Zenit (Russian: Зени́т, IPA: [zʲɪˈnʲit], Zenith) was a series of military photoreconnaissance satellites launched by the Soviet Union between 1961 and 1994. To conceal their nature, all flights were given the public Kosmos designation. Over a 33-year period, over five hundred Zenits were flown making it the most numerous type of satellite in the history of spaceflight.