It turns out that SpaceX might not be responsible for the rocket booster on course to slam into the Moon next month after all.
Bill Gray, who developed a software program used for tracking near-Earth objects known as Project Pluto, initially identified the rocket booster and calculated its Moon-impacting trajectory.
Gray was also the one who assessed that it was the spent second stage of a SpaceX rocket launched in 2015, but after additional analysis, has come out and said that it isn't SpaceX's space junk after all.
"I received an e-mail from Jon Giorgini at the Jet Propulsion Laboratory," Gray wrote in an update on Project Pluto's site. "JPL doesn't track space junk, but they do keep careful track of a lot of active spacecraft, including DSCOVR [the SpaceX rocket that launched in early 2015].
"Jon inquired about my statement that 'DSCOVR (and this rocket stage with it) passed close by the moon on 2015 February 13, two days after it was launched. Jon pointed out that JPL's Horizons system showed that the DSCOVR spacecraft's trajectory did not go particularly close to the moon. It would be a little strange if the second stage went right past the moon, while DSCOVR was in another part of the sky. There's always some separation, but this was suspiciously large.
"Prompted by Jon's e-mail," Gray continues, "I dug into my e-mail archives to remind myself why I had originally identified the object as the DSCOVR stage in the first place, seven years ago. I did that digging in full confidence it would prove that the object was, in fact, the DSCOVR second stage."
This is when Gray discovered that the evidence pointing to SpaceX's DSCOVR was far more circumstantial than it was direct.
"Further data confirmed that yes, [the rocket segment] had gone past the moon two days after DSCOVR's launch, and I and others came to accept the identification with the second stage as correct. The object had about the brightness we would expect, and had showed up at the expected time and moving in a reasonable orbit."
Further investigation, however, now points away from SpaceX and towards an earlier Chinese Chang'e 5-T1 launch in October 2014.
Tracking the object's orbit backwards to October 2014, Gray found that the object would have flown by the Moon just five days after the October 23, 2014, Chang'e 5-T1 launch, which is within the timeframe one would expect to see a fly-by given the Chinese rocket's launch trajectory.
There is other supporting evidence for this theory, but – as with the initial SpaceX identification – these are strong inferences from what we know, at best.
"In a sense, this remains 'circumstantial' evidence," Gray said. "But I would regard it as fairly convincing evidence, the sort where the jury would file out of the courtroom and come back in a few minutes with a conviction. So I am persuaded that the object about to hit the moon on 2022 Mar 4 at 12:25 UTC is actually the Chang'e 5-T1 rocket stage."
Analysis: can we all stop dumping our trash in space?
While it might be tempting to pin the blame on one space company or agency for any given piece of space junk, don't. Everyone is guilty, from legacy military-industrial contractors like Boeing and Lockheed Martin to Russia's Roscosmos to NASA and, yes, to SpaceX.
After all, when everyone assumed the space junk was SpaceX's booster, SpaceX didn't dispute it since it knows it left its second stage booster up in space. That means its spent rocket booster is still up there somewhere, so even if its the China National Space Administration's (CNSA) rocket booster that's going to hit the Moon in a little over two weeks, we actually don't know where the SpaceX booster is.
That's not good. It might be CSNA on March 4, but it could be SpaceX in July, or sometime in 2023 or whenever. And it might not hit the Moon, but it might threaten the International Space Station, or whatever else we decide to launch in the future.
For 60-plus years now we've been littering Earth's orbit with crap, and so unless we want to see low Earth orbit become a shooting gallery of debris zipping around the planet thousands of times faster than a bullet, we need to clean up our celestial front yard. And that starts by not making the problem any worse than it already is.
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