PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 
91109. TELEPHONE (818) 354-5011

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.

                         #####
The address for the Cassini Program's home page is 
http://www.jpl.nasa.gov/cassini.

#9605 MBM
1/29/96