Context
The US directed NASA to establish a Coordinated Lunar Time (LTC) to standardize cislunar operations with Earth’s universal time to enhance scientific missions.
Lunar Missions by Nations:
- In September 2025, NASA’s four-member Artemis crew is scheduled to fly around the moon.
- China will put its astronauts on the moon by 2030.
- India plans to land in 2040.
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Deadline for Coordinated Lunar Time (LTC)
The US has established a deadline of December 31, 2026, for NASA and its international partners to devise a strategy for LTC implementation. NASA has been directed to engage with the 39 nations who have signed the Artemis Accords for this project.
- Demand for Unified Lunar Time: In November 2022, the need for a unified lunar time was voiced globally by space agencies and academic organizations that agreed on “a common lunar reference time.’’
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Coordinated Lunar Time (LTC)
Standard for Cislunar Operations: The Coordinated Lunar Time (LTC) will be the standard to measure cislunar operations — space activities between the moon and Earth — with Coordinated Universal Time (UTC), the global time used to regulate time on Earth.
Artemis Accord:
- About: It is a US-led alliance seeking to facilitate international collaboration in planetary exploration and research.
- Members: The Accords have been signed by 26 countries till now. China and Russia are not part of this initiative.
- Principles of Artemis Accord:
- Not to use space for military purposes,
- A promise to cooperate on matters of safety of space assets and astronauts, and
- a willingness to share scientific data from space missions.
Artemis Programme: It aims to return to the moon, set up a permanent station there, and then use it for deep space exploration. |
- Need for LTC: In 2023, the European Space Agency (ESA) launched a project called ‘Moonlight’ to design satellites for astronauts and robotic explorers, which will be used to support NASA’s moon mission ‘Artemis.’
- During the project, discussions emerged regarding establishing a unified time zone for the moon and the approach to achieving it.
- On Earth, a 24-hour day is adhered to based on the planet’s rotation. However, the moon rotates much slower—every 29.5 Earth days.”
- Due to its slow rotation, it would be feasible to implement fewer time zones than Earth’s 24 time zones.
- This concept mirrors the structure of Coordinated Universal Time (UTC).
- Establishing a Permanent Human Presence on the Moon: With space agencies across the world aiming to establish a permanent human presence on the moon, LTC is required.
- Commercial operations on the lunar surface involving transactions and logistics will be more reliable with the LTC.
- Role of LTC in Lunar Navigation and Coordination: A dedicated global satellite navigation system (GNSS) for the moon is to be developed by 2030.
- This system will function similar to how the Global positioning system (GPS) and other navigation networks work on Earth.
- Thus, moon missions of various agencies will need an official lunar time to communicate with Earth-based stations and each other.
- All these must be linked to a single time reference, otherwise, coordination would become challenging.
Atomic Clocks:
Atomic clocks are devices that measure time based on the vibration of atoms are known for their extreme accuracy in measuring time.
- Solar time: Calculated by measuring the rotation of Earth on its axis relative to the Sun, is variable.
Coordinated Universal Time (UTC):
- About: The Coordinated Universal Time (UTC) was designed to accommodate the difference between solar time and atomic time.
- It is kept within 0.9 seconds of solar time to follow Earth’s rotation variations and within an exact number of seconds of the International Atomic Time (TAI).
- A weighted average of hundreds of atomic clocks produces the International Atomic Time (TAI).
- Currently, moon missions follow the time of the country which operates the spacecraft, while the International Space station (ISS) runs on the UTC. However, a standardised time for space and the moon is not followed.
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Features Needed for a Time Standard
- Traceability to Coordinated Lunar Time (LTC): Lunar Time is analogous to Terrestrial Time on Earth (TAI+ 32.184 seconds). Similar to Terrestrial Time, Lunar Time may be set through an ensemble of clocks on the moon.
- This time standard, i.e., LTC may directly employ or distribute the UTC offsets required to maintain local and UTC time within tolerance limits.
- Scalability beyond the Earth-Moon system: Conversion of LTC to UTC for operations involving interactions with Earth will be possible by using the above approach to set the LTC.
- This approach is also extensible to space environments beyond the Earth-Moon system (for example, for Mars).
- Accuracy for precision navigation and science: The LTC will give users in cislunar space a reference time standard near the gravitational environment in which they operate.
- Space assets can synchronize with each other with precision for navigation.
- Resilience to loss of contact with Earth: The reference time, LTC must survive independently when contact with Earth is lost.
- Unlike Earth, the moon will have only one time zone and daylight saving will be unnecessary.
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Global Positioning System (GPS):
- It is a satellite-based radio-navigation system used for monitoring and control.
- The modern GPS consists of 24 satellites moving around the earth in six orbits.
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Issues in Defining and Implementing Coordinated Lunar Time
- Gravitational Pull of Moon: The process of defining lunar time is complicated by the effect of the moon’s gravitational pull.
- As per special relativity theory, due to the weaker gravitational pull of the moon, a clock on the moon would run faster than one on Earth.
- Impact of Lunar Surface Position on Clock Speed: A clock’s speed would also change depending on its position on the lunar surface, because of the moon’s rotation.
- Any clock on the moon would gain 56 microseconds over 24 hours. Each lunar day spans approximately 29.5 Earth days.
- With the Artemis Programme aiming for a lunar landing as early as 2026, addressing this challenge for long-duration stays is imperative.
- It is estimated that at least three master clocks, synchronized with the moon’s natural pace, need to be installed. These clocks, along with an algorithm are expected to produce a more precise time standard.
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