Saturn's moon Rhea passes in front of Dione, as seen from Cassini.
These images are part of a "mutual event" sequence in which one moon passes close to or in front of another. These observations help scientists refine their understanding of the orbits of Saturn's moons. Rhea (1528 kilometers, 949 miles across) is about 2.1 million kilometers (1.3 million miles) from Cassini in this image. Dione (1123 kilometers, 698 miles across) is about 2.6 million kilometers (1.6 million miles) from Cassini.
The images were taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 22, 2009. Scales in the original images were 13 kilometers (8 miles) per pixel on Rhea and 16 kilometers (10 miles) per pixel on Dione. The images were contrast enhanced and magnified by a factor of two to enhance the visibility of surface features.
The Cassini Equinox Mission is a joint United States and European endeavor. 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 was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.