A quartet of Saturn's moons is seen here with the planet's F and A rings, but something special is happening to the moon in the middle of this Cassini image.
As Saturn approaches its August 2009 equinox, the planet's moons have been casting shadows onto the rings (see PIA11651). Now the rings take a turn casting a shadow on a moon. Tethys is just to the left of the center of the image, and the northern part of the moon is darkened by a shadow cast by Saturn's A ring.
From left to right, the moons shown are Mimas (396 kilometers, 246 miles across), Tethys (1062 kilometers, 660 miles across), Rhea (1528 kilometers, 949 miles across), and Pandora (81 kilometers, 50 miles across). Pandora is a tiny speck inside the rings.
This view looks toward the unilluminated side of the rings from about 1 degrees above the ringplane. The rings and Pandora have been brightened relative to the other moons to enhance visibility. The image was taken in green light with the Cassini spacecraft wide-angle camera on April 11, 2009. The view was acquired at a distance of approximately 1.4 million kilometers (870,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 21 degrees. Image scale on Tethys is about 82 kilometers pixels per pixel.
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.