As early as 15 December 1958 the NASA Program Study Committee foresaw use of the Juno V (later Saturn I) launch vehicle for ambitious deep-space missions. One of these, penciled in for accomplishment by JPL by October 1963, were two Jupiter and two Mercury controlled flybys by a 910to 1360kg spacecraft. This rather ambitious goal was never funded, and JPL was occupied with an early string of Ranger and Mariner failures. In May 1962, the JPL's Planetary Program Office commissioned a new study of advanced missions and spacecraft. In addition to Voyager with flights to Venus and Mars, a second kind of advanced spacecraft was examined - Navigator, which would explore the sun, comets, Mercury, and Jupiter and require still more powerful launch vehicles than the Saturn IB-Centaur. JPL thereafter became involved in Voyager development, and no more was heard of Navigator. The goals instead would be fulfilled by Mariner, Pioneer, Voyager, and Galileo spacecraft that would fly a series of successful missions in the last quarter of the 20th century.
Gross mass: 2,500 kg (5,500 lb).