Saturn's Moons At the turn of the twentieth century, 9 satellites of Saturn were known. In 1966, Dolfuss spotted an inner moon. In 1979, the Pioneer 11 fly-past mission photographed an inner moon. Insufficient data was gathered to characterise the orbits of these discoveries. In 1980, while the rings were edge on and glare was at a minimum, a methodical moon search was made. New detectors fitted to terrestrial telescopes revealed five additional satellites. Six months later, the first of the Voyagers arrived, enabling observation from a close vantage point. During their flybys, Voyager 1 and 2 discovered a further three moons, bringing the number of known satellites to 18. Saturn's Inner Moons - Cassini Movie On the right is the full list of Saturnian moons known prior to the launch of Cassini-Huygens. The moon count continues to rise as more asteroid-sized chunks of rock and ice are detected orbiting the planet. Further discoveries are expected. Cassini Site: Moon Update   Moon Discovery Orbit Radius Orbit Period Moon Size 1 Pan PAN 1980 Voyager 138,000 km 13.8 hrs 25 km irregular 2 Atlas AT-lus 1980 Voyager 138,000 km 14.5 hrs 32 km irregular 3 Prometheus pra-MEE-thee-us 1980 Voyager 139,000 km 14.7 hrs 102 km irregular 4 Pandora pan-DOOR-uh 1980 Voyager 142,000 km 15.1 hrs 84 km irregular 5 Janus JAY-nus 1980 Voyager 151,400 km 16.66 hrs 181 km irregular 6 Epimetheus ep-eh-MEE-thee-us 1979 Pioneer 151,500 km 16.68 hrs 116 km irregular 7 Mimas MY-mass 1789 Herschel 186,000 km 22.6 hrs 398 km diameter 8 Enceladus en-SELL-ah-dus 1789 Herschel 238,000 km 32.8 hrs 505 km diameter 9 Tethys TEE-thiss 1684 Cassini 295,000 km 45.3 hrs 1,071 km diameter 10 Telesto tah-LESS-toh 1980 Voyager 295,000 km 45.3 hrs 24 km irregular 11 Calypso kah-LIP-soh 1980 Voyager 295,000 km 45.3 hrs 22 km irregular 12 Dione dy-OH-nee 1684 Cassini 377,000 km 2.7 days 1,118 km diameter 13 Helene hel-EE-nee 1980 Voyager 377,000 km 2.7 days 33 km irregular 14 Rhea REE-ah 1672 Cassini 527,000 km 4.5 days 1,530 km diameter 15 Titan TITE-n 1655 Huygens 1,222,000 km 15.9 days 5,150 km diameter 16 Hyperion hi-PEER-ee-en 1848 Bond 1,481,000 km 21.3 days 266 km irregular 17 Iapetus eye-AP-eh-tuss 1671 Cassini 3,561,000 km 79.3 days 1460 km diameter 18 Phoebe FEE-bee 1898 Pickering 12,954,000 km 550 days 220 km diameter Data Sources: Fred Whipple, Orbiting the Sun, Harvard University Press, 1981 Lang and Whitney, Wanderers in Space, Cambridge University Press, 1991 Audose and Israel, The Cambridge Atlas of Astronomy 3rd Edition, Cambridge University Press, 1994 NASA JPL Cassini Site NASA Planetary Photojournal NASA Solar System Exploration: Saturn Moons