TERRIERS, also known as Explorer 76 and STEDI-2, is a student-built satellite intended to study the Earth's ionosphere. Although launched successfully by a Pegasus-XL rocket in 1999-May-18, its batteries were unable to recharge when it cannot track the Sun and therefore lost contact just two days later, resulting in a mission failure. It still remains in orbit as a derelict object as of 2023
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