Online Astronomy eText: Satellites (Moons)
The Satellites (Moons) of Saturn: Janus Link for sharing this page on Facebook
(mostly written in 2004, before the Cassini spacecraft reached Saturn)

Left, Janus as viewed by Voyager 2 in 1981
Right, Janus (in front of Saturn) as viewed by the Cassini spacecraft in 2006

Data for Janus

Discovered by Audouin Dollfus in 1966
Named after god of doorways, beginnings, and rising and setting of the Sun
Orbital size 151,472 km (about 94,000 miles) (co-orbital with Epimetheus)
Orbital eccentricity 1%
Orbital inclination 0.1 degrees
Orbital period 16.6 hours
Diameter 195 x 190 x 155 km (about 120 x 118 x 96 miles)
Mass, density and surface gravity very uncertain
Albedo (reflectivity) 80%