CAPE CANAVERAL, Fl. (WHTM) — It launched second but reached its target first.

On September 5, 1977, the Voyager 1 spacecraft blasted off from Cape Canaveral, Florida, on its way to planet Jupiter and points beyond. Voyager 2 launched a few weeks earlier, on August 20, 1977.

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The Voyager mission took advantage of a rare geometric arrangement of Jupiter, Saturn, Uranus, and Neptune in the late 1970s and the 1980s, an alignment that only takes place about every 185 years. This allowed the crafts to make a four-planet “grand tour”, using the gravity of each planet to “slingshot” the probe to the next, without large, heavy propulsion systems. Because of the position of Jupiter in relation to Earth at the time of the launches, Voyager 1 would actually reach the giant planet four months before Voyager 2.

Voyager 1’s observations of Jupiter started on January 6, 1979, and it made its closest approach of 216,837 miles from the planet’s center on March 5. By the time the spacecraft finished its flyby on April 13, 1979, it had returned 19,000 images of the giant planet and many of its satellites, most notably the moons Io, Europa, Ganymede, and Callisto. In addition, Voyager took readings on Jupiter’s atmosphere and magnetic field.

Then it was on to Saturn. Observations of that planet started on August 22, 1980. On November 11 the flyby began, with Voyager passing the Moons Titan and Thetis before making its closest approach to Saturn, then passing Mimas, Enceladus, Rhea, and Hyperion.

And with that, Voyager 1’s exploration of the planets was over. In order to fly past Titan, the trajectory of the spacecraft had to take it below Saturn’s south pole and away from the other outer planets. It would fall to Voyager 2 to get our first close-up shots of Uranus and Neptune.

Both Voyagers continue their journeys into interstellar space, and both of them continue to send back information about the boundary between the inner solar system and the rest of the galaxy. How much longer they will be able to perform is open to question; the power levels in the craft are slowly dropping, and some instruments have already been shut down to conserve energy. The best estimates are they will cease to function sometime in the 2030s.

Not bad for a space mission that was only planned to last five years…