(en) Mark Williamson, Spacecraft Technology : The Early Years, Institution of Engineering and Technology, , 400 p. (ISBN978-0-86341-553-1, lire en ligne), p. 4 october 1960 Courier 1B USA First active communications satellite (radio repeater).
(en) Daniel R. Glover (directeur de publication), Beyond The Ionosphere : Fifty Years of Satellite Communication, NASA, , 400 p. (ISBN978-0-470-54084-8, lire en ligne), Project Relay'