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Credit: NASA
American outer planets probe. One launch, 1989.10.18. The Galileo Jupiter orbiter was designed to perform in-depth studies of the giant planet's atmosphere, satellites, and surrounding magnetosphere. Jupiter orbiter and probe satellite operated by NASA, USA. Launched 1989.

Status: Operational 1989. First Launch: 1989-10-18. Last Launch: 1989-10-18. Number: 1 . Gross mass: 3,881 kg (8,556 lb). Height: 6.15 m (20.17 ft).

The spacecraft's primary mission was the deployment of an atmospheric probe into Jupiter's atmosphere. During interplanetary cruise, 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, a series of mission extensions and software improvisations resulted in the original science objectives being vastly exceeded. Galileo also performed two asteroid flybys and obtained images of the far side of Jupiter when Comet Shoemaker-Levy impacted in July 1994.

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. Following deployment of the probe, the spacecraft went into orbit around Jupiter to continue its investigations.

At the beginning of Galileo's interplanetary cruise, the planned deployment of the high gain antenna failed on 11 April 1991. Subsequent attempts to release it also failed. This forced use of the low gain antennas at an order-of-magnitude lower than planned data rate. Heroic efforts by JPL staff to develop workarounds resulted in virtually no loss of science data. During its flight to Jupiter, Galileo also performed the first and second asteroid flybys - Gaspra (October 1991) and Ida (August 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. The Galileo probe was released on 12 July 1995 and entered Jupiter's atmosphere on 7 December 1995. Problems with the tape recorder on 11 October 1995 also forced workarounds, but Galileo provided years of service in Jupiter orbit.

The orbiter was dual-spin stabilized. The spinning section (3 rpm) housed fields and particles instruments, antennas, propulsion system, computers, and most other support systems. The despun section provided fixed orientation for remote sensing instruments, star scanner, and gyros. The bipropellant propulsion system (HHM, NTO) from the Federal Republic of Germany used 12 x 10 N thrusters, 1 x 400 N main engine. S-band communications were through two omni low gain antennas (40 bps typical). The deployable 4.8 meter wire mesh high gain antenna failed to unfold and could not be used (planned downlink rate >100 kbps). Redundant flight computers with high level of fault protection kept Galileo operating throughout its extended mission.

The orbiter was powered by two radioisotope thermal generators (570 W BOL, 485 W EOL). An 11 meter deployable boom provided mounting for some science instruments. Orbiter Payload:

The probe consisted of a deceleration module, comprising an aeroshell and aft cover, for reentry and thermal control. A 2.5 m parachute controlled descent following deceleration module release. The descent module contained redundant L-band transmitters, an instrument package, and batteries. Downlink to the Orbiter was at 128 bps. Primary lithium-sulfur batteries (18 Ahr total) provided power during descent.

Probe Payload:



NASA NSSDC Master Catalog Description

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.

More at: Galileo.


Galileo probe American Jupiter atmospheric probe. Launched 1989.10.18 aboard the Galileo orbiter. Deployed from Galileo 13 July 1995; entered Jupiter atmosphere 7 December 1995.

Galileo-IOV PFM, FM2, FM3, FM4 Navigation satellite built by EADS Astrium for ESA, Europe. Launched 2011 - 2012.

Family: Outer planets. Country: USA. Engines: S400. Launch Vehicles: Space Shuttle. Launch Sites: Cape Canaveral, Cape Canaveral LC39B. Agency: JPL, NASA. Bibliography: 2, 279, 3738, 3739, 3740, 3741, 3742, 3743, 3744, 6.
Photo Gallery


Credit: Manufacturer Image

STS-34 Galileo spacecraft / IUS deployment sequence in OV-104's payload bay
Credit: NASA

STS-34 Galileo spacecraft / inertial upper stage (IUS) deployment
Credit: NASA

Moon taken by Galileo after completing its first Earth Gravity Assist
Credit: NASA

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