The ICRS constitutes the set of prescriptions and conventions together with the modelling required to define at any time a triad of axes. The System is realised by VLBI estimates of equatorial coordinates of a set of extragalactic compact radio sources, the International Celestial Reference Frame (ICRF). The ICRS can be connected to the International Terrestrial Reference System (ITRS) by use of the IERS Earth Orientation Parameters (EOP).

Contents	Equator/Pole and origin of Right Ascension.
Accuracy	Pole:	50 mas
	Origin of R.A.:	10 mas
Updates	/
Public access	http://hpiers.obspm.fr/icrs-pc/newwww/index.php
Format	/
Documentation	IERS Technical Note No. 23 IERS Conventions 2003, IERS Technical Note 32: 2. Conventional Celestial Reference System and Frame (PDF, 160KB, Not barrier-free file.) http://hpiers.obspm.fr/icrs-pc/newwww/index.php
Product Centre	IERS ICRS Centre