The Galileo spacecraft, which arrived at Jupiter on December 7, 1995, is conducting one of the most historic planetary exploration missions ever performed. The spacecraft consisted of two main components: an atmospheric entry probe and a planetary orbiter. The Probe plunged into the atmosphere of Jupiter on December 7, accomplishing the first direct sampling of the atmosphere of one of the outer giant planets and surviving the most difficult atmospheric entry ever attempted. On the same date the Orbiter was the first ever to be placed in orbit about Jupiter, and will return data about the Jovian system for a total of almost 2 years. Before reaching Jupiter, the spacecraft took the first closeup pictures of asteroids, discovering that one of them had a small satellite (about 1 mi or 1.6 km in diameter), and was the only platform that had a direct view of the impact of the comet Shoemaker-Levy 9 with Jupiter in July 1994.