[meteorite-list] NASA's Deep Impact Spacecraft Eyes Comet ISON

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 5 Feb 2013 13:45:03 -0800 (PST)
Message-ID: <201302052145.r15Lj3iR027467_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?release=2013-047

NASA's Deep Impact Spacecraft Eyes Comet ISON
Jet Propulsion Laboratory
February 05, 2013

PASADENA, Calif. - NASA's Deep Impact spacecraft has acquired its first
images of comet C/2012 S1 (ISON). The images were taken by the
spacecraft's Medium-Resolution Imager over a 36-hour period on Jan. 17
and 18, 2013, from a distance of 493 million miles (793 million
kilometers). Many scientists anticipate a bright future for comet ISON;
the spaceborne conglomeration of dust and ice may put on quite a show as
it passes through the inner solar system this fall.

"This is the fourth comet on which we have performed science
observations and the farthest point from Earth from which we've tried to
transmit data on a comet," said Tim Larson, project manager for the Deep
Impact spacecraft at NASA's Jet Propulsion Laboratory in Pasadena,
Calif. "The distance limits our bandwidth, so it's a little like
communicating through a modem after being used to DSL. But we're going
to coordinate our science collection and playback so we maximize our
return on this potentially spectacular comet."

Deep Impact has executed close flybys of two comets - Tempel 1 and
Hartley 2 - and performed scientific observations on two more - comet
Garradd and now ISON. The ISON imaging campaign is expected to yield
infrared data, and light curves (which are used in defining the comet's
rotation rate) in addition to visible-light images. A movie of comet
ISON was generated from initial data acquired during this campaign.
Preliminary results indicate that although the comet is still in the
outer solar system, more than 474 million miles (763 million kilometers)
from the sun, it is already active. As of Jan. 18, the tail extending
from ISON's nucleus was already more than 40,000 miles (64,400
kilometers) long.

Long-period comets like ISON are thought to arrive from the solar
system's Oort cloud, a giant spherical cloud of icy bodies surrounding
our solar system so far away its outer edge is about a third of the way
to the nearest star (other than our sun). Every once in a while, one of
these loose conglomerations of ice, rock, dust and organic compounds is
disturbed out of its established orbit in the Oort cloud by a passing
star or the combined gravitational effects of the stars in the Milky Way
galaxy. With these gravitational nudges, so begins a comet's eons-long,
arching plunge toward the inner solar system.

ISON was discovered on Sept. 21, 2012, by two Russian astronomers using
the International Scientific Optical Network's 16-inch (40-centimeter)
telescope near Kislovodsk. NASA's Near-Earth Object Program Office,
based at JPL, has plotted its orbit and determined that the comet is
more than likely making it first-ever sweep through the inner solar
system. Having not come this way before means the comet's pristine
surface has a higher probability of being laden with volatile material
just spoiling for some of the sun's energy to heat it up and help it
escape. With the exodus of these clean ices could come a boatload of
dust, held in check since the beginnings of our solar system. This
released gas and dust is what is seen on Earth as comprising a comet's
atmosphere (coma) and tail.

ISON will not be a threat to Earth - getting no closer to Earth than
about 40 million miles on Dec. 26, 2013. But stargazers will have an
opportunity to view the comet's head and tail before and after its
closest approach to the sun -- if the comet doesn't fade early or break
up before reaching the sun.

Launched in January 2005, NASA's Deep Impact spacecraft traveled about
268 million miles (431 million kilometers) to the vicinity of comet
Tempel 1. On July 3, 2005, the spacecraft deployed an impactor that was
essentially "run over" by the nucleus of Tempel 1 on July 4. Sixteen
days after comet encounter, the Deep Impact team placed the spacecraft
on a trajectory to fly past Earth in late December 2007. This extended
mission of the Deep Impact spacecraft culminated in the successful flyby
of comet Hartley 2 on Nov. 4, 2010. In January of 2012, the spacecraft
performed, from a distance, an imaging campaign on comet C/2009 P1
(Garradd).

To date, Deep Impact has traveled about 4.39 billion miles (7.06 billion
kilometers) in space.

JPL, a division of the California Institute of Technology in Pasadena,
manages the Deep Impact mission for NASA's Science Mission Directorate,
Washington. The mission is part of the Discovery Program managed at
NASA's Marshall Space Flight Center in Huntsville, Ala. The spacecraft
was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.

For more information about Deep Impact, visit:
http://solarsystem.nasa.gov/deepimpact .

DC Agle 818-393-9011
Jet Propulsion Laboratory, Pasadena, Calif.
agle at jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Dwayne.c.brown at nasa.gov

2013-047
Received on Tue 05 Feb 2013 04:45:03 PM PST