NASA has approved the retargeting of the EPOXI mission
for a flyby of comet Hartley 2 on Oct. 11, 2010. Hartley 2 was chosen
as EPOXI's destination after the initial target, comet Boethin, could
not be found. Scientists theorize comet Boethin may have broken up
into pieces too small for detection.
The EPOXI mission melds two compelling science investigations -- the
Extrasolar Planet Observation and Characterization and the Deep
Impact Extended Investigation. Both investigations will be performed
using the Deep Impact spacecraft.
In addition to investigating comet Hartley 2, the spacecraft will
point the larger of its two telescopes at nearby exosolar planetary
systems in late January 2008 to observe several previously discovered
planetary systems outside our solar system. It will study the
physical properties of giant planets and search for rings, moons and
planets as small as three Earth masses. It also will look at Earth as
though it were an exosolar planet to provide data that could become
the standard for characterizing these types of planets.
"The search for exosolar planetary systems is one of the most
intriguing explorations of our time, " said Drake Deming, EPOXI deputy
principal investigator at NASA's Goddard Space Flight Center,
Greenbelt, Md. "With EPOXI we have the potential to discover new
worlds and even analyze the light they emit to perhaps discover what
atmospheres they possess."
The mission's closest approach to the small half-mile-wide comet will
be about 620 miles. The spacecraft will employ the same suite of two
science instruments the Deep Impact spacecraft used during its prime
mission to guide an impactor into comet Tempel 1 in July 2005.
If EPOXI's observations of Hartley 2 show it is similar to one of the
other comets that have been observed, this new class of comets will
be defined for the first time. If the comet displays different
characteristics, it would deepen the mystery of cometary diversity.
"When comet Boethin could not be located, we went to our backup, which
is every bit as interesting but about two years farther down the
road, " said Tom Duxbury, EPOXI project manager at NASA's Jet
Propulsion Laboratory in Pasadena, Calif.
Mission controllers at JPL began directing EPOXI towards Hartley 2 on
Nov. 1. They commanded the spacecraft to perform a three-minute
rocket burn that changed the spacecraft's velocity. EPOXI's new
trajectory sets the stage for three Earth flybys, the first on Dec.
31, 2007. This places the spacecraft into an orbital "holding
pattern" until time for the optimal encounter of comet Hartley 2 in
2010.
"Hartley 2 is scientifically just as interesting as comet Boethin
because both have relatively small, active nuclei, " said Michael
A'Hearn, principal investigator for EPOXI at the University of
Maryland, College Park.
EPOXI's low mission cost of $40 million is achieved by taking
advantage of the existing Deep Impact spacecraft.
JPL manages EPOXI for NASA's Science Mission Directorate, Washington.
The spacecraft was built for NASA by Ball Aerospace & Technologies
Corp., Boulder, Colo.
For information about EPOXI, visit: http://www.nasa.gov/epoxi
US $65.00
