New Data Confirm 2020 SO to Be the Upper Centaur Rocket Booster From the 1960's
The object, discovered in September by astronomers searching for near-Earth asteroids, garnered interest in the planetary science community due to its size and unusual orbit.
Using data collected at NASA's Infrared Telescope Facility (IRTF) and orbit
analysis from the Center
for Near-Earth Object Studies (CNEOS) at NASA's Jet Propulsion
Laboratory, scientists have confirmed that Near-Earth Object (NEO) 2020 SO is,
in fact, a 1960's-Era
Centaur rocket booster.
The object, discovered in September by astronomers
searching for near-Earth asteroids from the NASA-funded Pan-STARRS1
survey telescope on Maui, garnered interest in the planetary science community
due to its size and unusual orbit and was studied by observatories around the
world.
Further analysis of 2020 SO's orbit revealed the object had
come close to Earth a few times over the decades, with one approach in 1966
bringing it close enough to suggest it may have originated from Earth.
Comparing this data with the history of previous NASA missions, Paul Chodas,
CNEOS director, concluded 2020 SO could be the Centaur upper stage rocket
booster from NASA's ill-fated 1966 Surveyor
2
mission to the Moon.
Equipped with this knowledge, a team led by Vishnu Reddy,
an associate professor and planetary scientist at the Lunar and Planetary Laboratory
at the University of Arizona, performed follow-up spectroscopy observations of
2020 SO using NASA's IRTF on Maunakea, Hawai'i.
"Due to extreme faintness of this object following CNEOS
prediction it was a challenging object to characterize" said Reddy. "We
got color observations with the Large Binocular Telescope, or LBT, that
suggested 2020 SO was not an asteroid."
Through a series of follow-up observations, Reddy and his
team analyzed 2020 SO's composition using NASA's IRTF and compared the spectrum
data from 2020 SO with that of 301 stainless steel, the material Centaur rocket
boosters were made of in the 1960's. While not immediately a perfect match,
Reddy and his team persisted, realizing the discrepancy in spectrum data could be
a result of analyzing fresh steel in a lab against steel that would have been
exposed to the harsh conditions of space weather for 54 years. This led Reddy
and his team to do some additional investigation.
"We knew that if we wanted to compare apples to
apples, we'd need to try to get spectral data from another Centaur rocket
booster that had been in Earth orbit for many years to then see if it better matched
2020 SO's spectrum," said Reddy. "Because of the extreme speed at
which Earth-orbiting Centaur boosters travel across the sky, we knew it would
be extremely difficult to lock on with the IRTF long enough to get a solid and
reliable data set."
However, on the morning of Dec. 1, Reddy and his team
pulled off what they thought would be impossible. They observed another Centaur
D rocket booster from 1971 launch of a communication satellite that was in
Geostationary Transfer Orbit, long enough to get a good spectrum. With this new
data, Reddy and his team were able to compare it against 2020 SO and found the
spectra to be consistent with each another, thus definitively concluding 2020
SO to also be a Centaur rocket booster.
"This conclusion was the result of a tremendous team
effort," said Reddy. "We were finally able to solve this mystery because
of the great work of Pan-STARRS, Paul Chodas and the team at CNEOS, LBT, IRTF, and
the observations around the world."
2020 SO made its closest approach to Earth on Dec. 1, 2020
and will remain within Earth's sphere of gravitational dominance - a region in
space called the "Hill sphere" that extends roughly 930,000 miles
(1.5 million kilometers) from our planet - until it escapes back into a new
orbit around the Sun in March 2021. As NASA-funded telescopes survey the skies
for asteroids that could pose an impact threat to Earth, the ability to
distinguish between natural and artificial objects is valuable as nations
continue to explore and more artificial objects find themselves in orbit about
the Sun. Astronomers will continue to observe this particular relic from the
early Space Age until it's gone.
For more information about NASA's Planetary Defense Coordination
Office, visit:
https://www.nasa.gov/planetarydefense
For asteroid and comet news and updates, follow @AsteroidWatch on
Twitter:
https://twitter.com/AsteroidWatch
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