These are non-operational imitations of the solar panels that provided electrical power to the Uhuru spacecraft, the first Small Astronomy Satellite, or SAS - 1. Uhuru was devoted exclusively to the study of non-solar x-rays in space was launched by an international team from a platform off the coast of Kenya on December 7, 1970. Transferred from NASA in 1976.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.