Equilibrium & Sustainability

Air Force paying to prevent ‘lunar traffic jams’

SpaceX/NASA via Associated Press

An Air Force research initiative is spending $7.5 million to head off the problem of “lunar traffic jams” — a potentially deadly hazard for the new generation of manned moon missions set to launch throughout the 2020s.

The collaboration between the Air Force Research Laboratory and University of Arizona will start by mapping the dozens of natural and human-made artifacts in the “chaotic environment” of lunar orbit.

But in doing so, they aim to develop a suite of techniques that could ultimately allow groups like the U.S. Space Force to track the coming generation of international traffic — including a new generation of Chinese missions — as they circle the moon.

“The orbital space around the Earth is becoming extremely congested, so the Space Force and Air Force Research Laboratory are trying to get ahead of the problem around the moon,” University of Arizona astronomer Roberto Furfaro said in a statement.

“The concern is that there are probably 50 Plus missions planned in the next eight years going to the moon,” Furfaro’s University of Arizona collaborator, Vishnu Reddy told The Hill

Putting stuff into space invariably brings the risk of collision — particularly since every successful launch requires an array of jettisoned debris like the Chinese booster rocket currently on track to crash into the lunar surface in March.

That crash signals a harbinger for the relatively pristine orbital environment of the moon: the arrival of the “traffic jams” that are becoming an increasingly serious problem in Earth’s orbit.

“The space debris problem is a mess,” Reddy said. “We’ve gone for 60-plus years of uncontrollably trashing everything in space, right? Imagine we had taken every car since the invention of the Model T, and every time the thing runs out of gas — you leave it to the side of the freeway and pick up a new car, wherever you drop it. That’s what we’ve been doing to space.”

So far, that junk largely orbits the Earth: according to NASA, there are currently 23,000 known objects in orbit —  although SpaceX alone has licenses to launch another 42,000.

The moon, by contrast, has perhaps a few dozen natural and human-made objects — largely the remnants of U.S., Russian, Chinese and Indian spacecraft, and are largely self-reported, Reddy and Furfaro told The Hill.

But more debris is coming. In addition to NASA’s Artemis missions, the Chinese have a full slate of ongoing and upcoming lunar missions. One Chinese spacecraft, a remnant of the Chang’e-5 moon sample-recovery mission, is currently in orbit around the moon, and in January Beijing released plans for both more Chang’e probes, a joint robot exploration with Russia and future crewed missions and a research station, according to a government press conference.

Every such launch means more debris in orbit around the moon — and more possibility that, for example, a discarded booster rocket will “recontact” a U.S. space vessel. For the U.S. Space Force, it also brings the possibility that earthbound conflicts will escalate into space. 

“Not everybody is friendly, right?” Furfaro, Reddy’s partner in the University of Arizona lunar surveying team, told the Hill. “We might have adversaries who try to cause harm or even restrict our action in space, and we need to be aware of that.”

“And one part of that is to understand their intention,” which Furfaro attempts to do by combining Reddy’s visual analysis with machine learning algorithms trained on the behavior of known spacecraft. 

“Because these things are hard,” Furfaro added. “At the end of the day, we’re talking about a dot.”

The grant is part of the nascent Space Force’s attempt to establish greater intelligence gathering capacities about the behavior of such dots in ever-deeper space. 

“Capabilities to detect, track and catalog objects from the Earth to the moon and beyond enable freedom of navigation critical to civil and commercial use of space. We are very excited to continue our collaborations with University of Arizona,” Benjamin Seibert, Space Control Mission Area lead for the Air Force Research Laboratory, said in a statement.

This is no easy task. Not only are the objects tiny, the moon is so bright — thanks to the sunlight reflecting off its white surface —  that it had long been thought impossible to track objects orbiting it. That dot of a spacecraft or debris disappeared into the lunar glare like “a firefly that’s flying around a searchlight,” Reddy said.  

Reddy described this exclusion zone — which astronomers sometimes call the Cone of Shame — as “kind of like the Bermuda Triangle, where you cannot track anything in the space because the moon is so bright, that everything would get lost.”

By combining established astronomy tools — telescope observation, spectroscopy — with new forms of machine learning, Reddy and Furfaro say they have managed to penetrate further into the cone than anyone has before.

“Not to brag too much about it, but you know if, if something is around the moon, and anyone can find it, it’s probably us,” Reddy said.

Their method came together by chance, he added. On Thanksgiving 2020, Reddy skipped dinner — “I’m a vegetarian” — to observe the Chang’e-5 from his backyard telescope.

Reddy realized that the moon almost entirely blocked out objects orbiting it — but not entirely. He was able to track the spacecraft into within 100 miles of the visible surface of the moon.

“It’s like, Wait a minute. Of course, it’s not black and white. It’s not like you know, it’s physics right? In the end. If the object is big enough, you will be able to track it no matter how close it gets the moon.”

The two realized that even though objects crossing the moon’s face or behind its back were invisible, there was a brief, distinctive flicker on either side as the Chang’e-5 passed from front to back or vice versa.

Using data from these brief glimpses that Reddy captured, Furfaro could then use machine learning to calculate where the craft might end up.

Doing so required grappling with one of the toughest problems in space physics: the three body problem, in which the gravity wells of multiple celestial objects — in this case the Earth, Moon and Sun — all tug on the same object, sending it careening on complex, nonlinear and hard-to-predict trajectories.

Add in the presence of active spacecraft, which are also able to change course, and the fact that it disappears on either side of the moon, and identification becomes even harder, Furfaro said. 

Once you lose an object, how do you know the object you recover “is the same,” Furfaro asked. “How do you fingerprint it?” he asked. 

These are the sorts of problem that that $7.5 million grant is intended to help them solve: to experiment with spectroscopy, which gives a view into what materials an extraterrestrial object is made of, to develop AI tools that can predict their behavior; and to see how economical a telescope the Space Force can get away with.

“You don’t need big telescopes. So that’s another thing to know. You can do a lot of it through its smaller telescope. The main thing is the algorithms that we use,” Reddy said.

The University of Arizona has a world-leading astronomy lab with a fleet of two dozen telescopes. “But the goal is to show what you can do with a modest telescope in this case, like a meter and smaller,” about twice the size of the one Reddy used that Thanksgiving to track the Chang’e 5 into the lunar flare.

The expansion of military scrutiny of the zone around the moon is “so new,” Reddy added. “We’re just trying to see what can we do with what we have — and so if you find okay, at this level we can’t see anything, then you know, what your limits are.”

Tags Air Force Space force

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