Aka known as Doppelgänger.
Set in the year 2069, the European Space Exploration Council has found another planet similar to earth on the other side of the sun. Two astronauts are sent to investigate the new planet however things go wrong with only one astronaut surviving, Colonel Glenn Ross. Ross is saved by a rescued and is returned to Earth however things start to appear off. Ross begins to question if he really has returned home.
Directed by Robert Parrish. Written by Story by Gerry and Sylvia Anderson (of Thunderbirds, Stingray, Space 1999 and Captain Scarlet and the Mysterons fame) This would be the first live action film by the Anderson duo.