[meteorite-list] NASA Goddard A Partner On Comet Cruise (CONTOUR)
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:01:35 2004
Bill Steigerwald June 17, 2002
Goddard Space Flight Center, Greenbelt, Md.
NASA GODDARD A PARTNER ON COMET CRUISE
NASA's Goddard Space Flight Center is supplying an instrument to provide key
data on the CONTOUR mission, set to explore at least two comets following
its July 1 launch from Cape Canaveral, Fla. The Goddard instrument will
explore the chemical composition of the comet nucleus, an icy core in the
head of the comet.
Goddard's Neutral Gas and Ion Mass Spectrometer (NGIMS) instrument will
sample ambient gas atoms and molecules in the comet's atmosphere (coma) as
CONTOUR zips past the nucleus. Sampling the coma gives information about a
comet's composition because the coma is comprised of dust and gas evaporated
from the nucleus. The coma appears as the bright "head" of a comet, and it
develops if a comet's orbit takes it close to the Sun, where solar heat and
radiation vaporize the comet's ices. (The nucleus is technically part of the
head also, but it is too small to see, and it is obscured by the coma.)
"It's truly exciting to have the opportunity to fly this close to the
nucleus of a comet for the first time," said Dr. Paul Mahaffy, a Goddard
Co-Investigator with the CONTOUR mission for NGIMS. "With NGIMS we'll sample
gases from Comet Encke and at least one more comet and hope to learn much
about the diversity of comets and how these bodies may have helped shape our
own environment in the distant past through delivery of water and organic
molecules. It has been a real privilege working with a uniquely talented
team at Goddard to develop this measurement capability."
NGIMS will identify the types and relative amounts of atoms and molecules in
the coma by creating ions (electrically charged atoms and molecules) from
neutral gas and then separating these by their mass to charge ratio using
electromagnetic fields. Since this ratio is often unique to a particular
atom or molecule, this separation, or mass spectrometry, can be used to
identify the atoms and molecules present in the coma.
Comets are thought to be relics left over from the formation of the solar
system. They are comprised of dust and frozen gasses that were present in
the primordial cloud that became the Sun and planets. Comets normally
inhabit the outer regions of the solar system, far from the Sun, where
frigid temperatures keep their ices completely frozen. There, a comet is
just a nucleus, very small and faint, without the much larger and brighter
coma or tail structure.
Occasionally, however, gravity from another solar system object, or perhaps
a passing star, disrupts a comet's orbit and sends it hurtling into the
inner solar system, where the coma forms. Sunlight and a stream of
electrified gas that blows constantly from the Sun, called the solar wind,
push dust and gas away from the coma in the direction opposite from the Sun,
giving a comet its familiar tail-like shape.
"Comets are the solar system's smallest bodies, but among its biggest
mysteries," says Dr. Joseph Veverka, CONTOUR's Principal Investigator from
Cornell University, Ithaca, N.Y. "We believe they hold the most primitive
materials in the solar system and that they played a role in shaping some of
the planets, but we really have more ideas about comets than facts. CONTOUR
will change that by coming closer to a comet nucleus than any spacecraft
ever has before and gathering detailed, comparative data on these dynamic
CONTOUR's flexible four-year mission plan includes encounters with comets
Encke (Nov. 12, 2003) and Schwassmann-Wachmann 3 (June 19, 2006), though it
can add a study of a "new" comet from the outer solar system should one be
discovered in time for CONTOUR to catch it. CONTOUR will examine each
comet's "heart," or nucleus, which scientists believe is a chunk of ice and
rock, often just a few kilometers across and hidden from Earth-based
telescopes beneath a dusty atmosphere and long tail.
The 8-sided solar-powered craft will fly as close as 100 kilometers (62
miles) to each nucleus, at top speeds that could cover the 56 kilometers
between Washington and Baltimore in two seconds. A 5-layer dust shield of
heavy Nextel and Kevlar fabric protects the compact probe from comet dust
and debris. CONTOUR's four scientific instruments will take pictures and
measure the chemical makeup of the nuclei while analyzing the surrounding
gases and dust.
The $159 million CONTOUR is the sixth mission in NASA's Discovery Program of
lower cost, scientifically focused exploration projects. The Johns Hopkins
University Applied Physics Laboratory (APL), Laurel, Md., manages the
mission, built the spacecraft and its two cameras, and will operate CONTOUR
during flight. NASA's Goddard Space Flight Center, Greenbelt, Md., provided
CONTOUR's neutral gas/ion mass spectrometer and von Hoerner & Sulger, GmbH,
Schwetzingen, Germany, built the dust analyzer. NASA's Jet Propulsion
Laboratory, Pasadena, Calif., will provide navigation and Deep Space Network
(DSN) support. Cornell's Veverka leads a science team of 18 co-investigators
from universities, industry, and government agencies in the U.S. and Europe.
CONTOUR is scheduled to lift off from Cape Canaveral Air Force Station,
Fla., on a three-stage Boeing Delta II rocket during a 25-day launch window
that opens July 1 at 2:56 a.m. EDT. The spacecraft will orbit Earth until
Aug. 15, when it should fire its main engine and enter its comet-chasing
orbit around the Sun.
NASA TV will provide live coverage of the launch beginning at 1:30 a.m. EDT.
More information on CONTOUR is available on the Web at:
Received on Wed 26 Jun 2002 12:21:18 PM PDT