[meteorite-list] Rosetta: To Chase a Comet

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?release=2014-015

Rosetta: To Chase a Comet
Jet Propulsion Laboratory
January 17, 2014

Comets are among the most beautiful and least understood nomads of the
night sky. To date, half a dozen of these most heavenly of heavenly
bodies have been visited by spacecraft in an attempt to unlock their
secrets. All these missions have had one thing in common: the high-speed
flyby. Like two ships passing in the night (or one ship and one icy
dirtball), they screamed past each other at hyper velocity -- providing
valuable insight, but fleeting glimpses, into the life of a comet. That
is, until Rosetta.

NASA is participating in the European Space Agency's Rosetta mission,
whose goal is to observe one such space-bound icy dirt ball from up
close -- for months on end. The spacecraft, festooned with 25
instruments between its lander and orbiter (including three from NASA),
is programmed to "wake up" from hibernation on Jan. 20. After a
check-out period, it will monitor comet 67P/Churyumov-Gerasimenko as it
makes its nosedive into, and then climb out of, the inner solar system.
Over 16 months, during which old 67P is expected to transform from a
small, frozen world into a roiling mass of ice and dust, complete with
surface eruptions, mini-earthquakes, basketball-sized, fluffy ice
particles and spewing jets of carbon dioxide and cyanide.

"We are going to be in the cometary catbird seat on this one," said
Claudia Alexander, project scientist for U.S. Rosetta from NASA's Jet
Propulsion Laboratory in Pasadena, Calif. "To have an extended presence
in the neighborhood of a comet as it goes through so many changes should
change our perspective on what it is to be a comet."

Since work began on Rosetta back in 1993, scientists and engineers from
all over Europe and the United States have been combining their talents
to build an orbiter and a lander for this unique expedition. NASA's
contribution includes three of the orbiter's instruments (an ultraviolet
spectrometer called Alice; the Microwave Instrument for Rosetta Orbiter;
and the Ion and Electron Sensor. NASA is also providing part of the
electronics package for an instrument called the Double Focusing Mass
Spectrometer, which is part of the Swiss-built Rosetta Orbiter
Spectrometer for Ion and Neutral Analysis instrument. NASA is also
providing U.S. science investigators for selected non-U.S. instruments
and is involved to a greater or lesser degree in seven of the mission's
25 instruments. NASA's Deep Space Network provides support for ESA's
Ground Station Network for spacecraft tracking and navigation.

"All the instruments aboard Rosetta and the Philae lander are designed
to work synergistically," said Sam Gulkis of JPL, the principal
investigator for the Microwave Instrument for Rosetta Orbiter. "They
will all work together to create the most complete picture of a comet to
date, telling us how the comet works, what it is made of, and what it
can tell us about the origins of the solar system."

The three NASA-supplied instruments are part of the orbiter's scientific
payload. Rosetta's Microwave Instrument for Rosetta Orbiter specializes
in the thermal properties. The instrument combines a spectrometer and
radiometer, so it can sense temperature and identify chemicals located
on or near the comet's surface, and even in the dust and ices jetting
out from it. The instrument will also see the gaseous activity through
the dusty cloud of material. Rosetta scientists will use it to determine
how different materials in the comet change from ice to gas, and to
observe how much it changes in temperature as it approaches the sun.

Like the Microwave for Rosetta Orbiter, the Alice instrument contains a
spectrometer. But Alice looks at the ultraviolet portion of the
spectrum. Alice will analyze gases in the coma and tail and measure the
comet's production rates of water and carbon monoxide and dioxide. It
will provide information on the surface composition of the nucleus, and
make a potentially key measurement of argon, which will be a big clue
about what the temperature was in the primordial solar system when the
comet's nucleus originally formed (more than 4.6 billion years ago).

The Rosetta orbiter's Ion and Electron Sensor is part of a suite of five
instruments to characterize the plasma environment of the comet -- in
particular, its coma, which develops when the comet approaches the sun.
The sun's outer atmosphere, the solar wind, interacts with the gas
flowing out from the comet, and the instrument will measure the charged
particles it comes in contact with as the orbiter approaches the comet's
nucleus.

All three instruments are slated to begin science collection by early
summer. Along with the pure science they will provide, their data are
expected to help Rosetta project management determine where to attempt
to land their Philae lander on the comet in November.

"It feels good to be part of a team that is on the cusp of making some
space exploration history," said Art Chmielewski, NASA's project manager
for US Rosetta, based at JPL. "There are so many exciting elements and
big milestones coming up in this mission that it feels like I should buy
a ticket and a big box of popcorn. Rosetta is going to be a remarkable
ride."

Rosetta is a mission of the European Space Agency, Paris, with
contributions from its member states and NASA. Rosetta's Philae lander
is provided by a consortium led by the German Aerospace Center, the Max
Planck Institute for Solar System Research, the French National Space
Agency and the Italian Space Agency. JPL manages the U.S. contribution
of the Rosetta mission for NASA's Science Mission Directorate in
Washington. The Microwave Instrument for the Rosetta Orbiter was built
at JPL and JPL is home to its principal investigator, Samuel Gulkis. The
Southwest Research Institute, San Antonio, developed the Rosetta
orbiter's Ion and Electron Sensor (IES) and is home to its principal
investigator, James Burch. The Southwest Research Institute, Boulder,
Colo., developed the Alice instrument and is home to its principal
investigator, Alan Stern.

More information about Rosetta is available online at:
http://www.esa.int/rosetta and http://rosetta.jpl.nasa.gov .

DC Agle/Jia-Rui Cook 818-393-9011/818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
agle at jpl.nasa.gov / jccook at jpl.nasa.gov

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

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

2014-015