Motion of Saturn's Satellites
This sequence of 100 sec exposures taken with HST's Wide Field and Planetary Camera (WFPC2) in planetary mode on 10 August 1995 shows three of the smaller satellites of Saturn, as well as the newly discovered object 1995S5. Epimetheus is the smaller co-orbital satellite and about 120 km in diameter, while 88 km diameter Pandora is the outer shepherd satellite of the narrow F Ring. 1995S5 appears as a faint smudge in the plane of the rings. The outward orbital motions of Pandora and 1995S5 are apparent, as are the displacements of Epimetheus and Mimas to the north and south of the ring plane, due to the slight inclinations of their orbits relative to Saturn's equator. The brightness of 1995S5 is consistent with an object of diameter 50 km or less.
These images were obtained approximately one hour before the Earth crossed Saturn's ring plane and an 8922 A methane band filter was used to reduce the scattered light from the planet. An average of several earlier frames was subtracted from each image to remove the edge-on rings, and so reveal the fainter satellites. Some residual artifacts of this subtraction process are visible. Structure on the planet is due to cloud features which changed position as the planet rotated. Unlabelled bright spots and streaks are due to cosmic ray hits on the detector.