The Second Extension of the International Celestial Reference Frame: ICRF-EXT.1

We use very long baseline interferometry data obtained between mid-1995 and the end of 2002 May together with older data to extend and revise the International Celestial Reference Frame ( ICRF). Revised positions of ICRF candidate and "other'' sources, based on inclusion of the additional data, are presented. Positions, in the frame of the ICRF, for an additional 109 new sources are also presented. All but four of the new sources are located north of delta = -30degrees. Positions of the ICRF defining sources remain unchanged. We present a summary of current astrometric and geodetic observing programs and discuss the evolution and future of the ICRF.

[1]  Michael Shao,et al.  SIM: the space interferometry mission , 1998, Astronomical Telescopes and Instrumentation.

[2]  Patrick Charlot,et al.  VLBA Observations of Radio Reference Frame Sources. II. Source Classification Based on Intrinsic Structure , 1996 .

[3]  A. Rogers Very Long Baseline Interferometry with Large Effective Bandwidth for Phase‐Delay Measurements , 1970 .

[4]  A. M. Gontier,et al.  Stability of the extragalactic VLBI reference frame , 2001 .

[5]  E. F. Arias,et al.  Representation of the International Celestial Reference System (ICRS) by different sets of selected radio sources , 2004 .

[6]  Patrick Charlot,et al.  The International Celestial Reference Frame as Realized by Very Long Baseline Interferometry , 1998 .

[7]  Thomas A. Clark,et al.  Radio-source positions from VLBI , 1986 .

[8]  A. Niell Global mapping functions for the atmosphere delay at radio wavelengths , 1996 .

[9]  W. E. Himwich,et al.  Reference Frames from CDP VLBI Data , 2013 .

[10]  M. Feissel-Vernier Selecting stable extragalactic compact radio sources from the permanent astrogeodetic VLBI program , 2003 .

[11]  P. Charlot,et al.  VLBA Observations of Radio Reference Frame Sources. III. Astrometric Suitability of an Additional 225 Sources , 2000 .

[12]  Patrick Charlot,et al.  VLBA OBSERVATIONS OF RADIO REFERENCE FRAME SOURCES. II. ASTROMETRIC SUITABILITY BASED ON OBSERVED STRUCTURE , 1997 .

[13]  C. Bizouard,et al.  Remaining error sources in the nutation at the submilliarc second level , 2003 .

[14]  Thomas A. Clark,et al.  Measurement of horizontal motions in Alaska using very long baseline interferometry , 1990 .

[15]  E. Fomalont,et al.  The VLBA Calibrator Survey—VCS1 , 2002, astro-ph/0201414.

[16]  Alan Whitney,et al.  Precision Geodesy Using the Mark-III Very-Long-Baseline Interferometer System , 1985, IEEE Transactions on Geoscience and Remote Sensing.

[17]  D. MacMillan,et al.  The Second VLBA Calibrator Survey: VCS2 , 2003 .

[18]  D. S. MacMillan,et al.  Atmospheric gradients and the VLBI terrestrial and celestial reference frames , 1997 .

[19]  NASA Space Geodesy Program: GSFC data analysis, 1992. Crustal Dynamics Project VLBI geodetic results, 1979 - 1991 , 1993 .

[20]  K. Johnston,et al.  Extragalactic Radio Source Selection for Use in Directly Linking Optical Astrometric Observations to the Radio Reference Frame , 2001 .

[21]  Alan R. Whitney The Mark IV VLBI Data-Acquisition and Correlation System , 1993 .