The American NASA, with support from European and Japanese partners, is developing concepts for a lunar navigation system that could be deployed as early as the late 2020s. In July, the China National Space Administration (CNSA) presented its plans to deploy a constellation of 21 communications and navigation satellites for lunar missions.
These projects have emerged because full-scale activities and research on the Moon are planned to begin in the coming years, which will require complex logistics, including positioning, navigation, and timing systems that are actively used in terrestrial infrastructure. NASA, as part of the Artemis program, hopes to land astronauts in the South Pole region of the Moon, which will require reliable communication links and precise positioning services. China also intends to land on the Moon by the end of the decade, and many government and private organizations will send research vehicles there in the near future.
The commercial space sector is exploring the opportunities that the young lunar economy holds: resource extraction, low-gravity manufacturing, scientific research, and tourism. This will require a robust satellite system that is suitable for the Moon, at least in certain regions. While the initial focus will be on the South Pole, navigation and communications should be provided in that region, but in the long term, coverage of the entire moon will be required.
Challenges and Considerations
These projects will require answering several difficult questions. For example, the question of time. Lunar missions are measured based on the lunar cycle of night and day, which last for two Earth weeks; but the Moon does not yet have a standard scale similar to the Universal Time System, which is the basis for all Earth clocks.
The ability to accurately measure time has led to the emergence of Earth satellite navigation systems: the American GPS, the Chinese BeiDou, and the European Galileo. Satellites in all of these constellations are equipped with atomic clocks, which help determine time with an accuracy of several billionths of a second. Locations on Earth are calculated based on the time it takes for satellite signals to reach ground receivers — a shift of one nanosecond gives an error of 30 cm. Therefore, accurate determination of time is also important in lunar conditions, but there is one complication: the clocks on the Moon run slightly faster than on Earth — this is how the general theory of relativity works, which states that massive objects slow down the flow of time.
The clocks on the Moon move ahead of the Earth’s by about 56 microseconds per day, according to the results of a study published by NIST scientists. At the same time, the relative motion of the Moon has the opposite effect on the clocks, slightly slowing them down, but this factor is not pronounced enough to significantly affect the gravitational effect that speeds them up.
Future Developments
The exact configuration of the lunar satellite constellations has not yet been determined. The American NASA, the European ESA and the Japanese JAXA are currently supervising navigation system projects that will be developed jointly with commercial partners. At NASA, it is the Lunar Communication Relay and Navigation System; at ESA, the Moonlight Initiative; at JAXA, the Lunar Navigation Satellite System. And they will all be united in a compatible structure, LunaNet, which will ensure interaction between partner projects. That is, each participant works on its own project, but they will all work in a single system.
It is assumed that the European Moonlight will be represented by a group of at least five devices: one large communications satellite and four navigation satellites, which will be placed in special orbits to optimize coverage at the South Pole, notes NIX Solutions. This will provide 15 hours of reliable signal reception per day, but the Moonlight architecture allows for scalability, that is, for more complex missions, it will be possible to launch new devices.
The opinions of China and other countries regarding lunar navigation systems are still unknown – it is possible that there will be several of them on the Moon, as on Earth. In March, the country launched a satellite called Queqiao-2 into lunar orbit, designed to act as a relay satellite. However, in some international forums, China has expressed “interest in achieving international compatibility.”
We’ll keep you updated on the progress of these lunar navigation systems as new developments emerge.