Earth orientation and related reference frames

1993 ◽  
pp. 99-111 ◽  
Author(s):  
M. Feissel ◽  
D. Bourquard ◽  
P. Charlot ◽  
E. Eisop ◽  
N. Essaifi ◽  
...  
Keyword(s):  
Reference Frames ◽  
Earth Orientation

scholarly journals Consistency of CDP and IRIS VLBI Earth orientation results

1988 ◽  
Vol 128 ◽  
pp. 187-192 ◽  
Author(s):  
A. Mallama ◽  
T. A. Clark ◽  
J. W. Ryan
Keyword(s):  
Data Centers ◽  
Reference Frames ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
The Past ◽  
The Earth ◽  
Formal Error ◽  
Orientation Parameters ◽  
Iris Data

This study compares the earth orientation results obtained by the NASA CDP and the NGS IRIS experiments. The results agree at about one combined formal error (two milliarcseconds) after small biases (one to three milliarcseconds) have been removed from each component. Furthermore the biases are found to correspond to small rotations between the reference frames, principally the terrestrial frame, for the two sets of experiments. In the past the CDP data has not been used in combined solutions of earth orientation parameters prepared by the data centers at the U.S.N.O. and the B.I.H. The authors propose that these data should be included because they are distinct from the IRIS data and represent an important supplement to those data. We also point out that the total number of observations is about equal in the CDP and IRIS experiment sets.

Earth Orientation Parameter Estimation by Integrating VLBI and GNSS on the Observation Level

2021 ◽  
Author(s):  
Jungang Wang ◽  
Kyriakos Balidakis ◽  
Maorong Ge ◽  
Robert Heinkelmann ◽  
Harald Schuh
Keyword(s):  
Polar Motion ◽  
Reference Frames ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Earth Orientation ◽  
Long Baseline ◽  
Space Geodetic Techniques ◽  
Global Navigation Satellite ◽  
The Impact ◽  
Globally Distributed

<p>The terrestrial and celestial reference frames are linked by the Earth Orientation Parameters (EOP), which describe the irregularities of the Earth's rotation and are determined by the space geodetic techniques, namely, Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). The satellite geodetic techniques (SLR, GNSS, and DORIS) cannot determine the UT1-UTC or celestial pole offsets (CPO), rendering VLBI the only technique capable of determining full EOP set. On the other hand, the GNSS technique provides precise polar motion estimates due to the continuous observations from a globally distributed network. Integrating VLBI and GNSS provides the full set of EOP and guarantees a superior accuracy than any single-technique solution.</p><p>In this study we focus on the integrated estimation of the full EOP set from GNSS and VLBI. Using five VLBI continuous observing campaigns (CONT05–CONT17), the GNSS and VLBI observations are processed concurrently in a common least-squares estimator. The impact of applying global ties (EOP), local ties, and tropospheric ties, and combinations thereof is investigated. The polar motion estimates in integrated solution are dominated by the huge GNSS observations, and the accuracy in terms of weighted root mean squares (WRMS) is ~40 μas compared to the IERS 14 C04 product, which is much better than that of the VLBI-only solution. The UT1-UTC and CPO in the integrated solution also show slight improvement compared to the VLBI-only solution. Moreover, the CPO agreement between the two networks in CONT17, i.e., the VLBA and IVS networks, shows an improvement of 20% to 40% in the integrated solution with different types of ties applied.</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 Baseline-dependent clock offsets in VLBI data analysis

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.

scholarly journals Monitoring UT1 from astro-geodetic techniques at the EOP Center of the IERS

2009 ◽  
Vol 5 (H15) ◽  
pp. 207-208
Author(s):  
D. Gambis ◽  
C. Bizouard
Keyword(s):  
Time Scales ◽  
Orbit Determination ◽  
Earth Rotation ◽  
Reference Frames ◽  
Very Long Baseline Interferometry ◽  
Space Geodesy ◽  
Earth Orientation ◽  
Long Baseline ◽  
The Earth ◽  
Fluid Layers

AbstractMonitoring the Earth rotation is essential in various domains linked to reference frames firstly with applications in orbit determination, space geodesy or Astronomy. Secondly for geophysical studies where are involved mass motions within the different external fluid layers, atmosphere, hydrosphere, core and mantle of the earth, this on time scales ranging from a few hours to decades. The Earth Orientation Centre of the IERS is continuously monitoring the earth orientation variations from results derived from the various astro-geodetic techniques. It has in particular the task of deriving an optimal combined series of UT1 which is now based mainly on Very Long Baseline Interferometry (VLBI) with some contribution of LOD derived from GPS. We give here a brief summary concerning the contribution of the various techniques to UT1 and in aprticular how the use of LOD derived from GPS can improve the combination. More details are available in Gambis (2004) and Bizouard and Gambis (2009) and the website http://hpiers.obspm.fr/eop-pc/

scholarly journals On the eve of the 100th anniversary of IAU Commission 19/A2 “Rotation of the Earth”

2018 ◽  
Vol 13 (S349) ◽  
pp. 325-331
Author(s):  
Zinovy Malkin ◽  
Richard Gross ◽  
Dennis McCarthy ◽  
Aleksander Brzeziński ◽  
Nicole Capitaine ◽  
...  
Keyword(s):  
Earth Rotation ◽  
Reference Frames ◽  
International Association ◽  
General Assembly ◽  
Reference Systems ◽  
Standing Committee ◽  
Earth Orientation ◽  
Terrestrial Reference Frames ◽  
The Earth ◽  
Rotation Of The Earth

AbstractIAU Commission 19 began in 1919 with the birth of the IAU at the Brussels Conference, where Standing Committee 19 on Latitude Variations was established as one of 32 standing committees. At the first IAU General Assembly in 1922, Standing Committee 19 became Commission 19 “Variation of Latitude”. In the beginning, the main topic of the Commission was the investigation of polar motion. Later, its activities included observations and theory of Earth rotation and connections between Earth orientation variations and geophysical phenomena. As a result, in 1964 at the XII IAU General Assembly, the Commission was renamed “Rotation of the Earth”. The investigation of Earth orientation variations is primarily based on observations of natural and artificial celestial objects. Therefore, maintenance of the international terrestrial and celestial reference frames, as well as the coordinate transformation between the frames and the improvement of the model of precession/nutation, have always been among the primary Commission topics. In 1987, the IAU through Commissions 19 and 31 “Time” established, jointly with the International Union of Geodesy and Geophysics, what is now known as the International Earth Rotation and Reference Systems Service. Commission 19 continued to work to develop methods to improve the accuracy and understanding of Earth orientation variations and related reference systems and frames as well as theoretical studies of Earth rotation. In 2015, Commission 19 was renewed as Commission A2 “Rotation of the Earth” continuing Commission 19’s functions and linking the astronomical community to other scientific organizations such as the International Association of Geodesy, International VLBI Service for Geodesy and Astrometry, International GNSS Service, International Laser Ranging Service and International DORIS Service. During its entire history, IAU Commission 19/A2 has always worked in close cooperation with these and other related services to improve the accuracy and consistency of the Earth orientation parameters and celestial and terrestrial reference frames.

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