They also want to measure the length of a Saturn day, learn more about planet's magnetic field, map its internal structure and take close-up pictures of the planet's powerful aurora. Cassini even could discover a moon-like mass inside Saturn, which could explain some mysterious wave motions detected in the C-ring, Spilker said.
"The rings are actually a very sensitive detector of what's going on inside Saturn," Spilker said last week during a webcast meeting of the National Academy of Sciences Committee on Astrobiology and Planetary Science.
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"We saw a series of waves in the rings and they were damping in the wrong direction. Usually, when there's resonance with a moon, the waves damp out toward the moon. These particular waves were damping in toward Saturn. It looks almost like you have a mass or like tiny moon inside Saturn itself," Spilker said.
The journey in toward Saturn promises suspense. Scientists aren't exactly sure how many particles Cassini might encounter as it flies closer to Saturn. To be on the safe side, Cassini will makes its first few close passes using its big communications antenna as a shield. If too many particles hit the antenna, Cassini can fly that way the rest of the mission, Spilker said.
"In just a little over an hour, you go from north pole to south pole, through the ring gap. You're going incredibly fast -- 75,000 mph. That's why even a particle a millimeter or so in size hitting in the wrong place wouldn't be so good for Cassini," Spilker said.
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"Fortunately, most of the particles we encounter are more like smoke," added Cassini project manager Earl Maize.
"For the Grand Finale, we strive to make the probability of serious impact less than a few percent, although four of the 22 passes in the Grand Finale slightly exceed that threshold. That being said, our models and risk calculations are very conservative and we expect to be absolutely fine," Maize wrote in an email to Discovery News.
Beginning Nov. 30, Cassini's orbit will be shifted so that it passes just beyond the outer edge of the main rings. During these weekly orbits, Cassini will fly within 4,850 miles of the center of the narrow F ring.
In April, a flyby Saturn's large moon Titan will bend Cassini's trajectory so that the spacecraft leaps across all the rings. Cassini's first dive through the unexplored 1,500-mile gap between Saturn and its rings is scheduled for April 27.