Saturn's moon Prometheus, Cassini image. This small moon of Saturn is 86 kilometres across. This view looks towards the anti-Saturn side and was obtained in visible light. The image was acquired at a distance of approximately 37,000 kilometres. Prometheus orbits Saturn just inside the narrow F ring, which is seen at top. The Cassini spacecraft has been surveying the Saturnian system since 2004, with its mission scheduled to end in September 2017. Image data obtained on 6 December 2015, by the narrow-angle camera of Cassini's Imaging Science Subsystem (ISS).