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Galileo Orbiter



The Galileo mission consists of two spacecraft: an orbiter and an atmospheric probe. The orbiter will be the sixth spacecraft to explore the Jovian magnetosphere, but the first to be placed into orbit around the giant planet. Scientific objectives addressed by the orbiter are to: (1) investigate the circulation and dynamics of the Jovian atmosphere; (2) investigate the upper Jovian atmosphere and ionosphere; (3) characterize the morphology, geology, and physical state of the Galilean satellites; (4) investigate the composition and distribution of surface minerals on the Galilean satellites; (5) determine the gravitational and magnetic fields and dynamic properties of the Galilean satellites; (6) study the atmospheres, ionospheres, and extended gas clouds of the Galilean satellites; (7) study the interaction of the Jovian magnetosphere with the Galilean satellites; and, (8) characterize the vector magnetic field and the energy spectra, composition, and angular distribution of energetic particles and plasma to a distance of 150 Rj.

The structure of the orbiter is divided into two sections. The main body of the spacecraft, comprised of the electronics bays, propellant system, RTG and science booms, and high-gain antenna, rotates at rates of 3.25 or 10.5 rpm. The despun section, aft of the main body, uses an electric motor to drive it counter to the rotation of the main section. This dual spin attitude control system accommodates instruments which require stable, accurate pointing (the imaging instruments) and those which benefit from repetitive, broad-angular coverage (the various particles and fields instruments). The length of the spacecraft is 9 m and, with the high-gain antenna (HGA) deployed, is 4.6 m in diameter.

Power is provided to the spacecraft through the use of two radioisotope thermal generators (RTGs), each of which is located at the end of a short boom. The magnetometer sensors and plasma wave antenna are located on yet another boom, 10.9 m in length.

Although it was intended that communications with the Deep Space Network (DSN) would be primarily through the HGA (which would remain pointing toward the Earth at all times), thermal constraints forced the use of the two low-gain antennas prior to the first Earth flyby. HGA deployment was planned thereafter, but at least three of the HGA "ribs" were unable to be moved much beyond their launch configurations, thereby jeopardizing the total science return of the mission. Several attempts have been made to deploy the antenna through a variety of techniques.

Alternate Names

  • Jupiter Orbiter
  • Galileo
  • 20298

Facts in Brief

Launch Date: 1989-10-18
Launch Vehicle: Shuttle-Inertial Upper Stage
Launch Site: Cape Canaveral, United States
Mass: 2380.0 kg
Nominal Power: 570.0 W

Funding Agencies

  • NASA-Office of Space Science Applications (United States)
  • Deutsche Forschunganstalt fuer Luft- und Raumfahrt (DLR, nee DFVLR) (Federal Republic of Germany)


  • Astronomy
  • Engineering
  • Earth Science
  • Planetary Science
  • Solar Physics
  • Space Physics

Additional Information

Questions or comments about this spacecraft can be directed to: Dr. Edwin V. Bell, II.



NameRoleOriginal AffiliationE-mail
Mr. Henry C. BrintonProgram ScientistNASA Headquarters 
Mr. William J. O'NeilProject ManagerNASA Jet Propulsion Laboratory 
Mr. Donald T. KettererProgram ManagerNASA
Dr. Torrence V. JohnsonProject ScientistNASA Jet Propulsion

Selected References

Johnson, T. V., et al., Galileo Venus encounter, Science, 253, No. 5027, 1516-1518, Sept. 1991.

Johnson, T. V., et al., Space science reviews volume of Galileo mission overview, Space Sci. Rev., 60, No. 1-4, 3-21, May 1992.

Kerr, R. A., Galileo turns geology upside down on Jupiter's icy moons, Science, 274, No. 5286, 341, Oct. 1996.

Other Galileo Information/Data at NSSDCA

NSSDCA Master Catalog Information

Galileo Probe
Galileo Probe experiments

STS 34 (Galileo deployment mission)

Event Information

Galileo probe timeline of events
Galileo orbiter event information


Index of images taken by Galileo in the NSSDCA Photo Gallery
Galileo Images of Callisto
Galileo Images of Ganymede
Galileo Images of Europa
Galileo Images of Io

JPL Press Releases

Surprising early science results from the Galileo probe
More science results from the Galileo probe
Science results from the first Io flyby!
Science results from the first Ganymede flyby!
Possible discovery of liquid water on Europa
Possible discovery of ionosphere on Io
More about water on Europa
Wet and dry spots on Jupiter
Discovery of ionosphere on Europa

Galileo's tape recorder problem (NASA press release, 10/12/95)
Galileo's fixed tape recorder (NASA press release, 10/21/95)
More about Galileo's tape recorder (NASA press release, 10/26/95)


Galileo and the Comet Shoemaker-Levy 9 impact on Jupiter
Galileo lunar data

Obtain Galileo position data (heliographic coordinates)

Related Information/Data at NSSDCA

Venus page
Earth page
Moon page
Jupiter page
Asteroid & Comets page

Other Sources of Galileo Orbiter Information/Data


Galileo Project Home Page (NASA JPL)

Experiment Teams

Solid State Imaging (SSI) (NASA JPL)
Magnetometer (MAG) (UCLA)
Ultraviolet/Extreme Ultraviolet Spectrometer (UVS/EUVS) (U. Colorado)
Dust Detector (DDS) (MPI) Data
Heavy Ion Counter (HIC) page (Cal. Tech.)
Near Infrared Mapping Spectrometer (NIMS) (UCLA)

Plasma Wave (PWS) (U. Iowa)
Plasma Particle (PLS) (U. Iowa)
PLS and PWS (U. Iowa) Data

Energetic Particles Detector (EPD) (JHU/APL)
Energetic Particles Detector (EPD) Data


Online from Jupiter (K-12 student/teacher information/activities)

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