International Celestial Reference System

The International Celestial Reference System ( ICRS ) or International heaven reference system is the agreed international, global reference system of Cartesian coordinates of the solar system. Its origin is the barycenter ( center of mass ) of the solar system. The axes are defined by the celestial reference pole and the spring equinox, the middle layer is determined by the direction of relations with extraterrestrial targets.

In Fundamental Catalogue 5 ( FK5 ) of the IAU system of celestial coordinates is realized by continuous long-term observation of the mean places of 1535 fundamental stars for the epoch J2000.0.

By determining the coordinates of 608 extragalactic sources of radiation, a concrete frame of reference of the ICRS is created, the International Celestial Reference Frame ( ICRF ).

The orientation parameters of the Earth over the stars and other geophysical data are provided by the International Earth Rotation and Reference Systems Service ( IERS ) are available.