A probe sent to explore Jupiter, launched from space shuttle orbiter Atlantis (mission STS-34) on October 18, 1989. It is named after the Italian scientist who discovered Jupiter's four large moons. Galileo is roughly similar to the successful Voyager spacecraft in design, but in addition carries an instrument probe designed to plunge into Jupiter's thick atmosphere and report on the conditions there. The main spacecraft will go into orbit around the giant planet, and change orbit several times so that it can rendezvous with many of Jupiter's moons. Originally it was planned that Galileo would take a direct 21- year flight to Jupiter, being boosted from the shuttle by a liquid-propellant Centaur upper stage. But the use of liquid- propellant boosters was banned for safety reasons after the Challenger disaster. The replacement solid-propellant IUS (inertial upper stage) was much less powerful, which forced a slower roundabout flight path that would take Galileo 6 years to reach its target. After launch in 1989, Galileo gradually built up speed by gaining gravitational energy as it flew past first Venus (February 1990), then Earth (December 1990) and then Earth again (December 1992). These manoeuvres put it on course for a rendezvous with Jupiter in December 1995. The kind of trajectory Galileo has followed is called VEEGA (Venus-Earth-Earth gravity assist). Scheduled encounters along the route included the asteroids Gaspra (October 1991) and Ida (August 1993). Unfortunately, early in the mission Galileo's umbrella-like antenna jammed and attempts to free it failed. This led to the likelihood of there being a very much reduced photographic coverage than planned.
