Since 1998 Jan 1, the ICRS (International Celestial Reference System) has been adopted by the UAI as the conventional reference system. It replaced the FK5 from which its conception is basically different: it is based on the assumption that some objects of the universe emitting in the radio wavelengths have no sensible proper motions. We discuss the characteristics of the ICRS and of the ICRF (International Celestial Reference Frame), which is its practical realization.
Journées 1999 - systèmes de référence spatio-temporels & IX. Lohrmann-Kolloquium. Motion of celestial bodies, astrometry and astronomical reference frames
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- Reference Systems