A consistent definition of time among operators in space is critical to successful space situational awareness capabilities, navigation, and communications. Image: IM_photo/Shutterstock.com
By: FEDweek StaffIn a rare if not unprecedented directive citing Albert Einstein’s theory of relativity as its basis, the White House has issued what it called “the first-ever U.S. government policy memorandum on time standards at and around celestial bodies other than Earth.”
“As NASA, private companies, and space agencies around the world launch missions to the Moon, Mars, and beyond, it’s important that we establish celestial time standards for safety and accuracy,” said the Office of Science and Technology Policy in a posting. “A consistent definition of time among operators in space is critical to successful space situational awareness capabilities, navigation, and communications, all of which are foundational to enable interoperability across the U.S. government and with international partners.”
The memo directs NASA to work with the Commerce, Defense, State, and Transportation to deliver a strategy for the implementation by the end of 2026 for “Coordinated Lunar Time,” to act as a standard and that can be tied to Coordinated Universal Time, the primary time standard globally used to regulate clocks and time on Earth.
Says the memo: “Due to general and special relativity, the length of a second defined on Earth will appear distorted to an observer under different gravitational conditions, or to an observer moving at a high relative velocity. For example, to an observer on the Moon, an Earth-based clock will appear to lose on average 58.7 microseconds per Earth-day with additional periodic variations. This holds important implications for developing standards and capabilities for operating on or around the Moon.
“Additionally, the navigation accuracy a system can achieve with signals from multiple space-based assets, such as a person navigating on Earth with signals from Global Positioning System satellites, depends on the synchronization of those assets with each other. At the Moon, synchronizing each lunar asset with an Earth-based time standard is difficult — due to relativistic effects, events that appear simultaneous at the Earth (e.g., the start of a broadcast signal) are not simultaneous to an observer at the Moon,” it says.
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