The Galileo spacecraft was designed to study Jupiter's atmosphere, satellites, and surrounding magnetosphere for two years. It was carried into space by the shuttle Atlantis on October 18, 1989. Galileo spent five years traveling to Jupiter, where it will become the first spacecraft to make direct measurements from an instrumented probe within Jupiter's atmosphere. It will also become the first spacecraft to conduct long-term observations of Jupiter, its magnetosphere, and satellites from orbit around Jupiter. But Galileo has already earned a "first" -- the first spacecraft to encounter an asteroid and to photograph an asteroid's moon.
The Galileo orbiter, weighing 2-1/2 tons, was designed and developed by the Jet Propulsion Laboratory, which manages the mission for NASA. The 340-kilogram (746-pound) atmospheric probe was developed by NASA's Ames Research Center. Hughes Aircraft Company acted as the prime contractor. The German government is a partner in the mission through its provisions of the spacecraft propulsion subsystem and two science experiments. The spacecraft carries 10 scientific instruments, six of which are located on the probe. The spacecraft's radio link to Earth and the probe-to-orbiter radio link are also used to conduct scientific investigations.