In 1973, the mission was named Mariner Jupiter-Saturn 1977 and was intended to go only as far as Jupiter and Saturn, as seen in the old mission logo. In March 1977 the mission name was changed to Voyager. In October 1978, a fact sheet mentioned the possibility of sending Voyager 2 to Uranus and Neptune. Voyager engineers had (unofficially) designed and built the spacecraft to be capable of navigating to Uranus and Neptune. Onboard computers were reprogrammed during the voyage, giving the spacecraft the ability to successfully return many more images and much more information than was expected

Photograph: Nasa