Onizuka Air Force Station was a United States Air Force installation in Santa Clara County, California, just outside the city limits of Sunnyvale, at the intersection of U.S. Route 101 and State Route 237. Its main building, known locally as the Blue Cube, was large, pale blue, and windowless, with an array of parabolic dish antennas used for communication with remote tracking stations used to control military satellites. Onizuka AFS was operated by the 21st Space Operations Squadron, a geographically separated unit (GSU) of the 50th Space Wing.