scholarly journals New Celestial Reference System

1980 ◽  
Vol 56 ◽  
pp. 305-316
Author(s):  
P. K. Seidelmann ◽  
G. H. Kaplan ◽  
T. C. Van Flandern
Keyword(s):  
Reference System ◽  
Reference Systems ◽  
Coordinate Systems ◽  
Strong Link ◽  
The Earth ◽  
Celestial Reference System ◽  
Observational Techniques ◽  
New System ◽  
Astronomical Constants ◽  
Planetary Theories

AbstractThe IAU (1976) System of Astronomical Constants, the FK5 and new lunar and planetary theories are being introduced in 1984. The investigation and planning for the transition has revealed the complex interdependencies between observational techniques and the reference systems, and their strong link to the rotating and orbiting Earth. The inaccuracies in our knowledge of the star positions, astronomical constants and the rotation and motion of the Earth are embedded in subtle ways in the observations and the reference coordinate systems. For example, the FK4 reference system in 1950.0 coordinates rotates with respect to an inertial system. Details are given for the conversion to the new system.

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 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.

scholarly journals 4 Ephemerides (Ephemerides)

1991 ◽  
Vol 21 (1) ◽  
pp. 1-6
Keyword(s):  
Working Group ◽  
Reference System ◽  
Reference Frames ◽  
General Assembly ◽  
Reference Systems ◽  
The Earth ◽  
Astronomical Constants ◽  
Future Reference

This report covers the period from 1 July 1987 to 30 June 1990. The ephemerides that have been published during this period have made use of the system of astronomical constants adopted at the 16th General Assembly of the IAU in Grenoble. At the same time that the use of the FK5 system on the J2000 epoch is increasing and catalogues are becoming available for that system, there is an IAU Working Group on Reference Systems with subgroups on astronomical constants, nutation of the Earth, time and reference frames/origin. The purpose is to define a future reference system and resolve some of the difficulties that occur in the system. It is anticipated that this Working Group will develop recommendations for consideration at the 21st General Assembly of the IAU.

scholarly journals The Celestial Reference System in Relativistic Framework

1990 ◽  
Vol 141 ◽  
pp. 99-110
Author(s):  
Han Chun-Hao ◽  
Huang Tian-Yi ◽  
Xu Bang-Xin
Keyword(s):  
Coordinate System ◽  
Reference Frame ◽  
Reference System ◽  
Light Deflection ◽  
Coordinate Systems ◽  
Definition Of ◽  
Celestial Sphere ◽  
Celestial Reference System ◽  
Relativistic Framework

The concept of reference system, reference frame, coordinate system and celestial sphere in a relativistic framework are given. The problems on the choice of celestial coordinate systems and the definition of the light deflection are discussed. Our suggestions are listed in Sec. 5.

scholarly journals High Delity Elastic Green's Functions for Subduction Zone Models Consistent With the Global Standard Geodetic Reference System

2020 ◽  
Author(s):  
Takane Hori ◽  
Ryoichiro Agata ◽  
Tsuyoshi Ichimura ◽  
Kohei Fujita ◽  
Takuma Yamaguchi ◽  
...  
Keyword(s):  
Reference System ◽  
Subduction Zones ◽  
Structural Models ◽  
Tsunami Hazard ◽  
Geodetic Reference System ◽  
Coordinate Systems ◽  
Ellipsoidal Shape ◽  
The Earth ◽  
Hazard Assessments ◽  
Realistic Topography

Abstract Green's functions (GFs) for elastic deformation due to unit slip on the fault plane comprise an essential tool for estimating earthquake rupture and underground preparation processes. These estimation results are often applied to generate important information for public such as seismic and tsunami hazard assessments. So, it is important to minimize the distortion of the estimation results on the numerical models used for calculating GFs to guarantee assessment reliability. For this purpose, we here calculated GFs based on a numerical model that is of high delity to obtain realistic topography and subsurface structural models of the Earth. We targeted two well-known subduction zones in Japan, the Nankai Trough and the Japan Trench. For these subduction zones, databases for realistic topography and subsurface structural models of the Earth are available in the \Japan integrated velocity structure model version 1", which was proposed for earthquake hazard assessments conducted by the Japanese government.Furthermore, in order to eliminate inconsistencies in data processing of the calculated and observed response, we used the same coordinate systems for processing GFs as those adopted widely to process space geodetic observation data for surface displacements. The ellipsoidal shape of the Earth, which is often approximated with a projected plane or a spherical shape, was also incorporated by faithfully following the denitions of the coordinate systems in Geodetic Reference System 1980, which is the global standard for space geodesy. To calculate elastic GFs based on such high delity subduction zone databases with the ellipsoidal shape of the Earth, we introduced the nite element (FE) method. In the FE meshes, the resolution of the topography and subsurface structure is the same as that of the original databases. Recent development of the state-of-the-art computation techniques for the rapid calculation of crustal deformation using large-scale FE models allows for GF calculation based on such a high delity model. However, it is generally not easy to perform such calculations. Thus, we released a library for the GFs calculated in this study to the geoscience community on a web server, aiming to contribute more reliable seismic and tsunami hazard assessment.

scholarly journals The Reference Systems

1979 ◽  
Vol 82 ◽  
pp. 151-163 ◽  
Author(s):  
J. Kovalevsky
Keyword(s):  
Observational Constraints ◽  
Reference Systems ◽  
Coordinate Systems ◽  
The Earth

In order to discuss accurately the motions of the Earth in space, it is necessary to define rigorously two readily accessible reference systems. The conception and the realization of celestial absolute systems and terrestrial coordinate systems are discussed. It is suggested that these systems of reference ought to be defined with a minimum of theoretical or observational constraints. Examples of such ideal reference systems are given, together with some desirable properties for intermediate systems.

Magnitudes and Spectra of Important Dynamical Phenomena

1975 ◽  
Vol 26 ◽  
pp. 63-77
Author(s):  
E. P. Fedotov
Keyword(s):  
Polar Motion ◽  
Continental Drift ◽  
Earth’S Rotation ◽  
Reference Systems ◽  
Coordinate Systems ◽  
Gravitation Field ◽  
Earth's Rotation ◽  
The Earth ◽  
Rigid Attachment ◽  
Body Tides

AbstractThe axes of coordinate systems used in geodynamics are believed to be attached to a number of physical points on the surface of the Earth. This is true when measurements of the distances (ranging) are dealt with. On the other hand, the axes of reference systems used by the BIH and IFMS are attached not to the points themselves but to a pencil of plumb lines at these points. For the case of observations with radio interferometers being used for the study of Earth’s rotation, the rotating frame of reference could be attached in some prescribed way toihebaselines of the interferometers.But in no case is rigid attachment possible, because both the above points and lines move relative to each other. We should search for another way to define the reference systems for geodynamics. With that end in view, a knowledge of magnitudes of pertinent dynamical phenomena becomes vital.This paper considers the effects of some dynamical phenomena upon the distances between the points on. the Earth’s surface and upon the angles between plumb lines and, possibly, also between baselines of radio interferometers. In particular, this paper discusses body tides, continental drift, internal motion within crustal blocks, redistribution of mass which can affect the directions of plumb lines, etc. Polar motion and variations in the rate of Earth’s rotation will be also touched upon as far as these phenomena contribute to deformation of the Earth and its gravitation field.The results are summarised in diagrams showing how the variations of the above distances and angles depend upon both time and positions on the Earth. In other words, the power spectrum of the variation will be presented as a function of time and distance expressed either in kilometers or in degrees of arc on the Earth’s surface.

General Principles for the Realization of Reference Systems for Earth Dynamics

1975 ◽  
Vol 26 ◽  
pp. 261-267 ◽  
Author(s):  
G. Veis
Keyword(s):  
Reference System ◽  
Reference Systems ◽  
The Earth ◽  
Direct Measurements ◽  
Planets And Satellites ◽  
Definition Of ◽  
Earth Dynamics ◽  
Dynamic Phenomena ◽  
Selection Of ◽  
Better Than

A reference system is useful to express conveniently the location of a point and to study kinematic and dynamic phenomena. Although the definition of a reference system is theoretically very simple, its realization becomes very fifficult since it must be achieved by measurements reduced and expressed in this system.A referenoe system can be materialized by direct measurements of the coordinates or, more frequently, indirectly by measuring differential quantities and calculating the coordinates “de proche en proche.” The accuracy of the system definition cannot be better than the accuracy of the measurements themselves.For Earth dynamics we need a reference system related to the Earth, but since observations of other bodies such as galaxies, stars, planets, and satellites also may be required, the reference systems in which the positions of these bodies are expressed must also be related to the selected terrestrial system.To optimize the selection of a reference system one must consider both the phase of the operations for the establishment of the system and the phase of the utilization of the system, because the establishment of a reference system is not the final goal.

scholarly journals Use of Gravity Measurements in Defining and Realizing Reference Systems for Geodynamics

1980 ◽  
Vol 56 ◽  
pp. 217-223
Author(s):  
J. D. Boulanger ◽  
N. N. Pariisky ◽  
L. P. Pellinen
Keyword(s):  
Reference System ◽  
Reference Ellipsoid ◽  
Reference Points ◽  
Sufficient Information ◽  
Reference Systems ◽  
The Earth ◽  
Gravity Measurements ◽  
Terrestrial Reference System

AbstractSingle measurements of gravity cannot give sufficient information about the position of measuring points with respect to some terrestrial reference system. Only a set of gravimetric stations all over the Earth combined with a determination of their coordinates allows one to determine (from the solution of Molodensky’s problem) the heights of these stations with respect to a level ellipsoid with center at the geocenter. Given in addition their heights above some reference ellipsoid, whose position in the Earth’s body is fixed through a set of reference points on its surface, the position of the geocenter in the same reference system may be obtained.

scholarly journals Motions of Artificial Satellites and Coordinate Systems

1980 ◽  
Vol 56 ◽  
pp. 233-237
Author(s):  
Yoshihide Kozai
Keyword(s):  
Reference System ◽  
Artificial Satellites ◽  
Reference Systems ◽  
Coordinate Systems ◽  
Advantages And Disadvantages

AbstractIn order to compute satellite motions with centimeter accuracy, the reference system, to which they are referred, should be carefully chosen. In fact there are many kinds of the reference systems. In this paper advantages and disadvantages of various reference systems are discussed.

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