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GALILEO

Galileo changed the way we look at our solar system. When the spacecraft plunged
into Jupiter's crushing atmosphere on Sept. 21, 2003, it was being deliberately
destroyed to protect one of its own discoveries—a possible ocean beneath the icy
crust of the moon Europa.


Occurred 21 years ago

Mission Type

Orbiter and Atmospheric Probe

launch vehicle

Space Shuttle Atlantis (STS-34)

Launch

Oct. 18, 1989

STATUS

Successful

Galileo orbited Jupiter for almost eight years, and made close passes by all the
planet's major moons. Its camera and nine other instruments sent back reports
that allowed scientists to determine, among other things, that Jupiter’s icy
moon Europa probably has a subsurface ocean with more water than the total
amount found in Earth's ocean. It discovered that the volcanoes of the moon Io
repeatedly and rapidly resurface the little world. The spacecraft sent back data
indicating Jupiter's giant moon Ganymede possesses its own magnetic field.
Galileo even carried a small probe that it deployed and sent deep into the
atmosphere of Jupiter. The probe took readings for almost an hour before it was
crushed by overwhelming pressure.

Unable to render the provided source
Experience the entire Galileo mission with this 3D simulation that uses real
spacecraft data to recreate the mission's historic flight path.
NASA/VTAD
   
 * Mission Overview
 * Quick Facts
 * Top 10 Science Results
 * End of Mission
   


GALILEO MISSION OVERVIEW

NASA's Galileo spacecraft orbited Jupiter for almost eight years, and made close
passes by its major moons.

The spacecraft was launched from the cargo bay of space shuttle Atlantis on Oct.
18, 1989. It started orbiting Jupiter in December 1995. The primary mission was
completed in December 1997, and then was extended three times. The mission ended
when the spacecraft deliberately impacted Jupiter on Sept. 21, 2003.

Read More
An illustration of NASA's Galileo spacecraft at Jupiter and one its moons.
NASA


GALILEO QUICK FACTS

Launched into Earth orbit from the Space Shuttle Atlantis in 1989, the mission
went on to orbit Jupiter 34 times.

The orbiter weighed 2 1/2 tons (223 kilograms) at launch and measured 17 feet (5
.3 meters) from the top of the low-gain antenna to the bottom of the probe.

Read More
This photo from Nov. 1, 1984 shows the Galileo orbiter under construction at
NASA's Jet Propulsion Laboratory.
NASA / JPL-Caltech


TOP 10 SCIENCE RESULTS

Four spacecraft had previously flown by the Jupiter system, but Galileo was the
first to enter orbit around the planet.

Like the famed astronomer for which it was named, Galileo would study the King
of Planets over an extended period, in finer detail than was ever possible
before.

Read More
These images of Jupiter show the luminous night-side impact of fragment W of
Comet Shoemaker-Levy 9. The images were taken by the Galileo spacecraft on July
22, 1994. NASA/JPL-Caltech/Galileo Imaging Team


GALILEO END OF MISSION

Galileo was deliberately destroyed to protect one of its own discoveries—a
possible ocean beneath the icy crust of the moon Europa.

On the day of impact, it took Galileo's radio signals about 52 minutes to travel
between the spacecraft and Earth.

Read More
An artist's impression of the Galileo orbiter beginning to burn up in Jupiter's
atmosphere. Galileo's 14-year mission to explore the Jovian system ended on 21
Sept. 2003 when the spacecraft was deliberately sent into Jupiter's atmosphere.


QUICK FACTS


FIRSTS

   
 * Galileo was the first spacecraft to orbit an outer planet.
 * It was the first spacecraft to deploy an entry probe into an outer planet's
   atmosphere.
 * It completed the first flyby and imaging of an asteroid (Gaspra, and later,
   Ida).
 * It made the first, and so far only, direct observation of a comet colliding
   with a planet’s atmosphere (Shoemaker-Levy 9).
 * It was the first spacecraft to operate in a giant planet magnetosphere long
   enough to identify its global structure and to investigate its dynamics.
   


SPACECRAFT

This photo from Nov. 1, 1984 shows the Galileo orbiter under construction at
NASA's Jet Propulsion Laboratory.
NASA / JPL-Caltech

Dimensions:  5.3 meters (17 feet) high; magnetometer boom extends 11 meters (36
feet) to one side

Weight:  2,223 kilograms (2½ tons, or 4,902 pounds), including 118 kilograms
(260 pounds) of science instruments and 925 kilograms (2040 pounds) of
propellant

Power:  570 watts (at launch) from radioisotope thermoelectric generators

Science instruments:  Solid-state imaging camera, near-infrared mapping
spectrometer, ultraviolet spectrometer, photopolarimeter radiometer,
magnetometer, energetic particles detector, plasma investigation, plasma wave
subsystem, dust detector, heavy ion counter


ATMOSPHERIC PROBE

Size:  127 centimeters (50 inches) diameter, 91 centimeters (36 inches) high

Weight:  339 kilograms (750 pounds)

Science instruments:  Atmospheric structure, neutral mass spectrometer, helium
abundance, nephelometer, net flux radiometer, lightning/energetic particles,
doppler wind experiment


MISSION

Launch:  Oct. 18, 1989 from Kennedy Space Center, Florida, on space shuttle
Atlantis (STS-34)

Primary mission:  October 1989 to December 1997

Extended missions:  Three, from 1997 to 2003

Venus flyby:  Feb. 10, 1990, at altitude of 16,000 km (10,000 mi)

Earth flybys:  Dec. 8, 1990, at altitude of 960 km (597 mi); Dec. 8, 1992 at
altitude of 303 km (188 mi)

Asteroid Gaspra flyby:  Oct. 29, 1991, at 1,601 km (1,000 mi)

Comet Shoemaker-Levy 9:  Impacts of comet fragments into Jupiter observed while
en route in July 1994

Asteroid Ida flyby:  Aug. 28, 1993, at 2,400 km (1,400 mi)

Atmospheric probe release:  July 12, 1995

Probe speed into Jupiter's atmosphere:  47.6 km per second (106,000 mi per hour)

Jupiter arrival and orbit insertion:  Dec. 7, 1995

Probe atmospheric entry and relay:  Dec. 7, 1995

Number of Jupiter orbits during entire mission: 34

Number of flybys of Jupiter moons:  Io 7, Callisto 8, Ganymede 8, Europa 11,
Amalthea 1

Total distance traveled from launch to final impact: 4,631,778,000 kilometers
(approx. 2.8 billion miles)

Speed of spacecraft at time of impact: 48.2 kilometers per second (nearly
108,000 miles per hour)


PROGRAM

Cost:  Total from start of planning through end of mission is $1.39 billion. 
International contribution estimated at an additional $110 million

Partners:  More than 100 scientists from United States, Great Britain, Germany,
France, Canada and Sweden carried out Galileo's experiments.  NASA's Ames
Research Center, Mountain View, Calif., responsible for atmosphere probe, built
by Hughes Aircraft Company, El Segundo, Calif.  Radioisotope thermoelectric
generators designed and built by General Electric Co. for the U.S. Department of
Energy

Approximate number of people who worked on some portion of the Galileo mission: 
800

The Galileo project was managed by the Jet Propulsion Laboratory, Pasadena, a
division of the California Institute of Technology.  JPL designed and built the
Galileo orbiter, and operated the mission.

At NASA Headquarters, Dr. Barry Geldzahler was Galileo program manager and Dr.
Denis Bogan was the program scientist. At JPL, the position of project manager
has been held successively by John Casani, Richard Spehalski, Bill O'Neil, Bob
Mitchell, Jim Erickson, Eilene Theilig, and Dr. Claudia J. Alexander.  Dr.
Torrence V. Johnson was project scientist.

NASA's Ames Research Center, Moffett Field, Calif., managed the descent probe,
which was built by Hughes Aircraft Co, El Segundo, Calif.  The position of probe
manager was held successively by Joel Sperans, Benny Chinn and Marcie Smith. 
The probe scientist was Dr. Richard E. Young. 


MEDIA

10 Images




TOP 10 SCIENCE RESULTS

     
 1.  The descent probe measured atmospheric elements and found that their
     relative abundances were different than on the Sun, indicating Jupiter's
     evolution since the planet formed out of the solar nebula.
 2.  Galileo made a first observation of ammonia clouds in another planet's
     atmosphere.The atmosphere seems to create ammonia ice particles of material
     from lower depths, but only in "fresh" clouds.
 3.  Io's extensive volcanic activity may be 100 times greater than that found
     on Earth's.The heat and frequency of eruption are reminiscent of early
     Earth.
 4.  Io's complex plasma interactions in Io's atmosphere include support for
     currents and coupling to Jupiter's atmosphere.
 5.  Evidence supports a theory that liquid oceans exist under Europa's icy
     surface.
 6.  Ganymede is the first satellite known to possess a magnetic field.
 7.  Galileo magnetic data provide evidence that Europa, Ganymede and Callisto
     have a liquid-saltwater layer.
 8.  Europa, Ganymede, and Callisto all provide evidence of a thin atmospheric
     layer known as a 'surface-bound exosphere'.
 9.  Jupiter's ring system is formed by dust kicked up as interplanetary
     meteoroids smash into the planet's four small inner moons.  The outermost
     ring is actually two rings, one embedded with the other.
 10. Galileo was the first spacecraft to dwell in a giant planet magnetosphere
     long enough to identify its global structure and to investigate its
     dynamics.
     




MISSION OVERVIEW

Galileo's journey to Jupiter.
NASA/JPL-Caltech

NASA's Galileo spacecraft was designed to study the large, gaseous planet
Jupiter, its moons and its surrounding magnetosphere, which is a magnetic bubble
surrounding the planet.  The craft was named for the Italian Renaissance
scientist who discovered Jupiter's major moons in 1610.

The primary mission at Jupiter began when the spacecraft entered orbit in
December 1995 and its descent probe, which had been released five months
earlier, dove into the giant planet's atmosphere.  The primary mission included
a 23-month, 11-orbit tour of the Jovian system, including 10 close encounters of
Jupiter's major moons.

Although the primary mission was completed in December 1997, the mission was
extended three times. Galileo had 35 encounters of Jupiter's major moons – 11
with Europa, eight with Callisto, eight with Ganymede, seven with Io and one
with Amalthea. The mission ended when the spacecraft impacted Jupiter on Sept.
21, 2003.

Deployment of NASA Galileo and the IUS from the cargo bay of STS-34 Atlantis at
7:15 p.m. EDT on October 18, 1989. P-35213
NASA


LAUNCH

The Galileo spacecraft and its two-stage Inertial Upper Stage were carried into
Earth orbit on October 18, 1989 by space shuttle Atlantis on mission STS-34. The
two-stage Inertial Upper Stage solid rocket then accelerated the spacecraft out
of Earth orbit toward the planet Venus for the first of three planetary "gravity
assists" designed to boost Galileo toward Jupiter. In a gravity assist, the
spacecraft flies close enough to a planet to be propelled by its gravity,
creating a "slingshot" effect for the spacecraft. The Galileo mission had
originally been designed for a direct flight of about three and a half years to
Jupiter, using a three-stage Inertial Upper Stage.  When that booster was
canceled, plans were changed to a Centaur upper stage, and ultimately to the
twostage Inertial Upper Stage, which precluded a direct trajectory.  To save the
project, Galileo engineers designed a flight path using planetary gravity
assists.


VENUS AND EARTH FLYBYS

After flying past Venus at an altitude of 16,000 kilometers (nearly 10,000
miles) on

February 10, 1990, the spacecraft swung past Earth at an altitude of 960
kilometers (597 miles) on December 8, 1990.  That flyby increased Galileo's
speed enough to send it on a two-year elliptical orbit around the Sun.  The
spacecraft returned for a second Earth swingby on December 8, 1992, at an
altitude of 303 kilometers (188 miles). With this, Galileo left Earth for the
third and final time and headed toward Jupiter.

The flight path provided opportunities for scientific observations. Scientists
obtained the first views of mid-level clouds on Venus and confirmed the presence
of lightning on that planet.  They also made many Earth observations, mapped the
surface of Earth's Moon, and observed its north polar regions.

Because of the modification in Galileo's trajectory, the spacecraft was exposed
to a hotter environment than originally planned.  To protect it from the Sun,
project engineers devised a set of sunshades and pointed the top of the
spacecraft toward the Sun, with the umbrella-like high-gain antenna furled until
well after the first Earth flyby in December 1990.  Flight controllers stayed in
touch with the spacecraft through a pair of low-gain antennas, which send and
receive data at a much slower rate.


HIGH-GAIN ANTENNA

The spacecraft was scheduled to deploy its 4.8-meter-diameter (16-foot)
high-gain antenna in April 1991 as Galileo moved away from the Sun and the risk
of overheating ended. The antenna, however, failed to deploy fully.

A special team performed extensive tests and determined that a few (probably
three) of the antenna's 18 ribs were held by friction in the closed position.
Despite exhaustive efforts to free the ribs, the antenna would not deploy.  From
1993 to 1996, extensive new flight and ground software was developed, and ground
stations of NASA's Deep Space Network were enhanced in order to perform the
mission using the spacecraft's low-gain antennas.

This color picture is made from images taken by Galileo about 14 minutes before
its closest approach to asteroid 243 Ida and its moon, Dactyl, on August 28,
1993. The images used are from the sequence in which Ida's moon was originally
discovered;
NASA/JPL-Caltech


ASTEROID FLYBYS

Galileo became the first spacecraft ever to encounter an asteroid when it passed
Gaspra on October 29, 1991. It flew within just 1,601 kilometers (1,000 miles)
of the stony asteroid's center at a relative speed of about 8 kilometers per
second (18,000 miles per hour).  Pictures and other data revealed a cratered,
complex, irregular body about 20 by 12 by 11 kilometers (12.4 by 7.4 by 6.8
miles), with a thin covering of dust and rubble.

On August 28, 1993, Galileo carried out a second asteroid encounter, this time
with a larger, more distant asteroid named Ida. Ida is about 55 kilometers (34
miles) long and 24 kilometers (15 miles) wide. Observations indicated that both
Ida and Gaspra have magnetic fields, although Ida is older and its surface is
covered with craters.  Scientists discovered that Ida boasts its own moon,
making it the first asteroid known to have a natural satellite.  The tiny moon,
named Dactyl, has a diameter of only about 1.5 kilometers (less than a mile). 
By determining Dactyl's orbit, scientists estimated Ida's density.

Eight impacts from Comet Shoemaker-Levy 9 are visible in this Hubble Space
Telescope image from Jupiter taken in 1994. The smallest features in this image
are 124 miles (200 kilometers) across.
NASA/Hubble Space Telescope Comet Team


COMET SHOEMAKER-LEVY 9 IMPACT INTO JUPITER

The discovery of Comet Shoemaker-Levy 9 in March 1993 provided an exciting
opportunity for Galileo's science teams and other astronomers. The comet was
breaking up as it orbited Jupiter, and was headed to dive into the giant
planet's atmosphere in July 1994.

The Galileo spacecraft, approaching Jupiter, was the only observation platform
with a direct view of the comet’s impact area on Jupiter's far side.  Despite
the uncertainty of the predicted impact times, Galileo team members
pre-programmed the spacecraft's science instruments to collect data and were
able to obtain spectacular images of the comet impacts.


JUPITER ARRIVAL

On July 13, 1995, Galileo's descent probe, which had been carried aboard the
parent spacecraft, was released and began a five-month freefall toward Jupiter.
The probe had no engine or thrusters, so its flight path was established by
pointing of the Galileo orbiter before the probe was released.  Two weeks later,
Galileo used its main rocket engine for the first time as it readjusted its
flight path to arrive at the proper point at Jupiter.

Arrival day on December 7, 1995, turned out to be an extremely busy 24-hour
period. When Galileo first reached Jupiter and while the probe was still
approaching the planet, the orbiter flew by two of Jupiter's major moons –
Europa and Io. Galileo passed Europa at an altitude of about 33,000 kilometers
(20,000 miles), while the Io approach was at an altitude of about 900 kilometers
(600 miles). 

About four hours after leaving Io, the orbiter made its closest approach to
Jupiter, encountering 25 times more radiation than the level considered deadly
for humans.


DESCENT PROBE

Eight minutes later, the orbiter started receiving data from the descent probe,
which slammed into the top of the Jovian atmosphere at a comet-like speed of
170,000 kilometers per hour (106,000 miles per hour).  In the process, the probe
withstood temperatures twice as hot as the Sun's surface.  The probe slowed by
aerodynamic braking for about two minutes before deploying its parachute and
dropping a heat shield.

The wok-shaped probe floated down about 200 kilometers (125 miles) through the
clouds, transmitting data to the orbiter on sunlight and heat flux, pressure,
temperature, winds, lightning and atmospheric composition. Fifty-eight minutes
into its descent, high temperatures silenced the probe's transmitters.  The
probe sent data from a depth with a pressure 23 times that of the average on
Earth's surface, more than twice the mission requirement.

An hour after receiving the last transmission from the probe, at a point about
200,000 kilometers (130,000 miles) above the planet, the Galileo spacecraft
fired its main engine to brake into orbit around Jupiter.

This first orbit lasted about seven months. Galileo fired its thrusters at its
farthest point in the orbit to keep it from coming so close to the giant planet
on later orbits.  This adjustment helped mitigate possible damage to spacecraft
sensors and computer chips from Jupiter's intense radiation environment.

During this first orbit, new software was installed which gave the orbiter
extensive new onboard data processing capabilities.  It permitted data
compression, enabling the spacecraft to transmit up to 10 times the number of
pictures and other measurements that would have been possible otherwise.

In addition, hardware changes on the ground and adjustments to the
spacecraft-toEarth communication system increased the average telemetry rate
tenfold.   Although the problem with the high-gain antenna prevented some of the
mission's original objectives from being met, the great majority were.  So many
new objectives were achieved that scientists feel Galileo has produced
considerably more science than ever envisioned at the project's start 20 years
ago.


ORBITAL TOUR

During its primary mission orbital tour, Galileo's itinerary included four
flybys of Jupiter's moon Ganymede, three of Callisto and three of Europa.  These
encounters were about 100 to 1,000 times closer than those performed by NASA's
Voyager 1 and 2 spacecraft during their Jupiter flybys in 1979.  Galileo's
instruments scanned and scrutinized the surface and features of each moon. After
about a week of intensive observation, with its tape recorder full of data, the
spacecraft spent the next one to two months-until the next encounter in orbital
"cruise"-playing back the information in transmissions to Earth.


EXTENDED MISSIONS

A two-year extension, the Galileo Europa Mission, began in December 1997 and
included intensive study of Europa through eight consecutive close encounters. 
The flybys added to knowledge about Europa's frozen surface and the intriguing
prospect that liquid oceans may lie underneath. The Galileo Europa Mission
provided a valuable opportunity to make additional flybys' of the volcanic moon
Io.  The prime mission provided only one opportunity for close-up study of Io. 
Galileo had two encounters of Io during the Europa Mission, gathering new
information on Io's volcanic activity. In addition, Galileo studied Callisto in
four flybys. The Galileo Millennium Mission added another year of operations,
including more flybys of Io and Ganymede, plus joint studies with the Cassini
spacecraft as it passed Jupiter in December 2000 for a gravity assist toward
Saturn.

A line drawing of the Galileo orbiter.
NASA/JPL-Caltech


HOW THE SPACECRAFT WORKED

The Galileo orbiter weighed 2,223 kilograms at launch (2-1/2 tons) and measured
5.3 meters (17 feet) from the top of the low-gain antenna to the bottom of the
probe. The orbiter features an innovative "dual-spin" design. Most spacecraft
are stabilized in flight either by spinning around a major axis, or by
maintaining a fixed orientation in space, referenced to the Sun and another
star. As the first dual-spin planetary spacecraft, Galileo combines these
techniques. A spinning section rotates at about 3 rpm, and a "despun" section is
counter-rotated to provide a fixed orientation for cameras and other remote
sensors. A star scanner on the spinning side determines orientation and spin
rate; gyroscopes on the despun side provide the basis for measuring turns and
pointing instruments.

The power supply, propulsion module and most of the computers and control
electronics are mounted on the spinning section. The spinning section also
carries instruments to study magnetic fields and charged particles.  These
instruments include magnetometer sensors mounted on an 11-meter (36-foot) boom
to minimize interference from the spacecraft's electronics; a plasma instrument
to detect low-energy charged particles; and a plasma-wave detector to study
electromagnetic waves generated by the particles.  There is also a high-energy
particle detector and a detector of cosmic and Jovian dust, an extreme
ultraviolet detector associated with the ultraviolet spectrometer, and a heavy
ion counter to assess potentially hazardous charged-particle environments the
spacecraft flies through.

Galileo's de-spun section carries instruments that need to be held steady. 
These instruments include the camera system; the near-infrared mapping
spectrometer to make multispectral images for atmosphere and surface chemical
analysis; the ultraviolet spectrometer to study gases; and the
photopolarimeter-radiometer to measure radiant and reflected energy. The camera
system obtains images of Jupiter's satellites at resolutions from 20 to 1,000
times better than the best possible from NASA's Voyager spacecraft; its
charge-coupled-device (CCD) sensor is much more sensitive than previous
spacecraft cameras and is able to detect a broader color band. Galileo's de-spun
section also carries a dish antenna that picked up the descent probe's signals
during its fall into Jupiter's atmosphere.

The spacecraft's propulsion module consists of twelve 10-newton
(2.25-pound-force) thrusters and a single 400-newton (90-pound-force) engine
which use monomethylhydrazine fuel and nitrogen-tetroxide oxidizer. The
propulsion system was developed and built by Messerschmitt-Bolkow-Blohm (MBB)
and provided by the Federal Republic of Germany as NASA's major international
partner on Galileo.

Because radio signals take more than one hour to travel from Earth to Jupiter
and back, the Galileo spacecraft was designed to operate from computer
instructions sent to it in advance and stored in spacecraft memory. A single
master sequence of com-

mands can cover a period ranging from weeks to months of quiet operations
between flybys of Jupiter's moons.  During busy encounter operations, one
sequence of commands covers only about a week.

These sequences operate through flight software installed in the spacecraft
computers, with built-in automatic fault protection software designed to put
Galileo in a safe state in case of computer glitches or other unforeseen
circumstance.  Electrical power is provided by two radioisotope thermoelectric
generators. Heat produced by natural radioactive decay of plutonium is converted
to electricity (570 watts at launch, 485 at the end of the mission) to operate
the orbiter spacecraft's equipment. This is the same type of power source used
on other NASA missions including Viking to Mars, Voyager and Pioneer to the
outer planets, Ulysses to study the Sun, and Cassini to Saturn.


DESCENT PROBE

Galileo's descent probe had a mass of 339 kilograms (750 pounds), and included a
deceleration module to slow and protect the descent module. The deceleration
module consisted of an aeroshell and an aft cover designed to block heat
generated by friction during atmospheric entry. Inside the aeroshells were the
descent module and its 2.5meter (8-foot) parachute. The descent module carried a
radio transmitter and seven scientific instruments.  These were devices to
measure temperature, pressure and deceleration, atmospheric composition, clouds,
particles, and light and radio emissions from lightning and energetic particles
in Jupiter's radiation belts.


ORBITER INSTRUMENTS

The Galileo orbiter spacecraft carries 11 scientific instruments. Another seven
were on the descent probe. One engineering instrument on the orbiter, originally
for measurements to aid design of future spacecraft, also collects scientific
information.


END OF MISSION

An artist's impression of the Galileo orbiter beginning to burn up in Jupiter's
atmosphere. Galileo's 14-year mission to explore the Jovian system ended on 21
Sept. 2003 when the spacecraft was deliberately sent into Jupiter's atmosphere.


GALILEO TASTED JUPITER ON ITS FINAL PLUNGE

In the end, the Galileo spacecraft got a taste of Jupiter before taking a final
plunge into the planet's crushing atmosphere, ending the mission on Sunday,
Sept. 21, 2003.

The spacecraft was purposely put on a collision course with Jupiter to eliminate
any chance of an unwanted impact between the spacecraft and Jupiter’s moon
Europa, which Galileo discovered is likely to have a subsurface ocean. The long
planned impact was necessary because the spacecraft's onboard propellant was
depleted. Without propellant, the spacecraft would not be able to point its
antenna toward Earth nor adjust its trajectory, so controlling the spacecraft
would no longer be possible.

"It has been a fabulous mission for planetary science, and it is hard to see it
come to an end," Dr. Claudia Alexander, Galileo project manager at NASA's Jet
Propulsion Laboratory, said in 2003.

Launched in the cargo bay of Space Shuttle Atlantis in 1989, the mission
produced a string of discoveries while circling the solar system's largest
planet, Jupiter, 34 times. Galileo was the first mission to measure Jupiter's
atmosphere directly with a descent probe and the first to conduct long-term
observations of the jovian system from orbit.  It found evidence of subsurface
liquid layers of saltwater on Europa, Ganymede and Callisto and it examined a
diversity of volcanic activity on Io.  Galileo is the first spacecraft to fly by
an asteroid and the first to discover a moon of an asteroid. 

NASA extended the mission three times to continue taking advantage of Galileo's
unique capabilities for accomplishing valuable science.  The mission was
possible because it drew its power from two long-lasting radioisotope
thermoelectric generators provided by the Department of Energy.

From launch to impact, the spacecraft has traveled 4,631,778,000 kilometers
(about 2.8 billion miles).

Its entry point into the giant planet’s atmosphere was about 1/4 degree south of
Jupiter's equator. If there were observers floating along at the cloud tops,
they would see Galileo streaming in from a point about 22 degrees above the
local horizon. Streaming in could also be described as screaming in, as the
speed of the craft relative to those observers would be 48.2 kilometers per
second (nearly 108,000 miles per hour). That is the equivalent of traveling from
Los Angeles to New York City in 82 seconds. In comparison, the Galileo
atmospheric probe, aerodynamically designed to slow down when entering, and
parachute gently through the clouds, first reached the atmosphere at a slightly
more modest 47.6 kilometers per second (106,500 miles per hour).

"This is a very exciting time for us as we draw to a close on this historic
mission and look back at its science discoveries," said Dr. Charles Elachi, who
was director of JPL in 2003. "Galileo taught us so much about Jupiter but there
is still much to be learned, and for that we look with promise to future
missions."

Keep Exploring


DISCOVER MORE TOPICS FROM NASA

James Webb Space Telescope

Perseverance Rover

Parker Solar Probe

Juno

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