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| EXPLORING THE JUPITER SYSTEM | |||||
| Jupiter | Moons | Oceans | Volcanos | Rings | Radio |
| JIMO | Galileo | Cassini | Pioneer | Voyager | Resources |
Galileo's long journey ended in 2003:
The Eight-Year Tour Closed Spectacularly
It was launched from Earth in 1989. It arrived at Jupiter in 1995. Then, after touring the Jovian system for eight years, the Galileo spacecraft was intentionally flown into the giant gas planet on September 21, 2003, bringing to an end a mission that had spanned some 30 years from concept through mission execution.
Despite an array of difficulties, the spacecraft and the team behind it overcame numerous obstacles to give us a close-up look at Jupiter and its inner moons that was far more detailed than the glimpses afforded us by the earlier Voyager and Pioneer flybys.SOME OF GALILEO'S ACHIEVEMENTS:
New satellites of Jupiter
Close-ups of Io's volcanic plumes
Massive ice rafts on Europa
Possible salty ocean under Europa's ice
Ganymede's magnetic field
Magnetic field of Callisto
Possible ocean on Callisto
Space rocks near Amalthea
Geologic diversity of four largest moons
First close-up of an asteroid, Gaspra
Asteroids have moons, Ida and Dactyl
Detecting Jupiter's massive thunderstorms
Close up of Earth rotation during flybys
Look-back image of Earth and the Moon
and enough data for decades' more work.
NASA's flight team for the Jupiter-orbiting Galileo spacecraft ceased operations at the end of February 2003 after a final playback of scientific data from the interplanetary probe's tape recorder.
The team transmitted commands to the spacecraft's computer so it could manage the short remaining life of the robotic explorer. Galileo was ordered to coast for seven months, then transmit a final few hours of science measurements in real time, before a September 21, 2003, plunge into Jupiter's atmosphere.
Wealth of data. In the years since astronauts deployed Galileo from the cargo bay of shuttle Atlantis in 1989, the spacecraft produced a string of discoveries about asteroids, a fragmented comet, Jupiter's atmosphere, Jupiter's magnetic environment, and the geologic diversity of Jupiter's four largest moons.
The probe's prime mission had ended six years earlier, after two years of orbiting Jupiter. NASA extended the mission three times to take advantage of Galileo's long life and unique capabilities for accomplishing valuable science.
Protecting Europa. By 2003, the spacecraft's propellant was nearly depleted. Without fuel, Galileo could neither point its antenna toward Earth nor adjust its trajectory. That made controlling the spacecraft impossible. So, the flight team at NASA's Jet Propulsion Laboratory (JPL) ordered Galileo to dive into the crushing pressure of Jupiter's atmosphere.
That removed the possibility of an impact on the moon Europa. Galileo's discovery of a possible subsurface ocean on Europa had raised thoughts of the possibility of life there and concern about protecting that moon.
Near the big planet. Galileo passed closer to Jupiter on November 5, 2002, than it had ever before. It flew near the inner moon Amalthea and through part of Jupiter's gossamer ring as it began its 35th and last orbit around the giant planet.
The elongated farewell loop also took Galileo farther from Jupiter than it had been since before it entered orbit around the big gas planet in 1995. It flew out 16 million miles by April 14 when it headed back in for the impact with Jupiter.
NASA took its time in transmitting to Earth the science data recorded on the tape recorder during the November 2002 flyby while the flight team repaired radiation damage to the tape recorder in December. The playback was received by NASA's Deep Space Network antenna at Goldstone, California.
Whence Galileo?
Galileo was launched from Cape Canaveral in 1989 and has been exploring Jupiter and its moons since 1995.
Despite the fact that the Galileo interplanetary spacecraft's main antenna never opened properly after its 1989 launch from Earth, once it arrived at the planet Jupiter in 1995 the probe managed to relay thousands of stunning images through its backup antenna.
From those photos, planetary scientists learned a great deal about violent thunderstorms on Jupiter, huge volcanic eruptions on its moon Io, and much more.
Mission extensions. Two years after the probe started exploring Jupiter and its moons, NASA in December 1997 extended the mission of the Galileo interplanetary spacecraft for 24 months. After that time period came and went, NASA continued to work with the durable robot explorer.
Galileo's mission was extended a total of three times to take advantage of the spacecraft's extraordinary durability. Galileo was telling scientists about more than just Europa and Io during its thrice-extended mission.
Looping through the Jovian system. Galileo was orbiting Jupiter in elongated loops after its arrival there in 1995. Four of its close flybys of Jupiter's moons were at Io.
After eight Europa encounters, mission controllers flew the spacecraft past Jupiter's moon Callisto four times.
That path nudged the probe through the Io torus, a giant doughnut-shaped collection of charged particles that surrounds Jupiter's moon Io. Researchers hoped to learn as much about the torus as they could, including what created it and what effect it has on Jupiter's many other moons.
Finally, Galileo flew near the small inner moon Amalthea once before its mission-ending plunge into the crushing pressure of Jupiter's atmosphere in 2003.
Pleasing results. Scientists were extremely pleased by what the probe discovered over the eight years at Jupiter. Highlights of the robot's voyage include:DSN. NASA's Deep Space Network, wtih three huge antenna sites on Earth, provided the communication link for interplanetary spacecraft. How DSN works »
- Discovering spectacular thunderstorms on Jupiter with lightning bolts 10 to 100 times more powerful than those on Earth.
- Detecting a magnetic field, stronger than the planet Mercury's, around Jupiter's largest moon, Ganymede.
- Learning that Europa, Io and Ganymede all have metallic cores. Oddly, Callisto does not.
- Observing massive volcanic eruptions on Io, including one that covered an area the size of Arizona in four months.
Once many. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, managed Galileo for NASA's Office of Space Science, Washington, D.C.
The Galileo flight team had numbered about 300 people at its peak during the prime mission. Team members now work on other NASA deep space exploration missions managed by JPL.
Source: NASA Jet Propulsion Laboratory
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