Why the Moon Needs a Space Traffic Control System

“Magnificent desolation.”

These are the words used by Buzz Aldrin to describe the vast void of the lunar landscape before he first walked on its surface in July 1969. But what if the moon – or rather its orbit – was not so sorry after all? What if it felt more like, say, the gridlocked traffic of a rush-hour commute in Los Angeles? And if indeed?


Given that a grand total of 12 people have walked on the surface of the moon in human history, this may seem highly hypothetical. However, it’s also a troubling notion that researchers at the University of Arizona, a university that helped map the moon’s surface for Aldrin’s famous 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 Vehicle Branch — envisions what is, essentially, the world’s first traffic control system. lunar air to the world. Intended to keep an eye on space traffic in the currently untracked cislunar region between our planet and the Moon, it will help avoid lunar traffic jams – and, possibly, even deadly collisions.

And it’s happening sooner than you think at a lunar mission near you.

Like an abandoned parking lot in space

It was NASA scientist Don Kessler who, in 1978, first pointed out the danger posed by the extremely high density of objects circulating in low Earth orbit and how these could set off a chain reaction cascade of possible collisions. (Watch the 2013 movie debut Gravity to see how devastating it could be.)

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

“Let’s imagine that, since the invention of the automobile, you took the car from the factory and put gasoline in it, then [drive it until it runs out of gas]drop it and get a new car,” Vishnu Reddy, an associate professor at the University of Arizona’s Lunar and Planetary Laboratory, told Digital Trends. “That’s what we did in space. Whenever a spacecraft runs out of fuel – and it can be a fully functional spacecraft – you drop it and launch a new payload. [Over time] things are piling up.

The problem, he said, is one of visibility: both literal and figurative. “Space is kind of an unsolvable problem,” Reddy explained. “It’s not like an environmental disaster, is it? You know, there’s an oil spill, you see the pelicans covered in oil, it triggers a visceral reaction. You show a point in the sky to anyone and most people don’t care. It’s like, why should I care – until the cell phone stops working or the GPS stops working or the football stops playing on the TV. This is where people react.

Debris polluting the lunar orbit

The Moon and Earth seen from the International Space Station.

While space debris in Earth’s orbit has received some attention, the problem of lunar space junk is widely discovered. That’s because, for now at least, it’s not a problem.

By Reddy’s own admission, the lunar orbit channel is currently still 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 moon-orbiting satellites, the only notable ones (perhaps the only ones entirely) include NASA’s Lunar Reconnaissance Orbiter, two Artemis spacecraft (P1 and P2), and the Chang’e 5-T1 from China. That’s less major congestion than the equivalent of spotting another car during an hour-long drive through rural Wyoming.

A concept image of the Artemis 1 Orion capsule.
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 Los Angeles Freeway tomorrow. Or, to avoid exaggeration, at least a little busier than it currently is.

“We had the initial exploration of the moon in the [1960s]”, Reddy said. “Then there was a quiet period in the middle, for the last 50 years or so. But now there is 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, in lunar orbit too.

It could also prove disruptive to satellites and potentially dangerous for spaceflight missions – manned or unmanned.

The idea of ​​taking a proactive approach to air traffic control is of course not new. This is exactly what happened with traditional terrestrial air traffic control. The first serious attempts to develop surveillance and air traffic control rules began in 1922, several years after the first International Air Convention of 1919. The first person who could officially call himself a professional air traffic controller, Archie League of St Louis, Missouri, began work in 1929. Although air travel was beginning to take off (pun semi-intentionally) at this time, it was still in its infancy compared to what it would become. With 173,000 passengers fly in the United States in 1929, compared to 926 million passengers transported to 2019, the skies weren’t exactly crowded. Nonetheless, it was deemed that a solution was needed – although it was likely to be based on projected growth.

“I come from the world of asteroid trackers”

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

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

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

His own background, he noted, is “mostly doing planetary defense.” “I come from the world of asteroid tracking, so a lot of the tools that we apply to this particular problem are based on planetary defense tools and technologies,” he explained. “The asteroid community has been tracking very small objects, far from Earth, for decades. We take advantage of a large number of 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 every 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 Launch of Artemis 1, NASA’s superheavy launch vehicle, with the aim of sending an uncrewed Orion spacecraft into a retrograde orbit of the moon.

A graphic of the route NASA's Artemis 1 will take on its mission to the moon.

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

A good question is what would be the enforcement power of a space traffic control system like this. Let’s say, for the sake of argument, that a Chinese satellite poses a possible existential threat to a US space launch – or, when that airspace becomes more crowded, two craft are at risk of a possible collision. Who becomes the one claiming the right of way in a possible alien chicken game? Difficult question. “I don’t think we have execution capability,” Reddy said. “It’s more of an academic exercise [right now].”

Another future challenge, which has yet to be unpacked, could involve launching actual space missions to deploy additional orbital resources that can help monitor unseen areas of Earth, such as objects hidden behind the moon. (Who knows: it could even serve as a test for similar initiatives on other planets like Mars, which would require the establishment of entirely new infrastructure due to the difficulty of monitoring them from Earth. “I think that we are already planning to do something about space traffic management around Mars,” he said.)

For now, however, the team will be happy if this proof of concept demonstrates its value as a tool to support our continued space interests – and rekindle fascination with the moon.

“Our goal is to mature this and demonstrate that something like this can be sustained and can be useful,” Reddy said. “Then we will pass it on to the people who have the real responsibility of maintaining this.”

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