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International Celestial Reference System and its realizations

January 08, 2023

The International Celestial Reference System (ICRS) is the current standard celestial reference system adopted by the International Astronomical Union (IAU). Its origin is at the barycenter of the Solar System, with axes that are intended to "show no global rotation with respect to a set of distant extragalactic objects".[1][2] This fixed reference system differs from previous reference systems, which had been based on Catalogues of Fundamental Stars that had published the positions of stars based on direct "observations of [their] equatorial coordinates, right ascension and declination" [3] and had adopted as "privileged axes ... the mean equator and the dynamical equinox" at a particular date and time.[4]

The International Celestial Reference Frame (ICRF) is a realization of the International Celestial Reference System using reference celestial sources observed at radio wavelengths. In the context of the ICRS, a reference frame (RF) is the physical realization of a reference system, i.e., the reference frame is the set of numerical coordinates of the reference sources, derived using the procedures spelled out by the ICRS.[5]

More specifically, the ICRF is an inertial barycentric reference frame whose axes are defined by the measured positions of extragalactic sources (mainly quasars) observed using very long baseline interferometry while the Gaia-CRF is an inertial barycentric reference frame defined by optically measured positions of extragalactic sources by the Gaia satellite and whose axes are rotated to conform to the ICRF. Although general relativity implies that there are no true inertial frames around gravitating bodies, these reference frames are important because they do not exhibit any measurable angular rotation since the extragalactic sources used to define the ICRF and the Gaia-CRF are so far away. The ICRF and the Gaia-CRF are now the standard reference frames used to define the positions of astronomical objects.[6]

Reference systems and frames

It is useful to distinguish reference systems and reference frames. A reference frame has been defined as "a catalogue of the adopted coordinates of a set of reference objects that serves to define, or realize, a particular coordinate frame".[7] A reference system is a broader concept, encompassing "the totality of procedures, models and constants that are required for the use of one or more reference frames".[7][8]

Realizations

The ICRF is based on hundreds of extra-galactic radio sources, mostly quasars, distributed around the entire sky. Because they are so distant, they are apparently stationary to our current technology, yet their positions can be measured very accurately by Very Long Baseline Interferometry (VLBI). The positions of most are known to 1 milliarcsecond (mas) or better.[9]

In August 1997, the International Astronomical Union resolved in Resolution B2 of its XXIIIrd General Assembly "that the Hipparcos Catalogue shall be the primary realization of the ICRS at optical wavelengths."[6] The Hipparcos Celestial Reference Frame (HCRF) is based on a subset of about 100,000 stars in the Hipparcos Catalogue.[10] In August 2021 the International Astronomical Union decided in Resolution B3 of its XXXIst General Assembly "that as from 1 January 2022, the fundamental realization of the International Celestial Reference System (ICRS) shall comprise the Third Realization of the International Celestial Reference Frame (ICRF3) for the radio domain and the Gaia-CRF3 for the optical domain."[6]

Radio wavelengths (ICRF)

ICRF1

The ICRF, now called ICRF1, was adopted by the International Astronomical Union (IAU) as of 1 January 1998.[2] ICRF1 was oriented to the axes of the ICRS, which reflected the prior astronomical reference frame The Fifth Fundamental Catalog (FK5). It had an angular noise floor of approximately 250 microarcseconds (μas) and a reference axis stability of approximately 20 μas; this was an order-of-magnitude improvement over the previous reference frame derived from (FK5).[11][12] The ICRF1 contains 212 defining sources and also contains positions of 396 additional non-defining sources for reference. The positions of these sources have been adjusted in later extensions to the catalogue. ICRF1 agrees with the orientation of the Fifth Fundamental Catalog (FK5) "J2000.0" frame to within the (lower) precision of the latter.[2]

ICRF2

An updated reference frame ICRF2 was created in 2009.[12][13] The update was a joint collaboration of the International Astronomical Union, the International Earth Rotation and Reference Systems Service, and the International VLBI Service for Geodesy and Astrometry.[14] ICRF2 is defined by the position of 295 compact radio sources (97 of which also define ICRF1). Alignment of ICRF2 with ICRF1-Ext2, the second extension of ICRF1, was made with 138 sources common to both reference frames. Including non-defining sources, it comprises 3414 sources measured using very-long-baseline interferometry. The ICRF2 has a noise floor of approximately 40 μas and an axis stability of approximately 10 μas. Maintenance of the ICRF2 will be accomplished by a set of 295 sources that have especially good positional stability and unambiguous spatial structure.[15]

The data used to derive the reference frame come from approximately 30 years of VLBI observations, from 1979 to 2009.[12] Radio observations in both the S-band (2.3 GHz) and X-band (8.4 GHz) were recorded simultaneously to allow correction for ionospheric effects. The observations resulted in about 6.5 million group-delay measurements among pairs of telescopes. The group delays were processed with software that takes into account atmospheric and geophysical processes. The positions of the reference sources were treated as unknowns to be solved for by minimizing the mean squared error across group-delay measurements. The solution was constrained to be consistent with the International Terrestrial Reference Frame (ITRF2008) and earth orientation parameters (EOP) systems.[16]

ICRF3

ICRF3 is the third major revision of the ICRF, and was adopted by the IAU in August 2018, to become effective 1 January 2019. The modeling incorporates the effect of the galactocentric acceleration of the solar system, a new feature over and above ICRF2. ICRF3 also includes measurements at three frequency bands, providing three independent, and slightly different, realizations of the ICRS: dual frequency measurements at 8.4 GHz (X band) and 2.3 GHz (S band) for 4536 sources; measurements of 824 sources at 24 GHz (K band), and dual frequency measurements at 32 GHz (Ka band) and 8.4 GHz (X band) for 678 sources. Of these, 303 sources, uniformly distributed on the sky, are identified as "defining sources" which fix the axes of the frame. ICRF3 also increases the number of defining sources in the southern sky.[17][18][19]

Optical wavelengths

Hipparcos Celestial Reference Frame (HCRF)

In 1991 the International Astronomical Union recommended "that observing programmes be undertaken or continued in order to ... determine the relationship between catalogues of extragalactic source positions and ... the [stars of the] FK5 and Hipparcos catalogues."[1] Using a variety of linking techniques, the coordinate axes defined by the Hipparcos catalogue were aligned with the extragalactic radio frame.[20] In August 1997, the International Astronomical Union recognized in Resolution B2 of its XXIIIrd General Assembly "That the Hipparcos Catalogue was finalized in 1996 and that its coordinate frame is aligned to that of the frame of the extragalactic sources [ICRF1] with one sigma uncertainties of ±0.6 milliarcseconds (mas)" and resolved "that the Hipparcos Catalogue shall be the primary realization of the ICRS at optical wavelengths."[2]

Second Gaia celestial reference frame (Gaia–CRF2)

The second Gaia celestial reference frame (Gaia–CRF2), based on 22 months of observations of over half a million extragalactic sources by the Gaia spacecraft, appeared in 2018 and has been described as "the first full-fledged optical realisation of the ICRS, that is to say, an optical reference frame built only on extragalactic sources." The axes of Gaia-CRF2 were aligned to a prototype version of the forthcoming ICRF3 using 2820 objects common to Gaia-CRF2 and to the ICRF3 prototype.[21][22]

Third Gaia celestial reference frame (Gaia–CRF3)

The third Gaia celestial reference frame (Gaia–CRF3) is based on 33 months of observations of 1,614,173 extragalactic sources. As with The earlier Hipparcos and Gaia reference frames, the axes of Gaia-CRF3 were aligned to 3142 optical counterparts of ICRF-3 in the S/X frequency bands.[23][24] In August 2021 the International Astronomical Union noted that the Gaia-CRF3 had "largely superseded the Hipparcos Catalogue" and was "de facto the optical realization of the Celestial Reference Frame within the astronomical community." Consequently, the IAU decided that Gaia-CRF3 shall be "the fundamental realization of the International Celestial Reference System (ICRS) ... for the optical domain."[6]

See also

References

  1. ^ a b The XXIst General Assembly of the International Astronomical Union (1991). "Resolution No. A4; Recommendations from the Working Group on Reference System" (PDF). Resolutions adopted at the General Assemblies. International Astronomical Union. Retrieved 13 June 2022.
  2. ^ a b c d The XXlIIrd General Assembly of the International Astronomical Union (1997). "Resolution No B2; On the international celestial reference system" (PDF). Resolutions adopted at the General Assemblies. International Astronomical Union. Retrieved 13 June 2022.
  3. ^ Walter, Hans G.; Sovers, Oscar J. (2000), Astrometry of Fundamental Catalogues: The Evolution from Optical to Radio Reference Frames, Berlin: Springer, p. 1, ISBN 9783540674368
  4. ^ Arias, E.F.; Charlot, P.; Feissel, M.; Lestrade, J.-F. (1995), "The Extragalactic Reference System of the International Earth Rotation Service, ICRS", Astronomy and Astrophysics, 303: 604–608
  5. ^ "International Celestial Reference System (ICRS)". aa.usno.navy.mil. US Naval Observatory. Retrieved 23 June 2022.
  6. ^ a b c d The XXXIst General Assembly of the International Astronomical Union (2021). "Resolution B3, On the Gaia Celestial Reference Frame" (PDF). Resolutions adopted at the General Assemblies. International Astronomical Union. Retrieved 9 June 2022.
  7. ^ a b Wilkins, G.A. (1990). "The Past, Present and Future of Reference Systems for Astronomy and Geodesy". In Lieske, J. H.; Abalakin, V. K (eds.). Symposium - International Astronomical Union, Inertial Coordinate System on the Sky. Symposium - International Astronomical Union. Vol. 141. Cambridge University Press. pp. 39–46. doi:10.1017/S0074180900086149.
  8. ^ "International Celestial Reference System (ICRS)". U.S. Naval Observatory, Astronomical Applications. Retrieved 24 June 2022. A reference system ... defines the origin and fundamental planes (or axes) of the coordinate system. It also specifies all of the constants, models, and algorithms used to transform between observable quantities and reference data that conform to the system. A reference frame consists of a set of identifiable fiducial points on the sky (specific astronomical objects), along with their coordinates, that serves as the practical realization of a reference system.
  9. ^ "International Celestial Reference System (ICRS)". U.S. Naval Observatory, Astronomical Applications. Retrieved 23 June 2022.
  10. ^ "International Celestial Reference System (ICRS)". U S Naval Observatory, Astronomical Applications Department. Retrieved 22 June 2022.
  11. ^ Ma, C.; Arias, E. F.; Eubanks, T. M.; et al. (July 1998), "The International Celestial Reference Frame as Realized by Very Long Baseline Interferometry", Astronomical Journal, 116: 516–546, doi:10.1086/300408, S2CID 120005941, retrieved 18 June 2022
  12. ^ a b c (PDF). International Earth Rotation and Reference Systems Service (IERS). Archived from the original (PDF) on 25 July 2015. Retrieved 5 April 2014.
  13. ^ Steigerwald, Bell. "NASA - New Celestial Map Gives Directions for GPS". www.nasa.gov. NASA. Retrieved 5 June 2018.
  14. ^ Fey, Alan L. "The International Celestial Reference Frame". usno.navy.mil. US Naval Observatory (USNO). Retrieved 23 June 2022.
  15. ^ Boboltz, David A.; Gaume, R. A.; Fey, A. L.; Ma, C.; Gordon, D. (1 January 2010). "The Second Realization of the International Celestial Reference Frame (ICRF2) by Very Long Baseline Interferometry". AAS. p. 469.06. Bibcode:2010AAS...21546906B. Retrieved 18 July 2022.
  16. ^ Fey, A. L.; Gordon, D.; Jacobs, C. S.; Ma, C.; Gaume, R. A.; Arias, E. F.; Bianco, G.; Boboltz, D. A.; Böckmann, S.; Bolotin, S.; Charlot, P.; Collioud, A.; Engelhardt, G.; Gipson, J.; Gontier, A.-M.; Heinkelmann, R.; Kurdubov, S.; Lambert, S.; Lytvyn, S.; MacMillan, D. S.; Malkin, Z.; Nothnagel, A.; Ojha, R.; Skurikhina, E.; Sokolova, J.; Souchay, J.; Sovers, O. J.; Tesmer, V.; Titov, O.; Wang, G.; Zharov, V. (24 July 2015). "The Second Realization of the International Celestial Reference Frame by Very Long Baseline Interferometry". The Astronomical Journal. 150 (2): 58. doi:10.1088/0004-6256/150/2/58. hdl:11603/17528. ISSN 1538-3881. S2CID 3281444.
  17. ^ Charlot, P.; Jacobs, C.S.; Gordon, D.; et al. (2020). "The third realization of the International Celestial Reference Frame by very long baseline interferometry". Astronomy and Astrophysics. 644 (A159): A159. doi:10.1051/0004-6361/202038368. S2CID 225068756. Retrieved 16 June 2022.
  18. ^ "The ICRF". IERS ICRS Center. Paris Observatory. Retrieved 25 December 2018.
  19. ^ "The International Celestial Reference System (ICRS)". International Earth Rotation and Reference Systems Service. Retrieved 11 February 2020.
  20. ^ Kovalevsky, J.; Lindegren, L.; Perryman, M.A.C.; et al. (1997). "The Hipparcos Catalogue as a realisation of the extragalactic reference system". Astronomy and Astrophysics. 323: 620–633. Retrieved 20 June 2022.
  21. ^ Gaia Collaboration; Mignard, F.; Klioner, S.; Lindegren, L.; et al. (2018), "Gaia Data Release 2. The celestial reference frame (Gaia-CRF2)", Astronomy & Astrophysics, 616 (A14): A14, arXiv:1804.09377, Bibcode:2018A&A...616A..14G, doi:10.1051/0004-6361/201832916, S2CID 52838272
  22. ^ Lindegren, L.; Hernandez, J.; Bombrun, A.; Klioner, S.; et al. (2018), "Gaia Data Release 2 – The astrometric solution", Astronomy & Astrophysics, 616 (A2): A2, arXiv:1804.09366, Bibcode:2018A&A...616A...2L, doi:10.1051/0004-6361/201832727, S2CID 54497421
  23. ^ Gaia Collaboration (2022), "Gaia Early Data Release 3: The celestial reference frame (Gaia-CRF3)", Astronomy & Astrophysics, doi:10.1051/0004-6361/202243483, S2CID 248405779, retrieved 16 June 2022
  24. ^ "Gaia Early Data Release 3 (Gaia EDR3)". ESA. Retrieved 12 December 2020.

Further reading

  • Kovalevsky, Jean; Mueller, Ivan Istvan; Kołaczek, Barbara (1989) Reference Frames in Astronomy and Geophysics, Astrophysics and Space Science Library, Volume 154 Kluwer Academic Publishers ISBN 9780792301820
  • Jean Souchay; Martine Feissel-Vernier, eds. (2006). IERS Technical Notes - The International Celestial Reference System and Frame (Technical report). Frankfurt am Main: International Earth Rotation and Reference Systems Service (IERS) and Verlag des Bundesamts für Kartographie und Geodäsie. ISBN 3-89888-802-9. IERS Technical Note 34.

External links

  • International Celestial Reference System (ICRS) from USNO
  • Overview of ICRS and ICRF
  • IERS Conventions 2003 (defines ICRS and other related standards)
  • ICRF page from the International Earth Rotation Service
  • General information on the ICRS from IERS
  • ICRS Product Center

January 08, 2023
international, celestial, reference, system, realizations, international, celestial, reference, system, icrs, current, standard, celestial, reference, system, adopted, international, astronomical, union, origin, barycenter, solar, system, with, axes, that, int. The International Celestial Reference System ICRS is the current standard celestial reference system adopted by the International Astronomical Union IAU Its origin is at the barycenter of the Solar System with axes that are intended to show no global rotation with respect to a set of distant extragalactic objects 1 2 This fixed reference system differs from previous reference systems which had been based on Catalogues of Fundamental Stars that had published the positions of stars based on direct observations of their equatorial coordinates right ascension and declination 3 and had adopted as privileged axes the mean equator and the dynamical equinox at a particular date and time 4 The International Celestial Reference Frame ICRF is a realization of the International Celestial Reference System using reference celestial sources observed at radio wavelengths In the context of the ICRS a reference frame RF is the physical realization of a reference system i e the reference frame is the set of numerical coordinates of the reference sources derived using the procedures spelled out by the ICRS 5 More specifically the ICRF is an inertial barycentric reference frame whose axes are defined by the measured positions of extragalactic sources mainly quasars observed using very long baseline interferometry while the Gaia CRF is an inertial barycentric reference frame defined by optically measured positions of extragalactic sources by the Gaia satellite and whose axes are rotated to conform to the ICRF Although general relativity implies that there are no true inertial frames around gravitating bodies these reference frames are important because they do not exhibit any measurable angular rotation since the extragalactic sources used to define the ICRF and the Gaia CRF are so far away The ICRF and the Gaia CRF are now the standard reference frames used to define the positions of astronomical objects 6 Contents 1 Reference systems and frames 2 Realizations 2 1 Radio wavelengths ICRF 2 1 1 ICRF1 2 1 2 ICRF2 2 1 3 ICRF3 2 2 Optical wavelengths 2 2 1 Hipparcos Celestial Reference Frame HCRF 2 2 2 Second Gaia celestial reference frame Gaia CRF2 2 2 3 Third Gaia celestial reference frame Gaia CRF3 3 See also 4 References 5 Further reading 6 External linksReference systems and frames EditIt is useful to distinguish reference systems and reference frames A reference frame has been defined as a catalogue of the adopted coordinates of a set of reference objects that serves to define or realize a particular coordinate frame 7 A reference system is a broader concept encompassing the totality of procedures models and constants that are required for the use of one or more reference frames 7 8 Realizations EditThe ICRF is based on hundreds of extra galactic radio sources mostly quasars distributed around the entire sky Because they are so distant they are apparently stationary to our current technology yet their positions can be measured very accurately by Very Long Baseline Interferometry VLBI The positions of most are known to 1 milliarcsecond mas or better 9 In August 1997 the International Astronomical Union resolved in Resolution B2 of its XXIIIrd General Assembly that the Hipparcos Catalogue shall be the primary realization of the ICRS at optical wavelengths 6 The Hipparcos Celestial Reference Frame HCRF is based on a subset of about 100 000 stars in the Hipparcos Catalogue 10 In August 2021 the International Astronomical Union decided in Resolution B3 of its XXXIst General Assembly that as from 1 January 2022 the fundamental realization of the International Celestial Reference System ICRS shall comprise the Third Realization of the International Celestial Reference Frame ICRF3 for the radio domain and the Gaia CRF3 for the optical domain 6 Radio wavelengths ICRF Edit ICRF1 Edit The ICRF now called ICRF1 was adopted by the International Astronomical Union IAU as of 1 January 1998 2 ICRF1 was oriented to the axes of the ICRS which reflected the prior astronomical reference frame The Fifth Fundamental Catalog FK5 It had an angular noise floor of approximately 250 microarcseconds mas and a reference axis stability of approximately 20 mas this was an order of magnitude improvement over the previous reference frame derived from FK5 11 12 The ICRF1 contains 212 defining sources and also contains positions of 396 additional non defining sources for reference The positions of these sources have been adjusted in later extensions to the catalogue ICRF1 agrees with the orientation of the Fifth Fundamental Catalog FK5 J2000 0 frame to within the lower precision of the latter 2 ICRF2 Edit An updated reference frame ICRF2 was created in 2009 12 13 The update was a joint collaboration of the International Astronomical Union the International Earth Rotation and Reference Systems Service and the International VLBI Service for Geodesy and Astrometry 14 ICRF2 is defined by the position of 295 compact radio sources 97 of which also define ICRF1 Alignment of ICRF2 with ICRF1 Ext2 the second extension of ICRF1 was made with 138 sources common to both reference frames Including non defining sources it comprises 3414 sources measured using very long baseline interferometry The ICRF2 has a noise floor of approximately 40 mas and an axis stability of approximately 10 mas Maintenance of the ICRF2 will be accomplished by a set of 295 sources that have especially good positional stability and unambiguous spatial structure 15 The data used to derive the reference frame come from approximately 30 years of VLBI observations from 1979 to 2009 12 Radio observations in both the S band 2 3 GHz and X band 8 4 GHz were recorded simultaneously to allow correction for ionospheric effects The observations resulted in about 6 5 million group delay measurements among pairs of telescopes The group delays were processed with software that takes into account atmospheric and geophysical processes The positions of the reference sources were treated as unknowns to be solved for by minimizing the mean squared error across group delay measurements The solution was constrained to be consistent with the International Terrestrial Reference Frame ITRF2008 and earth orientation parameters EOP systems 16 ICRF3 Edit ICRF3 is the third major revision of the ICRF and was adopted by the IAU in August 2018 to become effective 1 January 2019 The modeling incorporates the effect of the galactocentric acceleration of the solar system a new feature over and above ICRF2 ICRF3 also includes measurements at three frequency bands providing three independent and slightly different realizations of the ICRS dual frequency measurements at 8 4 GHz X band and 2 3 GHz S band for 4536 sources measurements of 824 sources at 24 GHz K band and dual frequency measurements at 32 GHz Ka band and 8 4 GHz X band for 678 sources Of these 303 sources uniformly distributed on the sky are identified as defining sources which fix the axes of the frame ICRF3 also increases the number of defining sources in the southern sky 17 18 19 Optical wavelengths Edit Hipparcos Celestial Reference Frame HCRF Edit In 1991 the International Astronomical Union recommended that observing programmes be undertaken or continued in order to determine the relationship between catalogues of extragalactic source positions and the stars of the FK5 and Hipparcos catalogues 1 Using a variety of linking techniques the coordinate axes defined by the Hipparcos catalogue were aligned with the extragalactic radio frame 20 In August 1997 the International Astronomical Union recognized in Resolution B2 of its XXIIIrd General Assembly That the Hipparcos Catalogue was finalized in 1996 and that its coordinate frame is aligned to that of the frame of the extragalactic sources ICRF1 with one sigma uncertainties of 0 6 milliarcseconds mas and resolved that the Hipparcos Catalogue shall be the primary realization of the ICRS at optical wavelengths 2 Second Gaia celestial reference frame Gaia CRF2 Edit The second Gaia celestial reference frame Gaia CRF2 based on 22 months of observations of over half a million extragalactic sources by the Gaia spacecraft appeared in 2018 and has been described as the first full fledged optical realisation of the ICRS that is to say an optical reference frame built only on extragalactic sources The axes of Gaia CRF2 were aligned to a prototype version of the forthcoming ICRF3 using 2820 objects common to Gaia CRF2 and to the ICRF3 prototype 21 22 Third Gaia celestial reference frame Gaia CRF3 Edit The third Gaia celestial reference frame Gaia CRF3 is based on 33 months of observations of 1 614 173 extragalactic sources As with The earlier Hipparcos and Gaia reference frames the axes of Gaia CRF3 were aligned to 3142 optical counterparts of ICRF 3 in the S X frequency bands 23 24 In August 2021 the International Astronomical Union noted that the Gaia CRF3 had largely superseded the Hipparcos Catalogue and was de facto the optical realization of the Celestial Reference Frame within the astronomical community Consequently the IAU decided that Gaia CRF3 shall be the fundamental realization of the International Celestial Reference System ICRS for the optical domain 6 See also EditAstrometry Astronomy Barycentric and geocentric celestial reference systems International Terrestrial Reference System and FrameReferences Edit a b The XXIst General Assembly of the International Astronomical Union 1991 Resolution No A4 Recommendations from the Working Group on Reference System PDF Resolutions adopted at the General Assemblies International Astronomical Union Retrieved 13 June 2022 a b c d The XXlIIrd General Assembly of the International Astronomical Union 1997 Resolution No B2 On the international celestial reference system PDF Resolutions adopted at the General Assemblies International Astronomical Union Retrieved 13 June 2022 Walter Hans G Sovers Oscar J 2000 Astrometry of Fundamental Catalogues The Evolution from Optical to Radio Reference Frames Berlin Springer p 1 ISBN 9783540674368 Arias E F Charlot P Feissel M Lestrade J F 1995 The Extragalactic Reference System of the International Earth Rotation Service ICRS Astronomy and Astrophysics 303 604 608 International Celestial Reference System ICRS aa usno navy mil US Naval Observatory Retrieved 23 June 2022 a b c d The XXXIst General Assembly of the International Astronomical Union 2021 Resolution B3 On the Gaia Celestial Reference Frame PDF Resolutions adopted at the General Assemblies International Astronomical Union Retrieved 9 June 2022 a b Wilkins G A 1990 The Past Present and Future of Reference Systems for Astronomy and Geodesy In Lieske J H Abalakin V K eds Symposium International Astronomical Union Inertial Coordinate System on the Sky Symposium International Astronomical Union Vol 141 Cambridge University Press pp 39 46 doi 10 1017 S0074180900086149 International Celestial Reference System ICRS U S Naval Observatory Astronomical Applications Retrieved 24 June 2022 A reference system defines the origin and fundamental planes or axes of the coordinate system It also specifies all of the constants models and algorithms used to transform between observable quantities and reference data that conform to the system A reference frame consists of a set of identifiable fiducial points on the sky specific astronomical objects along with their coordinates that serves as the practical realization of a reference system International Celestial Reference System ICRS U S Naval Observatory Astronomical Applications Retrieved 23 June 2022 International Celestial Reference System ICRS U S Naval Observatory Astronomical Applications Department Retrieved 22 June 2022 Ma C Arias E F Eubanks T M et al July 1998 The International Celestial Reference Frame as Realized by Very Long Baseline Interferometry Astronomical Journal 116 516 546 doi 10 1086 300408 S2CID 120005941 retrieved 18 June 2022 a b c IERS Technical Note No 35 The Second Realization of the International Celestial Reference Frame by Very Long Baseline Interferometry PDF International Earth Rotation and Reference Systems Service IERS Archived from the original PDF on 25 July 2015 Retrieved 5 April 2014 Steigerwald Bell NASA New Celestial Map Gives Directions for GPS www nasa gov NASA Retrieved 5 June 2018 Fey Alan L The International Celestial Reference Frame usno navy mil US Naval Observatory USNO Retrieved 23 June 2022 Boboltz David A Gaume R A Fey A L Ma C Gordon D 1 January 2010 The Second Realization of the International Celestial Reference Frame ICRF2 by Very Long Baseline Interferometry AAS p 469 06 Bibcode 2010AAS 21546906B Retrieved 18 July 2022 Fey A L Gordon D Jacobs C S Ma C Gaume R A Arias E F Bianco G Boboltz D A Bockmann S Bolotin S Charlot P Collioud A Engelhardt G Gipson J Gontier A M Heinkelmann R Kurdubov S Lambert S Lytvyn S MacMillan D S Malkin Z Nothnagel A Ojha R Skurikhina E Sokolova J Souchay J Sovers O J Tesmer V Titov O Wang G Zharov V 24 July 2015 The Second Realization of the International Celestial Reference Frame by Very Long Baseline Interferometry The Astronomical Journal 150 2 58 doi 10 1088 0004 6256 150 2 58 hdl 11603 17528 ISSN 1538 3881 S2CID 3281444 Charlot P Jacobs C S Gordon D et al 2020 The third realization of the International Celestial Reference Frame by very long baseline interferometry Astronomy and Astrophysics 644 A159 A159 doi 10 1051 0004 6361 202038368 S2CID 225068756 Retrieved 16 June 2022 The ICRF IERS ICRS Center Paris Observatory Retrieved 25 December 2018 The International Celestial Reference System ICRS International Earth Rotation and Reference Systems Service Retrieved 11 February 2020 Kovalevsky J Lindegren L Perryman M A C et al 1997 The Hipparcos Catalogue as a realisation of the extragalactic reference system Astronomy and Astrophysics 323 620 633 Retrieved 20 June 2022 Gaia Collaboration Mignard F Klioner S Lindegren L et al 2018 Gaia Data Release 2 The celestial reference frame Gaia CRF2 Astronomy amp Astrophysics 616 A14 A14 arXiv 1804 09377 Bibcode 2018A amp A 616A 14G doi 10 1051 0004 6361 201832916 S2CID 52838272 Lindegren L Hernandez J Bombrun A Klioner S et al 2018 Gaia Data Release 2 The astrometric solution Astronomy amp Astrophysics 616 A2 A2 arXiv 1804 09366 Bibcode 2018A amp A 616A 2L doi 10 1051 0004 6361 201832727 S2CID 54497421 Gaia Collaboration 2022 Gaia Early Data Release 3 The celestial reference frame Gaia CRF3 Astronomy amp Astrophysics doi 10 1051 0004 6361 202243483 S2CID 248405779 retrieved 16 June 2022 Gaia Early Data Release 3 Gaia EDR3 ESA Retrieved 12 December 2020 Further reading EditKovalevsky Jean Mueller Ivan Istvan Kolaczek Barbara 1989 Reference Frames in Astronomy and Geophysics Astrophysics and Space Science Library Volume 154 Kluwer Academic Publishers ISBN 9780792301820 Jean Souchay Martine Feissel Vernier eds 2006 IERS Technical Notes The International Celestial Reference System and Frame Technical report Frankfurt am Main International Earth Rotation and Reference Systems Service IERS and Verlag des Bundesamts fur Kartographie und Geodasie ISBN 3 89888 802 9 IERS Technical Note 34 External links EditInternational Celestial Reference System ICRS from USNO Overview of ICRS and ICRF IERS Conventions 2003 defines ICRS and other related standards ICRF page from the International Earth Rotation Service General information on the ICRS from IERS ICRS Product CenterPortals Astronomy Stars Spaceflight Outer space Solar System Retrieved from https en wikipedia org w index php title International Celestial Reference System and its realizations amp oldid 1131242268, wikipedia, wiki, book, books, library,

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