process of generation satellite orbital parameters which have to be compatible with the corresponding satellite clock corrections and the Earth orientation parameters. This study focuses on producing uninterrupted series of satellite orbit and clock products using different criteria and assesses these products using PPP. The double-difference processing technique was used to achieve the goal of this study by Bernese GPS software version 5.0. Twenty-two globally distributed IGS stations were selected to run PPP based on the generated products and then compare the results with corresponding PPP results which were created based on the IGS rapid products. The comparison pointed to a significant improvement in the generated precise products which have considerably increased the precision of positions. What is more, this study stated that there is an observable agreement between the horizontal positions accuracies which are generated using different techniques for modeling the reference frame.  

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