scholarly journals Fixed Point Method to Analyze Differences between Hipparcos and ICRF2

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
María José Martínez Usó ◽  
Francisco J. Marco Castillo ◽  
José Antonio López Ortí
Keyword(s):  
Fixed Point ◽  
Reference System ◽  
Radio Sources ◽  
Reduction Processes ◽  
International Astronomical ◽  
Hipparcos Catalogue ◽  
Working Groups ◽  
Celestial Reference System ◽  
Celestial Reference Frame ◽  
Current Representation

From 1998, the International Astronomical Union (IAU) adopted a new Celestial Reference System: the International Celestial Reference System (ICRS). The first optical materialization was the Hipparcos catalogue, defining the Hipparcos Celestial Reference Frame (HCRF). The compilation of subsequent radio sources catalogues culminated in the current representation of the ICRF, the ICRF2 catalogue that is not sufficiently dense to cover all astrometrical purposes. Linking Hipparcos and ICRF2 is essential to uniformize the reference regardless of whether it is visible (HCRF) or not (ICRF). Many working groups provide their own complementary catalogs, some of whose sources are also in the ICRF2, with different reduction processes for positions. The point is that they provide information in more than one reference for a small number of objects. Some of these projects have been used by us to study the Hipparcos-ICRF2 differences: a certain number of couples of catalogs can be interrelated using a set of parameters. With these couples, we build a closed cycle with the same ending and departure couple. The parameters obtained from each couple affect the next; thus we have an iterative process whose fixed point is the solution that stabilizes it, providing a preliminary link for Hipparcos-ICRF2.

scholarly journals Maintenance of the ICRF: Optical

1998 ◽  
Vol 11 (1) ◽  
pp. 322-324
Author(s):  
N. Zacharias
Keyword(s):  
Reference System ◽  
High Accuracy ◽  
Radio Sources ◽  
Practical Realization ◽  
Proper Motions ◽  
Hipparcos Catalogue ◽  
Optical Wavelengths ◽  
The Mean ◽  
Celestial Reference System ◽  
Celestial Reference Frame

The International Celestial Reference Frame (ICRF) is presently realized by the positions of 608 compact, extragalactic radio sources (Ma & Feissel 1997) with milliarcsecond (mas) and sub-mas accuracy, all being on the same system, the International Celestial Reference System (ICRS). The Hipparcos Catalogue (ESA 1997) is the practical realization of the ICRF at optical wavelengths, giving high accuracy positions (≈1 mas) and proper motions (≈1 mas/yr) for 117955 stars (ESA 1997). The link between the radio and optical frames has been achieved by various methods (Kovalevsky et al. 1997). The accuracy of this link is estimated to be 0.6 mas at the mean epoch of Hipparcos (1991.25) for the orientation, and 0.25 mas/year for the system rotation.

scholarly journals Extension of The Optical Reference Frame: Ground Based

1998 ◽  
Vol 11 (1) ◽  
pp. 300-303
Author(s):  
N. Zacharias
Keyword(s):  
Reference Frame ◽  
Radio Sources ◽  
Proper Motions ◽  
Magnitude Range ◽  
Optical Reference ◽  
Hipparcos Catalogue ◽  
Optical Wavelengths ◽  
The Mean ◽  
Celestial Reference System ◽  
Celestial Reference Frame

The International Celestial Reference Frame (ICRF) is realized by the positions of 608 compact extragalactic radio sources (Ma & Feissel 1997) with milliarcsecond (mas) and sub-mas accuracy, all being on the same system, the International Celestial Reference System (ICRS). The Hipparcos Catalogue (ESA 1997) is the practical realization of the ICRF at optical wavelengths, giving accurate positions (≈ 1 mas) at the mean epoch of 1991.25 and proper motions (≈ 1 mas/yr) for 117995 stars. This is about 2.5 stars per square degree, most being in the 7 to 9 magnitude range and a few as faint as 12. However, for many astronomical applications the Hipparcos Catalogue is not dense enough and does not reach faint enough magnitudes. The Tycho Catalogue (ESA 1997) provides accurate positions (≈ 25 mas) for about one million stars to magnitude 11, but lacks precise proper motions. Ground-based observations are an efficient way to complement the Hipparcos mission and to extend the optical reference frame to fainter magnitudes and yield a denser grid of astrometric standard stars. New reductions of early epoch photographic data will be used to provide highly accurate proper motions for stars to about magnitude 12. Current and new observational projects will extend the optical reference frame to even fainter magnitudes.

scholarly journals The Hipparcos Extragalactic Link

1995 ◽  
Vol 166 ◽  
pp. 127-132 ◽  
Author(s):  
Jean Kovalevsky
Keyword(s):  
Reference Frames ◽  
Hubble Space Telescope ◽  
Visible Spectrum ◽  
Proper Motions ◽  
Time Intervals ◽  
Hipparcos Catalogue ◽  
Celestial Reference System ◽  
Celestial Reference Frame ◽  
Galactic Radio ◽  
Better Than

In conformity with the IAU resolutions on reference frames adopted in 1991, the Hipparcos catalogue will represent, in the visible spectrum, the celestial reference system defined by fixed positions of extra-galactic radio-sources. This will be realized by the strongest possible link between the IERS celestial reference frame with positions and/or proper motions of the largest possible number of Hipparcos stars determined also with respect to extragalactic objects. The data which will be used must be available before April 1995. It will include the following: positions and proper motions of radio stars observed by VLBI, VLA and MERLIN; photographic positions in fields including quasars; proper motions with respect to galaxies of the Lick, Yale, and Kiev programs, proper motions derived from pairs of photographic plates taken at large time intervals; and possibly data acquired by Hubble Space Telescope and from Earth's rotation data. The organization of the tasks within the working group is briefly described. The final accuracy of the link is expected to be of the order of, or better than, half a milliarcsecond.

scholarly journals Extension of the Optical Reference Frame:Space Based

1998 ◽  
Vol 11 (1) ◽  
pp. 304-306
Author(s):  
S. Röser
Keyword(s):  
Reference Frame ◽  
General Assembly ◽  
Radio Sources ◽  
Practical Realization ◽  
The Earth ◽  
Optical Reference ◽  
Hipparcos Catalogue ◽  
Optical Wavelengths ◽  
Celestial Reference Frame ◽  
23Rd General

At its 23rd General Assembly, Kyoto 1997, the IAU decided that the International Celestial Reference Frame (ICRF) should be defined by the positions of 608 compact extragalactic radio sources (Ma & Feissel 1997), with the Hipparcos Catalogue (ESA 1997) being its practical realization at optical wavelengths. Although the Hipparcos instrument was unable to observe the defining sources of the ICRF directly in the optical regime, it is linked to the ICRF via a number of auxiliary observations (Kovalevsky et al. 1997). The Hipparcos Catalogue is the first celestial reference frame which is constructed from observations not made from the surface of the Earth.

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 Reference Catalogues — Present Status and Future Prospects

1994 ◽  
Vol 161 ◽  
pp. 261-270
Author(s):  
S. Roeser
Keyword(s):  
Reference Frame ◽  
Present Status ◽  
Reference System ◽  
Radio Sources ◽  
Proper Motions ◽  
Future Prospects ◽  
Practical Applications ◽  
Optical Wavelengths ◽  
Near Future ◽  
Celestial Reference Frame

The present celestial reference frame is represented by the positions and proper motions of the 4500 stars in the Fifth Fundamental Catalogue (FK5). For practical applications it is extended by the catalogues IRS (International Reference Stars) and PPM (Positions and Proper Motions). According to resolutions of the IAU the FK5 system will be replaced by a purely kinematically defined reference system defined by extragalactic radio sources in the near future. At optical wavelengths, the forthcoming Hipparcos Output Catalogue will be linked to the extragalactic system.

On discussion of the consequences of revolution in astrometry at the start of XXI century

2018 ◽  
Vol 930 (12) ◽  
pp. 44-53 ◽  
Author(s):  
S.A. Tolchelnikova
Keyword(s):  
Reference System ◽  
Radio Sources ◽  
International Astronomical Union ◽  
New Born ◽  
International Astronomical ◽  
Optical Reference

The purpose of the paper is to draw attention to the problems emerged in optical astrometry. It had to be developed by specialists in a new-born branch of radio physics named radio astrometry. The methods of the science with ancient origin were not familiar to them. The first step of reforms was the decision of International Astronomical Union about replacement of the International optical reference system by the radio reference system ICRS (ICRF). The decision retarded the development not only of fundamental astrometry and related sciences, but of astrophysics as well. 19 years passed after the decision, but radio frame (ICRF) is not used for reference either in space or in ground-based observations, or in geodesy as a reference for coordinates on Earth. The arguments of those who lobbied for the transition to radio sources remain unconfirmed

scholarly journals The First Decade of the IERS

2000 ◽  
Vol 178 ◽  
pp. 201-213 ◽  
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.

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.

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