On September 5, 1977, a Titan IIIE-Centaur rocket carried Voyager 1 away from Cape Canaveral. Its twin, Voyager 2, had left sixteen days earlier, but Voyager 1 would take a faster trajectory toward Jupiter and Saturn. The launch began one of the longest-running experiments in human exploration: an instrumented spacecraft reading distant worlds, then the space between stars.
The name can mislead. Voyager 1 did not launch first, and it was not aimed at every outer planet. Its particular path and Saturn’s moon Titan shaped what it could see and where it went afterward.
A narrow planetary opening
The mission planners used a favorable geometry among outer planets and gravity assists to extend the reach of relatively small spacecraft. A flyby of Jupiter could bend and accelerate the trajectory toward Saturn. Voyager 1 was sent on the route that would take it close to Titan, a moon whose thick atmosphere had made it an especially compelling target.
NASA’s launch record dates lift-off to September 5, 1977, at 8:56 a.m. local time. The mission carried cameras, spectrometers, magnetometers and other instruments to examine atmospheres, rings, moons and magnetic environments. These were coordinated measurements, not simply a sequence of photographs.
Jupiter and Saturn
Voyager 1 reached Jupiter in March 1979. Its observations revealed active volcanoes on Io, a remarkable discovery that showed a moon could be geologically alive. The spacecraft mapped turbulent cloud systems and investigated Jupiter’s magnetosphere and its moons. In November 1980 it passed Saturn, studying rings and the planet’s atmosphere while making the planned close approach to Titan.
The Titan encounter changed Voyager 1’s trajectory. It went above the plane in which the major planets orbit, so a Uranus or Neptune flyby was no longer possible for this spacecraft. Voyager 2, following a different route, continued to those planets. The mission design involved a real trade-off between a close look at Titan and the option for further planetary encounters.
Beyond the planetary tour
Once the cameras’ main targets were behind it, Voyager 1 continued measuring particles, plasma waves and magnetic fields. The Sun’s wind carves a vast bubble—the heliosphere—into interstellar material. NASA identifies an August 2012 crossing into interstellar space based on multiple lines of instrument evidence. That does not mean Voyager left the gravitational reach of the Solar System or crossed the distant Oort Cloud.
A spacecraft launched for encounters measured in years became a probe of a boundary that could not be visited any other way. Its golden record also carried sounds and images selected to represent Earth, although the scientific instruments remain the basis for what we know of its journey.
See Science & Space for more missions, or return to the September 5 edition.
Sources and method
Launch date and time are checked against NASA’s launch image record; encounters and mission status against NASA’s Voyager 1 mission profile and the JPL mission account. The accompanying spacecraft image is contextual, not an image of the launch.
