[meteorite-list] Rosetta Set to Harpoon a Comet Tomorrow

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 11 Nov 2014 22:14:05 -0800 (PST)
Message-ID: <201411120614.sAC6E5ui001774_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?feature=4373

European Spacecraft Set to Harpoon a Comet Tomorrow
Jet Propulsion Laboratory
November 11, 2014

Early tomorrow morning, the European Space Agency's Rosetta spacecraft
will deploy its comet lander, "Philae." A little over seven hours later
(8 a.m. PST/11 a.m. EST), the experiment-laden, harpoon-firing Philae
is scheduled to touch down on the surface of comet 67P/Churyumov-Gerasimenko.
It will be the first time in history that a spacecraft has attempted a
soft landing on a comet. Rosetta is an international mission led by the
European Space Agency (ESA), with instruments provided by its member states,
and additional support and instruments provided by NASA.

"I know it sounds like something out of Moby Dick, but when you think
about the gravity field of a comet, it makes a lot of sense to harpoon
one," said Art Chmielewski, project manager for the U.S. participation
in Rosetta, from NASA's Jet Propulsion Laboratory in Pasadena, California.
"Comet 67P has approximately 100,000 times less gravity than Earth does.
So, if you don't want to float away, you have to go to extraordinary measures
to attach yourself to its dusty surface. The Philae lander has two harpoons,
shock-absorbing landing gear, and a drill located on each of the lander's
three feet. It even has a small, upward-firing rocket engine. All this
to help keep it on the surface."

The descent of Philae begins at 1:03 a.m. PST (4:03 a.m. EST) when Rosetta
releases the 220-pound (100-kilogram) Philae from an altitude of about
14 miles (23 kilometers) from the center of the comet's nucleus. As Philae
descends, it will fall slowly without propulsion or guidance, gradually
gathering speed in the comet's weak gravitational field. During the seven-hour
descent, the lander will take images and conduct science experiments,
sampling the environment close to the comet. It will take a "farewell"
image of the Rosetta orbiter shortly after separation, along with a number
of images as it approaches the comet surface.

The targeted landing site is called Agilkia after an island in the Nile
River in southern of Egypt where ancient buildings from the Nile's flooded
Philae island were relocated. Once the lander has touched down and safely
anchored, it will begin a primary science mission, which extends to about
two-and-a-half days. Philae will take a panorama of its surroundings and
perform on-the-spot analysis of the composition of the comet's surface.
It can drill samples from a depth of nine inches (23 centimeters) and
feed them to the onboard laboratory for analysis. The lander will also
measure electrical and mechanical characteristics of the surface of the
nucleus.

After the Philae landing is completed, Rosetta will begin the next major
part of its mission, the escort phase. The orbiter will continue to maneuver
around the comet at walking pace, collecting dust and gas samples and
making remote sensing observations as the comet warms up and the nucleus
and its environment evolve. The comet will reach its closest point to
the sun (perihelion) in August 2015. Rosetta will then track the waning
of activity as the comet heads back toward the cold, far reaches of the
outer solar system, through 2015.

Three NASA science instruments are aboard the Rosetta spacecraft; the
Microwave Instrument for Rosetta Orbiter (MIRO); an ultraviolet spectrometer
called Alice, and the Ion and Electron Sensor (IES). They are part of
a suite of 11 science instruments on the orbiter.

MIRO is designed to provide data on how gas and dust leave the surface
of the nucleus to form the coma and tail that give comets their intrinsic
beauty. Studying the surface temperature and evolution of the coma and
tail provides information on how the comet evolves as it approaches and
leaves the vicinity of the sun. MIRO has the ability to study water, carbon
monoxide, ammonia and methanol.

Alice will analyze gases in the comet's coma, which is the bright envelope
of gas around the nucleus of the comet developed as a comet approaches
the sun. Alice also will measure the rate at which the comet produces
water, carbon monoxide and carbon dioxide. These measurements will provide
valuable information about the surface composition of the nucleus.

Alice also will measure the amount of argon present, an important clue
about the temperature of the solar system at the time the comet's nucleus
originally formed more than 4.6 billion years ago.

IES is part of a suite of five instruments to analyze the plasma environment
of the comet, particularly the coma. The instrument will measure the charged
particles in the sun's outer atmosphere, or solar wind, as they interact
with the gas flowing out from the comet while Rosetta is drawing nearer
to the comet's nucleus.

NASA also provided part of the electronics package for the Double Focusing
Mass Spectrometer, which is part of the Swiss-built Rosetta Orbiter Spectrometer
for Ion and Neutral Analysis (ROSINA) instrument. ROSINA is the first
instrument in space with sufficient resolution to be able to distinguish
between molecular nitrogen and carbon monoxide, two molecules with approximately
the same mass. Clear identification of nitrogen will help scientists understand
conditions at the time the solar system was formed.

U.S. scientists are partnering on several non-U.S. instruments and are
involved in seven of the mission's 26 instrument collaborations. NASA's
Deep Space Network is supporting ESA's Ground Station Network for spacecraft
tracking and navigation.

"Landing a spacecraft on a comet is a remarkable challenge and we wish
them well," said Claudia Alexander, project scientist for the U.S. Rosetta
project from JPL. "It is the overture, opening for what has already become
an exciting mission of exploration. Whatever happens tomorrow, the main
part of the Rosetta mission will continue with the Rosetta orbiter monitoring
the comet as it sweeps through the inner-solar system."

Comets are time capsules containing primitive material left over from
the epoch when the sun and its planets formed. Rosetta's lander will obtain
the first images taken from a comet's surface and will provide comprehensive
analysis of the comet's possible primordial composition by drilling into
the surface. Rosetta also will be the first spacecraft to witness at close
proximity how a comet changes as it is subjected to the increasing intensity
of the sun's radiation. Observations will help scientists learn more about
the origin and evolution of our solar system and the role comets may have
played in seeding Earth with water, and perhaps even life.

Rosetta is a European Space Agency mission with contributions from its
member states and NASA. Rosetta's Philae lander is provided by a consortium
led by the German Aerospace Center, Cologne; Max Planck Institute for
Solar System Research, Gottingen; National Center of Space Studies of
France (CNES), Paris; and the Italian Space Agency, Rome. NASA's Jet Propulsion
Laboratory in Pasadena, California, a division of the California Institute
of Technology, manages the U.S. participation in the Rosetta mission for
NASA's Science Mission Directorate in Washington.

For more information on the U.S. instruments aboard Rosetta, visit:

http://rosetta.jpl.nasa.gov

More information about Rosetta is available at:

http://www.esa.int/rosetta

Media Contact
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

Markus Bauer
011-31-71-565-6799
European Space Agency, Noordwijk, Netherlands
markus.bauer at esa.int

2014-392
Received on Wed 12 Nov 2014 01:14:05 AM PST