This is one of the two full-size mock-up solar panels that were used as part of integration tests in building the International Ultraviolet Explorer. Built at Goddard Space Flight Center to test integration and fit of the equipment to be carried on the mission. The IUE satellite with its solar panels was transferred in March 1983 from NASA's Goddard Spaceflight Center.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.