Galileo

Galileo was designed to perform in-depth studies of Jupiter's atmosphere, satellites, and surrounding magnetosphere. The mission was named in honor of Galileo Galilei, the Italian Renaissance scientist who discovered Jupiter's major moons in 1610. The spacecraft's primary mission was the deployment of an atmospheric probe into Jupiter's atmosphere (Dec. 7, 1995). Following deployment, the vehicle went into orbit around Jupiter to continue its investigations. During its interplanetary cruise, the planned deployment of Galileo's high gain antenna failed, forcing use of the its low gain antennas at much lower than planned data rates. Despite the failure, it is believed approximately 70% of the original science objectives will be achieved. During its flight to Jupiter, Galileo also performed the 1st and 2nd asteroid flybys - Gaspra (Oct. 1991) and Ida (Aug. 1993). Galileo was also the only vehicle in a position to obtain images of the far side of Jupiter when more than 20 fragments of Comet Shoemaker-Levy plunged into Jupiter's atmosphere in July 1994.

Spacecraft
Orbiter: Dual-spin stabilized. Spinning section (3 rpm) houses fields and particles instruments, antennas, propulsion system, computers, most other support systems. Despun section provides fixed orientation for remote sensing insturments, star scanner, gyros. Bipropellant propulsion system (HHM, NTO) from Federal Republic of Germany uses 12 10N thrusters, 1 400N main engine. S-band communications through 2 omni LGAs (40 bps typical), deployable 4.8 meter wire mesh HGA failed to deploy (planned downlink rate >100 kbps). Redundant flight computers with high level of fault protection. Powered by 2 RTGs (570W BOL, 485W EOL). 11 meter deployable boom for some science instruments. Probe: Deceleration module, consisting of aeroshell and aft cover, to slow initial descent and provide thermal control. 2.5 m parachute controls descent following deceleration module release. Descent module contains redundant L-band transmitters, instrument package, batteries. Downlink to Orbiter at 128 bps. Primary lithium-sulphur batteries (18 Ahr total) provide power during descent.

Payload
Orbiter: Near-Infrared Mapping Spectrometer (NIMS) - makes multispectral images for atmosphere and surface chemical analysis, Ultraviolet Spectrometer (UVS) - studies gases, Solid-State Imager (SSI) - visible imaging with 800 x 800 array CCD, Photopolarimeter (PPR) - measures radiant and reflected energy, Magnetometers (MAG), Dust Detection Experiment (DDE), Plasma Investigation (PLS), Energetic Particle Detector (EPD), Plasma Wave Investigation (PWS), Radio Science Probe: Atmosphere Structure Experiment - measures temperature, pressure and deceleration, Probe Mass Spectrometer - atmospheric composition studies, Helium Abundance Detector - atmospheric composition studies, Probe Nephelometer - cloud location and cloud-particle observations, Net Flux Radiometer - measures the difference, upward versus downward, in radiant energy flux at each altitude, Lightning and Energetic Particles - measures light and radio emissions associated with lightning and energetic particles in Jupiter's radiation belts.

Country of Origin	United States
Customer/User	NASA, JPL
Manufacturer(s)	JPL, NASA Ames Research Center
Size	Orbiter height 6.15 m; Probe height 0.9 m
Orbit	6 year trajectory with gravity assists at Venus, Earth (twice). Also performed flybys of Gaspra and Ida asteroids. Entered Jupiter orbit 12/7/95. 23 month orbital mission with 10 satellite encounters.
Design Life	8 years
Related Sites	JPL Galileo Summary Galileo Home Page

Launch Facts

Name	Int'l Desig.	Date	Site	Vehicle	Orbit	Mass(kg)
Notes
Galileo	1989-084B	10/18/89	ESMC	STS 34	Jupiter	3881
Deployed from STS-34 10/18/89; entered Jupiter orbit 12/7/95; investigations of Jupiter's moons, atmosphere, magnetosphere; antenna failed to deploy
Galileo Probe	1989-084E	10/18/89	ESMC	STS 34	Jupiter	339
Atmospheric probe; deployed from Galileo 7/13/95; entered Jupiter atmosphere 12/7/95