Against a Hail of Stars
August 8, 2008
Tethys appears here, against a background of star trails, in a view acquired as the icy moon exited Saturn's shadow. Tethys is illuminated in this view by two main sources: reflected "ringshine" and refracted sunlight passing through the edge of Saturn's atmosphere.
An observer viewing Saturn from the moon's surface would see the planet's southern hemisphere aglow with dimly reflected sunlight bouncing off the rings, called ringshine. They would also witness the beginning of an orbital sunrise.
The Cassini spacecraft shared a similar perspective when it acquired the images for In Saturn's Shadow (the principal difference being that Tethys is nearly in the ringplane and Cassini was 15 degrees above the ringplane when it acquired the images for the color mosaic.)
A long exposure time was required in order to image Tethys while it was in shadow, resulting in the stars' normally point-like images being smeared into streaks.
The view looks toward the northern hemisphere of Tethys (1,062 kilometers, or 660 miles across) from 36 degrees above the moon's equator. The image was taken in visible light with the Cassini spacecraft wide-angle camera on June 30, 2008. The view was acquired at a distance of approximately 263,000 kilometers (163,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 52 degrees. Image scale is 16 kilometers (10 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 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