Space Junk That Will Hit Moon Is Likely From China, Not SpaceX

A piece of space junk that is on track to crash into the Moon next month is likely a booster from a Chinese lunar mission, and not the second stage of a SpaceX Falcon 9 rocket as originally reported by VICE and other publications. The spacecraft is on track to impact the far side of the Moon on March 4, which will make it the first artificial object to unintentionally hit the lunar surface.

Bill Gray, an astronomer and ​​author of space object-tracking software, has been keeping tabs on this object for years. He initially identified it as a booster from the February 2015 launch of NASA’s Deep Space Climate Observatory, a mission that was delivered to space by SpaceX, and shared his hunch in a recent blog post. 

Over the weekend, though, Gray updated the post with new findings that suggest the object is most likely a booster from China’s Chang'e 5-T1 mission, launched in 2014. The correction was prompted by discussions with other experts about the possible trajectories of high-altitude space junk, which Gray notes are often very difficult to identify (in fact, there are several objects in high orbits with as-yet unknown origins).

In an email to VICE, Gray said that astronomers probably won’t get any further confirmation of the real identity of this object before it impacts. That said, he did credit Scott Tilley, an amateur radio observer and satellite tracker, with finding one possible clue to look out for: Radio signals from a private lunar probe called the Manfred Memorial Moon Mission (4M), which was attached to the third stage booster of Chang'e 5-T1.

“The transmitter had both battery power and a small solar panel,” Gray said. “It was tracked for about a month after launch, and then the battery ran down. But if the solar panel happens to be suitably illuminated, there would be some chance of getting a noticeable radio signal. There's a specific message being broadcast at a specific frequency.”

“If that can be detected—which I should say is a somewhat big 'if'—it would tip things from being 99.9 percent sure to being 100 percent sure” of the object’s identity, he added. 

After seven years of wandering high-altitude space, the odds that this transmitter is still active are indeed low. However, Tilley is looking out for any faint signals from the 4M probe just in case.

It would certainly be fascinating to catch some ghostly radio signals from a dead mission that is destined to smash into the Moon in a few weeks. But even if 4M remains silent, the imminent lunar impact has raised a lot of public awareness about the issue of space debris. Gray thinks this attention might inspire spacecraft operators to put more consideration into the ultimate fates of their spent parts.

“I think it possible that the attention this particular case is getting will cause everybody launching objects out there to think about junk disposal,” he said. “There are several possibilities (deliberately aim at the Moon, or an ocean on Earth, or put the object in orbit around the Sun). There are good arguments for any of them. Usually, one or more of the options can be implemented without too much trouble. But just leaving bits of trash to float around aimlessly for a decade or so is, in my opinion, not a good choice.”

“If junk disposal gets more attention in such cases, it should not be all that difficult to keep high-altitude orbits clean, nor should it be difficult to keep track of existing high-altitude trash and the inevitable bits that, despite good efforts, are added to it,” he concluded. “The real problem is keeping low-earth orbits clean; we are losing that battle. There is a lot more junk there, and it's usually not easy to find a way to get rid of it.”