scholarly journals Models and nomenclature in Earth rotation

2009 ◽  
Vol 5 (S261) ◽  
pp. 69-78
Author(s):  
Nicole Capitaine
Keyword(s):  
Earth Model ◽  
Earth’S Rotation ◽  
New Paradigm ◽  
Earth Orientation Parameters ◽  
Earth's Rotation ◽  
Fundamental Astronomy ◽  
Rigid Earth ◽  
Definition Of ◽  
Celestial Reference System ◽  
Orientation Parameters

AbstractThe celestial Earth's orientation is required for many applications in fundamental astronomy and geodesy; it is currently determined with sub-milliarcsecond accuracy by astro-geodetic observations. Models for that orientation rely on solutions for the rotation of a rigid Earth model and on the geophysical representation of non-rigid Earth effects. Important IAU 2000/2006 resolutions on reference systems have been passed (and endorsed by the IUGG) that recommend a new paradigm and high accuracy models to be used in the transformation from terrestrial to celestial systems. This paper reviews the consequences of these resolutions on the adopted Earth orientation parameters, IAU precession-nutation models and associated nomenclature. It summarizes the fundamental aspects of the current IAU precession-nutation models and reports on the consideration of General Relativity (GR) in the solutions. This shows that the current definitions and nomenclature for Earth's rotation are compliant with GR and that the IAU precession-nutation is compliant with the IAU 2000 definition of the geocentric celestial reference system in the GR framework; however, the underlying Earth's rotation models basically are Newtonian.

scholarly journals Definition of the Celestial Ephemeris Pole and the Celestial Ephemeris Origin

2000 ◽  
Vol 180 ◽  
pp. 153-163 ◽  
Author(s):  
Nicole Capitaine
Keyword(s):  
Earth Rotation ◽  
Polar Motion ◽  
Sidereal Time ◽  
Earth Orientation Parameters ◽  
Current Definition ◽  
The Earth ◽  
Definition Of ◽  
Celestial Reference System ◽  
Orientation Parameters ◽  
New Strategies

AbstractThe adoption of the International Celestial Reference System (ICRS) by the IAU in use since 1 January 1998, and the accuracy achieved by the most recent models and observations of Earth rotation call for a redefinition of the Earth Orientation Parameters (EOP). First, the precession-nutation parameters and Greenwich sidereal time, which are currently defined in the FK5 System, have to be re-defined to be consistent with the ICRS. Second, the current definition of the Celestial Ephemeris Pole (CEP) has to be extended in order to be consistent with the most recent models for nutation and polar motion at a microarsecond accuracy including diurnal and sub-diurnal components, as well as with new strategies of observations. Such issues have been under consideration by the subgroup T5 named “Computational Consequences” of the IAU Working Group “ICRS”. This paper gives, as the basis for future recommendations, the preliminary proposals of the subgroup T5 for a modern definition of the CEP, for the definition of more basic EOP in the ICRS and for the choice of a new origin on the equator of the CEP in place of the equinox. Then, the paper emphasizes the use of the Celestial Ephemeris Origin (CEO) which is defined as the “non-rotating origin” in the celestial frame on the equator of the CEP.

Overview and Proposition for a Modern Definition of the CEP

2000 ◽  
Vol 178 ◽  
pp. 571-584
Author(s):  
Nicole Capitaine
Keyword(s):  
Working Group ◽  
Polar Motion ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
The Earth ◽  
Conventional Models ◽  
Definition Of ◽  
Orientation Parameters ◽  
Observational Procedure

AbstractThe current IAU conventional models for precession and nutation are referred to the Celestial Ephemeris Pole (CEP). However, the concept corresponding to the CEP is not clear and cannot easily be extended to the most recent models and observations. Its realization is actually dependent both on the model used for precession, nutation and polar motion and on the observational procedure for estimating the Earth orientation parameters. A new definition of the CEP should therefore be given in order to be in agreement with modern models and observations at a microarsecond level. This paper reviews the various realizations of the pole according to the models and observations and discusses the proposals for a modern definition of the CEP that are under consideration within the work of the subgroup T5 entitled “Computational Consequences” of the “ICRS” IAU Working Group.

scholarly journals A Terrestrial Reference System Consistent with WGRS

1991 ◽  
Vol 127 ◽  
pp. 211-214 ◽  
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.

scholarly journals Earth Orientation Parameters 1899.7-1992.0 In The Hipparcos Reference Frame

1998 ◽  
Vol 11 (1) ◽  
pp. 553-553
Author(s):  
J. Vondrák ◽  
C. Ron ◽  
I. Pešek ◽  
A. Čepek
Keyword(s):  
Polar Motion ◽  
Universal Time ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
The Earth ◽  
Hipparcos Catalogue ◽  
Time Variations ◽  
Celestial Reference System ◽  
Orientation Parameters ◽  
Made In

The optical astrometry observations of latitude/universal time variations made with 48 instruments at 31 observatories are used to determine the Earth orientation parameters (EOP) since the beginning of the century. The Hipparcos Catalogue is used to bring more than four million individual observations, made in the interval 1899.7-1992.0, into the International Celestial Reference System. The Earth orientation parameters (polar motion, celestial pole offsets and, since 1956.0, also universal time UT1) are determined at 5-day intervals, with average uncertainties ranging from 8 mas (in the eighties) to about 40 mas (in the forties). Making use of very long series of ground-based observations, the solution also leads to the improvement of proper motions of about ten per cent of the observed Hipparcos stars, with precision of ±0.2 — 0.5 mas/yr. In addition, 474 auxiliary parameters, describing the rheological properties of the Earth and seasonal deviations of the observations at contributing observatories, are found. The new solution provides the EOP series suitable for further analyses, e.g., for studying long-periodic polar motion, length-of-day changes or precession/nutation.

scholarly journals Permanent Milliarcsecond Link of Celestial and Terrestrial Reference Systems

1991 ◽  
Vol 127 ◽  
pp. 101-107
Author(s):  
M. Feissel
Keyword(s):  
Reference System ◽  
Artificial Satellites ◽  
Radio Sources ◽  
Reference Systems ◽  
International Earth Rotation Service ◽  
Earth Orientation Parameters ◽  
Long Baseline ◽  
The Earth ◽  
Celestial Reference System ◽  
Orientation Parameters

AbstractThe celestial reference system and the terrestial reference system of the International Earth Rotation Service (IERS) are realized on the basis of observation programs in Very Long Baseline radio Interferometry and laser ranging to the Moon and artificial satellites. The celestial frame is materialized by the equatorial coordinates of radio sources observed in VLBI; the terrestrial frame is materialized by the cartesian coordinates of the terrestrial sites monitored by the three techniques. Series of the Earth Orientation Parameters are derived from the same observations. These series provide a permanent link between the celestial system and the terrestrial system at the level of 0.001”.The global adjustment in which the reference systems are defined and realized is described, and the metrological properties of the frames and of the derived EOP are evaluated.

scholarly journals The CEP and Geophysical Interpretation of Modern Earth Rotation Observations

2000 ◽  
Vol 178 ◽  
pp. 585-594 ◽  
Author(s):  
Aleksander Brzeziński
Keyword(s):  
Earth Rotation ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
Conceptual Definition ◽  
The Earth ◽  
Geophysical Interpretation ◽  
Definition Of ◽  
Geophysical Fluids ◽  
Orientation Parameters ◽  
Excitation Parameters

AbstractThe definition of the Celestial Ephemeris Pole (CEP) which is the pole of reference for precession and nutation, should be revised taking into account recent advances in observation and theory. This paper reviews the current realization of the CEP and discusses possible extensions of both the conceptual definition and the realization of the CEP. Attention is focused on the corresponding connections between the Earth orientation parameters describing rotational variations and the related excitation parameters expressing dynamics of the geophysical fluids.

scholarly journals The space–time references of BeiDou Navigation Satellite System

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Chunhao Han ◽  
Li Liu ◽  
Zhiwu Cai ◽  
Yuting Lin
Keyword(s):  
Reference System ◽  
Time Synchronization ◽  
Satellite System ◽  
Space Time ◽  
Earth Orientation Parameters ◽  
Beidou Navigation Satellite System ◽  
The Earth ◽  
Celestial Reference System ◽  
Orientation Parameters ◽  
Master Control

AbstractThe BeiDou Navigation Satellite System (BDS) is essentially a precise time measurement and time synchronization system for a large-scale space near the Earth. General relativity is the basic theoretical framework for the information processing in the master control station of BDS. Having introduced the basic conceptions of relativistic space–time reference systems, the space–time references of BDS are analyzed and the function and acquisition method of the Earth Orientation Parameters (EOP) are briefly discussed. The basic space reference of BDS is BeiDou Coordinate System (BDCS), and the time standard is the BDS Time (BDT). BDCS and BDT are the realizations of the Geocentric Terrestrial Reference System (GTRS) and the Terrestrial Time (TT) for BDS, respectively. The station coordinates in the BDCS are consistent with those in International Terrestrial Reference Frame (ITRF)2014 at the cm–level and the difference in scale is about $$1.1 \times 10^{ - 8}$$ 1.1 × 10 - 8 . The time deviation of BDT relative to International Atomic Time (TAI) is less than 50 ns and the frequency deviation is less than $$2 \times 10^{ - 14}$$ 2 × 10 - 14 . The Geocentric Celestial Reference System (GCRS) and the solar Barycentric Celestial Reference System (BCRS) are also involved in the operation of BDS. The observation models for time synchronization and precise orbit determination are established within the GCRS framework. The coordinate transformation between BDCS and GCRS is consistent with the International Earth Rotation and Reference Systems Service (IERS). In the autonomous operation mode without the support of the ground master control station, Earth Orientation Parameters (EOP) is obtained by means of long-term prediction and on-board observation. The observation models for the on-board astrometry should be established within the BCRS framework.

scholarly journals Estimation of VGOS Station Coordinates

2020 ◽  
Author(s):  
Markus Mikschi ◽  
Johannes Böhm ◽  
Matthias Schartner
Keyword(s):  
Global Solution ◽  
Very Long Baseline Interferometry ◽  
A Priori ◽  
Terrestrial Reference Frame ◽  
Normal Equation ◽  
Earth Orientation Parameters ◽  
Long Baseline ◽  
Station Coordinates ◽  
Definition Of ◽  
Orientation Parameters

<p>With the number of available VGOS (VLBI Global Observing System) sessions rising, precise coordinates for the participating stations become more important. While station coordinates can be estimated during the VLBI (Very Long Baseline Interferometry) analysis, the definition of the geodetic datum via Not-Net-Rotation (NNR) and No-Net-Translation (NNT) conditions requires at least three participating stations with precise a priori coordinates. The VGOS station network is currently independent of the International Terrestrial Reference Frame (ITRF), as none of the stations have participated in a solution for the ITRF in VGOS mode. By estimating the VGOS station coordinates based on ITRF coordinates, originating from local surveying and solutions of S/X observations by now converted stations, a link to the ITRF can be established. First a global solution, which is the combination of individual sessions on the normal equation level, of the five VGOS CONT17 sessions was calculated. The datum was defined by WESTFORD, ISHIOKA and WETTZ13S whereby the coordinates of the first two stations are known from S/X observations and of the latter from local surveying. With velocities from adjacent stations, the estimated coordinates were used to calculate a global solution of the 2019 VGOS sessions. The obtained coordinates were assessed on basis of formal errors, coordinate repeatability and comparisons of estimated Earth Orientation Parameters (EOP) time series with fixed station coordinates to the 14 C04 a priori dataset.</p>

scholarly journals Definition and realization of the celestial intermediate reference system

2007 ◽  
Vol 3 (S248) ◽  
pp. 367-373 ◽  
Author(s):  
N. Capitaine
Keyword(s):  
Reference System ◽  
Reference Systems ◽  
The Earth ◽  
Fundamental Astronomy ◽  
International Terrestrial Reference System ◽  
Terrestrial Reference System ◽  
Rotation Of The Earth ◽  
Definition Of ◽  
Sidereal Rotation ◽  
Celestial Reference System

AbstractThe transformation between the International Terrestrial Reference System (ITRS) and the Geocentric Celestial Reference system (GCRS) is an essential part of the models to be used when dealing with Earth's rotation or when computing directions of celestial objects in various systems. The 2000 and 2006 IAU resolutions on reference systems have modified the way the Earth orientation is expressed and adopted high accuracy models for expressing the relevant quantities for the transformation from terrestrial to celestial systems. First, the IAU 2000 Resolutions have refined the definition of the astronomical reference systems and transformations between them and adopted the IAU 2000 precession-nutation. Then, the IAU 2006 Resolutions have adopted a new precession model that is consistent with dynamical theories and have addressed definition, terminology or orientation issues relative to reference systems and time scales that needed to be specified after the adoption of the IAU 2000 resolutions. These in particular provide a refined definition of the pole (the Celestial intermediate pole, CIP) and the origin (the Celestial intermediate origin, CIO) on the CIP equator as well as a rigorous definition of sidereal rotation of the Earth. These also allow an accurate realization of the celestial intermediate system linked to the CIP and the CIO that replaces the classical celestial system based on the true equator and equinox of date. This talk explains the changes resulting from the joint IAU 2000/2006 resolutions and reviews the consequences on the concepts, nomenclature, models and conventions in fundamental astronomy that are suitable for modern and future realizations of reference systems. Realization of the celestial intermediate reference system ensuring a micro-arc-second accuracy is detailed.

Sign in / Sign up

Export Citation Format

Share Document