Hampered by a communications antenna that never unfurled, the Galileo spacecraft became known as the plucky mission that overcame major obstacles. During more than 6 years of touring Jupiter and its four largest moons, the spacecraft managed to radio some 5 gigabytes of data to Earth, including more than 14,000 images. It has recorded towering volcanic plumes above Jupiter’s moon Io, gathered evidence that Europa might have an ocean beneath its icy carapace, and investigated the intense radiation environment near Jupiter.
Now, 13 years after its launch, the mission is winding down. During several flybys of Io, Galileo has received nearly 4 times the radiation dose it was designed to endure. On Jan. 17, a half-hour before the craft took its last swing past Io’s rarely glimpsed Jupiter-facing side, radiation damage caused Galileo to temporarily shut down. As a result, the craft never took close-up images as it passed just 102 kilometers from the moon’s surface.
In addition, the spacecraft has nearly run out of the hydrazine fuel needed to keep its only working antenna pointed toward Earth.
NASA decided last month to permanently shut down the craft’s two cameras, a visible-light detector, and a near-infrared mapping spectrometer. Another light-sensing device, a combination photopolarimeter and radiometer, has also been switched off.
Those moves will save NASA some $750 thousand, but they mean that when Galileo flies within 500 km of the inner Jovian moon Amalthea in November, it will be blind. Only a magnetic field sensor and a high-energy-particle detector will continue to operate. Scientists also hope to generate a detailed gravity map of Amalthea by studying small changes in the speed of the craft as it passes by.
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The Galileo team will officially disband next January, 9 months before the craft is set to plow into Jupiter. The huge planet was chosen for Galileo’s demise to ensure the craft would not crash into Europa and destroy any life that might exist below its surface.