Newly Discovered Object Could be a Leftover Apollo Rocket Stage
Click on the above image to see animations showing how J002E3 was
captured into its current chaotic orbit around the Earth.
September 11, 2002
Near-Earth Object Program Office
An analysis of the orbital motion of the newly discovered
object J002E3 indicates that it could be a leftover Saturn V
third stage from one of the Apollo missions, most likely
the Apollo 12 mission, launched on November 14, 1969.
The new object was discovered on September 3 by Bill Yeung,
who noted that it was moving quite rapidly. Initial orbit
computations by the Minor Planet Center indicated that the
object was only about twice as far away as the Moon, and
was actually in orbit about our planet. This fact, combined
with the rather faint intrinsic magnitude, immediately led
astronomers to suspect that the object is actually a
spacecraft or rocket body, not an asteroid. But the object
could not be associated with any recent launch.
J002E3 is currently observable at magnitude 16.5; it is
easily detectable in asteroid surveys, and even bright enough
to be seen by many amateur astronomers. If it is a
leftover piece from an old launch, why was it not discovered
until last week? A backwards analysis of the orbital motion
provides the answer: the object was apparently captured by
the Earth from heliocentric orbit in April of this year.
The capture occurred when the object passed near the Earth's
L1 Lagrange point, a location where the gravity of the Earth
and Sun approximately cancel. This point serves as a "portal"
between the regions of space controlled by the Earth and Sun.
J002E3 is the first known case of an object being captured
by the Earth, although Jupiter has been known to capture
comets via the same mechanism. (For example, Comet
Shoemaker-Levy 9, which collided with Jupiter in 1994, had
been captured by Jupiter decades earlier.)
Analysis of J002E3's pre-capture orbit about the Sun
shows that the object was always inside the Earth's
orbit, and that it may have come within the Earth's
vicinity in the early 1970s or late 1960s. Many of the
test cases in our analysis in fact passed through
the L1 portal, back into Earth orbit (going backwards
in time) during the early 1970s. In other words, this
object was very likely orbiting the Earth during
this period before escaping into the heliocentric orbit
from which it was captured in 2002. It seems quite
likely that this object is one of the Apollo Saturn
S-IVB third stages which flew by the Moon during this
era (Apollos 8 through 12). The brightness of J002E3
seems to match the expected brightness of an S-IVB
stage. Further circumstantial evidence suggests that
this object is in fact the Apollo 12 stage, which was
left in a very distant Earth orbit after it passed by
the Moon on November 18, 1969. This spent rocket body
was last seen in an Earth orbit with a period of 43
days, not much different from J002E3's current orbit.
Apollo 12 at Pad A, Launch Complex 39, Kennedy Space
NASA Photo ID: S69-56596.
Photograph taken from the Apollo 8 spacecraft looking back at the Saturn V
third (S-IVB) stage from which the spacecraft had just separated following
translunar injection. NASA Photo ID: AS08-16-2584.
Copyright Boeing Company. Photograph of the Saturn V third stage used for Apollo 11.
The future motion of J002E3 is also very interesting.
A similar orbital analysis which takes into account
the current orbit uncertainties shows that the object
has a surprisingly large 20 percent chance of impacting
the Moon in 2003. Such a lunar impact would not be
unprecedented: NASA intentionally impacted five Apollo
S-IVB stages on the Moon from 1970 through 1972
(Apollos 13 through 17), as an experiment to study the
interior structure of the Moon. Looking further into
the future is problematic, due to the chaotic nature of
J002E3's orbit, but our current analysis shows the object
to have about a 3 percent chance of impacting the Earth
within the next 10 years. This should not be of
concern to the public. Apollo stages have impacted the
Earth before, in the 1960s, and the larger Skylab
re-entered in the 1970s. (The even larger Mir Space
Station was intentionally impacted into the Pacific
Ocean in 2001.)
Additional positional observations of this object are
being received daily, and our knowledge and modeling of
its orbit continues to improve. The collision
probabilities mentioned above will change as we are able
to make more precise predictions.