"We survived the plane of the ring crossing between the F and G rings," the US space mission control said in a statement late on Wednesday. Saturn's huge rings are composed of dust particles
The Cassini probe is set to become the first spacecraft to orbit Saturn and its 31 icy moons.
The truck-sized probe has spent the past seven years travelling 3.5 billion kilometres on a mission to study the sixth planet from the Sun.
Cassini and its piggy-backed lander, Huygens, will make the closest approach to Saturn of its 11-year mission at about 0100 GMT on Thursday.
It is then scheduled to begin a crucial manoeuvre scientists call a Saturn orbit insertion.
Scientists will first turn the probe's dish-shaped antenna to face forward in a "protective attitude" designed to shield it from impact from the mostly dust-sized particles that make up Saturn's rings.
Cassini flies closest to Saturn during the first of its 76 planned orbits. It will come within 80,230km of the planet's centre and about a quarter of that distance from its cloud tops.
Described as the world's most scientifically capable space probe, it will spend four years studying Saturn, its rings and its known moons.
Nasa, the European Space Agency, the Agenzia Spaziale Italiana and scientists from 17 European nations began building Cassini-Huygens in 1995, although planning began in the 1980s.
Huygens, named after the 17th century Dutch scientist who discovered Saturn's rings, sets off for Titan on Christmas Eve to observe the moon's methane-rich atmosphere and search for complex organic molecules on its surface.
Cassini is expected to send back the first data and images from its close encounter with Saturn on Thursday morning.