A Long and Winding Road: Cassini Celebrates 15 Years

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

Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

News feature: 2012-325 Oct. 15, 2012

A Long and Winding Road: Cassini Celebrates 15 Years

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.php?release=2012-325&cid=release_2012-325

Today, NASA's Cassini spacecraft celebrates 15 years of uninterrupted drive
time, earning it a place among the ultimate interplanetary road warriors.

Since launching on Oct. 15, 1997, the spacecraft has logged more than 3.8
billion miles (6.1 billion kilometers) of exploration – enough to circle Earth more
than 152,000 times. After flying by Venus twice, Earth, and then Jupiter on its
way to Saturn, Cassini pulled into orbit around the ringed planet in 2004 and has
been spending its last eight years weaving around Saturn, its glittering rings and
intriguing moons.

And, lest it be accused of refusing to write home, Cassini has sent back some
444 gigabytes of scientific data so far, including more than 300,000 images. More
than 2,500 reports have been published in scientific journals based on Cassini
data, describing the discovery of the plume of water ice and organic particles
spewing from the moon Enceladus; the first views of the hydrocarbon-filled lakes
of Saturn's largest moon Titan; the atmospheric upheaval from a rare, monstrous
storm on Saturn and many other curious phenomena.

"As Cassini conducts the most in-depth survey of a giant planet to date, the
spacecraft has been flying the most complex gravity-assisted trajectory ever
attempted," said Robert Mitchell, Cassini program manager at NASA's Jet
Propulsion Laboratory in Pasadena, Calif. "Each flyby of Titan, for example, is
like threading the eye of the needle. And we've done it 87 times so far, with
accuracies generally within about one mile [1.6 kilometers], and all controlled
from Earth about one billion miles [1.5 billion kilometers] away."

The complexity comes in part from the spacecraft lining up visits to more than a
dozen of Saturn's 60-plus moons and sometimes swinging up to get views of
poles of the planet and moons. Cassini then works its way back to orbiting
around Saturn's equator, while staying on track to hit its next targeted flyby. The
turn-by-turn directions that mission planners write also have to factor in the
gravitational influences of the moons and a limited fuel supply.

"I'm proud to say Cassini has accomplished all of this every year on-budget, with
relatively few health issues," Mitchell said. "Cassini is entering middle age, with
the associated signs of the passage of years, but it's doing remarkably well and
doesn't require any major surgery."

The smooth, white paint of the high-gain antenna probably now feels rough to the
touch, and some of the blankets around the body of the spacecraft are probably
pitted with tiny holes from micrometeoroids. But Cassini still retains redundancy
on its critical engineering systems, and the team expects it to return millions
more bytes of scientific data as it continues to sniff, taste, watch and listen to the
Saturn system.

And that's a good thing, because Cassini still has a daring, unique mission ahead
of it. Spring has only recently begun to creep over the northern hemisphere of
Saturn and its moons, so scientists are only beginning to understand the change
wrought by the turning of the seasons. No other spacecraft has been able to
observe such a transformation at a giant planet.

Starting in November 2016, Cassini will begin a series of orbits that wind it ever
closer to Saturn. Those orbits kick off just outside Saturn's F ring, the outermost
of the main rings. Then in April 2017, one final close encounter with Titan will put
Cassini on a trajectory that will pass by Saturn inside its innermost ring, a
whisper away from the top of Saturn's atmosphere. After 22 such close passes,
the gravitational perturbation from one final distant Titan encounter will bring
Cassini ever closer. On Sept. 15, 2017, after entry into Saturn's atmosphere, the
spacecraft will be crushed and vaporized by the pressure and temperature of
Saturn's final embrace to protect worlds like Enceladus and Titan, with liquid
water oceans under their icy crusts that might harbor conditions for life.

"Cassini has many more miles to go before it sleeps, and many more questions
that we scientists want answered," said Linda Spilker, Cassini project scientist at
JPL. "In fact, its last orbits may be the most thrilling of all, because we'll be able
to find out what it's like close in to the planet, with data that cannot be gathered
any other way."

A new illustrated timeline of Cassin's 15 years of exploration is available at:
http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4646 .

The Cassini-Huygens mission is a cooperative project of NASA, ESA and the
Italian Space Agency. JPL manages the mission for NASA's Science Mission
Directorate in Washington. The Cassini orbiter and its two onboard cameras
were designed, developed and assembled at JPL. JPL is managed for NASA by
the California Institute of Technology in Pasadena.

For more information about the mission, visit: http://www.nasa.gov/cassini and
http://saturn.jpl.nasa.gov .

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