Galileo project
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.
This article is about the Jupiter probe project. For the spacecraft itself, see Galileo (spacecraft). For the navigation satellites, see Galileo (satellite navigation). For the project to study UFOs, see The Galileo Project. For astronomy education resource, see Project Galileo.Names
Jupiter Orbiter Probe
Jupiter orbiter
1989-084B
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]
December 8, 1995, 01:16 UTC SCET
Controlled entry into Jupiter
September 21, 2003, 18:57:18 UTC
February 10, 1990[4]
16,000 kilometers (9,900 mi)
December 8, 1990 and December 8, 1992
960 kilometers (600 mi) and 303 kilometers (188 mi)
October 29, 1991
1,601 kilometers (995 mi)
August 28, 1993
2,400 kilometers (1,500 mi)
Orbiter
December 8, 1995, 01:16 UTC SCET
December 7, 1995, 22:04 UTC SCET[5]
06°05′N 04°04′W / 6.083°N 4.067°W
at entry interface
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
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.
Jupiter is the largest planet in the Solar System, with more than twice the mass of all the other planets combined.[6] Consideration of sending a probe to Jupiter began as early as 1959, when the National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL) developed four mission concepts:
Two missions to Jupiter, Pioneer 10 and Pioneer 11, were approved in 1969, with NASA's Ames Research Center given responsibility for planning the missions.[8] Pioneer 10 was launched in March 1972 and passed within 200,000 kilometers (120,000 mi) of Jupiter in December 1973. It was followed by Pioneer 11, which was launched in April 1973, and passed within 34,000 kilometers (21,000 mi) of Jupiter in December 1974, before heading on to an encounter with Saturn.[9] They were followed by the more advanced Voyager 1 and Voyager 2 spacecraft, which were launched on 5 September and 20 August 1977 respectively, and reached Jupiter in March and July 1979.[10][a]
Earth encounters[edit]
Flybys[edit]
Galileo made two course corrections on April 9 to 12 and May 11 to 12, 1990, to alter its velocity by 35 meters per second (110 ft/s).[61] 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.[81] This was 8 km (5 mi) higher than predicted, and the time of the closest approach was within a second of the prediction. It was the first time that a deep space probe had returned to Earth from interplanetary space.[61] A second flyby of Earth was at 304 km (189 mi) at 15:09:25 UTC on December 8, 1992.[81] This time the spacecraft passed within a kilometer of its aiming point over the South Atlantic. This was so accurate that a scheduled course correction was cancelled, thereby saving 5 kilograms (11 lb) of propellant.[92]
Timeline of the probe's atmospheric entry
Jupiter's clouds - expected and actual results of Galileo's atmospheric probe mission
