Integrated scientific and societal user requirements and functional specifications for the GGOS

As discussed in the previous chapters, the terrestrial reference frame is the foundation for virtually all space-based and ground-based Earth observations. Through its tie to the celestial reference frame by the time-dependent Earth rotation parameters it is also fundamentally important for interplanetary spacecraft tracking and navigation. Providing an accurate, stable, homogeneous, and maintainable terrestrial reference frame, celestial reference frame, and the Earth rotation parameters linking them together is one of the essential goals of GGOS.