Jet Propulsion Laboratory (U.S.). Spacecraft Data Systems Section.

Project Voyager, originally called "Mariner Jupiter/Saturn 1977," was approved by NASA and the U.S. Congress in June 1972. It was a dual spacecraft long-range mission that conducted a "Grand Tour" of the Outer Planets, visiting Jupiter, Saturn, Uranus, Neptune, as well as various planetary satellites, and continued beyond to the outer reaches of the Solar System. The project was managed by the Jet Propulsion Laboratory (JPL).

The name of the project was changed from "Mariner Jupiter/Saturn" to "Voyager" in early March 1977. A March 16, 1977 memo from Project Manager John Casani officially notified personnel that the project was to be known only as Voyager.

Three spacecraft were fabricated. VGR77-1 was the Proof-Test Model, and was not launched. VGR77-2 was designated as Flight 1 (Voyager 2) and VGR77-3 was designated as Flight 2 (Voyager 1). The proof-test model is on display in the von Karman Auditorium at JPL. The Smithsonian's Air and Space Museum has a non-flyable Engineering Test Model on display.

The Proof-Test Model was identified as having possible later use in two instances. The first use would be in case of a failure of one of the Voyager spacecraft. In that case, the remaining spacecraft would not be deflected to Uranus because of what was deemed the more important Titan encounter and occultation. The PTM would be launched from the Space Shuttle in the November 1980 Jupiter launch window, and use a gravity-assist trajectory with Jupiter to make a Uranus encounter. In reality, the first Shuttle launch occurred in April 1981, and the window would have been missed. The second possibility was a Multiple Asteroid Encounter, after launching the Voyager PTM from the Shuttle. The spacecraft would use a Mars swingby maneuver to possibly achieve a rendezvous with a single asteroid.

Voyager 2 was launched on August 20, 1977, and Voyager 1 was launched on September 5, 1977. Both Voyager spacecraft continue to send back scientific telemetry, two decades after leaving Earth, and will continue doing so until power runs out in both spacecraft, around 2017.

From the description of Voyager Computer Command Subsystem Document Collection, 1967-1977. (Jet Propulsion Laboratory Library and Archives). WorldCat record id: 733100114