A Lunar Celestial Reference System

The International Celestial Reference System (ICRS) was adopted as the standard celestial reference system by the International Astronomical Union (IAU) through two resolutions in the 1990s. It was designed to be non-rotating with respect to distant extragalactic objects, with its origin fixed at the barycenter of the solar system, and serves as a common standard to define the positions and motions of all astronomical objects. Although the ICRS is applicable everywhere, it is not always the most practical system to express positioning and navigation, particularly in regard to the regions around rotating bodies. The motion of Earth orbiting satellites, for example, can be tracked using the Geocentric Celestial Reference System (GCRS), a system oriented about Earth’s center of mass. This global standard aids scientists and engineers by providing a common framework for operators to conveniently characterize Earth-orbiting resident space objects (RSOs).

The dawn of the Artemis era has introduced a need for a Lunar Celestial Reference System (LCRS), as an analog to the Earth-based GCRS. This system would serve as a simple tool for characterizing operations in the near-lunar environment, particularly for orbiting satellites and spacecraft. While the mathematics are not new, as they would mirror the GCRS framework, they are far from straightforward. It would also be important to establish the practical region of space for its use, along with appropriate transition locations from other reference systems. This presentation will touch on all aspects of this proposed system, including its development, implementation, and likely uses.