[News Terms] NASA to Establish 'Dal Standard Time'

The Moon's clock is about 56 microseconds faster than Earth's per 24 hours
Currently using UTC, spacecraft cannot synchronize time, raising 'collision' concerns
"International agreement needed through international organizations and Artemis Accords"

'Lunar Time Coordinated (LTC)' refers to the standard time on the Moon, which follows a different time progression system than Earth. It is analyzed to potentially provide a reference for missions on the Moon that require extreme accuracy.

On the Moon, it takes an average of 29.5 Earth days from one noon (the time when the Sun crosses the meridian) to the next noon.

China launched the manned spacecraft Shenzhou 17 on October 26 last year from the Jiuquan Satellite Launch Center in Gansu Province, carrying it on the Long March 2F Yao rocket.
[Photo by Beijing AFP/ Yonhap News]

Since the Moon's gravity is about one-sixth that of Earth's, according to the theory of special relativity, clocks on the Moon run faster than those on Earth. This means that a clock on the Moon gains about 56 microseconds (μs: one-millionth of a second) every 24 hours. Additionally, due to the Moon's rotation, the time can vary depending on the location where the clock is placed.

Currently, missions related to the Moon use 'Universal Time Coordinated (UTC),' which has been in effect since January 1, 1972, as the standard. This method synchronizes signals obtained through two-way communication chronometers onboard spacecraft and large deep-space antennas on Earth with UTC. Instead of using the Moon's own time, Earth standard time is borrowed and used as the standard time.

Using UTC as the standard on the Moon is effective when a small number of spacecraft independently carry out missions, but spacecraft on the Moon cannot verify time with each other, inevitably causing confusion. Although the Moon's surface area is larger than the combined areas of the United States and China, the 'prime spots' suitable for building bases are limited, so collisions in these areas may be unavoidable.

To establish a standard time for the Moon, at least three master atomic clocks must first be installed on the Moon to understand the natural time pace there. By analyzing this pace with algorithms, a more accurate virtual lunar clock can be created, and a decision can be made on which method to use to define the Moon's standard time among various options.

The most straightforward method is to align the Moon's time with Earth's UTC. This involves setting the Moon's virtual time to Earth's UTC at regular intervals, which has the advantage of being easy for humans on Earth to use.

Another method is to make the Moon's virtual clock its own time standard. This approach avoids confusion even if communication with Earth is lost, maintains navigation and communication safety, and can be applied to planets with more difficult communication than the Moon, such as Mars. However, this method requires further research on how to reconcile the difference between the Moon's day length and Earth's day length.

The lunar lander SLIM, launched by the Japan Aerospace Exploration Agency (JAXA), successfully made a soft landing on the lunar surface approximately 55 meters east of the originally targeted landing site. The image shows SLIM landing on the lunar surface on January 20.
[Photo by EPA-JAXA/Yonhap News]

On the 2nd (local time), Reuters reported that the White House has instructed NASA and other agencies to create a unified standard time for the Moon and other celestial bodies by 2026.

The White House Office of Science and Technology Policy (OSTP) stated, "Without a standard time, it will be difficult to safely guarantee data transmission between spacecraft or synchronize communication between Earth, the Moon, and astronauts," adding, "International consensus through existing international organizations and the Artemis Accords will be necessary to define how to implement LTC."

Thirty-six countries participate in the Artemis Accords, but China and Russia are not among them. Thanks to the importance of the Moon base as a potential source of mineral resources and a foothold for missions to Mars and other destinations, not only countries like the United States and China but also private companies have recently been accelerating lunar exploration.

Japan became the fifth country to send a spacecraft to the Moon last January, and India became the first country to land a spacecraft near the lunar south pole last year. China aims to send a manned exploration spacecraft to the Moon by 2030. NASA is pushing for a mission to return astronauts to the Moon in September 2026 and a mission in September 2025 where four astronauts orbit the Moon and return.