Lunar exploration will see renewed momentum in the coming decade, with dozens of missions and plans to establish permanent bases. These projects bring countless challenges with them. One of them is a subtle but fundamental question: what time is it on the moon? Scientists around the world who deal with dimensions and their measurement, called metrologists, are working to find an answer.
“We’ve only just begun to look at this question,” says Cheryl Gramling, a space engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The moon currently has no independent time. Each lunar mission uses its own time scale, which is linked by the respective team on Earth to coordinated universal time (UTC) – the standard by which clocks on Earth are set. However, this method is relatively inaccurate, and the spacecraft exploring the moon do not synchronize time with each other. This approach works when there are only a few independent missions on the moon, but it becomes a problem when multiple spacecraft are working together. In addition, the space agencies want to follow the missions in the future with the help of satellite navigation, which depends on precise time signals.