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Cassini Spacecraft

Cassini in the testing chamber. The large gold disk on the front of the craft is the Huygens probe. Photo credit: NASA/JPL.
...is the first spacecraft ever to orbit Saturn thanks to a complex maneuver that allowed it to slip through the giant planet's rings and become captured by the planet's gravity. Cassini, the largest interplanetary spacecraft ever launched by NASA, also successfully launched the European Space Agency's Huygens probe, which dropped through the atmosphere of Saturn's biggest moon, Titan, returning photos of a surface that until now had been hidden for all human history.

Specs
Launch date: October 15, 1997
Launch vehicle: Titan IVB/Centaur
Saturn arrival date: July 1, 2004
Launch mass: 5,574 kilograms (6.1 tons), includes 2,442 kilograms (5,384 pounds) spacecraft and 3,132 kilograms
(6,905 pounds) fuel
Total flight path: 5 billion kilometers (3 billion, 200 million miles)
Maximum speed: 15.5 kilometers per second (34,680 miles per hour) after Earth gravitational boost
Power: 700 watts of electrical power comes from three radioisotope thermoelectric generators
Communications: three antennas, operating at microwave frequency. The large white dish on Cassini is the 2-way high-gain antenna.

History
A map of Cassini's trip through the solar system. Click above for a larger version of the image in PDF format. Courtesy of NASA/JPL.
Cassini's history is still being written. Launched in October 1997, Cassini picked up speed by using the gravity of other planets, swinging by Venus twice, then Earth, then Jupiter. Cassini needed the gravitational assists to make it far out into the solar system. Now Cassini is well into its four year mission at Saturn, since its arrival in July 2004.

Cassini is actually made up of two parts: the Cassini orbiter and the Huygens probe. The orbiter is the main part of the craft, and it carries 12 scientific experiments along with the Huygens probe which had been attached to its side prior to being jettisoned into the atmosphere of Saturn’s largest moon, Titan. On the way to Saturn, Cassini searched for gravitational waves throughout the solar system and photographed any planets and moons that it passed. Now that Cassini has arrived at Saturn it is busy with many measurements including:

  • Examining the gravitational field of Saturn, its rings and moons using radio waves
  • Taking photos in visible, near-ultraviolet (UV) and near-infrared (IR) light
  • Mapping the surface of Titan using radar
  • Studying particles around Saturn and its moons to learn about their atmospheres and ionospheres
  • Determining the structure and chemical composition of surfaces and atmospheres of Saturn, its moons and rings
  • Recording temperatures from the rings, atmospheres and surfaces of Saturn and its moons
  • Studying ice and dust grains in the Saturn system
  • Investigating plasma waves and how they interact with Saturn's magnetic field
  • Discovering how the solar wind interacts with Saturn's magnetosphere
  • Studying Saturn's magnetic field and how it interacts with Saturn's rings, moons and solar wind
  • Measuring ultraviolet energy from atmospheres, surfaces and rings
The Huygens probe at JPL before launch. Photo courtesy of NASA/JPL.

The Huygens probe, contributed by the European Space Agency, carries eight more experiments. The probe was released from the main Cassini spacecraft on December 24, 2004, and reached Titan on January 14, 2005 where it dropped through the thick atmosphere to land on the surface. The Huygens experiments allowed the probe to:

  • Take pictures of Titan's atmosphere and surface
  • Measure particle temperatures
  • Examine the physical properties, chemical composition and structure of Titan's atmosphere
  • Study clouds, winds and particles in Titan's atmosphere
  • Explore the physical properties of the surface of Titan

An artist's conception of Cassini releasing the Huygens Probe. Image courtesy of NASA/JPL.
During the missions of Cassini and Huygens, Cassini communicates with Earth using three microwave antennas. The large white dish on top of Cassini is the high-gain antenna—it can send and receive data a lot faster than the other antennas on board. The dish also doubled as a shield to protect Cassini from the heat when the spacecraft was close to the sun during the period shortly after its launch. As Cassini got closer to Saturn, cold temperatures became a much bigger problem, so Cassini carries heaters and is wrapped in an insulating blanket. Cassini runs on about 700 watts of electrical power, produced by radioisotope thermoelectric generators (RTGs). The generators are powered by the heat given off by a small amount of plutonium as it naturally decays. RTGs were chosen to power the instruments on board because they will last for at least 11 years, giving Cassini plenty of time to reach Saturn and complete its mission.

The Science Center's Cassini Spacecraft
The Cassini spacecraft and Huygens probe on display at the Science Center are full-scale engineering models, on loan to us from NASA Jet Propulsion Laboratory. Cassini is displayed with insulating blankets on the outside, and some of the blankets are pulled back to show the craft underneath.

Cassini-Huygens Links
Cassini-Huygens: Mission to Saturn and Titan
This comprehensive collection of sites from NASA's Jet Propulsion Laboratory (JPL) is the Internet authority on the Cassini mission. On the Cassini-Huygens site, you can find the latest news and photos from Cassini, detailed information on the craft's construction and function, and facts about Saturn and its moons. The main page also features links to sites detailing Cassini's flyby around Jupiter.

Kids Space
JPL created this Cassini site just for kids. The site includes instructions and printouts for building two different models of the Cassini spacecraft, as well as a cool interactive map that tells where you can find Saturn in the night sky—looking from your neighborhood!

European Space Agency
Learn more about the science behind the Huygens probe at the European Space Agency's official site.

Basics of Space Flight
Dive into this comprehensive collection of information about the science behind space flight, including quizzes, simulations and more.

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