Synchronizing Watches between Earth and Moon Development, Implementation, and Challenges of Artemis Integrated Timing Architecture

The development of a common, consolidated, and consistent time distribution architecture for the Artemis enterprise is documented within this paper with a focus on the implementation challenges and concerns specific to lunar-centric timing systems. A summary of the short-term and long-term needs is presented to provide context for the sensitivity to time knowledge accuracy. Coordinating time across mission operation centers separated by large distances and under the influence of different gravitational fields adds complexity to the clock synchronization process, yet is necessary to achieve the navigation accuracy and meet Moon to Mars objectives. While initial missions are expected to have limited sensitivity to time knowledge uncertainty, long-term use cases and infrastructure become increasingly reliant on tight timing synchronization. To address this, the Artemis missions are projecting to initially use mathematical representations of lunar time for surface system operations by the second lunar surface mission. As communication and position, navigation, and time (PNT) infrastructures are deployed, they form the basis for broad time dissemination and synchronization, shifting the burden from the lunar user and the dependence away from terrestrial operators. The use of a consistent lunar time scale through a unified distribution network will enable the long-term exploration goals laid out for lunar science and exploration. As on Earth, a realizable uniform time scale will lower the barrier to entry to encourage a lunar ecosystem.