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http://www.jpl.nasa.gov/news/news.php?feature=4888

Small Asteroid to Pass Close to Earth March 8
Jet Propulsion Laboratory
UPDATED ON FEB. 25 AT 2:40 P.M. PT:

Additional observations of asteroid 2013 TX68 have been obtained, refining
its orbital path and moving the date of the asteroid's Earth flyby from
March 5 to March 8.

The observations, from archived images provided by the NASA-funded Pan-STARRS asteroid survey, enabled scientists at NASA's Center for Near-Earth Object Studies (CNEOS) at the Jet Propulsion Laboratory in Pasadena, California,
to refine their earlier flyby and distance predictions, reconfirming that
the asteroid poses no threat to Earth.

"We already knew this asteroid, 2013 TX68, would safely fly past Earth
in early March, but this additional data allow us to get a better handle
on its orbital path," said Paul Chodas, manager of CNEOS. "The data indicate that this small asteroid will probably pass much farther away from Earth
than previously thought."

Marco Micheli of the European Space Agency's NEO Coordination Centre (NEOCC/SpaceDys)
in Frascati, Italy, is the astronomer who identified the object in the archived images, measured its position, and provided these observations
to the Minor Planet Center in Cambridge, Massachusetts.

CNEOS's new prediction for 2013 TX68 is that it will fly by roughly 3
million miles (5 million kilometers) from our planet. There is still a
chance that it could pass closer, but certainly no closer than 15,000
miles (24,000 kilometers) above Earth's surface. The new observations
also better constrain the path of 2013 TX68 in future years; CNEOS has determined that 2013 TX68 cannot impact Earth over the next century.

"There is no concern whatsoever regarding this asteroid - unless you were interested in seeing it with a telescope," said Chodas. "Prospects for observing this asteroid, which were not very good to begin with, are now
even worse because the asteroid is likely to be farther away, and therefore dimmer than previously believed."

Orbit calculations of asteroids are constantly updated based on observations reported to the Minor Planet Center. This results in projections of minimum, maximum and nominal distances from Earth, which can sometimes have a wide disparity due to limited data. Over time, with additional observations
added to the equation, scientists are able to refine and narrow the orbit uncertanties.

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