Saturn's moon Dione, Cassini image. Titan is in the background. Dione has a diameter of 1130 kilometres and is the densest of Saturn's moons. Titan, the largest moon of Saturn, has a diameter of 5150 kilometres. The Cassini-Huygens spacecraft was launched in 1997 to investigate Saturn, its rings and its moons. This image was obtained on 10 April 2010, with Cassini's narrow-angle camera. This is the Saturn-facing hemisphere of Dione, with sunlight coming from the left.