IAU – International Astronomical Union

The IAU is the international organization responsible for promoting and coordinating astronomy and related scientific research. It defines astronomical standards, conventions, and nomenclature, including celestial reference systems used in geodesy. In geodesy, the IAU provides the framework for the International Celestial Reference Frame (ICRF) and Earth orientation conventions, ensuring consistent connection between celestial and terrestrial reference systems.

More Info: https://www.iau.org/