Voyager: Taking a picture of home
The pale blue dot caught in a thin strip of light on the left of the this image is Earth.
Voyager 1 captured this image from a distance of six billion kilometres (four billion miles). In it Earth is less than a pixel in size.
The image, taken in 1990, prompted astronomer Carl Sagan to say simply: "That's here. That's home. That's us."
In this clip from the BBC Four documentary, Voyager: to the final frontier, Dallas Campbell describes how the picture came about.