The ICRF: 2010 and Beyond

摘要

This paper considers future directions for improving the International Celestial Reference Frame (ICRF) over the next 10 years. The current ICRF includes a total of 717 extragalactic objects, most of which have position accuracies of 250-1000 microarcseconds (μas). Beyond 2010, the radio realization of the ICRF may be disputed by new instruments like the GAIA optical astrometric satellite which will observe 500 000 extragalactic objects with astrometric precision of 10-100 μas. The IVS should prepare for this challenge by improving as far as possible the present ICRF accuracy and source density. Position accuracies better than 100 μas may soon be achievable considering possible modeling refinements (troposphere, source structure) and improved instrumentation. Recent initiatives to densify the ICRF as well as future possibilities to massively increase the number of sources are discussed. Over 10+ years, the realization of an ultra-accurate extragalactic reference frame at both optical and radio wavelengths is an exciting perspective not only for astrometry but also for studying physics of active galactic nuclei.