ESA's Huygens Probe Set to Detach From Cassini Orbiter

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.

Press Release: 2004-295 December 21, 2004

European Space Agency's Huygens Probe Set to Detach From Cassini
Orbiter

The highlights of the first year of the Cassini-Huygens mission
to Saturn can be broken into two chapters: first, the arrival of
the Cassini orbiter at Saturn in June, and second, the release of
the Huygens probe on Dec. 24, 2004, on a path toward Titan.

The Huygens probe, built and managed by the European Space Agency
(ESA), is bolted to Cassini and fed electrical power through an
umbilical cable. It has been riding along during the nearly
seven-year journey to Saturn largely in a "sleep" mode, awakened
every six months for three-hour instrument and engineering
checkups. In three days, it will be cut loose from its mother
ship and will coast toward Saturn's moon Titan, arriving on Jan.
14, 2005.

"As partners with ESA, one of our obligations was to carry the
Huygens probe to Saturn and drop it off at Titan," said Robert T.
Mitchell, Cassini program manager at NASA's Jet Propulsion
Laboratory, Pasadena, Calif. "We've done the first part, and on
Christmas Eve we will release Huygens and tension-loaded springs
will gently push it away from Cassini onto a ballistic free-fall
path to Titan."

Once freed from Cassini, the Huygens probe will remain dormant
until the onboard timer wakes it up shortly before the probe
reaches Titan's upper atmosphere on Jan. 14. Then it will begin
a dramatic plunge through Titan's murky atmosphere, tasting the
chemical makeup and composition as it descends to touch down on
its surface. The data gathered during this 2-1/2 hour descent
will be transmitted from the probe to the Cassini orbiter.
Afterward, Cassini will point its antenna to Earth and relay the
data through NASA's Deep Space Network to JPL and on to ESA's
Space Operations Center in Darmstadt, Germany, which serves as
the operations center for the Huygens probe mission. From this
control center, ESA engineers will be tracking the probe and
scientists will be standing by to process the data from the
probe's six instruments.

Currently, both the orbiter and the probe are on an impact
trajectory with Titan. This is the only way to ensure that
Cassini delivers the probe in the right location. A confirmation
of successful release is expected to be received from NASA's Deep
Space Network tracking stations at Madrid, Spain and Goldstone,
Calif., shortly before 8:00 p.m. PST on Dec. 24. A team of JPL
engineers and ESA mission managers will be monitoring spacecraft
activities at JPL during the release phase of the mission.

On Dec. 27, the Cassini orbiter will perform a deflection
maneuver to keep it from following Huygens into Titan's
atmosphere. This maneuver will also establish the required
geometry between the probe and the orbiter for radio
communications during the probe descent.

Two of the instruments on ESA's Huygens probe, the descent imager
and spectral radiometer camera and the gas chromatograph-mass
spectrometer, are contributions from NASA and American academia.

The imaging camera will take advantage of the Huygens probe's
rotation, using two imagers to observe the surface of Titan
during the late stages of descent for a view of the regions
around the impact site. A side-looking imager will view the
horizon and the underside of any cloud deck. More than just a
camera, the instrument is designed to measure concentrations of
argon and methane in the atmosphere and determine the size and
density of particles. The instrument will also determine if the
local surface is a solid or liquid, and if solid, its topography.
The principal investigator is Dr. Martin G. Tomasko of the
University of Arizona, Tucson, Ariz.

Although Titan's atmosphere is primarily nitrogen and methane,
scientists believe it contains many other gases that are present
only in small amounts. These trace gases can reveal critical
details about the origin and evolution of Titan's atmosphere.
Because trace gases are rare, they are difficult or impossible to
observe remotely, so direct measurements must be made.

The gas chromatograph-mass spectrometer instrument will sample
gas directly from Titan's atmosphere as the Huygens probe
descends by parachute. Data from the instrument will allow
researchers to investigate the chemical composition, origin and
evolution of the atmosphere of Titan. The instrument was designed
and built by NASA's Goddard Space Flight Center, Greenbelt, Md.,
and is led by the principal investigator, Dr. Hasso Niemann.

Updates on the Huygens probe release will be available at:
http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .
The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. JPL, a
division of the California Institute of Technology in Pasadena,
manages the Cassini mission for NASA's Science Mission
Directorate, Washington, D.C. JPL designed, developed and
assembled the Cassini orbiter. The European Space Agency built
and managed the development of the Huygens probe and is in charge
of the probe operations. The Italian Space Agency provided the
high-gain antenna, much of the radio system and elements of
several of Cassini's science instruments.
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