NASA's Cassini spacecraft has begun a manoeuvre to make a first-ever "dive" through the space between the planet Saturn and its rings.

The gap between the planet and its rings "is a region no spacecraft has ever explored", NASA said.

The orbiter was set to use its antenna, shaped like a disc, as a shield to deflect ring particles during the manoeuvre.

This would render the spaceship unreachable while its instruments would remain on, the agency said.

NASA would have its first opportunity to reconnect with Cassini early on Thursday, just after 3am (1pm AEST), it said.

The first dive is part of Cassini's grand finale, which NASA says is a six-month "daring" set of orbits it likened to a whole new mission, including 22 weekly dives between Saturn and its rings.

Cassini, launched in 1997, has been orbiting Saturn since 2004, providing data about the planet and its moons.

It is scheduled to make a last plunge into the planet in September, ending its mission.

Earlier this month, NASA said Cassini had captured evidence of the ingredients needed to support life on Saturn's moon Enceladus.

DPA