[meteorite-list] See the Space Junk that Might Hit the Moon

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:08:26 2004
Message-ID: <200209161527.IAA11181_at_zagami.jpl.nasa.gov>

http://space.com/news/space_junk_020916.html

See the Space Junk that Might Hit the Moon
By Robert Roy Britt
space.com
16 September 2002

A group of asteroid researchers photographed and animated Earth's
newest satellite, an object captured recently by Earth's gravity and
one that is likely a hunk of Apollo-era junk that's wandering home.

The astronomers, at Fort Bend Astronomy Club in Texas, used an
18-inch telescope and an electronic CCD camera, said club member
Len Casady.

The newfound object orbits Earth about twice as far away as the Moon
and has a 20 percent chance of hitting the Moon next year. It can
only be directly seen in very large telescopes, roughly 18 inches
(0.46 meter) and bigger. It can likely be imaged with smaller
telescopes, down to about 8 inches (0.2 meter), if they are
equipped with CCD cameras that collect light over long exposures.

Some researchers speculated the object, temporarily designated J002E3,
might be a natural satellite -- an asteroid captured into orbit. But
Paul Chodas at NASA's Jet Propulsion Laboratory ran computer
simulations, reported early Thursday, that suggest it is a Saturn V
third stage rocket booster, most likely from the Apollo 12 mission,
launched in 1969.

Desktop computer work

Chodas told SPACE.com late Thursday he can't put exact odds on what the
object is, but that it is "very unlikely to be a natural object." He
used data on the satellite's position and path to model its history on a
desktop computer.

Chodas said the real work was not running the computer model but rather
the manual effort of interpreting the results and investigating various
possibilities.

"My Pentium 3 machine is far from state-of-the-art, but it can propagate
a sample orbit back 30 years in less than a second," he said. "I often
try tens of thousands or even hundreds of thousands of sample orbits,
all slightly different, and propagate them backwards or forwards for
decades in order to study the various possible outcomes."

Chodas also models newly found asteroids with similar software to learn
whether they might have a chance of hitting Earth.

His simulations found that J002E3 -- initially thought to be an asteroid
when discovered on Sept. 3 -- also has a 3 percent chance of re-entering
Earth's atmosphere over the next decade. Both odds may change as more
observations are gathered and fed into the computer model.

Watching the impact

If the object were to hit the Moon, Chodas said astronomers could
possibly observe the impact if it occurred on the side of the Moon
facing Earth.

"Modern Earth-based sensors, especially those in the infrared
wavelengths, would probably be able detect such an impact," he said.

Five Apollo rocket stages were purposely crashed into the Moon in the
1960s to calibrate seismic instruments that had been left on the Moon by
earlier missions and to investigate the lunar crust.

J002E3 is currently at magnitude 16.5 on a scale used by astronomers to
denote brightness. Larger numbers indicated dimmer objects. The dimmest
object visible to the human eye is around magnitude 6.0 under totally
dark skies. The brightest stars are near magnitude zero.
Received on Mon 16 Sep 2002 11:27:07 AM PDT