Cassini Spacecraft Dives Between Saturn and Its Rings

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NASA Spacecraft Dives Between Saturn and Its Rings
Jet Propulsion Laboratory
April 27, 2017

"In the grandest tradition of exploration, NASA's Cassini spacecraft has
once again blazed a trail, showing us new wonders and demonstrating where
our curiosity can take us if we dare," said Jim Green, director of the
Planetary Science Division at NASA Headquarters in Washington.

As it dove through the gap, Cassini came within about 1,900 miles (3,000
kilometers) of Saturn's cloud tops (where the air pressure is 1 bar --
comparable to the atmospheric pressure of Earth at sea level) and within
about 200 miles (300 kilometers) of the innermost visible edge of the
rings.

While mission managers were confident Cassini would pass through the gap
successfully, they took extra precautions with this first dive, as the
region had never been explored.

"No spacecraft has ever been this close to Saturn before. We could only
rely on predictions, based on our experience with Saturn's other rings,
of what we thought this gap between the rings and Saturn would be like,"
said Cassini Project Manager Earl Maize of NASA's Jet Propulsion Laboratory
in Pasadena, California. "I am delighted to report that Cassini shot through
the gap just as we planned and has come out the other side in excellent
shape."

The gap between the rings and the top of Saturn's atmosphere is about
1,500 miles (2,000 kilometers) wide. The best models for the region suggested
that if there were ring particles in the area where Cassini crossed the
ring plane, they would be tiny, on the scale of smoke particles. The spacecraft
zipped through this region at speeds of about 77,000 mph (124,000 kph)
relative to the planet, so small particles hitting a sensitive area could
potentially have disabled the spacecraft.

As a protective measure, the spacecraft used its large, dish-shaped high-gain
antenna (13 feet or 4 meters across) as a shield, orienting it in the
direction of oncoming ring particles. This meant that the spacecraft was
out of contact with Earth during the ring-plane crossing, which took place
at 2 a.m. PDT (5 a.m. EDT) on April 26. Cassini was programmed to collect
science data while close to the planet and turn toward Earth to make contact
about 20 hours after the crossing.

Cassini's next dive through the gap is scheduled for May 2.

Launched in 1997, Cassini arrived at Saturn in 2004. Following its last
close flyby of the large moon Titan on April 21 PDT (April 22 EDT), Cassini
began what mission planners are calling its "Grand Finale." During this
final chapter, Cassini loops Saturn approximately once per week, making
a total of 22 dives between the rings and the planet. Data from this first
dive will help engineers understand if and how they will need to protect
the spacecraft on its future ring-plane crossings. The spacecraft is on
a trajectory that will eventually plunge into Saturn's atmosphere -- and
end Cassini's mission -- on Sept. 15, 2017.

More information about Cassini's Grand Finale, including images and video,
is available at:

https://saturn.jpl.nasa.gov/grandfinale

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European
Space Agency) and the Italian Space Agency. JPL, a division of Caltech
in Pasadena, California, manages the mission for NASA's Science Mission
Directorate. JPL designed, developed and assembled the Cassini orbiter.

More information about Cassini is at:

http://www.nasa.gov/cassini

http://saturn.jpl.nasa.gov

News Media Contact
Preston Dyches
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-7013
preston...@jpl.nasa.gov

Dwayne Brown/Laurie Cantillo
NASA Headquarters, Washington
202-358-1726 / 202-358-1077
Dwayne....@nasa.gov / Laura.l....@nasa.gov

2017-126