Saturn's moon Telesto is visible below and to the left of center in this
image from the Cassini spacecraft.
Telesto (24 kilometers, or 15 miles across) shares the orbit of Saturn's
moon Tethys (1,071 kilometers, or 665 miles across), leading the larger
moon in its path by 60 degrees. Similarly sized Calypso (22 kilometers,
or 14 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 moons 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. 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 the 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 Cassini spacecraft narrow
angle camera on Jan. 18, 2005, at 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 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 team is based at
the Space Science Institute, Boulder, Colo.
For more information about the Cassini-Huygens mission, visit
http://saturn.jpl.nasa.gov and the Cassini imaging team home page,
http://ciclops.org.
