UFO was a 1970 British television science fiction series about an alien invasion of Earth. Created by Gerry and Sylvia Anderson with Reg Hill it was produced by the Andersons and Century 21 Productions. UFO was first broadcast in the UK and Canada in 1970, and in US over the next two years. A single season of 26 episodes (including the pilot) was filmed.
Following the syndication in the US and initial favourable ratings, a possible second series was scoped; this eventually became Space 1999.
The series’ premise was that in 1980 (!), Earth is being visited by aliens from a dying planet, who are abducting humans and harvesting their organs for their own bodies. The alien incursions may also be a prelude to a possible full-scale invasion. The series’ main cast of characters are the staff of a secret, high-technology international military agency called SHADO (an acronym for Supreme Headquarters, Alien Defence Organisation) established to defend Earth and humanity against the mysterious aliens and learn more about them, while at the same time keeping the threat of an alien invasion hidden from the public.