complete, Voyager 2 was cleared for an extended mission to Uranus and Neptune, fulfilling the goal of a Grand Tour as proposed in 1964. The planets originally to be visited in the Grand Tour Note: Pluto was still classified as a planet when the Grand Tour was proposed and at the time New Horizons was launched. See also Interplanetary Transport Network References External links The Outer Solar System: A Program for Exploration Report of a Study by the Space Science Board, June 1969 NASA programs Voyager program