September 17, 2004
The Cassini spacecraft has sighted the tiny moon Atlas, which is seen here for the first time since Voyager 1 flew past Saturn in 1980.
Cassini's narrow angle camera captured a sequence of 112 images in visible light, which were used to create this movie of Atlas and other moons racing around the outer edge of Saturn's rings. Over the course of almost five and one-quarter hours, Cassini watched the moons as they circled the planet, snapping 1.2-second exposures about 12 minutes apart. These images were part of a sequence designed specifically to search for small moons near Saturn's F ring. Contrast was enhanced in the images, and the rings themselves were overexposed intentionally, to make these small moons visible.
A group of three moons can be seen rounding the right loop of Saturn's rings, followed by a fourth moon. In the first group, the moon exterior to Saturn's thin, knotted F ring is Epimetheus (116 kilometers, 72 miles across); the two moons interior to the F ring are Prometheus (102 kilometers, 63 miles across) and tiny unresolved Atlas (32 kilometers, 20 miles across). The fourth moon seen here, exterior to the F ring and tagging along behind the others, is Pandora (84 kilometers, 52 miles across).
At the same time, on the left side, we see Janus (181 kilometers, 113 miles across). Janus continues in its orbit and reappears on the right side of the movie, while the other quartet of moons soon emerges on the left side. A faint 11th magnitude star remains at a constant distance from the right loop of the rings.
The view is taken looking upward from Cassini's southern vantage point beneath the ring plane. The moons visible here are orbiting Saturn in a plane that is tilted 67 degrees away from the viewer.
These images were taken on May 26 and 27, 2004, from a distance of approximately 19.2 million kilometers (11.9 million miles) from Saturn. The image scale is approximately 114 kilometers (71 miles) per pixel.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras, were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.