THE CELESTIAL REFERENCE FRAME AT 24 AND 43 GHz. I. ASTROMETRY

We present astrometric results for compact extragalactic objects observed with the Very Long Baseline Array at radio frequencies of 24 and 43 GHz. Data were obtained from ten 24 hr observing sessions made over a five-year period. These observations were motivated by the need to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies to enable improved deep space navigation after 2016 and to improve state-of-the-art astrometry. Source coordinates for 268 sources were estimated at 24 GHz and for 131 sources at 43 GHz. The median formal uncertainties of right ascension and declination at 24 GHz are 0.08 and 0.15 mas, respectively. Median formal uncertainties at 43 GHz are 0.20 and 0.35 mas, respectively. Weighted root-mean-square differences between the 24 and 43 GHz positions and astrometric positions based on simultaneous 2.3 and 8.4 GHz Very Long Baseline Interferometry observations, such as the ICRF, are less than about 0.3 mas in both coordinates. With observations over five years we have achieved a precision at 24 GHz approaching that of the ICRF but unaccounted systematic errors limit the overall accuracy of the catalogs.

[1]  Alan Lee Fey,et al.  The Proper Motion of 4C 39.25 , 1997 .

[2]  Giorgio Sedmak,et al.  Acquisition, processing and archiving of astronomical images , 1990 .

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

[4]  Gabor E. Lanyi,et al.  A comparison of mapped and measured total ionospheric electron content using global positioning system and beacon satellite observations , 1988 .

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

[6]  J. M. Benson.  The VLBA Correlator , 1995 .

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

[8]  First results from MASIV: The microarcsecond scintillation-induced variability survey , 2003, astro-ph/0306484.

[9]  Jaume Sanz,et al.  New approaches in global ionospheric determination using ground GPS data , 1999 .

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

[11]  Gerd Gendt,et al.  The International GPS Service: Celebrating the 10th anniversary and looking to the next decade , 2005 .

[12]  Patrick Charlot,et al.  The Second Extension of the International Celestial Reference Frame: ICRF-EXT.1 , 2004 .

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

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

[15]  Christopher S. Jacobs,et al.  Astrometry and geodesy with radio interferometry: experiments, models, results , 1998 .

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

[17]  Roger D. Blandford,et al.  Relativistic jets as compact radio sources , 1979 .

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

[19]  Anthony J. Mannucci,et al.  A global mapping technique for GPS‐derived ionospheric total electron content measurements , 1998 .

[20]  James S. Border,et al.  Angular Position Determination of Spacecraft by Radio Interferometry , 2007, Proceedings of the IEEE.

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

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