The Wide-Field Infrared Explorer (WIRE) mission was designed to study the formation and evolution of galaxies by surveying the sky in the infrared wavelength band for four months. Its instrument was a 30-centimeter telescope feeding Silicon/Arsenic detectors, all encased in a cryostat filled with solid hydrogen. The telescope aperture was sealed on the ground and during launch by a cryostat closeout cover. The spacecraft was a three-axis stabilized Small Explorer (SMEX) bus combining standard SMEX architecture and components with new technologies, such as a composite structure and Gallium Arsenide solar arrays.