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 MurrillJuly 16, 1996
CASSINI SCIENTISTS MAP OUT STRATEGY TO EXPLORE SATURN
Recent observations of Saturn, its rings and moons are
helping an international team of scientists to update their
strategy for exploring the ringed planet as part of the Cassini
mission to Saturn, scheduled for launch next year from Cape
Cassini is an international mission being conducted by NASA,
the European Space Agency (ESA) and the Italian Space Agency
(ASI). The mission will send Cassini, a large NASA-built
spacecraft, into orbit around Saturn. Cassini will carry an ESA-
built probe to parachute to the surface of Saturn's largest moon,
Titan. ASI is providing Cassini's sophisticated
telecommunications system, which doubles as an imaging radar that
will gather data to produce images of Titan's hidden, haze-
Now being prepared for launch on Oct. 6, 1997, Cassini will
enter orbit around Saturn on July 1, 2004. On approach to
Titan, Cassini will release the Huygens probe, which will descend
through Titan's dense nitrogen atmosphere on Nov. 27, 2004.
Cassini will spend four years in orbit around Saturn to conduct
close-up tours of the planet, its rings, moons and magnetic
environment. The Cassini orbiter carries 12 science instruments
and the Huygens probe has six.
Recent images from NASA's Hubble Space Telescope and
observations from Earth-based astronomical facilities have
provided new information on Titan and Saturn's rings that are
useful to scientists now planning Cassini's voyage, said Dr.
Dennis Matson, Cassini project scientist at NASA's Jet Propulsion
In particular, Hubble images of Titan show clear
demarcations between two types of terrain that may represent a
solid rocky surface next to the lakes of liquid ethane and
methane that are thought to exist on Titan, Matson said.
"We've targeted the Huygens probe to descend to one of these
boundaries between the light and dark areas, which should give us
a good chance to study both kinds of terrain," said Matson. "The
Hubble images tell us we've done a good job in targeting that
Slightly larger than the planet Mercury, Titan appears to
have at least one continent. It is covered by a hazy, brownish
atmosphere that is organically rich and which may share many
characteristics with Earth's early atmosphere. The Huygens probe
is equipped with a camera and instruments to measure the
composition and structure of Titan's atmosphere surface.
Recent ground-based observations of Saturn's rings have
helped ensure that Cassini's flight path avoids areas where
particles associated with the outermost rings might pose a hazard
to the spacecraft, Matson said.
Science planning by the 250-plus scientists from 17
countries has reached an "intermediate level of detail in the
development phase," said Matson. "We've established our broad
goals and objectives for Saturn, its magnetic environment, the
rings, Titan and the icy moons Enceladus, Mimas and Iapetus.
"The issue we are working on now is how to plan the orbital
tour of Saturn so that we can collect key observations needed by
all of Cassini's science investigations," he said. "A lot of
observations need to be made and the challenge is to find ways to
put the spacecraft in all the right places at all the right times
to make all those observations."
At meetings in Europe and the U.S., Cassini scientists are
looking a different tour options to determine which has the
greatest advantages for the greatest number of instruments on
Cassini's science objectives call for at least four close
flybys of some of Saturn's more interesting moons. Among them
are Enceladus, made up almost entirely of water ice, with only a
few meteorite impact craters remaining on its surface. Cassini
will determine if this smooth-faced moon has some internal heat
source that melts the ice enough to erase its craters. A search
will be conducted for small, geyser-like volcanoes, which some
scientists suspect exists on Enceladus. The geysers may shoot
ice particles into space where they are captured by Saturn's
gravity to become part of the ring system.
Another icy moon of interest is Iapetus, unique because it
has two faces -- one side as bright as snow while the other is as
dark as asphalt. Cassini will study the surface composition of
this strange moon to determine the nature of the dark material
and whether it came from Iapetus' interior or was deposited by
some external source.
The complex rings of Saturn will be targeted for intensive
study by Cassini. The rings are a mixture of ice boulders, rock
and tiny ice crystals. They may represent remnants of one or
more moons shattered by Saturn's gravity, or perhaps by comet or
meteor strikes, or they may be the product of some other unknown
The magnetic environment that surrounds Saturn is called the
magnetosphere, and Cassini will study this structure in detail.
Space physics instruments on the spacecraft will study the
behavior of trapped, charged particles within this field in
addition to the interaction between the magnetic field and
Saturn's moons and rings. The instrument will also study the
relationship between the magnetosphere of Saturn and the constant
stream of charged particles from the Sun, called the solar wind.
One instrument called the Magnetosphere Imaging Instrument or
"MIMI" for short, will produce the first-ever image of Saturn's
Instruments on Cassini will see deep into Saturn's hydrogen-
helium atmosphere. Scientists expect to learn about the
atmospheric activity at different altitudes, to observe how
storms develop and disappear, and to discover the forces that
drive Saturn's high winds and storms.
The Cassini spacecraft is being assembled at JPL.
Instruments from universities and laboratories in the U.S. and
Europe are currently being integrated and tested. In Europe, the
Huygens probe is undergoing final assembly and test prior to
being shipped to NASA's Kennedy Space Center in Florida, where it
will be joined with the Cassini spacecraft and prepared for
launch next year.
JPL manages the Cassini program for NASA's Office of Space
Science. More information on the mission is available from the
Cassini home page at: