Posted: Tue, May 22, 2001, 3:18 PM ET (1918 GMT)
NASA is preparing for the Galileo spacecraft's final and closest flyby of Jupiter's moon Callisto on Friday. Galileo will pass just 123 km from the surface of Callisto at 7:24 am EDT (1124 GMT) May 25. The close flyby of the moon is primarily designed to put the spacecraft on course for a series of flybys of Io, the innermost of Jupiter's large Galilean moons, later this year. However, cameras and other instruments on the spacecraft will examine the moon, the outermost Galilean satellite, in detail during the flyby. This includes taking high-resolution images of the surface to measure the density of small craters which may give planetary scientists clues to the history of the moon's bombardment by asteroids and comets over the last four billion years. The flyby will be the 31st close pass to a Galilean moon since the spacecraft arrived at Jupiter in December 1995, and the eighth of Callisto. NASA plans three more flybys of Io and one of the smaller inner moon Amalthea before the mission ends in 2003.

Related Links:

•  NASA press release
•  Galileo web site