scholarly journals New Definition for the Celestial Pole and the Celestial Origin in the ICRS

2002 ◽  
Vol 12 ◽  
pp. 102-106
Author(s):  
Nicole Capitaine
Keyword(s):  
Earth Rotation ◽  
High Frequency ◽  
Reference System ◽  
Polar Motion ◽  
The Other ◽  
General Assembly ◽  
Practical Application ◽  
Celestial Pole ◽  
Definition Of ◽  
Celestial Reference System

AbstractTwo Resolutions have been submitted to the 24thGeneral Assembly of the IAU concerning the definition and use of the celestial pole of reference and the celestial origin. The aim of both resolutions is to provide new parameters for Earth rotation which are consistent with the properties of the International Celestial Reference System (ICRS), adopted from 1 January 1998 as the IAU celestial reference system. The definition of the parameters have also to be consistent with the precision and the temporal resolution of the current Earth rotation measurements as well as with the theory for nutation and polar motion at the microarcsecond level. This paper explains the basis of the resolutions as well as their practical application. One of the resolutions defines the “Celestial Intermediate Pole” (CIP) in order to replace the “Celestial Ephemeris Pole” (CEP) for the new IAU precession-nutation model; its specifies the way for taking into account the constant offset from the ICRS and the high frequency terms in polar motion and nutation. The other resolution recommends the use of the “non-rotating origin” (Guinot 1979) on the moving equator, for defining Earth rotation and UT1; it also recommends the use of the celestial and terrestrial coordinates of the CIP in the transformation from the celestial to the terrestrial systems.

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.

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 On High Frequency Polar Motion and Length of Day Variations

2000 ◽  
Vol 178 ◽  
pp. 545-554
Author(s):  
K. Arfa-Kaboodvand ◽  
E. Groten
Keyword(s):  
Frequency Spectrum ◽  
Earth Rotation ◽  
High Frequency ◽  
Polar Motion ◽  
Length Of Day ◽  
Physical Processes ◽  
Earth Orientation ◽  
Tidal Forces ◽  
Diurnal Range ◽  
Insight Into

AbstractThe 0.042-day Earth rotation data (diurnal and semidiurnal) computed by the International GPS Service were used to analyze the daily/sub-daily variations of polar motion (PM) and length of day (LOD). Systematic and advanced spectral analytical investigations of the degree of periodic variability have been carried out. They show that the prominent periodical components can be found at the tidal frequencies of zonal, tesseral and sectorial waves. These investigations should give better insight into the physical processes, which influence Earth orientation (i.e. due to the atmospheric and oceanic motions, tidal forces etc.). It should be the basis for the detailed modeling of excitation functions in the sub-diurnal range of the high-frequency spectrum.

scholarly journals Nutation and reference frame

1995 ◽  
Vol 10 ◽  
pp. 228-231
Author(s):  
N. Capitaine
Keyword(s):  
Perturbation Theory ◽  
Reference Frame ◽  
Euler Equations ◽  
Coordinate Transformation ◽  
Earth Rotation ◽  
Reference System ◽  
Reference Frames ◽  
Fundamental Importance ◽  
Terrestrial Reference System ◽  
Celestial Reference System

The reference frames are of fundamental importance in all kinds of the precession and nutation studies involving the theory, the coordinate transformation and the observations. The aim of this paper is to review all the frames used in such studies and to lead to a better consistency between them in order that theory and reductions of observations be referred, as close as possible, to the frames to which observables are actually sensitive.The equations of Earth rotation can be expressed either as Euler equations in the Terrestrial Reference System (TRS), or as perturbation theory in the Celestial Reference System (CRS) (Kinoshita 1977). Euler equations are transformed to the CRS in the astronomical approach (Woolard 1953) and solved by the method of variation of the parameters, whereas, in the geophysical approach (Melchior 1971), the solutions, first obtained in the TRS, are transformed to the CRS and then solved by an integration with respect to time.

scholarly journals Overview, Formulation and Current Situation for Precession-Nutation

1998 ◽  
Vol 11 (1) ◽  
pp. 153-157
Author(s):  
N. Capitaine
Keyword(s):  
Earth Rotation ◽  
High Accuracy ◽  
Current Situation ◽  
Model Combining ◽  
Conventional Models ◽  
Definition Of ◽  
New Formulation ◽  
Improved Model ◽  
Celestial Reference System ◽  
Current Procedure

Abstract This paper describes the conventional models for precession and nutation, the current procedure for taking them into account in the reduction of highly accurate observations, the recent IAU recommendations on this topic, as well as the current situation for theory and observations. This emphasizes the imperfections in the conventional models and in the current procedure which are not in consistency either with the adoption of the new International Conventional Celestial Reference System (ICRS) or with the high accuracy and resolution of the current observations of Earth rotation. This addresses the question of the adoption of a new formulation and of an improved model combining precession and nutation of the equator with respect to the ICRS as well as the adoption of a revised definition of the Celestial Ephemeris Pole.

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 Comparison between Astronomical and Geodetic Coordinates

1991 ◽  
Vol 127 ◽  
pp. 210-210
Author(s):  
A. Banni ◽  
A. Poma ◽  
E. Proverbio ◽  
E. Falchi ◽  
F. Resta ◽  
...  
Keyword(s):  
Earth Rotation ◽  
Reference System ◽  
Temporal Variations ◽  
Coordinate Frame ◽  
Local Conditions ◽  
Geodetic Coordinates ◽  
Terrestrial Reference System ◽  
Definition Of

A requirement for solving Earth rotation problems is the definition of a terrestrial reference system (or systems) and the determination of a terrestrial coordinate frame (or frames). In this context it is important to determine the positions of the observing sites and their temporal variations and establish the dependence of the observations on local conditions and observing methods.In situ concurrent observations are therefore important. In this paper we report the results of a comparison between astronomical and geodetic coordinates derived from different observations at the Cagliari Observatory and the Carloforte latitude station.

scholarly journals Summary of IAU Joint Discussion 16, “The International Celestial Reference System, Maintenance and Future Realizations

2005 ◽  
Vol 13 ◽  
pp. 595-600
Author(s):  
Dennis D. McCarthy
Keyword(s):  
Working Group ◽  
Reference System ◽  
Reference Frames ◽  
General Assembly ◽  
Division 1 ◽  
The Future ◽  
System Maintenance ◽  
The Subject ◽  
The One ◽  
Celestial Reference System

AbstractThe IAU Joint Discussion 16 (JD16) was held in conjunction with the XXVth General Assembly in July, 2003. Papers related to the maintenance of the International Celestial Reference System were presented in the one-day session, and these were followed by discussion that pointed out the need for standard nomenclature. This issue was addressed by the formation of a Division 1 Working Group on the subject. JD16 also pointed out the requirement for a dynamical expression for precession which was addressed by the creation of a Division 1 Working Group on Precession and the Ecliptic. It also showed that although plans are being implemented to provide reference frames for the future, there is a need for improved coordination of astrometric observations. Finally it should be noted that the discussion pointed out the concern for the future organization of IAU Division 1.

scholarly journals Science Education as an Instrument for the Enhancement of National Security in Nigeria.

2019 ◽  
pp. 201-209
Author(s):  
Regina I. E.
Keyword(s):  
Science Education ◽  
National Security ◽  
Learning Process ◽  
National Development ◽  
The Other ◽  
Practical Application ◽  
Life Long Learning ◽  
Security Challenges ◽  
The Many ◽  
Definition Of

Education is conceived to be a life-long learning process that begins with the birth and ends with the death of a person. Education has equally been defined as a process by which individuals are assisted formally through proper direction and guidance to develop their capacities for their own benefit and that of the society. Science education on the other hand is a field of study that exposes learners to the contents as well as the methodology (processes) of acquiring scientific knowledge for practical application in relevant and applicable areas of life endeavours.This paper critically examined the dimensions of national security in Nigeria, the essence of government vis-à-vis citizens expectation, the definition of national security, the issue of insecurity, the many security challenges bedeviling the country and how Science education as an instrument can be used for the enhancement of national security in Nigeria. Since national security is important for national development, it is therefore meaningless to talk of development in the absence of national security. In otherwords, insecurity in a nation is a treat to development. In a state of insecurity, development is as elusive as a mirage. Useful recommendations were also made.

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