GALILEO
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Environmental testing
Final assembly
Deployment
The journey begins
Into the clouds
At Jupiter
Technical information
 GALILEO
See the 2 year extended Galileo Europa Mission

Environmental Testing




Before its shuttle launch, the Galileo orbiter was tested in a space simulation chamber. The test chamber was designed to subject the craft to approximately the same environmental conditions that it will encounter in space.








Final Assembly



The Galileo spacecraft is being prepared for mating to its Inertial Upper tage, which will propel it on its six-year journey from the Earth to Jupiter. The black and gold fabric that covers the spacecraft is designed to protect it from both the heat of the sun and the chill of interplanetary space. The conical structure near the bottom of the spacecraft conceals the atmospheric probe, which entered the Jovian atmosphere in 1995.






Deployment


The Galileo spacecraft and its Inertial Upper Stage booster rocket were deployed from the space shuttle Atlantis October 18, 1989. Shortly thereafter, the booster rocket fired and separated, sending Galileo on its six-year journey to the planet Jupiter.




The Journey Begins



This artist's concept depicts the Inertial Upper Stage booster rocket firing shortly after its deployment from the shuttle Atlantis. Galileo's complex trajectory to Jupiter flung it by Venus once and then back to Earth for two fly-bys. Each pass added kinetic energy to the spacecraft, increasing its velocity so that it could reach Jupiter with a relatively small amount of fuel.





Into the Clouds


In December 1995, Galileo's atmospheric probe plunged into the clouds of Jupiter, giving scientists their first glimpse into the planet's atmosphere. The Galileo orbiter relayed probe information back to Earth. It then started studying and maping Jupiter's major satellites from as near as a few hundred kilometers and monitoring Jupiter's atmosphere and magnetosphere






Galileo at Jupiter


The Galileo spacecraft as it passed by Io, just prior to Jupiter orbit insertion, is shown in this artist's rendering. The orbiter useed the combination of a gravity assist from Io and a rocket thrust to enter orbit. Between these events, the orbiter relayed to Earth information received from the atmospheric probe descending through Jupiter's clouds. Note that the high gain antenna (dish-shaped antenna) were not deployed as shown here, due to malfunction of the deployment mechanism.


TECHNICAL INFORMATION

There are four cameras onboard the Galileo spacecraft. The Solid-State Imaging instrument (SSI), which takes photos in visible light, a photopolarimeter-radiometer will measure the polarization of light scattered from Jupiter's clouds and the satellites' surfaces, by a process like using polarized sunglasses to cut down on glare. In addition, its infrared channels will sound the atmosphere and measure satellite temperatures. The near-infrared mapping spectrometer will map the satellites, looking for different minerals across their surfaces. It will also study cloud structure and gas composition in the jovian atmosphere. An ultraviolet spectrometer and extreme ultraviolet spectrometer will investigate volatile excape and surface composition of the Galilean satellites, the Io plasma torus, small and large scale properties of the Jupiter clouds, and the composition, structure, and evolution of Jupiter's upper atmosphere.

All four cameras are mounted on a scan platform, located near the bottom of the orbiter. This section of the spacecraft can be "despun," or kept from spinning with the rest of the orbiter--otherwise, all the images would be blurry.

Why does Galileo spin?
 Unlike previous planetary spacecraft, Galileo features a "dual spin" design: part of the orbiter rotates constantly at three revolutions per minute, and part of the spacecraft remains fixed in inertial space. This means that the orbiter can easily accomodate magnetospheric experiments (which need to take measurements while rapidly sweeping about) while also providing stability and a fixed orientation for cameras and other sensors. The spin rate can be increased to 10 revolutions per minute for additional stability during major propulsive maneuvers.

After a six-year journey from Earth, Galileo arrived at Jupiter on December 7, 1995. In moves designed to lock the spacecraft in orbit around the gaseous giant planet, Galileo swung by the moon Io, then fired its main engine, and in between, collected the precious data from the atmospheric probe it dropped five months earlier. For two years and 11 orbits during its Prime Mission, Galileo has revealed an array of fascinating details about Jupiter and its moons. Ganymede is the first moon in the solar system known to have its own magnetic field. Callisto's covering of craters is layered with a fine dust. Io's surface has been changing since the Voyagers saw it in 1979. And scientists have now seen evidence that an ocean has existed in recent geologic history under Europa's crust of ice.

Originally scheduled to end its exploration on December 7, 1997, NASA and Congress have approved the extension of Galileo' studies through the last day of 1999, in three phases each with tightly focused objectives: the Europa Campaign ("Ice"), Perijove Reduction/Jupiter Water Study/Io Torus Passages ("Water"), and the Io Campaign ("Fire").
After this extended mission is completed, Galileo will no longer return science data, but will keep slicing through the intense radiation near Io's orbit, and regularly report on its health until it is silenced by radiation damage.

Module Mass
(Kg) 		Usable propellant mass Thrusters Instrument payload Payload mass Electric
power
Orbiter 2,223Kg 925 Kg 12 thrusters (10N)
400N engine 		10 instruments 118 Kg RTGs, 570-470 W
Probe 339 Kg -- -- 6 instruments 30 Kg battery
730w-h


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