The spacecraft Galileo made a close encounter Thursday with the largest of Jupiter's moons, Ganymede, marking the beginning of a grand tour of the giant planet.
Galileo made its first flyby of Ganymede, coming within 524 miles of the planet-sized hunk of ice and rock, at 2.29 a.m. EDT. Confirmation of the flyby was received at the Jet Propulsion Laboratory (JPL) from the spacecraft at 3.04 a.m. EDT Thursday.Pictures of Ganymede, which is bigger than the planet Mercury and three-quarters the size of Mars, are expected to be received back on Earth in a steady flow over the next few days, JPL spokesman Frank O'Donnell said Thursday.
Pictures of the Jovian moon will be released by JPL, which is run by NASA, on July 10.
To celebrate the flyby - the first of many over the course of the next two years - the Galileo team of scientists and their friends and families were treated to a party at JPL. Cheers went up from the 250 partygoers as confirmation of the flyby was received.
"It was an exciting moment for everyone. Some of these people have dedicated most of their careers to this project," O'Donnell said. Galileo was conceived in the early 1970s and given the go-ahead by Congress in 1977.
With a diameter of 3,269 miles, Ganymede is the largest moon in the universe and has many Earthlike geological features, such as craters, large valleys and mountains. Galileo's instruments started taking continuous measurements of the moon Sunday as the spacecraft approached Ganymede.
A probe from the two-and-a-half-ton spacecraft successfully entered the Jovian atmosphere Dec. 7 and transmitted data for about 45 minutes before burning up as planned in the planet's gaseous environment.