Lunar Coordinated Time (LTC) is intended to help ensure synchronization between the various lunar activities planned under the Artemis program.
Timekeeping is essential for space travel. It ensures that orbital maneuvers take place correctly, helps communications between spacecraft to remain secure and avoids positioning and mapping errors.
In other words, without it, lunar exploration would become very complicated.
We can blame Einstein and his theory of relativity for part of the problem. Time is felt differently in different gravitational conditions, an effect known as time dilation.
"The same clock we have on Earth would move at a different pace on the Moon," Kevin Coggins, NASA's head of space communications and navigation, told Reuters.
On the Moon, clocks move faster than their terrestrial counterparts by 58.7 microseconds per day. While most humans don't notice such a small difference, spacecraft certainly do.
Currently, spacecraft in low Earth orbit, such as GPS satellites and the International Space Station, work on the basis of Coordinated Universal Time (UTC).
But even in these cases, it is necessary to make periodic corrections for time dilation, otherwise GPS systems would lose accuracy and eventually fail.
According to Universe Today, the Apollo lunar missions in the 1960s-70s were based on Houston time.
Scott Alan Johnston
Mission control was the astronauts' timekeeper - although the astronauts took sidereal measurements using the stars to make sure they were on course and on time - which was enough for short lunar visits with just two vehicles (a command module and a landing module).
But with dozens of countries and private companies vying for long-term lunar exploration under the Artemis program, a shared timing system is going to be vital.
"Think of the atomic clocks at the US Naval Observatory (in Washington). They are the heartbeat of the nation, synchronizing everything. We'll want a heartbeat on the Moon," said Coggins.
NASA will need international cooperation to implement the LTC. UTC, the global standard for earth timekeeping, is managed by the International Bureau of Weights and Measures, and the LTC will probably have to be submitted to the same body to ensure that its implementation is accepted internationally.
The White House memorandum proposing the LTC recognized the need for international agreements to make it a reality. It suggested facilitating LTC through existing international bodies, but also through the Artemis Accords, a recent 36-nation agreement that defines guidelines for cooperative space exploration.
According to the memorandum, plans for the LTC should be completed by the end of 2026.
