PUBLIC INFORMATION 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
Contact: Mary Beth Murrill (818) 354-6478
FOR IMMEDIATE RELEASE
January 29, 1996
KEY COMPONENTS INSTALLED ON SATURN-BOUND SPACECRAFT
Computer brains, an electronic inner ear and the spacecraft
equivalent of a cardiovascular system have been successfully
installed into NASA's Cassini spacecraft, bound for a launch to
Saturn in 1997.
Engineers and technicians at the Jet Propulsion Laboratory
(JPL), Pasadena, CA, this month completed installation of this
key flight hardware on the Cassini spacecraft framework in JPL's
spacecraft assembly facility clean room.
Also included among the many critical Cassini milestones met
this month was the successful 200-minute engine firing of the
spacecraft's main rocket engine last week, and successful
completion of launch-like vibration testing for Cassini's Huygens
probe. This conical payload of science instruments, provided by
the European Space Agency (ESA), will be deployed from the
orbiter and parachute to the surface of Saturn's moon Titan, in a
manner similar to the recent successful mission of the Galileo
atmospheric probe into Jupiter.
"The Cassini team has done an excellent job of keeping the
program on track to complete the orbiter and probe on schedule
and within budget," said Richard J. Spehalski, Cassini program
manager at JPL, which manages the effort for NASA. "Our
challenge in 1996 will be to maintain our momentum as all the
spacecraft elements come together."
Last week, Cassini's attitude and articulation control
subsystem (AACS) was integrated. The AACS allows the spacecraft
to maintain its bearings in space. It joined the already-
installed power and pyro subsystem (PPS), which governs the flow
of electricity through seven miles of cabling that will link all
of Cassini's systems, and the command and data subsystem (CDS)
which acts essentially as Cassini's brain, controlling all
spacecraft functions.
While the Cassini spacecraft is assembled in the clean room,
engineers and technicians in an adjacent shirtsleeve environment
are remotely controlling the new subsystems in tests that run
each through the commands and phenomena they will experience in
flight.
This complex computer-based ground system largely resembles
that which will be used to control Cassini once in flight, and it
allows the Cassini team to identify problems and make changes
needed in the flight operations system well ahead of launch.
Last week also marked the successful completion of a
critical 200-minute test firing of one of the two spacecraft
rocket engines, demonstrating the capability of the main engine
assembly including the successful operation of JPL-developed
engine gimbal actuators -- sophisticated devices that fine-tune
the motion and pointing of the spacecraft's two engines.
The engine gimbal actuators, based upon the design of unique
actuators used on the orbiter spacecraft for the Viking missions
to Mars in the mid-1970s come into play during spacecraft course
corrections and in the critical braking maneuver that Cassini
must perform when it arrives at Saturn in July 2004. There,
Cassini must fire one of its engines for about 90 minutes to
brake into orbit around the ringed planet. The two redundant
engines are mounted side-by-side at the base of the Saturn
orbiter, and the engine that fires must be pointed so that the
rocket thrust is directed through the spacecraft's center of
gravity. The engine gimbal actuators, responding to commands from
the attitude and articulation control subsystem, will make
constant minute adjustments in the engine's position to
compensate for the shifting weight of more than 3,100 kilograms
(6,800 pounds) of propellant.
Important tests of Cassini's multiple-frequency radio system
were also successfully completed this month at JPL. In addition,
ESA, assembling the Huygens probe in Otterbrun, Germany, received
hardware for U.S.-provided Titan science instruments -- a
qualification model of the gas chromatograph/mass spectrometer
from NASA's Goddard Space Flight Center, Greenbelt, MD, and the
flight model of the descent imager/spectral radiometer from the
University of Arizona.
Integration of Cassini components will continue through
October this year, readying the spacecraft for dynamic and other
testing in the space-like environment of the solar-thermal vacuum
chamber at JPL. The spacecraft will be shipped to Cape
Canaveral, FL, in late April 1997 for an October 1997 launch.
Cassini a joint mission of NASA, ESA and the Italian Space
Agency (ASI). The main Cassini spacecraft will orbit Saturn to
provide four years of close-up data on the moons, rings, planet
and Saturn's magnetic and charged particle environment. The
Huygens Titan probe is provided by ESA, and Cassini's
sophisticated radio antenna is provided by ASI. JPL manages the
overall mission for NASA.
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The address for the Cassini Program's home page is
http://www.jpl.nasa.gov/cassini.
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