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RPS: Radioisotope Power Systems
Cassini-Huygens
Artist's rendering of Cassini arriving at Saturn
Artist's rendering of Cassini arriving at Saturn

Cassini: Mission to the Saturn system

  • Launched on October 15, 1997
  • First spacecraft to orbit Saturn
  • RTGs still operating
  • Currently exploring Saturn, its rings and moons
  • Carried the battery-powered Huygens probe
  • Both Cassini and Huygens probe enabled by radioisotope heater units

Powered by: three GPHS-RTGs, with heat from 117 RHUs

The Cassini orbiter includes 82 strategically placed radioisotope heater units, while Huygens carried 35 of the units. Each RHU produces about 1 watt of thermal power.

Goals: An international endeavor involving 17 nations, Cassini was designed to explore the Saturn system from orbit: the planet and its atmosphere, rings and magnetosphere, and its moons, particularly the large smog-enshrouded moon Titan and the other icy satellites. Cassini carried Europe's Huygens probe to its rendezvous with Titan. Although Huygens used battery power on its descent to Titan, the Cassini RTGs provided power to the probe en route to the Saturn system.

Accomplishments: After successfully completing the first in-depth, up-close study of Saturn and its realm from orbit, Cassini is on an extended mission to follow up on the many discoveries made during its primary 4-year mission. Among the most surprising discoveries were geysers erupting on Enceladus and the dynamic effects of it and other moons on Saturn's rings.

The Huygens probe successfully parachuted to a landing on surface of Titan, achieving the first-ever landing in the outer solar system on January 14, 2005. Cassini's observations of Titan have given scientists a glimpse of what our home planet might have been like before life evolved on Earth.

More about Cassini >

Cassini RTG Safety >

Images from Cassini >

More about the Huygens probe >

Images from Huygens >
Cassini image of Saturn's moon Titan, the rings and a ring moon
Cassini image of Saturn's moon Titan, the rings and a ring moon


Cassini image showing plumes of icy material erupting from Enceladus
Plumes of icy material erupting from Enceladus
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Last Updated: 13 Jul 2013