Production of the series began in 1973, but the first episode wasn't broadcast until 1975.
Originally conceived as a new season of "UFO" (1970). The plot would have had the aliens from that series trying to destroy SHADO's moonbase by knocking the moon out of orbit.
Season two of the series differs noticeably from the first, due to a large number of cast changes as well as set redecoration, redesigned uniforms, and a move towards more action-oriented stories.
At the time, this was the most expensive series ever produced for British TV or for syndication.
Maya's makeup undergoes a subtle change as Season 2 goes on. Initially, she has brown ears as large "sideburns." In later episodes, her ears are normal colored, and her sideburns are thinned out.
In Britain, the second season was broadcast over the course of two years, with part shown in the autumn/winter of 1976-77, then a season break until August 1977, with new episodes running into the fall. The final two episodes were broadcast months apart in 1978.
A third season of 13 episodes was planned, with production set to start in the autumn of 1977, however low sales of the series in America forced a last-minute cancellation.
Barry Morse decided to leave the series after Season 1 had ended. An explanation of his absence was written into the first episode of Season 2, "The Metamorph", but never made it to the finished episode. Dialog was to indicate he had been in a faulty spacesuit.
'Catherine Schell' made a guest appearance in the episode _{Guardian of Piri}_ before taking on the role of Maya in the second season.
All of the Italian male guest stars of the first season were dubbed by Robert Rietty.
Though only seen briefly in a flashback in the episode "Devil's Planet", Dr. Helena Russell (Barbara Bain) is the only character to appear in all 48 episodes of the show.
Often when a ship particularly one of the Eagles used by the members of moonbase alpha lose control or are making a treacherous maneuver, the face of the pilot and passenger start to wobble and flap. This is done by blasting air at the faces of the actors.
Robert Culp and Catherine Ross were Sylvia Anderson's choices for the leads.
Moonbase Alpha's final fate was revealed in a short film made for the 1999 convention, where original cast member Zienia Merton described the final abandonment of Moonbase Alpha for their new home on an unnamed planet, and is considered canon for the series.