Non-linear VLBI station motions and their impact on the celestial reference frame and Earth orientation parameters

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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ITRF2005: A new release of the International Terrestrial Reference Frame based on time series of station positions and Earth Orientation Parameters

Journal of Geophysical Research Atmospheres ◽

10.1029/2007jb004949 ◽

2007 ◽

Vol 112 (B9) ◽

Cited By ~ 612

Author(s):

Z. Altamimi ◽

X. Collilieux ◽

J. Legrand ◽

B. Garayt ◽

C. Boucher

Keyword(s):

Time Series ◽

Reference Frame ◽

Terrestrial Reference Frame ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

International Terrestrial Reference Frame ◽

Orientation Parameters

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

Symposium - International Astronomical Union ◽

10.1017/s0074180900127962 ◽

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.

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

Journal of Engineering ◽

10.31026/j.eng.2018.09.08 ◽

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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The First Decade of the IERS

International Astronomical Union Colloquium ◽

10.1017/s0252921100061340 ◽

2000 ◽

Vol 178 ◽

pp. 201-213 ◽

Cited By ~ 1

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.

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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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The IDS Contribution to the ITRF2020

10.5194/egusphere-egu21-2315 ◽

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

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 &#160;have re-analyzed all the DORIS observations from the fifteen DORIS satellites from January 1993 to December 2020.0.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.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.

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Essential Geodetic Variables: Earth Orientation Parameters

10.5194/egusphere-egu2020-2434 ◽

2020 ◽

Author(s):

Richard Gross

Keyword(s):

Reference Frame ◽

Temporal Resolution ◽

Earth Rotation ◽

International Association ◽

Global Navigation Satellite Systems ◽

Earth System ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

The Earth ◽

Orientation Parameters

The Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) provides the basis on which future advances in geosciences can be built. By considering the Earth system as a whole (including the geosphere, hydrosphere, cryosphere, atmosphere and biosphere), monitoring Earth system components and their interactions by geodetic techniques and studying them from the geodetic point of view, the geodetic community provides the global geosciences community with a powerful tool consisting mainly of high-quality services, standards and references, and theoretical and observational innovations. A new initiative within GGOS is to define Essential Geodetic Variables. Essential Geodetic Variables (EGVs) are observed variables that are crucial (essential) to characterizing the geodetic properties of the Earth and that are key to sustainable geodetic observations. Once a list of EGVs has been determined, requirements can be assigned to them such as the accuracy with which the variables need to be determined, their spatial and temporal resolution, latency, etc. These requirements on the EGVs can then be used to assign requirements to EGV-dependent products like the terrestrial reference frame. The EGV requirements can also be used to derive requirements on the systems that are used to observe the EGVs, helping to lead to a more sustainable geodetic observing system for reference frame determination and numerous other scientific and societal applications.For the Earth's rotation, the essential variables can be considered to be the five Earth orientation parameters (EOPs), namely, the x- and y-components of polar motion (xp, yp), the x- and y-components of nutation/precession (X, Y), and the spin parameter UT1. Related to these five Essential Earth Rotation Variables are the sub-variables of their time rates-of-change and the derived variables of the excitation functions (&#967;x, &#967;y, and length-of-day). The Essential Earth Rotation Variables are currently observed by the operational techniques of lunar and satellite laser ranging, very long baseline interferometry, global navigation satellite systems, and Doppler orbitography and radiopositioning integrated by satellite. In the future, the emerging techniques of ring laser gyroscopes and superfluid helium gyroscopes can be expected to routinely observe parameters related to the Essential Earth Rotation Variables. The GGOS requirements on the five Essential Earth Rotation Variables (that is, on the five EOPs) are "ERP-001-EOP: Earth Orientation Parameters will be determined with an accuracy of 1 mm, a temporal resolution of 1 hour, and a latency of 1 week; near real-time determinations of the Earth Orientation Parameters will be determined with an accuracy of 3 mm" (Plag and Pearlman, 2009, p. 223). Currently, the best-determined EOPs have an accuracy of about 1 mm, a temporal resolution of about 1 day, and a latency of about 2 weeks (Ray et al., 2017; http://www.igs.org/products). Thus, while the GGOS accuracy requirement on the Essential Earth Rotation Variables is currently being met, at least for some of the variables, the GGOS resolution and latency requirements are not being met.

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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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