ESA – P. Carril
- Dozens of moon missions are planned within the next decade.
- But right now, there is no satellite navigation system between the Earth and the moon.
- NASA and ESA are developing ways to help rockets navigate to the moon autonomously.
When NASA’s Artemis 1 mission successfully flew around the moon in November, it showed the world that humans are on track to go back.
NASA and the European Space Agency aim to put boots on the moon by 2025 and set up a permanent lunar base orbiting it within the next couple of years. China and Russia are also working together to establish a separate lunar base, with crewed landings set for 2036.
But right now, there is no GPS to get us there. Astronauts can’t navigate autonomously in deep space, and every mission relies on expertly trained engineers constantly directing the missions from the ground.
That will quickly become unsustainable with missions shuttling back and forth.
Space agencies are working to put satellite navigation, or satnav, on rockets traveling the 239,000 miles between Earth and the moon. They’re also planning to build a whole new navigation network around the moon. Here’s how.
How space agencies navigate today is cumbersome and expensive
It took hundreds of people to help Apollo mission rockets navigate to the moon. Here Apollo 11 staff are watching it lift off on July 16, 1969.
Today, the only way to go from point A to point B in space is to make complicated calculations based on physics, custom to every mission.
As the spacecraft moves through space, the only point of reference is the Earth. So it needs to ping a signal back to the Earth to understand where it is, which means there are massive blind spots.
NASA completely lost communication with Orion, the spacecraft used in the Artemis 1 mission, when it went behind the moon. For a few minutes, all the engineers could do was hold their breath and hope they’d see the spacecraft emerge unscathed on the other side.
This is resource-intensive and expensive, Javier Ventura-Traveset, chief engineer of ESA’s Galileo Navigation Science Office, told Insider. (The US government runs GPS; Galileo is the European version.)
What space exploration needs now is a way for spacecraft to triangulate their position from space, so they can navigate autonomously without input from the Earth.
Using Earth’s satellites to go to the moon could help
Surprisingly, the cheapest way to bring satnav to deep space is to harness the satellites around the Earth, Elizabeth Rooney, a senior engineer for Surrey Satellite Technology Ltd, told Insider. The company is working with ESA to develop satellite navigation in space.
There are a few big problems with this approach. Chief among them is that these satellites point toward the Earth.
That means that most of the satellites’ signal is blocked and only a little spills over. The bit that spills over is a lot weaker than the main signal, and it gets even weaker further away from Earth.
Beyond the Earth’s immediate perimeter, called here the space service volume, the earth blocks a lot of the signal coming from earth’s navigation satellites (here called GNSS satellites, for Global Navigation Satellite System).
Given all these constraints, it could seem like using this signal to navigate to the moon would be impossible. But engineers have spent decades developing sensitive detectors that could harness that signal from deep space.
And they succeeded.
In 2019, four satellites were able to determine their position in space using signals from the Earth’s GPS satellites.
They were 116,300 miles away — about halfway to the moon, Ventura-Traveset said.
We really need a way to go all the way to the moon autonomously
The next frontier is detecting that signal on the other half of the journey. But Ventura-Traveset is confident.
ESA and NASA have been refining their detectors that could harness signals from the Earth’s satellites, and are poised to test them on upcoming moon missions.
As part of ESA’s initiative, a detector will be mounted on a satellite orbiting the moon, called Lunar Pathfinder, to see if it can navigate autonomously.
ESA’s receiver, called NaviMoon, is due to launch onboard the Lunar Pathfinder satellite in 2025 or 2026. ESA predicts NaviMoon should be able to determine the satellite’s position with a precision of about 60 meters (about 200 feet), Ventura-Traveset said.
The hope is that thanks to this detector, the satellite should be able to navigate autonomously around the moon, he said. It’s also very lightweight, about 4 kilograms (8 pounds) altogether, and could replace a lot of the heavier equipment onboard a spacecraft.
The NaviMoon satnav receiver being tested.
NASA is also working on detectors, developed with the Italian Space Agency. They aim to launch the first of these receptors to the surface of the moon in 2024 as part of the Lunar GNSS Receiver Experiment.
There is a “little bit of a friendly competitive race” between ESA and NASA to bring Earth satnav signal to the moon, James Joseph “JJ” Miller, deputy director for Policy and Strategic Communications within the Space Communications and Navigation Program at NASA Headquarters, told Insider in an interview.
Miller said many other countries have started looking to invest in deep-space navigation technology.
“Everyone has come to understand that this is an emerging user that is not going away, that we actually have to prepare and make the cis-lunar space, all the space between the Earth and the moon, as robust and reliable as possible with these signals,” he said.
Eventually, we’ll need a satellite navigation network around the moon
In the second phase of ESA’s Moonlight, a network of satellites should help triangulate the position of spacecrafts at the surface.
The signal from Earth’s satellites may get spacecraft all the way to the moon, but once they’re on the surface, the signal won’t be very useful.
At that point, these signals can only reach what’s visible from the Earth, so the dark side of the moon and moon poles are off-limits.
So the plan is to give the moon its very own fleet of communication and navigation satellites, called the Moonlight initiative. The first node in Moonlight would be NASA’s Pathfinder satellite.
Ventura-Traveset said ESA aims to test a basic infrastructure of Moonlight by 2027, and a more comprehensive infrastructure by 2030.
“We would imagine a kind of architecture that includes both NASA and ESA satellites working together,” NASA’s Miller said.
Moon settlers will need high-speed internet
Satellites could help future moon astronauts navigate on the moon, as can be seen in this artist’s impression.
There is a more commercial aspect to bringing humans back to the moon. In the long run, moon settlers would need to set up camp so they can mine for minerals and water — which could be used to fuel rockets on the way to Mars.
Moon visitors will need to be able to communicate with Earth, talk to each other effectively, and be entertained, Ventura-Traveset said.
Down the line, moon settlers could have access to high-speed internet, video-conference with loved ones on Earth, stream shows, and create their own content from space, Ventura-Traveset said.
“I don’t think there’s anyone that would argue that that’s not the way we’re gonna go,” Ventura-Traveset said.