Saturn's moon Dione, Cassini image. Saturn is in the background, with shadows of its rings seen on its surface. Dione has a diameter of 1130 kilometres and is the densest of Saturn's moons. The Cassini-Huygens spacecraft was launched in 1997 to investigate Saturn, its rings and its moons. This image was taken by Cassini's wide-angle camera on the 11th October 2005 at a distance of 24,500 kilometres from Dione.