Which NASA mission first orbited Saturn and studied its rings for more than a decade?

Cassini–Huygens was the first mission to orbit Saturn and study the planet’s system for more than a decade.

The mission launched in October 1997 and reached Saturn in July 2004. NASA’s Cassini orbiter examined Saturn, its rings, magnetosphere, and moons, while the European Space Agency’s Huygens lander traveled to Titan attached to Cassini.

Cassini made extensive observations of Titan, Enceladus, and Saturn’s rings. It found methane lakes and seas on Titan, and detected water-rich plumes erupting from Enceladus’s south polar region. These discoveries made both moons important targets in the search for potentially habitable environments.

Huygens landed on Titan in January 2005, but the mission’s orbiter continued operating until September 2017. Cassini ended with the Grand Finale, a series of dives between Saturn and its innermost ring before the spacecraft entered Saturn’s atmosphere.