'Planet 46' by Gerry and Sylvia Anderson

When a planet-shattering planatomic missile is detected on a course for Earth, Commander Zero and Lieutenant 90 of the World Space Patrol Headquarters contact Steve Zodiac and the crew of Fireball XL5. Having destroyed the missile, Steve traces its source to the mysterious Planet 46; arriving on the barren surface in Fireball Junior, Steve and Venus soon find a door hidden inside a cave, but before they can investigate, they are both rendered unconscious. When Steve comes to he finds himself a prisoner of a race of Subterrains, who tell him that they are about to launch another missile to destroy Earth – and that Venus is on board as a hostage…

Paul Maxwell (Colonel Steve Zodiac / Okinawa Station), Sylvia Anderson (Doctor Venus), David Graham (Professor Matt Matic / Lieutenant 90 / Subterrain 1/ Canaveral Station / Jodrell Bank), John Bluthal (Commander Wilbur Zero / Subterrain Leader / Subterrain 2 / Woomera Rocket Range), Gerry Anderson (Robert the Robot)

Directed by Gerry Anderson
Produced by Gerry Anderson
Associate Producer Reg Hill

TX (UK - ITV):
25th March 1963

Notes:
*Introducing Colonel Steve Zodiac, Venus, Professor Matt Matic, Commander Zero, Lieutenant 90 and Robert the Robot