VSOP Survey meeting

The ATNF Canberra office hosted a meeting of the nucleus of the data reduction team for the VLBI Space Observatory Programme (VSOP) Survey Program, 10-24 November 2000. Each VSOP Survey observation is made using the HALCA satellite in conjunction with typically three ground telescopes over a six hour HALCA orbit. For the Southern Hemisphere component of the Survey, antennas at Mopra, Hobart, Ceduna and Hartebeesthoek are major contributors.

One of the main aims of the Survey is to study the statistical properties of active galactic nuclei at sub-milliarcsecond resolution, corresponding to brightness temperatures above 10¹² K (Hirabayashi et al., Publ. Astron. Soc. Japan 52, 997-1014, 2000). The complete VSOP Survey sample includes all catalogued extragalactic radio sources in the sky with a total flux density at 5 GHz greater than 0.95 Jy, spectral index a >-0.45, and Galactic latitude |b|>10°. In addition, 37 extragalactic sources with total flux densities greater than 5 Jy were included regardless of their spectral index and galactic latitude. Sources from this sample of 402 sources which did not have a correlated flux density greater than 0.3 Jy on long Earth baselines were excluded from the subset selected for VSOP observations. As of 2000 December, 195 of the 289 selected sources (69 per cent) have been observed.

With over 100 observations reduced so far, much of the meeting concentrated on assessing the data calibration to ensure consistency in the final Survey product. The data reduction team were able to closely compare data from different ground arrays and from different correlators and in doing so were able to identify areas that require attention. In particular, understanding the flux density scale was given a high priority and ATCA flux monitoring data combined with the VLBA Pre-Launch Survey data were most useful in achieving this.

The meeting was attended by Richard Dodson (University of Tasmania), Ed Fomalont and George Moellenbrock (NRAO), Shinji Horiuchi (NAO, Japan), Jim Lovell (ATNF) and Bill Scott (University of Calgary).

Ed "Crocodile Dundee" Fomalont prepares for his trip to central Australia

Following the Survey meeting, Ed and George visited ATNF in Marsfield where Ed presented a colloquium on "The Evolution of the radio lobes in Sco-X1".

More information on the VSOP Survey can be found at http://www.vsop.isas.ac.jp/survey

Jim Lovell
(Jim.Lovell@atnf.csiro.au)