Subject: Asteroid (2009 TM8)
From: adamod <[email-masked]>
Date: Wed, 21 Oct 2009 12:12:37 -0500

ATIG Members-

Last Friday evening Oct 16 CDT, yet another asteroid briefly came closer to
Earth than the Moon.  Flyby geometry for the interloper, provisionally
designated (2009 TM8), is illustrated in the attached geocentric plot.  With
the Moon and Sun roughly to the left of Earth in the geocentric plot, (2009
TM8) crossed Earth's heliocentric orbit ahead of our path around the Sun.
Earth flyby geometry therefore caused (2009 TM8) to lose some heliocentric
orbit energy.  This is apparent from the heliocentric plot spanning 2009 and
2010.  Note the shift to lower aphelion as the (2009 TM8) plot begins and
ends.

As of October 18, JPL's orbit solution for (2009 TM8) contained 36
observations over a 2-day arc.  By October 20, 48 observations had been
processed over the same arc.  Because (2009 TM8)'s Earth departure was
toward the Sun, I'm speculating the observation arc won't be extended later
in time very much.  The only significant improvement in the orbit solution
would come from a serendipitous pre-discovery observation.

Nevertheless, current knowledge of (2009 TM8)'s post-flyby heliocentric
orbit places its period very near two years.  To a 3-sigma uncertainty of
23.9 hours in closest approach time, the next Earth conjunction will be (you
guessed it) early on 2011 Oct 17 UTC.  Depending on how the statistics play
out, perigee could be as low as 178,600 km on that occasion.  I imagine
interest in reacquiring (2009 TM8) will be high during the summer/fall of
2011.

-Dan