Voyager 2

14:29:44 UTC, Complex 41

NASA launched Voyager 2 from Launch Complex 41 at Cape Canaveral Air Force Station on 20 August 1977 aboard a Titan IIIE-Centaur, at 10:29 a.m. local time. It went on the opening day of the launch window.

A faulty launch-vehicle valve indication held liftoff about five minutes. The Titan-Centaur then performed nearly flawlessly and injected the 721.9-kilogram spacecraft onto an accurate Jupiter-bound trajectory.

Numbered for arrival, not departure

This spacecraft launched first and is called Voyager 2. Its slower trajectory meant it would reach Jupiter and Saturn after Voyager 1, which left on 5 September.

It carried three radioisotope thermoelectric generators and, in NASA's count, 11 scientific investigations including radio science. A failed particle instrument had been replaced during final preparation.

What was actually funded

The prime mission at launch was detailed exploration of Jupiter and Saturn. Uranus and Neptune were preserved options in the trajectory geometry, not authorized objectives.

NASA authorized the Uranus continuation only after Voyager 2 completed its Saturn encounter with its instruments working.

The 1977 window had made that geometry possible in the first place: successive gravity assists could shorten a potential Neptune journey from roughly 30 years to 12.