GS Paper III

News Excerpt: 

NASA’s four-member Artemis crew is scheduled to fly around the moon in preparation for the space agency’s mission to land on the moon again.

More about News: 

• The White House Office of Science and Technology Policy (OSTP), directed its space agency, the National Aeronautics and Space Administration (NASA), 
• To establish a Coordinated Lunar Time (LTC) to standardize cislunar operations with the universal time followed on Earth.
• A consistent definition of time among operators in space is critical to successful space situational awareness capabilities, navigation, and communications.
• The difference between the passage of time on the moon and Earth, “Time appears to pass more slowly where gravity is stronger, like near celestial bodies.
• As a result, the length of a second on Earth is different to an observer under different gravitational conditions, such as on the moon.”
• The Coordinated Lunar Time will be the standard to measure cislunar operations on space activities between the moon and Earth with Coordinated Universal Time (UTC), the global time used to regulate time on Earth. 
• NASA has been directed to engage with the 39 nations who have signed the Artemis Accords for this project. 
• It is expected to present its consideration of the LTC by the end of this year, as part of its Moon-to-Mars Architecture Concept Review cycle.

What is Coordinated Lunar Time (LTC)?

• The European Space Agency (ESA) launched a project called 'Moonlight' in 2023 to design satellites for astronauts and robotic explorers to support NASA's moon mission 'Artemis.'
• While working on the project, questions arose about setting a single time zone for the moon and how to go about it.
• ESA engineers suggested that due to the moon's slow rotation (one rotation every 29.5 Earth days), it would be practical to have less than Earth's 24 time zones, ideally a single time zone for the moon. A single time zone for the moon would be natural and similar to the Coordinated Universal Time (UTC) used on Earth.
• The UTC was formulated in the 1960s and is based on a weighted average of hundreds of atomic clocks, which measure time based on the vibration of atoms, ensuring extreme accuracy.
• The UTC was designed as a way to accommodate the difference between solar time and atomic time, and is kept within 0.9 seconds of solar time to follow Earth’s rotation variations and within an exact number of seconds of the TAI.
• 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.
• The White House’s Celestial Time Standardization policy seeks to assign a time standard to each celestial body and its surrounding space environment.
• First focusing on the lunar surface and missions operating in cislunar space. It outlines the four features such a time standard must possess:
• Traceability to UTC: 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 both local time 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 synchronise with each other with precision for navigation.
• Resilience to loss of contact with Earth: The reference time – LTC – must survive independently when contact to Earth is lost.

Why is LTC needed?

• Earlier moon missions involved brief stays by astronauts on the lunar surface, after which they completed their work and returned to Earth.
• However, with the current objective of space agencies globally to create a permanent human settlement on the moon, there is a requirement for a Coordinated Lunar Time (LTC) standard.
• The Scientific American stated that the pressing need for LTC is due to the plan to create a dedicated global satellite navigation system (GNSS) for the moon by 2030. 
• This system will function similar to how the Global positioning system (GPS) and other navigation networks work on Earth.
• Moon missions of various agencies will need an official lunar time to communicate with Earth-based stations and each other. 
• All this has to trace to one kind of a time reference, otherwise you have chaos and things do not work together.
• Commercial operations on the lunar surface involving transactions and logistics will be more reliable with the LTC.

Issues in defining and implementing LTC

• The process of defining lunar time is complicated by the effect of the moon’s gravitational pull.
• The moon's weaker gravitational pull causes clocks on the lunar surface to run faster than those on Earth, as per the theory of special relativity.
• The speed of a clock on the moon would vary depending on its position due to the moon's rotation, further complicating time measurement.
• NASA estimates that a clock on the moon would gain 56 microseconds over 24 hours compared to Earth time.
• To establish an accurate lunar time standard, at least three master clocks that tick at the moon's natural pace need to be installed, and their output coupled with an algorithm.
• Lunar time needs to be practical for astronauts during extended stays on the moon, as each lunar day lasts 29.5 Earth days.
• With the Artemis Program aiming for a lunar landing as early as 2026, adapting to the challenge of lunar time measurement for long-duration stays is crucial.
• Once a working time system is established for the moon, similar time standards can be developed for other planetary destinations like Mars.