Epimetheus

Epimetheus is an inner satellite of Saturn. It is also known as Saturn XI. It is named after the mythological Epimetheus, brother of Prometheus. Discovery Epimetheus occupies essentially the same orbit as the moon Janus. Astronomers assumed that there was only one body in that orbit (disbelieving that two moons could share nearly identical orbits without colliding), and accordingly had difficulty determining their orbital characteristics. Observations were photographic and spaced widely apart in time, so that while the presence of two objects was not obvious, the observations were difficult to reconcile with a reasonable orbit. Audouin Dollfus observed a moon on 15 December 1966, which he proposed to be named "Janus". On 18 December, Richard Walker made a similar observation which is now credited as the discovery of Epimetheus. However, at the time, it was believed that there was only one moon, unofficially known as "Janus", in the given orbit.