US reckons it's about time the Moon had its own time zone

What's a few microseconds between friends? Quite a lot actually

NASA, which isn't known for timeliness, has been tasked by the White House with implementing a Coordinated Lunar Time (LTC) zone for the Moon traceable to Coordinated Universal Time (UTC).

Until now, most missions have operated on UTC, the successor to Greenwich Mean Time (GMT), as the reference time to work from. However, with lunar activity set to ramp in the coming decades, the US feels the need for time reference in cislunar space.

Part of the issue is that time runs differently as spacecraft venture away from Earth. The White House cited [PDF] the example of an Earth-based clock observed by someone on the Moon that would appear to lose an average of 58.7 microseconds per Earth day. This is not disastrous for talking on the radio, but it could be catastrophic for accurate navigation.

The Global Positioning System (GPS), for example, relies on highly accurate and synchronized clocks. Synchronizing a lunar asset with an Earth-based time standard is, therefore, difficult.

There is little detail on how the standard might be implemented. One suggestion is to set up atomic clocks on the Moon, similar to those used on Earth.

The US is not the only space agency to consider the problem of tracking time. The European Space Agency (ESA) has also been exploring the challenge of accurate timekeeping. ESA runs satellites and ground stations on what it calls "ESOC Time," named for its control center in Darmstadt, Germany.

ESA and NASA have been working on the LunaNet Interoperability Specification (LNIS), to be applied to future communication and navigation services on and around the Moon. Draft version 5 of LNIS was published on September 6, 2023.

The US wants LTC up and running by the end of December 2026, a bit late for the crewed Artemis III mission to the lunar surface, assuming current schedules are kept. The launch for Artemis III is still set for "no earlier than September 2026," and plans call for two of the four crew members to make their way down to the lunar surface.

Considering how much the Artemis program has slipped to date – the goal was 2024 then 2025 – there is every chance that the Moon might indeed get its own time zone or zones long before the surface is touched by flags and footprints once again. ®

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