Black-and-white photo of a huge rocket component in a giant hangar.
Enlarge / An Atlas-Centaur rocket booster being assembled at a Common Dynamics plant, circa 1962.

Fifty-four years in the past, NASA launched the Surveyor 2, an uncrewed mission to discover the floor of the Moon. Alas, the spacecraft went right into a tumble en route after a failed course-correction burn, and it slammed into the lunar floor at 2.7 kilometers per second. However the rocket booster used throughout its launch adopted a unique trajectory into area and has now begun orbiting the Earth. That is the conclusion of astronomers who’ve been finding out 2020 SO, an uncommon object first noticed this previous August.

NASA’s Surveyor program was designed to display the feasibility of launching, speaking with, controlling, and touchdown an uncrewed spacecraft on the Moon, thereby paving the best way for later crewed missions. Surveyor 1, launched on Might 30, 1966, was a convincing success, simply assembly its major goals, whereas additionally returning many photographs of the lunar floor and demanding engineering information. So NASA’s hopes have been excessive for constructing on that success with the second mission. The intent was to land Surveyor 2 on the Moon simply east of its predecessor to display the feasibility of an indirect method and touchdown.

After a collection of minor delays, Surveyor 2 launched efficiently on September 20, 1966, at 7:31:59.8 EST. The launch automobile was an Atlas-Centaur rocket utilizing liquid hydrogen and liquid oxygen as propellants. As soon as the Centaur’s engines have been shut down and the spacecraft had coasted for 66 seconds, Surveyor 2 departed from spent Centaur. The rocket expelled its residual propellants to set a secure distance between itself and the Surveyor 2, giving it a trajectory that might miss the Moon by a very good 5,675 kilometers and ship the rocket right into a photo voltaic orbit. That Centaur rocket is what astronomers have confirmed to be 2020 SO.

All the things gave the impression to be going easily for Surveyor 2. Its trajectory towards the Moon was virtually completely heading in the right direction, with only a mild burn wanted for a course correction 16.5 hours after launch. That is when issues went horribly flawed. The craft’s Vernier Engine 3 did not ignite together with the others, sending Surveyor 2 tumbling via area. NASA scientists tried to get the engine began 39 instances earlier than accepting defeat. That is once they tried to glean what helpful information they might from a collection of engineering exams earlier than Surveyor 2 crashed into the lunar floor on September 23, southeast of the crater Copernicus.

NASA by no means formally decided the reason for the engine’s failure to ignite, though a difficulty with the stream of MON-10 oxidizer appears to be the perpetrator. There have been 5 extra Surveyor missions, 4 of them profitable, earlier than NASA switched its focus to crewed exploration of the Moon.

In the meantime, the spent Centaur rocket continued on its merry approach via area and was just about forgotten—at the least till August of this 12 months, when astronomers utilizing the Panoramic Survey Telescope and Speedy Response System (Pan-STARRS) in Hawaii noticed a mysterious object in a photo voltaic orbit that was attributable to move shut by the Earth. The Pan-STARRS observatory is a key instrument in detecting fast-moving objects like new asteroids. However this new object, dubbed 2020 SO, was shifting too slowly to be an asteroid, and it additionally had a fairly unusual orbit.

Paul Chodas, who manages JPL’s Middle for Close to Earth Object Research, was among the many many scientists desirous to study extra about 2020 SO. He ran laptop simulations of its almost round path, noting that its orbit was barely tilted relative to Earth. Intrigued, Chodas ran the simulation in reverse and located that the article handed shut sufficient to Earth in September 1966 to have originated from there. In different phrases, 2020 SO may very well be the spent Centaur rocket that launched the doomed Surveyor 2, notably given its barely anomalous orbit. That’s proof that the article is being pushed round by the photons emitted by the Solar, so 2020 SO must be comparatively giant and have low mass, identical to an empty rocket booster. (Rocky asteroids, as compared, are comparatively small and large.)

Chodas despatched out an e-mail alert to his fellow astronomers around the globe, so everybody may assist observe 2020 SO’s progress over the subsequent few months because it moved nearer and nearer to Earth. Comply with-up spectroscopy observations yielded perception into the article’s composition, and the spectrum information was according to the chrome steel used to fabricate Centaur rocket boosters within the Nineteen Sixties. However the speculation wasn’t but a slam dunk, though the small discrepancies within the information may very well be defined by the weathering of the metal after 54 years of publicity to harsh area climate.

“We knew that if we needed to match apples to apples, we would have to attempt to get spectral information from one other Centaur rocket booster that had been in Earth orbit for a few years to then see if it higher matched 2020 SO’s spectrum,” mentioned Vishnu Reddy of the College of Arizona, who headed the staff that carried out the important follow-up observations. “Due to the intense velocity at which Earth-orbiting Centaur boosters journey throughout the sky, we knew it could be extraordinarily tough to lock on with the IRTF [NASA Infrared Telescope Facility] lengthy sufficient to get a stable and dependable information set.”

Right here and again once more

2020 SO was captured by Earth’s gravity in November and got here inside 27,400 miles from Earth on December 1. That is when Reddy and his colleagues on the IRTF have been capable of seize the infrared spectrum of one other Centaur D rocket booster—this time from a 1971 launch of a communication satellite tv for pc. After they in contrast that spectrum to the info gathered about 2020 SO, the spectra matched. 2020 SO can also be a Centaur rocket booster, probably the one used for the Surveyor 2 mission.

2020 SO is now shifting away from the Earth and will escape Earth’s gravity inside a number of months, at which level it is going to comply with a brand new photo voltaic orbit. However astronomers count on it to return to Earth in 2036, and they are going to be able to study much more when it does.

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