Galileo project

Galileo

Artist's concept of Galileo at Io with Jupiter in the background. The high-gain antenna is fully deployed in this illustration but in reality the antenna failed to extend.
Names	Jupiter Orbiter Probe
Mission type	Jupiter orbiter
Operator	NASA
COSPAR ID	1989-084B
SATCAT no.	20298
Website	solarsystem.nasa.gov/galileo/
Mission duration	Planned: 8 years, 1 month, 19 days Jupiter orbit: 7 years, 9 months, 13 days Final: 13 years, 11 months, 3 days
Distance travelled	4,631,778,000 km (2.88 billion mi)[1]
Spacecraft properties
Manufacturer	Jet Propulsion Laboratory[2] Messerschmitt-Bölkow-Blohm[2] General Electric[2] Hughes Aircraft Company[2]
Launch mass	Total: 2,560 kg (5,640 lb)[2] Orbiter: 2,220 kg (4,890 lb)[2] Probe: 340 kg (750 lb)[2]
Dry mass	Orbiter: 1,880 kg (4,140 lb)[2] Probe: 340 kg (750 lb)[2]
Payload mass	Orbiter: 118 kg (260 lb)[2] Probe: 30 kg (66 lb)[2]
Power	Orbiter: 570 watts[2] Probe: 730 watt-hours[2]
Start of mission
Launch date	October 18, 1989, 16:53:40 (1989-10-18UTC16:53:40) UTC[3]
Rocket	Space Shuttle Atlantis STS-34/IUS
Launch site	Kennedy LC-39B
Entered service	December 8, 1995, 01:16 UTC SCET
End of mission
Disposal	Controlled entry into Jupiter
Decay date	September 21, 2003, 18:57:18 (2003-09-21UTC18:57:19) UTC
Flyby of Venus (gravity assist)
Closest approach	February 10, 1990[4]
Distance	16,000 kilometers (9,900 mi)
Flyby of Earth (gravity assist)
Closest approach	December 8, 1990 and December 8, 1992
Distance	960 kilometers (600 mi) and 303 kilometers (188 mi)
Flyby of 951 Gaspra
Closest approach	October 29, 1991
Distance	1,601 kilometers (995 mi)
Flyby of 243 Ida
Closest approach	August 28, 1993
Distance	2,400 kilometers (1,500 mi)
Jupiter orbiter
Spacecraft component	Orbiter
Orbital insertion	December 8, 1995, 01:16 UTC SCET
Jupiter atmospheric probe
Spacecraft component	Probe
Atmospheric entry	December 7, 1995, 22:04 UTC SCET[5]
Impact site	06°05′N 04°04′W / 6.083°N 4.067°W / 6.083; -4.067 (Galileo Probe) at entry interface
Instruments SSI Solid-State Imager NIMS Near-Infrared Mapping Spectrometer UVS Ultraviolet Spectrometer PPR Photopolarimeter-Radiometer DDS Dust Detector Subsystem EPD Energetic Particles Detector HIC Heavy Ion Counter MAG Magnetometer PLS Plasma Subsystem PWS Plasma Wave Subsystem
NASA Flagship Program ← Voyager program Cassini–Huygens →

Galileo was an American robotic space program that studied the planet Jupiter and its moons, as well as several other Solar System bodies. Named after the Italian astronomer Galileo Galilei, the Galileo spacecraft consisted of an orbiter and an atmospheric entry probe. It was delivered into Earth orbit on October 18, 1989, by Space Shuttle Atlantis on the STS-34 mission, and arrived at Jupiter on December 7, 1995, after gravity assist flybys of Venus and Earth, and became the first spacecraft to orbit Jupiter. The spacecraft then launched the first probe to directly measure 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, as were the volcanism and plasma interactions on Io with Jupiter's atmosphere. The data Galileo collected supported the theory of a liquid ocean under the icy surface of Europa, and there were indications of similar liquid-saltwater layers under the surfaces of Ganymede and Callisto. Ganymede was shown to possess a magnetic field and the spacecraft found new evidence for exospheres around Europa, Ganymede, and Callisto. Galileo also discovered that Jupiter's faint ring system consists of dust from impact events on the four small inner moons. The extent and structure of Jupiter's magnetosphere was also mapped.

The primary mission concluded on December 7, 1997, but the Galileo orbiter commenced an extended mission known as the Galileo Europa Mission (GEM), which ran until December 31, 1999. By the time GEM ended, most of the spacecraft was operating well beyond its original design specifications, having absorbed three times the radiation exposure that it had been built to withstand. Many of the instruments were no longer operating at peak performance, but were still functional, so a second extension, the Galileo Millennium Mission (GMM) was authorized. On September 20, 2003, after 14 years in space and 8 years in the Jovian system, Galileo's mission was terminated by sending it into Jupiter's atmosphere at a speed of over 48 kilometers per second (30 mi/s) to eliminate the possibility of contaminating the moons with terrestrial bacteria.