Project Orbiter was a proposed United States spacecraft, an early competitor to Project Vanguard. It was jointly run by the United States Army and United States Navy. It was ultimately rejected by the Ad Hoc Committee on Special Capabilities, which selected Project Vanguard instead. Although the project was canceled on 3 August 1955, the basic design was used for the Juno I rocket which launched Explorer 1, the first satellite launched by the United States.