Cassini号探索土星环（常速朗读版）

原文
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.
On Wednesday, Cassini got a gravitational assist from Saturn’s big moon Titan. That put the spacecraft on course to graze Saturn’s main outer rings over the next five months.
The first orbit of this new venture begins Thursday.
Then at the beginning of next week, an engine firing by Cassini should seal the deal, with the spacecraft making its first ring crossing.