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Status of the International Celestial Reference Frame

Status of the International Celestial Reference Frame. Alan L. Fey 3 rd IVS General Meeting February 9-11, 2004. Outline. Brief ICRF Timeline The ICRF ICRF Ext.1 ICRF Ext.2 ICRF Maintenance. Brief ICRF Timeline. 1988 IAU sets up working group to establish new CRF

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Status of the International Celestial Reference Frame

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  1. Status of the International Celestial Reference Frame Alan L. Fey 3rd IVS General Meeting February 9-11, 2004

  2. Outline • Brief ICRF Timeline • The ICRF • ICRF Ext.1 • ICRF Ext.2 • ICRF Maintenance

  3. Brief ICRF Timeline • 1988 IAU sets up working group to establish new CRF • 1991 IAU establishes theoretical basis for new CRF • 1994 IAU defines fiducial points for CRF as EG objects • 1995 sub-group of IAU WGRF tasked to construct CRF • 1997 IAU establishes the ICRS and adopts the ICRF • 1998 ICRF replaces FK5 as fundamental frame • 1999 ICRF Ext.1 completed • 2004 ICRF Ext.2 completed

  4. The ICRF(Ma et al. 1998, AJ, 116, 516)http://www.iers.org/iers/pc/icrs/ • Compact extragalactic radio sources • Dual frequency 2.3/8.4 GHz MkIII VLBI • All available data through July 1995 • 1.6 million observations • Global solution using CALC/SOLVE • Not a combination catalog

  5. The ICRF continued(Ma et al. 1998, AJ, 116, 516)http://www.iers.org/iers/pc/icrs/ • 608 total sources • 212 Defining sources • 294 Candidate sources • 162 Other sources • Defines ICRS Axes to ~20 micro-arcsec • ICRS axes have independent existence • ICRF is just one “realization”

  6. Sky Distribution of 212 ICRF Defining Sources

  7. Sky Distribution of 608 ICRF Sources

  8. ICRF Ext.1(1998 IERS Annual Report)http://www.iers.org/iers/pc/icrs/ • “Maintenance” Release • Refine positions of candidate/other sources • Provide positions of new sources • Added available data through April 1999 • Additional 0.6 million observations • 461 sessions • ICRF Solution parameterization

  9. ICRF Ext.1 continued(1998 IERS Annual Report)http://www.iers.org/iers/pc/icrs/ • 667 total sources • 212 Defining (same positions as ICRF) • 294 Candidate (refined positions) • 102 Other (refined positions) • 59 New sources

  10. Sky Distribution of 59 New ICRF Ext.1 Sources

  11. ICRF Ext.2(Fey et al. 2004, submitted to the Astronomical Journal)soon to be available at http://www.iers.org/iers/pc/icrs/ • “Maintenance” Release • Refine positions of candidate/other sources • Provide positions of new sources • Added available data through May 2002 • Additional 1.2 million observations • 400 sessions • Includes VLBA RDV data (30 sessions) • ICRF Solution parameterization

  12. ICRF Ext.2 continued(Fey et al. 2004, submitted to the Astronomical Journal)soon to be available at http://www.iers.org/iers/pc/icrs/ • 717 total sources • 212 Defining (same positions as ICRF) • 294 Candidate (refined positions) • 102 Other (refined positions) • 59 New from ICRF Ext.1 (refined positions) • 50 New sources

  13. Sky Distribution of 50 New ICRF Ext.2 Sources

  14. Sky Distribution of 717 ICRF Ext.2 Sources

  15. ICRF Maintenance • IERS charged by IAU with maintenance • Maintenance activities are run jointly by • IERS ICRS Product Center • International VLBI Service • In coordination with • IAU Working Group on ICRS

  16. ICRF Maintenance continued • Active Observing programs • IVS CRF Series of Experiments • Concentrate on Southern Hemisphere for monitoring • Increase source density of defining sources in South • VLBA RDV Series of Experiments • Cycle through Northern Hemisphere sources for monitoring • Joint GSFC/USNO/NRAO program • In ICRF Ext.2, RDV data account for ~20% of all data!

  17. ICRF Maintenance continued • Active Observing programs continued • IVS Geodetic/EOP Experiments • Concentrates primarily on brightest, most stable sources • IVS coordinated activity • VLBA Calibrator Surveys (VCS) • Expand list of geodetic sources • Expand list of phase reference calibrators for imaging • Joint NRAO/GSFC program

  18. Sky Distribution of 1332 VCS-1 Sources(Beasley et al. 2002, ApJS,141,13)

  19. ICRF Maintenance continued • Active Observing Programs continued • EVN Experiments • Increase source density of defining sources in Northern Hemisphere • Primarily Bordeaux Observatory program • LBA CRF Series of Experiments • New sources for densification of Southern Hemisphere • Joint USNO/ATNF program

  20. Sky Distribution of 22 New Southern Sources(Fey et al. 2004, submitted to the Astronomical Journal)

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