There are roughly 130 million pieces of space debris orbiting Earth’s atmosphere. The world (specifically, the US Air Force) tracks only the biggest ones, about 22,300 pieces of debris larger than 10 centimeters (four inches), since they pose the biggest threat.
But this certainly leaves a lot of risk on the table—most debris is orbiting the planet at upwards of 22,000 miles per hour, which means a piece of debris as small as 0.2 millimeters can still cause significant damage to a satellite. Our current systems for tracking space debris are woefully inadequate.
NorthStar Earth & Space thinks it might have a remedy. The Canadian space company is developing a constellation of 40 satellites that will work to monitor and track space debris, with commercial service starting in 2021. NorthStar will track the debris with a combination of hyperspectral, infrared, and optical sensors. Its software analyzes that data they produce and creates forecasts to predict potential collisions. The Canadian government has reportedly already invested $13 million in developing the system.
Though it might seem counterintuitive to track space junk by sending more junk into space, NorthStar might be onto something. Most radar systems or telescopes that currently track space debris are ground-based and so have to handle atmospheric distortions to the data. A tracking system that’s based in orbit doesn’t have to worry about that, says John Crassidis, an expert on orbital debris at the University at Buffalo.
A vantage point from space—especially if the satellites are based in higher orbital altitudes like geosynchronous equatorial orbit, or GEO (over 22,000 miles or 35,000 kilometers above the surface)—also lets you track debris across a wider coverage area and catch sight of it more regularly, by an order of magnitude or more. NorthStar says its system, which will also make observations of Earth as well, will aim to monitor debris throughout most orbital levels.
“Just from a technical point of view, it’s a game-changer,” says Jean-Philippe Arseneau, chief of communications at NorthStar.
NorthStar is not the only one looking into this strategy. The US military is launching its own constellation of satellites to support debris tracking. The Space Based Surveillance System (SBSS) program has so far launched one satellite into low Earth orbit (LEO) in 2010, and four more into GEO.
Still, there are obstacles to contend with—namely, cost. It’s not cheap to build a satellite, launch it into space, and maintain it for regular operation. Age, radiation damage, and obsolescence can quickly cut the value and usefulness of the hardware. “Imagine driving a car for a million miles, and it has to work perfectly for 24 hours a day, and you can’t service it,” says Crassidis. “That’s what we do with satellites.” Issues that might seem minor here on the ground are magnified in space.
So how will NorthStar ensure that its instruments don’t simply add to the orbital debris field—a question already leveled at the likes of SpaceX (which wants to launch 12,000 satellites under its Starlink project)? That’s where things can get really unclear.
No international treaties stipulate what is and is not allowed in space insofar as mitigating and remediating junk is concerned. At most, the US has a pair of rules for LEO: satellites must retain enough fuel to deorbit at the end of their mission, and small LEO cubesats must deorbit within 25 years of launch. Crassidis thinks this is still way too long; he would much prefer a lifetime limit closer to 10 years or so.
Worse, there are no rules like this when it comes to GEO. “Those are never going to come down,” says Crassidis. The only recourse is to put them in a graveyard orbit (more than 310 miles beyond GEO). Even then, it's possible that the gravitational impacts of other solar system bodies (like Jupiter) could push these satellites back down and eventually threaten operational ones in GEO.
NorthStar itself disagrees with the notion that its satellites are potential additions to the orbital debris field. Arseneau says the company's work will end up helping to "organize space traffic management." In comparison to SpaceX's 12,000 Starlink satellites, NorthStar's constellation is “definitely not adding debris or traffic. It’s bringing much-needed solutions to this problem,” he says.
And as with most things involving space, we don't know what will happen till we get there. Sending more objects into space raises the risk of orbital collisions, but tracking objects in space gives us more opportunities to avoid collisions. Whether those benefits outweigh those risks remains to be seen.