Galileo Probe and Orbiter

Galileo Project Information

Physical Information


Launch Date: 18 October 1989 at 22:23 UTC
Launch Vehicle: Shuttle/Inertial Upper Stage
On-orbit mass: 2380 Kg
Power System: Radioisotope Thermal Generators (RTGs) of 570 W


Release Date: 13 July 1995 at 05:30 UTC
Entry Date: 07 December 1995 at 22:04 UTC (5:04 p.m. EST)
Launch Vehicle: Shuttle/Inertial Upper Stage
On-orbit mass: 335 Kg
Power System: Storage batteries of 580 W

Mission Overview

The Galileo mission consists of two spacecraft: an orbiter and an atmospheric probe. Launched during the STS 34 flight of the Atlantis orbiter, the two spacecraft were kicked out of Earth orbit by an inertial upper stage (IUS) rocket, sending them careening through the inner solar system. The trajectory which the spacecraft followed was called a VEEGA (Venus-Earth-Earth Gravity Assist), traveling first in toward the Sun for a gravity assist from Venus before encountering the Earth two times (spaced two years apart). These encounters with Venus and the Earth allowed Galileo to gain enough velocity to get it out to Jupiter.

During the flybys of Venus and the Earth, Galileo scientists took the opportunity to study these two planets as well as the Moon, making some unprecedented observations as a result. In addition, following each Earth flyby, Galileo made excursions as far out in the solar system as the asteroid belt, enabling scientists to make the first close-up studies of two asteroids, Gaspra and Ida. As is this were not sufficient, Galileo scientists were fortunate to be the only ones with a direct view of the Comet Shoemaker-Levy 9 fragment impacts on Jupiter. All of this was prior to the primary missions of sending an atmospheric probe into Jupiter's atmosphere and studying Jupiter, its satellites, and its magnetosphere for two years with the orbiter.

Interplanetary studies were also made sporadically by some of the other Galileo instruments, including the dust detector, magnetometer, and various plasma and particles detectors, during its six year journey to Jupiter.

The probe was released from the orbiter 147 days prior to its entry into the Jovian atmosphere on 7 December 1995.

Science Objectives

The science goals of the Galileo Probe were to:

  1. determine the chemical composition of the Jovian atmosphere;
  2. characterize the structure of the atmosphere to a depth of at least 10 bars;
  3. investigate the nature of cloud particles and the location and structure of cloud layers;
  4. examine the Jovian radiative heat balance;
  5. study the nature of Jovian lightning activity; and,
  6. measure the flux of energetic charged particles down to the top of the atmosphere.

The objectives of the Galileo 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.

Scientific firsts of the Galileo mission

Although Galileo was not the first mission to explore Jupiter (actually, it is the sixth), it has established a number of "firsts" during its journey.

Scientific results of the Galileo mission (so far)

A comprehensive list of the science results of Galileo would be longer than space permits. Here, then, is a short list of some important discoveries (in no particular order).

Other Galileo Information/Data at NSSDCA

NSSDCA Master Catalog Information

Information about the Galileo Orbiter
Information about Galileo Orbiter experiments
Information about Galileo Orbiter data

Information about the Galileo Probe
Information about Galileo Probe experiments

Information about Galileo Probe data

Information about STS 34 (Galileo deployment mission)

Event Information

Galileo probe timeline of events
Galileo orbiter event information

Images (on-line and on CD-ROM)

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

Order the Galileo imaging CD-ROM set

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 Information/Data


Galileo Project (NASA JPL)
Galileo Probe (NASA ARC)

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) (Cal. Tech.)
Near Infrared Mapping Spectrometer (NIMS) (UCLA)
Neutral Mass Spectrometer (NMS)

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) (U. Kansas) Data


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

NSSDCA Planetary page
NSSDCA Space Physics page

Dr. Edwin V. Bell, II
Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771
NASA Official: Dr. David R. Williams Version 2.0, 03 May 1996
Last Updated: Monday, 26-Nov-2018 10:07:03 EST