Saturn's moons Janus and Epimetheus are captured swinging around Saturn's rings and past Dione in this movie sequence from the Cassini spacecraft.
The spacecraft repeatedly imaged the two moons just as they were about to round the outside edge of the rings, which were out of view to the left. Janus and Epimetheus orbit Saturn at nearly the same distance and velocity, although (as seen here) Janus is several tens of thousands of kilometers ahead of Epimetheus and farther from Cassini. Dione is actually quite far in the background compared to the small moons.
At the beginning of the movie, Epimetheus (116 kilometers, or 72 miles across) is at the left, Janus (181 kilometers, or 113 miles across) is at the center, and Dione (1,126 kilometers, or 700 miles across) is at the right.
The movie was created using 18 clear-filter images taken over a period of about 30 minutes. The images were acquired by the Cassini spacecraft narrow-angle camera on Dec. 30, 2005, at a mean distance of approximately 2.3 million kilometers (1.4 million miles) from Janus and 2.3 million kilometers (1.4 million miles) from Epimetheus. The image scale is approximately 14 kilometers (9 miles) per pixel on Janus and Epimetheus, and 16 kilometers (10 miles) per pixel on Dione.
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 mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
Credit: NASA/JPL/Space Science Institute