Saturn is often referred to as a 'miniature-solar system' and the subject of this Cassini image - the small moon Telesto - is one reason why. In the image, Telesto is visible below and left of center.
Telesto (25 kilometers, 16 miles across) shares the orbit of Saturn's moon Tethys (1,062 kilometers, 660 miles across), leading the larger moon in its path by 60 degrees. Similarly sized Calypso (21 kilometers, 12 miles across) trails Tethys by the same amount. These positions, called Lagrange points, are dynamically stable. In being co-orbital moons of Tethys, Telesto and Calypso are like the Trojan asteroids of Jupiter, which occupy Lagrange points and orbit 60 degrees ahead and behind of Jupiter. The Saturnian moon Dione also has companion moons: Helene, which leads Dione in its orbit, and the Cassini-discovered trailing Lagrange moon, Polydeuces.
North on Saturn is to the upper left in this view. The image was taken at a Sun-Telesto-spacecraft, or phase, angle of 90 degrees. Thus, Telesto is seen here at a phase similar to that of a first-quarter Moon, where only half of the visible hemisphere is illuminated by sunlight.
The planet's night side is at upper right. The rings stretch across the top of the image, and are overexposed in this view.
The image was taken in visible light with the narrow angle camera on January 18, 2005, from a distance of approximately 3.7 million kilometers (2.3 million miles) from Telesto. Resolution in the image is 7 kilometers (4 miles) per pixel. Telesto has been brightened by a factor of two to aid visibility.
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 Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. 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.