Saturn's moon Calypso, Cassini image. Calypso, which measures 22 kilometres across, circles in the same orbit as the moon Tethys, but 60 degrees behind it. The Cassini-Huygens spacecraft was launched in 1997 to investigate Saturn, its rings and its moons. This image was taken by Cassini's narrow-angle camera on the 23rd September 2005 at a distance of 101,000 kilometres from Calypso.