Galileo was launched from the shuttle Atlantis (OV-104) in October, 1989. It was launched using a small booster rocket with insufficient power to reach Jupiter, requiring the astronauts to "borrow" energy to send it to its destination.
Journey to Jupiter
Due to the lack of sufficient fuel to reach Jupiter, Galileo was given a flight plan nicknamed "VEEGA" for "Venus-Earth-Earth Gravity Assist.", where it would slingshot once around Venus and twice around Earth in order to reach Jupiter.
Arrival at Jupiter and probe launch
In July, 1995 the Galileo spacecraft launched a probe to begin a solo flight into Jupiter.
Five months later, the probe sliced into Jupiter's atmosphere at one-hundred-six-thousand miles per hour. It slowed, released its parachute, and dropped its heat shield. As the probe descended through ninety-five miles of the top layers of the atmosphere, it collected fifty-eight minutes of data on the local weather. The data were sent to the spacecraft overhead, then transmitted back to Earth.
To get into orbit around Jupiter, Galileo used it's main engine in a precise maneuver.
On December 7, 1995 Galileo began its prime mission: a two-year study of the Jovian system.
Galileo traveled around Jupiter in elongated ovals --- each orbit lasting about two months. By traveling at different distances from Jupiter, Galileo sampled different parts of the planet's extensive magnetosphere. The orbits were designed for close-up flybys of Jupiter's largest moons.
To keep track of Galileo's journey, each orbit was numbered, and named for the moon that the spacecraft encountered at closest range. During orbit "C-3" for example --- the third orbit around Jupiter --- Galileo flew near the moon Callisto.
The data collected on Jupiter and the moons are stored on the on-board tape recorder. During the rest of the orbit, the data was sent to Earth using the low-gain antenna. At the same time, measurements are made of Jupiter's magnetosphere and transmitted back to Earth.
The intriguing data gathered during the eleven orbits of the prime mission left many questions to be answered. Since Galileo obviously was capable of much more, its mission was extended.
Galileo's prime mission ended on December 7, 1997. With more to learn, and the spacecraft in good health, NASA approved a two-year study called "GEM"—the Galileo Europa Mission. For fourteen more orbits, the spacecraft focused on ice, water, and fire: the icy moon Europa, which might have an ocean; Jupiter's thunderstorms; and the fiery volcanoes of Io.
The spacecraft came so close to Europa that if there were something there the size of a school bus, Galileo would have detected it. The additional observations of Europa supported the theory that an ocean of water currently exists below the surface. NASA began considering plans for future missions to orbit Europa, and perhaps to send a lander.
Approaching Io - Jupiter's innermost moon - meant surviving Jupiter's intense radiation, so these encounters were saved until last. When radiation upset the spacecraft's computer, engineers worked all night to get them back on line. But Galileo came through again, and even discovered a lava fountain erupting on Io.
These successful flybys led to another exciting mission - the Galileo Millennium Mission, extending into 2001. The data was collected on Io and Europa, and studies made of the effects of radiation on a spacecraft close in to Jupiter. The Cassini spacecraft, on its way to Saturn, swings by Jupiter in late 2000 and for a few weeks, both spacecraft observe the giant of our Solar System.
End of mission
The Galileo spacecraft's 14-year odyssey came to an end on Sunday, Sept. 21, when the spacecraft passed into Jupiter's shadow then disintegrated in the planet's dense atmosphere at 11:57 a.m. Pacific Daylight Time. The Deep Space Network tracking station in Goldstone, Calif., received the last signal at 12:43:14 PDT. The delay is due to the time it takes for the signal to travel to Earth.