Image: Warner Bros.

In mid-2012, the European Space Agency lost contact with its Envisat satellite—since then, it’s been aimlessly orbiting the Earth as a big piece of space junk that could destroy other satellites if there were to be a collision. According to a new paper by students at the University of Leicester, the corpse of a satellite could threaten to create a Gravity-like situation in which a collision creates a cloud of debris that could take down pretty much anything else that’s in orbit right now. 

The students are right to suggest that Envisat could cause an increase in the amount of space junk in low Earth orbit, but on the list of orbital things to worry about, it’s probably pretty low. Envisat’s relative position is well known and, though other satellites often pass nearby, they can maneuver out of the way, as one has already. Each year, two objects pass within 200 meters of the satellite.

More worrying are the 500,000 pieces of debris that orbit the Earth—most of them barely larger than a marble. NASA estimates that there are roughly 20,000 pieces of debris that are larger than a softball, with Envisat being one of those. 

Two relatively recent events have greatly increased the amount of space junk floating around up there: In a move that angered pretty much everyone, China purposefully destroyed an old weather satellite with an anti-satellite missile in 2007, which added more than 3,000 pieces of space junk to low Earth orbit. Then, in 2009, an old Russian satellite (which had lost communication with Earth, much like Envisat), collided with an American commercial satellite, creating another 2,000 pieces of space junk.

In the past, those collision events have happened and, though not ideal, they didn’t create a low-Earth orbit doomsday situation. As Nicholas Johnson, NASA’s chief scientist for orbital debris notes, “the greatest risk to space missions comes from non-trackable debris.” Because we have a grip on what Envisat is up to, other satellites can easily move out of its way if they’re on a collision trajectory. It’s something that’s done by the International Space Station and other satellites all the time. At nine meters wide, Envisat is certainly a bigger projectile than much of the space junk up there, but even smaller pieces, hurtling at 17,500 mph, can destroy a satellite.  

An artist’s rendering of all the space junk orbiting Earth. Image: CNES

In the paper, the students suggest that the ESA or another space agency should consider undertaking a mission to refuel Envisat, and to bring it to lower orbit where it can eventually be safely de-orbited. That’s a laudable goal, but one that might not be entirely feasible: They estimate it’d take 143 kg of hydrazine fuel to bring it out of orbit, which would cost just a few thousand dollars. But getting to and refueling Envisat is another story.

“The method of refueling the satellite is beyond the scope of this report, although possible methods should be considered in the future,” they write. “Even though a feasible amount of hydrazine is required, the cost and difficulty of getting it to Envisat may be too high.”

The students certainly aren’t the first people to consider the importance of cleaning up low-Earth orbit, and their idea isn’t nearly as outlandish as some of them. But Envisat is just one of thousands of possible threats.

And that’s where we should fall on this. If it’s possible to get Envisat out of orbit at a low price tag without risking further collisions, it’s worth it. If not, there are plenty of other pieces of debris to worry about instead.