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The Spacecraft
Spacecraft Basics

Sending humans into deep space isn't practical -- yet. But we can send a robot -- a spacecraft that observes, listens, and processes information and commands. A spacecraft listens to our commands through its antenna and radio receiver, and sends images and science data back to Earth.

An artist's depiction of the descent of the Probe through Jupiter's atmosphere.
An artist's depiction of the descent of the Probe through Jupiter's atmosphere.

The spacecraft's brain is a computer, which controls the scientific instruments. On its journey, the spacecraft needs fuel for its engines to burn -- a large engine is used for big changes such as entering orbit; and small thrusters fine-tune the direction. The probe did not need fuel --- it was released and captured by gravity as it plunged into Jupiter's atmosphere.

Planets and moons emit or reflect radiation. We use Galileo's scientific instruments to see different kinds of radiation --- and even to look through clouds or beneath the solid surface of a moon.

A camera sees the way we do, at wavelengths of light we've called "visible." But we are surrounded by other wavelengths of radiated energy that we cannot see. We talk on cellular phones -- they use radio waves -- cook in ovens that use microwaves, and change TV channels with remote-control units that use infrared. We avoid ultraviolet by wearing dark glasses and sun block.

There are 10 scientific instruments aboard the spacecraft. Some of the instruments are mounted on long arms so they don't pick up unwanted signals from the spacecraft. The probe used six instruments plus its radio to investigate Jupiter's atmosphere. In addition, we use Galileo's radio system for experiments.

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