Galileo (spacecraft)
Galileo was an American robotic space probe that studied the planet Jupiter and its moons, as well as the asteroids Gaspra and Ida. 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, during STS-34. Galileo arrived at Jupiter on December 7, 1995, after gravitational assist flybys of Venus and Earth, and became the first spacecraft to orbit an outer planet.[4]
This article is about the Jupiter probe. For the navigation satellite system, see Galileo (satellite navigation). For the Star Trek shuttle, see Galileo (Star Trek).Names
Jupiter Orbiter Probe
Jupiter orbiter
20298
- Planned: 8 years, 1 month, 19 days
- Jupiter orbit: 7 years, 9 months, 13 days
- Final: 13 years, 11 months, 3 days
4,631,778,000 km (2.88 billion mi)[1]
October 18, 1989, 16:53:40 UTC
December 8, 1995, 01:16 UTC SCET
Controlled entry into Jupiter
September 21, 2003, 18:57:18 UTC
Solid-State Imager
Solid-State Imager
Near-Infrared Mapping Spectrometer
Ultraviolet Spectrometer
Photopolarimeter-Radiometer
Dust Detector Subsystem
Energetic Particles Detector
Heavy Ion Counter
Magnetometer
Plasma Subsystem
Plasma Wave Subsystem
The Jet Propulsion Laboratory built the Galileo spacecraft and managed the Galileo program for NASA. West Germany's Messerschmitt-Bölkow-Blohm supplied the propulsion module. NASA's Ames Research Center managed the atmospheric probe, which was built by Hughes Aircraft Company. At launch, the orbiter and probe together had a mass of 2,562 kg (5,648 lb) and stood 6.15 m (20.2 ft) tall.
Spacecraft are normally stabilized either by spinning around a fixed axis or by maintaining a fixed orientation with reference to the Sun and a star. Galileo did both. One section of the spacecraft rotated at 3 revolutions per minute, keeping Galileo stable and holding six instruments that gathered data from many different directions, including the fields and particles instruments.
Galileo was intentionally destroyed in Jupiter's atmosphere on September 21, 2003. The next orbiter to be sent to Jupiter was Juno, which arrived on July 5, 2016.
Electrical power[edit]
At the time, solar panels were not practical at Jupiter's distance from the Sun; the spacecraft would have needed a minimum of 65 square meters (700 sq ft) of panels. Chemical batteries would likewise be prohibitively large due to technological limitations. The solution was two radioisotope thermoelectric generators (RTGs) which powered the spacecraft through the radioactive decay of plutonium-238. The heat emitted by this decay was converted into electricity through the solid-state Seebeck effect. This provided a reliable and long-lasting source of electricity unaffected by the cold environment and high-radiation fields in the Jovian system.[27][32]
Each GPHS-RTG, mounted on a 5-meter long (16 ft) boom, carried 7.8 kilograms (17 lb) of 238Pu. Each RTG contained 18 separate heat source modules, and each module encased four pellets of plutonium(IV) oxide, a ceramic material resistant to fracturing.[32] The plutonium was enriched to about 83.5 percent plutonium-238.[33] The modules were designed to survive a range of potential accidents: launch vehicle explosion or fire, re-entry into the atmosphere followed by land or water impact, and post-impact situations. An outer covering of graphite provided protection against the structural, thermal, and eroding environments of a potential re-entry into Earth's atmosphere. Additional graphite components provided impact protection, while iridium cladding of the RTGs provided post-impact containment.[32] The RTGs produced about 570 watts at launch. The power output initially decreased at the rate of 0.6 watts per month and was 493 watts when Galileo arrived at Jupiter.[3]
Mission type
1989-084E
20298
61.4 minutes
340 kg (750 lb)
October 18, 1989
STS-34 piggybacking with Galileo orbiter
Kennedy Space Center, Launch Complex 39B
Termination[edit]
Lacking the fuel to escape Jupiter's gravity well, at the end of Galileo's life, the probe was deliberately crashed into Jupiter on September 21, 2003, to prevent forward contamination of possible life of Jupiter's moon Europa.[68]