page_title: Galileo (spacecraft)
section_title: Radiation-related anomalies
hierarchical_section_title: Galileo (spacecraft) / Mission challenges / Radiation-related anomalies
caption_attribution_description: English: Original caption: Jupiter is shown with several important components of its magnetosphere in this artist's representation. The planet's magnetic field is represented by soft purple lines that connect its north and south magnetic poles. Jupiter's brilliant auroras glow at the poles, while the bright areas to the left and right of the planet's equator represent the regions of most intense charged particle radiation - Jupiter's inner radiation belts. The Juno spacecraft will, broadly speaking, pass between the planet and the most intense areas of radiation. This view visualizes only the inner part of the magnetosphere. The complete Jovian magnetosphere is an enormous, tadpole-shaped structure that balloons out to dozens of Jupiter widths around the planet. In the direction away from the sun, the magnetotail extends as far as the orbit of Saturn.
context_page_description: Galileo was an American uncrewed spacecraft that studied the planet Jupiter and its moons, as well as several other Solar System bodies. Named after the Italian astronomer Galileo Galilei, it consisted of an orbiter and an entry probe. It was delivered into Earth orbit on October 18, 1989 by Space Shuttle Atlantis. Galileo arrived at Jupiter on December 7, 1995, after gravitational assist flybys of Venus and Earth, and became the first spacecraft to orbit Jupiter. It launched the first probe into Jupiter, directly measuring its atmosphere. Despite suffering major antenna problems, Galileo achieved the first asteroid flyby, of 951 Gaspra, and discovered the first asteroid moon, Dactyl, around 243 Ida. In 1994, Galileo observed Comet Shoemaker–Levy 9's collision with Jupiter.
  Jupiter's atmospheric composition and ammonia clouds were recorded, the clouds possibly created by outflows from the lower depths of the atmosphere. Io's volcanism and plasma interactions with Jupiter's atmosphere were also recorded.
context_section_description: Jupiter's uniquely harsh radiation environment caused over 20 anomalies over the course of Galileo's mission, in addition to the incidents expanded upon below. Despite having exceeded its radiation design limit by at least a factor of three, the spacecraft survived all these anomalies. Work-arounds were found eventually for all of these problems, and Galileo was never rendered entirely non-functional by Jupiter's radiation. The radiation limits for Galileo's computers were based on data returned from Pioneers 10 and 11, since much of the design work was underway before the two Voyagers arrived at Jupiter in 1979.
  A typical effect of the radiation was that several of the science instruments suffered increased noise while within about 700,000 km (430,000 mi) of Jupiter. The SSI camera began producing totally white images when the spacecraft was hit by the exceptional 'Bastille Day' coronal mass ejection in 2000, and did so again on subsequent close approaches to Jupiter. The quartz crystal used as the frequency reference for the radio suffered permanent frequency shifts with each Jupiter approach. A spin detector failed, and the spacecraft gyro output was biased by the radiation environment.
  The most severe effects of the radiation were current leakages somewhere in the spacecraft's power bus, most likely across brushes at a spin bearing connecting rotor and stator sections of the orbiter. These current leakages triggered a reset of the onboard computer and caused it to go into safe mode. The resets occurred when the spacecraft was either close to Jupiter or in the region of space magnetically downstream of the Jupiter. A change to the software was made in April 1999 that allowed the onboard computer to detect these resets and autonomously recover, so as to avoid safe mode.
caption: Jupiter's inner magnetosphere and radiation belts
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