Dione steps in front of Tethys for a few minutes in an occultation, or mutual event. These events occur frequently for the Cassini spacecraft when it is orbiting close to the ringplane.
The image was taken in visible red light with the Cassini spacecraft narrow-angle camera on Feb. 10, 2006, at a distance of approximately 3.7 million kilometers (2.3 million miles) from Dione and 4 million kilometers (2.5 million miles) from Tethys. Resolution in the original image was 22 kilometers (14 miles) per pixel on Dione (1,126 kilometers, or 700 miles across) and 24 kilometers (15 miles) per pixel on Tethys (1,071 kilometers, or 665 miles across). The image has been magnified by a factor of two.
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