Explorer XI, launched on April 27, 1961, by a Juno II rocket, was NASA's first fully dedicated gamma-ray satellite. The satellite was built under a contract overseen by the Marshall Space Flight Center who also supplied the supporting electronic equipment. It carried a gamma-ray telescope built at MIT by W. Kraushaar and G. Clark, and was designed to detect gamma radiation above 50 MeV. During a period of just over 23 days in orbit it detected 22 true gamma-ray events as well as 22,000 events due to charged cosmic rays. The artifact in the collection is one of two backup-up satellites.
NASA transferred this to the Museum in 1975.
Transferred from the National Aeronautics and Space Administration