Time stands still for no one. Nor is it ever the same. Because time varies so much on Earth, UTC, or Coordinated Universal Time, was defined as time at mean sea level. UTC is only a theoretical ideal. To realize it, International Atomic Time (TAI) weighs the average of hundreds of atomic clocks around the world. UTC must periodically insert “leap seconds” to keep it aligned with Earth solar days since the rate of the Earth’s rotation changes, and solar days are not always the same.
As if that isn’t complicated enough, measurement of Time in
space differs depending on where you are.
The experience of time is slower where there is more gravity, so a
second is longer on Earth than it is on the Moon. It also is different from both these places
if someone is moving through space at a high rate of speed.
Since many governments, including the United States, and
commercial entities are interested in returning to the Moon and establishing a
presence there, as well as using it as a stopping point for going to Mars,
there needs to be a standard measurement of time in space, specifically in
cislunar space (i.e. the space lying between and the Earth and the Moon
including the Moon’s orbit). The White
House Office of Science and Technology Policy (OSTP) has released a directive for NASA and the Departments of Commerce, Defense, State, and Transportation to
establish and be ready to implement a unified time standard -- Coordinated
Lunar Time (LTC) – by December 31, 2026.
NASA will also coordinate with the countries who have signed the ArtemisAccords. Time standardization is necessary for safety purposes, as well as
economic development and international collaboration. According to the OSTP policy memorandum:
“The approach to establish time standards consists of the
definition, development, and implementation of a distinct reference time at
each celestial body and its surrounding space environment. Each new time
standard developed will include the following features:
1. Traceability to Coordinated
Universal Time (UTC);
2. Accuracy sufficient to support
precision navigation and science;
3. Resilience to loss of contact
with Earth; and
4. Scalability to space
environments beyond the Earth-Moon system
Federal agencies will develop celestial time standardization
with an initial focus on the lunar surface and missions operating in Cislunar
space, with sufficient traceability to support missions to other celestial
bodies.”
The White House Office of Science and Technology Policy was
created by the National Science and Technology Policy, Organization, andPriorities Act of 1976. The OSTP heads
the National Science and Technology Council (NSTC) and its Subcommittee on
Cislunar Science & Technology. The Subcommittee
developed the National Cislunar Science and Technology Strategy on which
the new policy memorandum builds.
White House Office of Science and Technology Policy Releases Celestial Time Standardization Policy
