page_title: Galileo (spacecraft)
section_title: Mission overview
hierarchical_section_title: Galileo (spacecraft) / Mission overview
caption_attribution_description: English: The Galileo spacecraft Europa Mission and Prime Mission Orbital Map.
context_page_description: Galileo was an American uncrewed spacecraft that studied the planet Jupiter and its moons, as well as several other Solar System bodies. Named after the Italian astronomer Galileo Galilei, it consisted of an orbiter and an entry probe. It was delivered into Earth orbit on October 18, 1989 by Space Shuttle Atlantis. Galileo arrived at Jupiter on December 7, 1995, after gravitational assist flybys of Venus and Earth, and became the first spacecraft to orbit Jupiter. It launched the first probe into Jupiter, directly measuring its atmosphere. Despite suffering major antenna problems, Galileo achieved the first asteroid flyby, of 951 Gaspra, and discovered the first asteroid moon, Dactyl, around 243 Ida. In 1994, Galileo observed Comet Shoemaker–Levy 9's collision with Jupiter.
  Jupiter's atmospheric composition and ammonia clouds were recorded, the clouds possibly created by outflows from the lower depths of the atmosphere. Io's volcanism and plasma interactions with Jupiter's atmosphere were also recorded.
context_section_description: Work on the spacecraft began at Jet Propulsion Laboratory in 1977, while the Voyager 1 and 2 missions were still being prepared for launch. Early plans called for a launch on Space Shuttle Columbia on what was then codenamed STS-23 in January 1982, but delays in the development of the Space Shuttle allowed more time for development of the probe. As the shuttle program got underway, Galileo was scheduled for launch in 1984, but this later slipped to 1985 and then to 1986. The mission was initially called the Jupiter Orbiter Probe; it was christened Galileo in 1978.
  Once the spacecraft was complete, its launch was scheduled for STS-61-G on-board  Atlantis on May 20 1986. The Inertial Upper Stage booster was going to be used at first, but this changed to the Centaur booster, then back to IUS after Challenger.
  The Centaur-G liquid hydrogen-fueled booster stage allowed a direct trajectory to Jupiter. The mission was further delayed by the hiatus in launches that occurred after the Space Shuttle Challenger disaster. New safety protocols introduced as a result of the disaster prohibited the use of the Centaur-G stage on the Shuttle, forcing Galileo to use a lower-powered Inertial Upper Stage solid-fuel booster. The mission was re-profiled in 1987 to use several gravitational slingshots, referred to as the Venus-Earth-Earth Gravity Assist or VEEGA maneuvers, to provide the additional velocity required to reach its destination. It was finally launched on October 18, 1989, by Space Shuttle Atlantis on the STS-34 mission.
  Galileo flew by Venus at 05:58:48 UTC on February 10, 1990, at a range of 16,106 km (10,008 mi). Having gained 8,030 km/h (4,990 mph) in speed, the spacecraft flew by Earth twice, the first time at a range of 960 km (600 mi) at 20:34:34 UTC on December 8, 1990, before approaching the S-type asteroid 951 Gaspra to a distance of 1,604 km (997 mi) at 22:37 UTC on October 29, 1991. Galileo then performed a second flyby of Earth at 303.1 km (188.3 mi) at 15:09:25 UTC on December 8, 1992, adding 13,320 km/h (8,280 mph) to its cumulative speed. Galileo performed close observations of a second asteroid, 243 Ida, at 16:51:59 UTC on August 28, 1993, at a range of 2,410 km (1,500 mi). The spacecraft discovered Ida has a moon, Dactyl, the first discovery of a natural satellite orbiting an asteroid. In 1994, Galileo was perfectly positioned to watch the fragments of Comet Shoemaker–Levy 9 crash into Jupiter, whereas terrestrial telescopes had to wait to see the impact sites as they rotated into view. After releasing its atmospheric probe on July 13, 1995, the Galileo orbiter became the first artificial satellite of Jupiter at 01:16 UTC on December 8, 1995, after it fired its main engine to enter a 198-day parking orbit.
  Galileo's prime mission was a two-year study of the Jovian system. The spacecraft traveled around Jupiter in elongated ellipses, each orbit lasting about two months. The differing distances from Jupiter afforded by these orbits allowed Galileo to sample different parts of the planet's extensive magnetosphere. The orbits were designed for close-up flybys of Jupiter's largest moons. Once the prime mission concluded, an extended mission started on December 7, 1997; the spacecraft made several flybys of Europa and Io. The closest approach was 180 km (110 mi) on October 15, 2001. The radiation environment near Io was very unhealthy for Galileo's systems, and so these flybys were saved for the extended mission when loss of the spacecraft would be more acceptable.
  Galileo's cameras were deactivated on January 17, 2002, after they had sustained irreparable radiation damage. NASA engineers were able to recover the damaged tape recorder electronics, and Galileo continued to return scientific data until it was deorbited in 2003, performing one last scientific experiment: a measurement of the moon Amalthea's mass as the spacecraft swung by it.
  On December 11, 2013, NASA reported, based on results from the Galileo mission, the detection of "clay-like minerals" (specifically, phyllosilicates), often associated with organic m
caption: Galileo's prime and extended mission orbits
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