User-Agent: Microsoft-Entourage/12.36.0.130206 Date: Mon, 17 Oct 2011 13:17:42 -0700 Subject: Asteroid 2009 TM8 From: Daniel Adamo Message-ID: Thread-Topic: Asteroid 2009 TM8 Thread-Index: AcpSca/v58R/2XbaSaKzjEXgJ7pWVYR1Dr4f Mime-version: 1.0 Content-type: multipart/alternative; boundary="B_3552762813_3968803" > This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. --B_3552762813_3968803 Content-type: text/plain; charset="US-ASCII" Content-transfer-encoding: 7bit ATIG Members- I'm impressed: after I sent out the notice at the bottom of this thread 2 years ago, one among us added an appropriate event to her calendar for today and has inquired what's become of 2009 TM8. Good question, Pam! Just before noon CDT today, I polled JPL's Small Bodies Database (SBDB) and found 2009 TM8's record hasn't received another observation since the 48 leading to its discovery. Because these observations extended over only 2 days (close to a 2-deg heliocentric arc), the integrity of the current 2008 TM8 orbit elements would be equivalent to those from low speed ground NAV tracking a Shuttle for half a minute. Indeed, the SBDB's Orbital Condition Code (OCC) for this NEO is 6, meaning 2009 TM8 is effectively lost. According to Harvard's Minor Planet Center, OCC = 6, is equivalent to a heliocentric downtrack error between 1692 and 7488 arc-seconds per decade. Consequently, in the two years since 2009 TM8 was discovered, its predicted heliocentric mean anomaly is probably in error from 0.1 to 0.4 deg. Since humanity insists on observing NEOs only from Earth, a very close approach by 2009 TM8 is required because its diameter is almost certainly less than 10 m. When mapped into a close-up geocentric viewing geometry, heliocentric position uncertainty places 2009 TM8 virtually anywhere in our sky this week. I'll be in touch with further details if this celestial needle in a haystack is rediscovered. Fortunately, an object less than 10 m in diameter won't do much damage if it enters Earth's atmosphere. -Dan From: Daniel Adamo Date: Wed, 21 Oct 2009 12:12:37 -0500 Subject: Asteroid 2009 TM8 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 --B_3552762813_3968803 Content-type: text/html; charset="US-ASCII" Content-transfer-encoding: quoted-printable Asteroid 2009 TM8 ATIG Members-

I'm impressed: after I sent out the notice at the bottom of this thread 2 y= ears ago, one among us added an appropriate event to her calendar for today = and has inquired what's become of 2009 TM8.  Good question, Pam!

Just before noon CDT today, I polled JPL's Small Bodies Database (SBDB) and= found 2009 TM8's record hasn't received another observation since the 48 le= ading to its discovery.  Because these observations extended over only = 2 days (close to a 2-deg heliocentric arc), the integrity of the current 200= 8 TM8 orbit elements would be equivalent to those from low speed ground NAV = tracking a Shuttle for half a minute.

Indeed, the SBDB's Orbital Condition Code (OCC) for this NEO is 6, meaning = 2009 TM8 is effectively lost.  According to Harvard's Minor Planet Cent= er, OCC =3D 6, is equivalent to a heliocentric downtrack error between 1692 an= d 7488 arc-seconds per decade.  Consequently, in the two years since 20= 09 TM8 was discovered, its predicted heliocentric mean anomaly is probably i= n error from 0.1 to 0.4 deg.  Since humanity insists on observing NEOs = only from Earth, a very close approach by 2009 TM8 is required because its d= iameter is almost certainly less than 10 m.  When mapped into a close-u= p geocentric viewing geometry, heliocentric position uncertainty places 2009= TM8 virtually anywhere in our sky this week.

I'll be in touch with further details if this celestial needle in a haystac= k is rediscovered.  Fortunately, an object less than 10 m in diameter w= on't do much damage if it enters Earth's atmosphere.

-Dan


From: Daniel Adamo <adamod@earthli= nk.net>
Date: Wed, 21 Oct 2009 12:12:37 -0500
Subject: Asteroid 2009 TM8

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, 2= 009 TM8 crossed Earth's heliocentric orbit ahead of our path around the Sun.=  Earth flyby geometry therefore caused 2009 TM8 to lose some heliocent= ric 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 observatio= ns 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 th= e Sun, I'm speculating the observation arc won't be extended later in time v= ery 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 orb= it 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 i= magine interest in reacquiring (2009 TM8) will be high during the summer/fal= l of 2011.

-Dan --B_3552762813_3968803--