Why the moon needs a space traffic control system

“Beautiful desolation.”

Those were the words Buzz Aldrin used to describe the vast emptiness of the lunar landscape before stepping on the surface for the first time in July 1969. all? What if it was more like, say, the traffic jam of a Los Angeles rush hour? What if indeed?


Given that a total of 12 people have walked on the moon’s surface in human history, that might seem like a huge hypothetical. However, it’s also a troubling idea that researchers at the University of Arizona, a university that helped map the moon’s surface for Aldrin’s famed Apollo 11 mission, are currently pondering a lot.

Their plan — for which the university recently received $7.5 million in funding from the Air Force Research Laboratory’s Space Vehicles Directorate — calls for what is essentially the world’s first air traffic control system on the moon. Intended to monitor space traffic in the currently untracked cislunar region between our planet and the moon, it will help avoid traffic congestion on the moon — and perhaps even deadly collisions.

And it’s coming to a moon mission near you sooner than you think.

Like a discarded parking space in space

It was NASA scientist Don Kessler in 1978 who first pointed out the danger posed by the extremely high density of objects circulating in low Earth orbit and how they can cause a chain reaction of possible collisions. (Watch the beginning of the 2013 movie Gravity to see just how devastating this can be.)

Today, about 23,000 pieces of space junk are tracked as they whiz around the Earth at speeds of about 17,500 miles per hour. Of these, only 3,500 are active payloads, while the rest — everything from dead satellite nodules to discarded rocket parts — are inactive, but still potentially dangerous debris.

“Imagine that since the invention of the car you take the car out of the factory and put gasoline in it, [drive it until it runs out of gas]drop it and get a new car,” Vishnu Reddy, an associate professor at the Lunar and Planetary Laboratory at the University of Arizona, told Custom Hour. “That’s what we’ve done in space. Every time a spacecraft runs out of fuel – and it could be a perfectly working spacecraft – you drop it and launch a new payload. [Over time] things pile up.”

The problem, he said, is one of visibility: both literally and figuratively. “Space is kind of a persistent problem,” Reddy explains. “It’s not like an environmental disaster, is it? You know, there’s an oil spill, you see the pelicans covered in oil, that’s causing a visceral reaction. You show everyone a dot in the sky and most people don’t care. It’s like, why should I worry – until the cell phone stops working or the GPS stops working or the football stops playing on the TV. Then people react.”

Moon orbit-polluting debris


While space junk in orbit has received a little attention, the problem of space junk on the moon has been largely uncovered. That’s because this isn’t a problem at least for the time being.

By Reddy’s own admission, the lunar orbital channel is currently relatively clear. Compared to the thousands of cataloged objects orbiting the Earth, there are only a few dozen payloads orbiting the Moon. Of the small handful of satellites orbiting the moon, the only notable (possibly the only one in full) are the NASA Lunar Reconnaissance Orbiter, two Artemis spacecraft (P1 and P2) and China’s Chang’e 5-T1. That’s less congestion than the equivalent of spotting another car on a multi-hour drive through rural Wyoming.

A concept image of the Artemis 1 Orion capsule. NASA

But just because it’s Wyoming today doesn’t mean it won’t be the highway in LA tomorrow. Or, to avoid exaggeration, at least a lot busier than now.

“We had the first exploration of the moon in the [1960s]’ said Reddy. “Then there was a quiet period in the middle, the last 50 years or so. But now there is a renewed interest in lunar exploration. Over the next eight years, we expect up to 50 payloads to go to the moon. We want to avoid the kind of situation we have on Earth [taking place] around the moon, also in orbit around the moon.”

This can also be disruptive to satellites and potentially dangerous for spaceflights, both with and without crew.

The idea of ​​proactively approaching air traffic control is of course not new. It is exactly what happened with traditional terrestrial air traffic control. The first serious efforts to develop rules for the supervision and control of air traffic came in 1922, several years after the inaugural International Air Convention of 1919. The first person to officially call himself a professional air traffic controller, Archie League from St. Louis, Missouri, began operating in 1929. Although air travel was beginning to take off at that time (pun semi-intended), it was still in its infancy compared to what it was to become. With 173,000 passengers flying into the US in 1929, compared to 926 million passengers carried in 2019, the skies weren’t exactly crowded. Nevertheless, it was considered that a solution was needed, even if it was probably based on expected growth.

‘I come from the world of tracking asteroids’

As the saying goes, the first step in solving a problem is to recognize that there is a problem to begin with. However, when it comes to solving a problem of this complexity, admitting the problem is far from the biggest hurdle. Fortunately, Reddy said, at least initially, that many of the current technologies used for tracking objects from Earth could be used for tracking lunar orbits.

Reddy and his students at the Lunar and Planetary Laboratory use special sensors in the university’s Biosphere 2 research facility to characterize cislunar objects. This suite of equipment includes multiple telescopes dedicated to the awareness of the space domain, including one built by a group of engineering students from the University of Arizona.

“A lot can be done with it” [the ground-based optical telescopes] we already have for doing geostationary things,” Reddy said. “It’s just that they’re weaker, so you have to expose the image for a long time and get a picture that’s deeper.”

His own background, he noted, is “mainly concerned with planetary defense.” “I come from the world of asteroid tracking, so a lot of the tools we apply to this particular problem rely on planetary defense tools and technologies,” he explained. “The asteroid community has been tracking very small objects far from Earth for decades. We use a lot of the software and techniques [for this project]†

I want to be a moon model

The ultimate goal of this project — and it’s already further along than you might think — is to build a model that accurately shows any object orbiting the moon. It will then highlight possible conjunctions (the fancy space term for crashes) between these objects and active payloads. Reddy said the tool will be used this year for the launch of Artemis 1, the debut of NASA’s super-heavy launch vehicle, which aims to send an unmanned Orion spacecraft into retrograde orbit of the moon.

The researchers are also making their model available to private space companies. “If a manufacturer comes up to us and says, ‘Hey, we’re doing this mission to the moon, can you please check for conjunctions?’ Yes, sure,” said Reddy. “That’s a service we’re going to provide. We want to avoid creating waste. It’s more work for us to keep track of a lot of things. Not that we’re lazy, but if we can avoid and keep [lunar orbit] clean, that’s better for all of us.”

A good question is how much enforcement power such a space traffic control system would have. For the sake of argument, let’s say a Chinese satellite poses a possible existential threat to a US space launch — or, as this airspace becomes more populated, two planes risk a possible collision. Who will be the one to claim right of way in a possible alien chicken game? Difficult question. “I don’t think we have any enforcement capacity,” Reddy said. “This is more of an academic exercise [right now]†

Another future challenge, yet to be unpacked, could be launching actual space missions to deploy additional orbital assets that can help monitor areas not visible from Earth, such as objects hidden behind the moon. . (Who knows: This could even serve as a trial run for similar initiatives on other planets like Mars, which would require the construction of completely new infrastructure due to the difficulty of tracking them from Earth.” I think we’re already planning to do something about the management of space traffic around Mars,” he said.)

For now, though, the team will be happy if this proof of concept proves its value as a tool to support our ongoing space interests — and rekindle the fascination with the moon.

“Our goal is to let this mature and show that something like this can be maintained and be useful,” said Reddy. “Then we pass it on to the people who have the real responsibility to keep this going.”

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