Mere weeks before the launch of the first Voyager spacecraft, NASA swaps Voyager 2 and Voyager 1. Repeated failures have plagued the attitude and articulation control and flight data subsystems in the spacecraft designated VGR77-2, leaving mission planners with doubt about its flightworthiness. VGR77-3 thus becomes Voyager 2, and VGR77-2 undergoes repairs to correct its problems before being designated Voyager 1. The two vehicles’ thermonuclear power sources are swapped, as whichever one is Voyager 2 will require a longer-lasting power source to power all instruments for possible visits to Uranus and Neptune following the 1981 Saturn encounter. (A third vehicle, VGR77-1, is an engineering test spare which eventually goes on display at the JPL campus in Pasadena.)
