Over the next nine months, the probe will dive through the vast belts of rock as it prepares to dump itself in Saturn’s atmosphere.
NASA scientists are set upon ditching the craft before it runs out of fuel, to preempt a collision with one of the planet’s 53 moons.
There’s a chance that Enceladus and Titan might harbour life, and a satellite from Earth poses a major contamination risk.
Before it crashes out, Cassini is expected to capture more stunning photographs and a rich pool of data about Saturn.
Magnetic field instrument principal investigator, Prof Michele Dougherty, told the BBC: “One of the big outstanding questions at Saturn, for example, is: we don’t know how long a day is. We have a large error. It’s 10.7 hours plus or minus 0.2 hours.
“Come and ask me afterwards but I think what we learn about the internal structure of the planet could be among the great discoveries of mission.”