J002E3

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J002E3 discovery images taken by Bill Yeung on September 3, 2002. J002E3 is in the circle.
Computer simulation of J002E3's motion, alternating between six Earth orbits and a heliocentric orbit (right-click and open in another tab or window to view animation)
S-IVB stage of Apollo 17. The one used for Apollo 12 is of identical type.

J002E3 is the designation given to an object in space discovered on September 3, 2002 by amateur astronomer Bill Yeung. Initially thought to be an asteroid, it has since been tentatively identified as the S-IVB third stage of the Apollo 12 Saturn V rocket (designated S-IVB-507), based on spectrographic evidence consistent with the paint used on the rockets.[1][2] The stage was intended to be injected into a permanent heliocentric orbit in November 1969, but is now believed instead to have gone into an unstable high Earth orbit which left Earth's proximity in 1971 and again in June 2003, with an approximately 40-year cycle between heliocentric and geocentric orbit.

Discovery[edit]

When it was first discovered, it was quickly found that the object was in an orbit around Earth. Astronomers were surprised at this, as the Moon is the only large object in orbit around the Earth,[note 1] and anything else would have been ejected long ago due to perturbations with the Earth, the Moon and the Sun.

Therefore, it probably entered into Earth orbit very recently, yet there was no recently launched spacecraft that matched the orbit of J002E3. One explanation could have been that it was a 30-meter-wide piece of rock, but University of Arizona astronomers found that spectral observations of the object indicated a strong correlation of absorption features with a combination of human-made materials including white paint, black paint, and aluminum, consistent with Saturn V rockets.[2] Back-tracing its orbit showed that the object had been orbiting the Sun for 31 years and had last been in the vicinity of the Earth in 1971. This seemed to suggest that it was a part of the Apollo 14 mission, but NASA knew the whereabouts of all hardware used for that mission; the third stage, for instance, was deliberately crashed into the Moon for seismic studies.

The most likely explanation appears to be the S-IVB third stage for Apollo 12.[1][2] NASA had originally planned to direct the S-IVB into a solar orbit, but an extra long burn of the ullage motors meant that venting the remaining propellant in the tank of the S-IVB did not give the rocket stage enough energy to escape the Earth–Moon system, and instead the stage ended up in a semi-stable orbit around the Earth after passing by the Moon on November 18, 1969.

It is thought that J002E3 left Earth orbit in June 2003, and that it may return to orbit the Earth in the mid-2040s.[1]

Reimpact risk[edit]

The object's Earth orbital paths occasionally take it within the radius of the Moon's orbit, and could result in eventual collision with Earth or the Moon. The Apollo 12 S-IVB had an empty mass of about 9,559 kilograms (21,074 pounds).[3] Objects of comparable mass enter Earth's atmosphere approximately 10 times a year.[4][5]

This is less than one-seventh of the 77,090-kilogram (169,950-pound) mass of the Skylab space station, which was constructed from a similar S-IVB and fell out of orbit on July 11, 1979.

See also[edit]

  • 6Q0B44E, space debris originally thought to be a meteoroid
  • 2006 RH120, a meteoroid originally thought to be space debris
  • 2007 VN84, an asteroid designation mistakenly given to the Rosetta spacecraft
  • 3753 Cruithne

Notes[edit]

  1. ^ Also believed to orbit the Earth are the Kordylewski clouds: large transient concentrations of dust at the Trojan points of the Earth–Moon system, discovered in 1956 by the Polish astronomer Kazimierz Kordylewski.

References[edit]

  1. ^ a b c Chodas, Paul; Chesley, Steve (2002-10-09). "J002E3: An Update". NASA. Retrieved 2013-09-18. 
  2. ^ a b c Jorgensen, K.; Rivkin, A.; Binzel, R.; Whitely, R.; Hergenrother, C.; Chodas, P.; Chesley, S.; Vilas, F. (May 2003). "Observations of J002E3: Possible Discovery of an Apollo Rocket Body". Bulletin of the American Astronomical Society 35: 981. 
  3. ^ Bilstein, Roger E. (August 1999). "Chapter 6". Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicle. DIANE Publishing. ISBN 978-0-7881-8186-3. 
  4. ^ Bland, Philip (December 2005). "The impact rate on Earth". Royal Society of London Philosophical Transactions Series A 363 (1837): 2793–2810. Bibcode:2005RSPTA.363.2793B. doi:10.1098/rsta.2005.1674. 
  5. ^ Bland, Philip A; Artemieva, Natalya A. (April 2006). "The rate of small impacts on Earth". Meteoritics 41 (4): 607–631. Bibcode:2006M&PS...41..607B. doi:10.1111/j.1945-5100.2006.tb00485.x. 

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