Astronaut
Astronaut was a term used for early Earth space travellers. Individuals that were part of the British and American space programmes were called "astronauts". (DW: The Ambassadors of Death) Wilfred Mott claimed to have always wanted to be an astronaut, when he noted he had accidentally become one after being transported to the Vinvocci spaceship. (DW: The End of Time)
The "Impossible Astronaut"
The Silence planted a post-hypnotic suggestion for the American government to aim towards landing on the moon, solely for their need of a space suit. Upon stealing the parts from the space program, the upgraded a space suit with 20 different kinds of alien technoloy and placed Melody Pond inside it in 1969. Footage of astronaut Neil Armstrong's first step on the Moon was later used to defeat the Silence by splicing in footage of Silent saying "you should kill us all on sight". (DW: The Impossible Astronaut, Day of the Moon)
In her adulthood, Melody Pond, now known as River Song, was kidnapped once again by Madame Kovarian and the Silence to be forced to act as their patsy for murdering the Eleventh Doctor; she was put in another upgraded space suit. River was submerged in Lake Silencio, Utah, to wait for the Doctor whom she would kill at 5:02pm on 22 April 2011. Kovarian explained that "an impossible astronaut will rise from the deep and strike the Time Lord dead". (DW: Closing Time) However, the Doctor cheated death as he had the Teselecta take his place with him safely in its left eye along with the TARDIS. (DW: The Wedding of River Song) This charade is what lead everyone who learned of this event to think that the Doctor truly died, to keep the Silence from planning more chances to kill him
