Asteroid 2011 MD passes dangerously close to Earth

The attached image demonstrates the very rapid (20sec.) motion of the near earth asteroid
2011 MD which passed only 7,400 miles from Earth on Monday. This photo from Arkansas Sky
Observatories (P. Clay Sherrod) was taken when the asteroid was about 12,000 miles distant
and only 12 hours from its closest brush by Earth. The image left the shutter open for 20
seconds while the large telescope followed the distant stars; you can clearly see the
motion (the bright streak near center) of this dangerously close asteroid as it streaks
to the southwest (from lower right to upper left, south is up in this photo), heading for
the close encounter with Earth on Monday, June 27.

From June 23 through June 26, the Arkansas Sky Observatories (ASO) Petit Jean Mountain
facility provided NASA's Jet Propulsion Laboratory Radar Sensing Team with over 120
precise orbital measurements of asteroid 2011 MD, a near-earth asteroid that barely missed
hitting the earth by less than 7,400 miles on Monday.

The object was reported on June 22 by the LINEAR sky survey (also a NASA observatory
discovery network) and by Monday, this 200 foot wide object grazed just outside of the
earth's atmosphere by 8,000 miles; by comparison, our moon in 234,000 miles average. NASA
had given the object a 5 percent chance of actually hitting the earth and the closest
point of impact was between the tip of South American and the continental shelf of
Antarctica.

When it was realized that this object had the potential to strike the earth, NASA's Radar
Sensing team, put out a call to all observatories with the capability and experience to
obtain precise measurements of the orbit of this object. Because of the very limited time
frame, less than two dozen observatories world wide were able to obtain quality
measurements.

Arkansas Sky Observatories' Clay Sherrod, working 5-hour periods on Thursday, Friday,
Saturday and Sunday nights, obtained nearly double the data of all other observatories
combined and was instrumental in providing data on the ever-changing orbit and incoming
trajectory of this speeding chunk of rock. In fact, Tokyo Astronomical Association's
Suichi Nakano regarded ASO's observations as the "highest quality" of all received in
terms of precision and consistency.

The new orbital data provided changes in astronomer's understanding of the exact path of
the asteroid as it approached earth, and passed it shortly after noon CDT on Monday. Each
night's observations were reduced into revised orbital plots that showed that the object
was indeed going to miss the Earth in 2011, but may return with the possibility of
impacting in coming years, since the orbit of the asteroid is very similar in many
respects to the orbit of the Earth as it goes around the sun; hence the two will cross
paths many times in coming years.

Indeed, the close approach of 2011 MD was the closest to Earth impact of any asteroid of
this size since scientists began watching these Near Earth Objects (NEOs) with
sophisticated computer operated telescopes similar to that at Arkansas Sky.

The 100 observations obtained by Sherrod are being used by the Goldstone Solar System Radar,
part of the JPL/NASA Deep Space Network.
Goldstone Deep Space Communications Complex , which is located about 35 miles north of
Barstow on the Ft. Irwin Military Base.

This radar team, headed by NASA's Dr. Lance Benner, has locked the world's largest
steerable radio telescope- the Goldstone main antenna, DSS14, a fully steerable, 70-meter,
parabolic reflector with horn feeds. Its 500-kilowatt transmitter is the world's most
powerful atX-band (8560 MHz, 3.5-cm).

The radar was literally bounced off of the tumbling and speeding asteroid for nearly six
hours and reflected back to the receiver of the same huge radio telescope; computers will
analyze the signals and be able to determine the density, size and shape of this
previously unknown celestial object. The antenna required Sherrod's data in order to
actually know precisely where to steer the huge reflector to point the radar beam
precisely at the asteroid as it passed the Earth on Sunday, June 26.

Although similar requests for precise orbital measurements reach Arkansas Sky Observatory
every week, this was perhaps the most successful to date in terms of the Petit Jean
Mountain observatory's contribution to the success of this major feat by the world's
largest steerable radio telescope.

Now that asteroid 2011 MD has passed safely out of the Earth's realm for now, NASA's JPL
is again receiving orbital measurements of yet another NEO - 2011 EZ78 - so that the
largest radio telescope in the world, Arecibo in Puerto Rico, can measure that solar
system object as it also passes close to the Earth later this year.