Cassini Mission: Fact Sheet

Published: Sept. 30, 1997

* The Cassini spacecraft is taking a roundabout route to Saturn. It will make two “slingshot” swings past Venus and one each past Earth and Jupiter to achieve the additional speed necessary to reach the Saturn system. When the Voyager spacecraft used a “gravity assist” from Jupiter in 1980, for example, it gained 16 miles per second of speed.

* The Cassini spacecraft is carrying a digital disk containing more than 600,000 signatures penned by people from 81 countries, as well as baby footprints and even cat and dog paw prints. The disk is riding on the spacecraft’s exterior.

* It will take more than one hour for signals to travel between Earth and the Cassini spacecraft. Saturn is about 900 million miles from the sun -- about 10 times further from the sun than Earth.

* Saturn is the second largest planet in the solar system behind Jupiter and is made up primarily of hydrogen and helium. It is about 9.5 times as wide as Earth. Saturn and its main rings would stretch from Earth to our moon.

* Saturn is the only planet in the solar system less dense than water. If there were a large enough ocean available in the universe, Saturn could float in it.

* CU-Boulder’s Ultraviolet Imaging Spectrograph, which took 10 years to develop, is about the size of a carry-on suitcase and weighs about 33 pounds.

* The Cassini mission is named in honor of 17th century French-Italian astronomer Jean Dominique Cassini, who discovered the large gap in Saturn’s main rings and also discovered several of its moons. Titan’s Huygens probe is named for Christiaan Huygens, who discovered Titan in 1655 and later confirmed the existence of Saturn’s elaborate ring system.

* The Cassini spacecraft is about the size of a 30-passenger school bus and weighs nearly six tons, more than half of which is rocket fuel. The orbiter will be powered by three radioisotope thermoelectric generators, which use heat from the natural decay of plutonium to generate current electricity. The same type of generators have been used on 23 previous space missions and are now flying on NASA’s Galileo and Ulysses spacecraft.

* Saturn has a massive cloud system, complex weather patterns and storms larger than the size of Earth. The colorful clouds of Saturn are composed of ammonia ice crystals. Winds on Saturn have been measured blowing in excess of 1,000 miles per hour.

* Communications with Cassini during the mission will be carried out through stations of NASA’s Deep Space Network in California, Spain and Australia. Data from the Huygens probe will be transmitted to an operations facility in Germany.

* Saturn actually has hundreds of bright ringlets composed of rock and ice particles. Shepherd moons found orbiting near the edges of some of the rings -- including Prometheus and Pandora, two moons each about 60 miles across that shepherd the F ring discovered by CU-Boulder’s Larry Esposito in 1979 -- have been found to gravitationally herd ring particles that otherwise would drift into space.

* Most scientists believe the surface of Titan is coated with the residue of sticky brown organic rain that may be many feet deep. The late astronomer Carl Sagan once hypothesized that Titan could conceivably spring to life if it was hit by an asteroid that generated sufficient heat to cause the organic molecules on the moon’s surface to generate primitive life.

* The European-built Huygens Probe will enter Titan’s atmosphere at about 13,000 miles per hour and will measure the pressure, temperature and properties of the atmosphere, including the chemical composition of the cloud system. A camera and radiometers also will take images of Titan’s clouds and surface during the descent.

* CU-Boulder’s Laboratory for Atmospheric and Space Physics has been involved in numerous NASA planetary missions, flying instruments on the 1971 Mariner Mission to Mars, the 1978 Voyager 2 tour of the Solar System that visited Jupiter, Saturn Uranus and Neptune, the 1979 Pioneer Venus Orbiter, the 1989 Galileo mission now at Jupiter and the Cassini mission. LASP scientists also are among the world’s leaders in garnering observation time on the Hubble Space Telescope.