The Van Allen probe's mission was meant to last two years, but ended up going for nearly seven.
According to the space agency's tracking, the rock is hurtling through space at more than 21,500 miles per hour.
Space.com on MSN
NASA project leader blames next-generation X-ray telescope cancellation on agency mismanagement
NASA is canceling the AXIS X-ray space telescope mission concept, saying it failed to meet key requirements. But the project leader thinks there's another reason.
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