This is where Moonlight will come in. The system may involve three navigation satellites in lunar orbit plus one dedicated to communication. This way, multiple satellites can ping Earth at any time, and the system would be resilient in the event of a single orbiter failure. (Because the moon has no atmosphere, satellites would be more vulnerable to solar storms and other space weather conditions than GPS or Galileo systems.)
Most of the technologies needed for Moonlight are already available, since ESA and NASA already have satellites in orbit around the Earth. But the lunar project comes with its own challenges. For example, if one placed an atomic clock on the moon and compared it to an identical clock on Earth, the lunar device would gain 56 microseconds every 24 hours. It would add up, eventually messing up the accuracy of the navigation systems.
This misalignment occurs because of general relativity, thanks to the moon’s weaker gravitational pull, Patla explains. Technically, the ideal measure of time would come from a atomic clock in the vacuum of space, where there is practically no gravity. Atomic clocks on Earth are affected by the planet’s gravity, but they are a known standard. Lunar time would be affected by a different gravitational pull which would contribute to the extra microseconds. Still, it’s not a big deal: Lunar jet lag is predictable and can be corrected.
There is also the question of what orbital path these satellites should take. Most satellites around Earth have circular orbits, which is useful for a population that is sparse at the planet’s poles and distributed in mid-latitudes. But realistically, most astronauts for the next decade or two will be stationed near the lunar south pole because it hosts frozen water that person want to mine. ESA plans to deploy the satellites in elliptical orbits so they have more time in range of the polar regions. Later, the agency and its partners could add satellites in different orbits to better cover other areas, and ground stations for more precision.
Satellites will use a different frequency (S-band, at approximately 2-2.5 megahertz) than their terrestrial counterparts (L-band, at approximately 1-1.6 MHz) so that their signals do not interfere with terrestrial communications or not disturb future radio telescopes on the far side of the moon.
ESA plans to launch a technology test satellite called Lunar Pathfinder by the end of 2025, and then have Moonlight in “initial operational capability” by the end of 2027, with a dedicated satellite providing limited communications and a first navigation telemetry signal. . The full constellation of – most likely – four satellites would be operational by the end of 2030.
And Moonlight will not be alone. NASA is developing its own analog system, working on a similar schedule. The Chinese space agency is also planning its constellation of satellites, and some of these spacecraft could be launched by the end of 2024, with the initial aim of supporting Chang’e 6, a lunar sample return mission. The Japanese space agency also has one in the works, with a demonstration mission scheduled for 2028.
These initiatives will play a fundamental role in the future of space travel, Ventura-Traveset said. New generations of spacecraft, including commercial ones, will not need complex and expensive antennas or landing systems; they can just tap into those. “There are over 250 missions over the next 10 years with the intention of going to the moon,” he says. “We need this infrastructure. It will be an accelerator for the lunar economy.
Philosophically, these programs represent a profound shift in the concept of timing, Nesvold says. “Throughout most of human history, we’ve used space to tell time, including plants, stars, and phases of the moon,” she says. “It was only relatively recently that we came up with this idea of clock technology, which allows us to coordinate with each other without depending on space. And now we are implementing this technology on the moon itself.
