International Celestial Reference System
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International Celestial Reference System[‚in·tər¦nash·ən·əl si¦les·chəl ′ref·rəns ‚sis·təm]
A system that is realized by the International Celestial Reference Frame, made up from the positions of extragalactic radio sources, and that encompasses the standard reference frames, the transformations between them, and all the constants and motions involved, as well as the time scales specified for the reference frames and origins involved. It was adopted by the International Astronomical Union in 1994 as the fundamental reference system.