Cassini crosses Saturn's rings

ToSeek · #1 (**permalink**) 12-July-2004, 05:11 PM

Article with cool Quicktime movie, with audio:

Saturn hailstorm

Quote:

Although the ring gaps appeared empty, they weren't. Innumerable bits of ring-dust were waiting for Cassini, and they plowed into the spacecraft at a relative speed of approximately 20 km/s. That's 45,000 mph!

"When we crossed the ring plane, we had roughly 100,000 total dust hits in less than five minutes," says Cassini science team member Don Gurnett of the University of Iowa. Fortunately the particles were small--"comparable in size to particles in cigarette smoke," he says. And most of the hits were to the spacecraft's tough high-gain antenna.

um3k · #2 (**permalink**) 12-July-2004, 06:54 PM

You mean they actually thought the gaps are empty? Even I know better than that! #-o

kucharek · #3 (**permalink**) 12-July-2004, 06:58 PM

Quote:

Originally Posted by um3k

You mean they actually thought the gaps are empty? Even I know better than that! #-o

100000 particles in a space that is crossed by the dish in five minutes: That is empty!

Doodler · #4 (**permalink**) 12-July-2004, 06:58 PM

Quote:

Originally Posted by um3k

You mean they actually thought the gaps are empty? Even I know better than that! #-o

Of course they knew the gaps weren't empty. They did shift the HGA to protect the probe as it passed through the rings. They knew something would be there, they just were caught off-guard by how much and what was actually there. They were prepared for the possibility of impacts, though.

Russ · #5 (**permalink**) 12-July-2004, 10:01 PM

When the Voyagers passed through there were no collisions detected. Close up pics. of the rings indicated that even the most dense rings were mostly empty space. Of course they didn't have any effective means of detecting particle collisions in the first place. Having the probe destroyed by a collision was the only real means they had of detecting one.

Karl · #6 (**permalink**) 12-July-2004, 10:18 PM

Voyager used the same dust detection method that Cassini did, particles hitting the spacecraft generating plasma noise. The noise was apparent in the spectrograms even if there was no high rate data being taken.

The Cassini dust instrument was not turned on till it was well clear of the ring plane crossing after SOI.

http://adsabs.harvard.edu/cgi-bin/np...GR....99.2261T

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