[meteorite-list] Countdown to Comet Flyby Down to Nine Days

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 27 Oct 2010 12:11:52 -0700 (PDT)
Message-ID: <201010271911.o9RJBqOd005046_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2010-349

Countdown to Comet Flyby Down to Nine Days
Jet Propulsion Laboratory
October 26, 2010

PASADENA, Calif. - NASA's EPOXI mission continues to close in on its
target, comet Hartley 2, at a rate of 12.5 kilometers (7.8 miles) per
second. On Nov. 4 at about 10:01 a.m. EDT (7:01 a.m. PDT) the spacecraft
will make its closest approach to the comet at a distance of about 700
kilometers (434 miles). It will be the fifth time that a comet has been
imaged close-up and the first time in history that two comets have been
imaged with the same instruments and same spatial resolution.

"Hartley 2 has already put on a great show with more than a few
surprises for the mission's science team," said EPOXI principal
investigator Mike A'Hearn from the University of Maryland, College Park.
"We expect more of the unexpected during encounter."

Science observations of comet Hartley 2 began on Sept. 5. The imaging
campaign is more than a tantalizing tease of things to come. It is
providing EPOXI's science team the best extended view of a comet in
history during its pass through the inner solar system. The observations
will continue through the encounter phase of the mission.

The hours surrounding comet encounter will be especially challenging for
the mission team as they are commanding a recycled spacecraft that was
not designed for this comet flyby. The spacecraft was designed and
employed successfully for NASA's Deep Impact encounter of comet Tempel 1
back on July 4, 2005. By recycling Deep Impact's already built, tested
and in-flight spacecraft, the EPOXI mission provided savings on the
order of 90% that of a hypothetical mission with similar goals, starting
from the ground up.

"If we were starting from scratch we'd probably move some of the
spacecraft's components to different locations," said Tim Larson,
project manager for the EPOXI mission from NASA's Jet Propulsion
Laboratory in Pasadena, Calif. "But we've developed a creative way to
work with what we have. This spacecraft, and mission team, have logged
3.2 billion miles over the past five years, and we are confident that we
have a successful plan in place to give Hartley 2 a thorough look-see."

The mission's encounter phase begins the evening of Nov. 3, when the
spacecraft is about 18 hours from the time of closest approach to the
comet's nucleus. At that time the spacecraft will stop transmitting
through its large high-gain antenna and reorient itself so its two
visible-light and one infrared imager maintain lock on the comet for the
next 24 hours-plus.

"When the encounter phase begins all images the spacecraft takes will be
stored aboard its two computers," said Larson. "Soon after we fly past
the comet at about 7 a.m. local time, we will be able to re-orient the
spacecraft so that we maintain imaging lock on the comet nucleus while
pointing our big high gain antenna at Earth."

At that point, the spacecraft will begin beaming down its cache of
cometary close-ups while continuing to take new images. It is expected
to take several hours for all the images held aboard spacecraft memory
to be downliked.

"We will be waiting," said A'Hearn. "The images at closest approach
won't get to Earth until many hours after the actual encounter due to
the way we use memory on the spacecraft. We will get some early hints at
how this nucleus differs from that of comet Tempel 1 based on five
images that will get to Earth only about one hour after closest approach."

EPOXI is an extended mission that utilizes the already "in-flight" Deep
Impact spacecraft to explore distinct celestial targets of opportunity.
The name EPOXI itself is a combination of the names for the two extended
mission components: the extrasolar planet observations, called
Extrasolar Planet Observations and Characterization (EPOCh), and the
flyby of comet Hartley 2, called the Deep Impact Extended Investigation
(DIXI). The spacecraft will continue to be referred to as "Deep Impact."

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the EPOXI
mission for NASA's Science Mission Directorate, Washington. The
University of Maryland, College Park, is home to the mission's principal
investigator, Michael A'Hearn. Drake Deming of NASA's Goddard Space
Flight Center, Greenbelt, Md., is the science lead for the mission's
extrasolar planet observations. The spacecraft was built for NASA by
Ball Aerospace & Technologies Corp., Boulder, Colo.

For more information about EPOXI visit http://www.nasa.gov/epoxi or
http://epoxi.umd.edu/.

DC Agle 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
agle at jpl.nasa.gov

Lee Tune 301-405-4679
University of Maryland, College Park
ltune at umd.edu

2010-349
Received on Wed 27 Oct 2010 03:11:52 PM PDT