What time is it on the moon?

This is where the moonlight comes in. The system may include three navigation satellites and one dedicated communications satellite in lunar orbit. In this way, many satellites can orbit the Earth at any time, and if one orbit fails, the system will be resilient. (Because the Moon has no atmosphere, the satellites are more vulnerable to solar storms and other space weather than GPS or Galileo systems.)

ESA and NASA already have satellites orbiting Earth, so much of the technology needed for moonlighting is already available. But the lunar project has its own problems. For example, if one were to place an atomic clock on the Moon and compare it to the same clock on Earth, the lunar instrument would gain 56 microseconds every 24 hours. That adds up, eventually destroying the accuracy of navigation systems.

This misalignment is caused by general relativity, thanks to the Moon’s low gravity, Patla says. Technically, accurate time measurement comes from an atomic clock in the vacuum of space, which has essentially no gravity. Atomic clocks on Earth are affected by the planet’s gravity, but they are known standards. Lunar time is affected by a different gravitational force that contributes an extra microsecond. Still, it’s not a big problem: the moon phase offset is predictable and can be adjusted.

There is also the question of what orbit those satellites should follow. Most of the satellites around Earth have circular orbits, and this is useful for a population that is sparse at the planet’s poles and spread throughout the mid-latitudes. But realistically, most astronauts in the next decade or two will be stationed near the moon’s south pole because it hosts the water ice that humans need to mine. ESA is looking to deploy its satellites in elliptical orbits so they have more time in the polar regions. Later, the agency and its partners could add satellites in different orbits to better cover other areas and ground stations for added precision.

The satellites use a different frequency (S-band, around 2 to 2.5 MHz) than their Earth counterparts (L-band, around 1 to 1.6 MHz) so that their signals do not interfere with or disrupt Earth-based communications. Future radio telescopes on the far side of the Moon.

ESA plans to launch a technology test satellite, Moonlight Pathfinder, in late 2025, followed by the launch of Moonlight’s “initial operational capability” in late 2027, providing limited communications services and carrying the first navigation signal. . The full constellation of four satellites will be operational by the end of 2030.

And Moonlight won’t be alone. NASA is working on a similar program by developing its own analog system. China’s space agency is also planning a constellation of satellites, some of which could be launched by the end of 2024. The initial goal is to support the Chang’e 6 lunar sample return mission. The Japanese space agency 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, says Ventura-Traveset. Newer spacecraft, including commercial ships, do not require complex, expensive antennas or landing systems. You can easily enter these. “There are over 250 missions to the moon in the next 10 years,” he says. “We must have this infrastructure. It will be an accelerator for the lunar economy.

Philosophically, these programs represent a major shift in the concept of timekeeping, says Nesvold. “For most of human history, we’ve used space to tell time, including plants, stars and phases of the moon,” she says. “We came up with this clock technology relatively recently, which allows us to coordinate with each other without being dependent on space. Now we are applying this technology to the moon.