NASA spacecraft embarks on ring-skimming mission at Saturn

Consider it a cosmic carousel with countless rings up for grabs.

NASA's Saturn-orbiting spacecraft, Cassini, has begun an unprecedented mission to skim the planet's rings.

Yesterday, Cassini got a gravitational assist from Saturn's big moon Titan. That put the spacecraft on course to graze Saturn's main outer rings.

The first orbit of this new venture begins Wednesday night. Then on Sunday, an engine firing by Cassini should seal the deal, with the spacecraft making its first ring crossing.

Launched nearly 20 years ago, Cassini will swoop down through the outer edge of rings every seven days. The spacecraft should make 20 dives through April, observing some of Saturn's many mini moons and even sampling ring particles. This will be Cassini's last hurrah before plunging into Saturn next September.