ICRF – International Celestial Reference Frame

The ICRF is the standard celestial reference frame used in astronomy and geodesy, defined by the precise positions of extragalactic radio sources, mainly quasars. It provides a stable, quasi-inertial coordinate system for measuring positions and motions of celestial objects. In geodesy, the ICRF is fundamental for VLBI observations, allowing accurate determination of Earth orientation parameters, satellite orbits, and the connection between terrestrial and celestial reference systems.

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