In yet another one of those twists that make us suppose that the world really does have a writers’ room, the researcher responsible for identifying the rocket stage that should collide with the Moon on March 4 made a correction: he now no longer believes that it is part of SpaceX’s Falcon 9 that launched the Dscovr satellite into space in 2015, but the last stage of the Chinese Long March-3C launcher that powered the Chang’e 5-T1 lunar mission in 2014.
The episode shows how difficult it is to track objects in space. The American Bill Gray, responsible for the original and notorious identification by the Project Pluto software for tracking near-Earth objects, received on Saturday (12) an email from Jon Giordini, a researcher at NASA’s Jet Propulsion Laboratory, indicating a discrepancy between the identification of the object in 2015 and the trajectory of the launch of Dscovr. The questioning prompted Gray to rummage through his own files.
The object in question was first detected by the Catalina Sky Survey, one of several near-Earth asteroid hunting projects, on March 14, 2015. Cataloged under the temporary acronym WE0913A, it would have passed close to the Moon two days after the launch of the Discover In the dialogue that astronomers who monitor asteroids have all the time via the internet, the Brazilian Cristóvão Jacques, from the Sonear observatory, even pointed out that the object was in Earth orbit, which suggested an artificial origin. Putting the two pieces of information together, Gray, even without having the precise trajectory of the Falcon 9’s flight with Dscovr, connected the two things, identifying it as the second stage of the rocket from Elon Musk’s company.
“Essentially, I had very good circumstantial evidence for the identification, but nothing conclusive,” Gray wrote in explaining the confusion. “This is nothing unusual. Identifying space junk on distant flights often requires a bit of detective work, and sometimes we never identify pieces of space junk.”
Fact is, looking at the original trajectory of SpaceX’s launch now, it’s clear that this is not the object that will crash into the Moon on March 4th. On the other hand, it turned out that there is a much better fit with another launch: that of the Chinese lunar mission Chang’e 5-T1, which in 2014 carried out a test of the model of a re-entry capsule that would bring samples of the natural satellite on Chang’e. 5, of 2020.
To match, in addition to the basic information Gray had, Jonathan McDowell, an expert in monitoring satellites and space debris, provided the orbital parameters of a cubesat (microsatellite) that flew Chang’e 5-T1 in 2014, and the fit with the WE0913A is very good. “In a way, this remains ‘circumstantial’ evidence,” says Gray. “But I would consider it pretty convincing evidence. So I’m persuaded that the object that will hit the Moon on March 4, 2022, at 12:25 UTC, is a rocket stage. [da missão] Chang’e 5-T1.”
Those who want to read more details of the saga, can check this page (in English). And everyone who wanted to fly into the neck of “evil billionaire” Elon Musk because of a space debris collision with the Moon can now jump to a new target: the Chinese space program.
Here, everything continues as before: the launch responsible for the future impact paved the way for an important scientific advance (in this case, the sample return mission Chang’e 5), the collision will be another interesting event for observation by lunar orbiters, collisions with the Moon are often planned strategies to avoid keeping space junk flying around and no one can point to any harm in forming just another small crater in lunar soil.
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