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From JPL: Mystery Solved!

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  • Laurent Pellerin
    First Confirmed Capture into Earth Orbit Is Likely Apollo Rocket September 20, 2002 Apollo 12 on launchpad, November 1969 Browse image Near-Earth Object site
    Message 1 of 1 , Sep 28, 2002
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      First Confirmed Capture into Earth Orbit Is Likely Apollo Rocket
      September 20, 2002


      Apollo 12 on launchpad, November 1969

      Browse image
      Near-Earth Object site

      NASA scientists have confirmed the first known capture of an
      object into Earth orbit from a Sun-centered orbit, thanks to
      continuing observations of what is most likely the long-lost third
      stage of a 1969 rocket to the Moon.

      "Last week we didn't know for sure that it had been captured,
      and now there's no doubt that it was captured in April of this year,"
      said Dr. Paul Chodas of the Near-Earth Object Program Office at
      NASA's Jet Propulsion Laboratory, Pasadena, Calif. "What's more, we
      are virtually certain that it originally escaped Earth orbit in March
      1971 and that it will escape again next June. It's only a temporary
      visitor."

      The object, named J002E3, was discovered Sept. 3 by Canadian
      amateur astronomer Bill Yeung, observing from El Centro, Calif.
      Increasingly precise orbital calculations made possible from a second
      week of positional observations have nearly ruled out any chance the
      object will hit the Moon or enter Earth's atmosphere before it
      departs Earth orbit, Chodas said. Calculations made about a week
      after the discovery left higher impact possibilities, but now the
      chances of impact are less than 1 percent at either the Moon or
      Earth, and a third week of observations will likely push the odds to
      zero. The object is too small to be considered hazardous, in any
      case.

      More than 100 measurements of the object's position have now
      been reported from more than a dozen amateur astronomers, said JPL's
      Dr. Steven Chesley. The two weeks of movement tracked by those
      observations make up about a sixth of one orbit around Earth.
      Scientists can extrapolate the object's path for years into the
      future and years into the past from that short arc. "The observations
      coming in are from a loosely organized network of dedicated amateur
      observers. Their data have been vital in determining this object's
      past and future paths," Chesley said.

      The object escaped from Earth orbit in March 1971, Chodas
      said. That fits its most likely identity as the third stage of the
      Saturn rocket that took Apollo 12 astronauts to the Moon in November
      1969. The 18-meter-long (60-foot-long) third stage was last seen in
      an elongated 43-day orbit around Earth, not much different from
      J002E3's current orbit. It probably completed nine or 10 Earth
      orbits, then swung far enough toward the Sun to be pulled into a Sun-
      centered orbit, he said. The transition happened through a
      special "portal" located at the L1 Lagrangian point, where the
      gravitational pulls of the Sun and Earth are approximately equal.

      Analysis this week by researchers from the University of
      Arizona, Tucson, and the Massachusetts Institute of Technology,
      Cambridge, suggests that J002E3's surface is white paint rather than
      more asteroid-like material. If it is not from the Apollo 12 rocket,
      some less likely possibilities are one of the four 7-meter-long (22-
      foot-long) panels that enclosed lunar modules from six Apollo
      missions or rocket stages from Soviet or U.S. unmanned lunar
      missions. Those are less likely because they seem too small to match
      the object's observed brightness, and they are not known to have been
      left in orbits that could have escaped Earth. Additional observations
      in coming weeks may pin down the identification.

      After J002E3 escaped Earth's gravity in 1971, it raced Earth
      in circles around the Sun, but it had an inner lane, so it completed
      33 solar orbits in the time it took Earth to complete 31. In 1986,
      the object lapped Earth on the inside, too far away to be snagged by
      Earth's gravity. This year, it was about to lap Earth again but
      passed too close to the L1 portal and Earth captured it.

      The transition between Earth-centered dynamics and Sun-
      centered dynamics has been understood theoretically for years and has
      been used for designing orbits of some spacecraft, but this is the
      first time a capture into Earth orbit has been confirmed, Chodas
      said. Comet Shoemaker-Levy 9, which struck Jupiter in 1994, made this
      kind of transition into Jupiter's orbit several decades earlier.
      NASA's Genesis spacecraft, currently collecting samples of solar-wind
      material near the L1 point, will use a similar maneuver for a low-
      energy return to Earth with the samples in 2004.

      Earth won't have seen the last of J002E3 when this peripatetic
      bit of space junk escapes after its sixth orbit in mid-2003. It will
      shift from solar orbit to Earth orbit again in decades ahead. "This
      type of orbit can't last very long," Chodas said. "That's one reason
      it would be very unlikely to find an asteroid with an orbit like
      this." Within several thousand years, the object will likely end its
      travels by hitting the Moon or Earth. That is not cause for concern,
      though. Five rocket stages like the Apollo 12 third stage were
      crashed into the Moon intentionally as part of seismic research, and
      several others harmlessly disintegrated when they re-entered Earth's
      atmosphere.

      Images of J002E3's calculated path are available at
      http://neo.jpl.nasa.gov

      JPL, a division of the California Institute of Technology in
      Pasadena, manages the Near-Earth Object Program for NASA's Office of
      Space Science, Washington, D.C.
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