Voyager Mission

The Voyager Mission is a series of unmanned space missions conducted by the U.S.A. The mission consists of a pair of unmanned scientific probes, Voyager 1 and Voyager 2.

Once every 176 years the giant planets Jupiter, Saturn, Uranus, and Neptune align in such a pattern that a spacecraft launched from Earth to Jupiter at just the right time can visit the other three planets on the same mission using a technique called gravity assist. NASA space scientists named this multiple giant planet encounter mission the “Grand Tour” and took advantage of a unique celestial alignment opportunity in 1977 by launching two sophisticated spacecraft called Voyager 1 and 2. Each Voyager spacecraft had a mass of 825 kg and carried a complement of scientific instruments to investigate the outer planets and their many moons and intriguing ring systems. These instruments, provided electric power by a long-lived nuclear system called a radioisotope thermoelectric generator (RTG), recorded spectacular close-up images of the giant outer planets and their interesting moon systems, explored complex ring systems, and measured properties of the interplanetary medium.

Taking advantage of the 1977 Grand Tour launch window, the Voyager 2 spacecraft lifted off from Cape Canaveral, Florida, on August 20, 1977, onboard a Titan-Centaur rocket. (NASA called the first Voyager spacecraft launched Voyager 2 because the second Voyager spacecraft to be launched eventually would overtake it and become Voyager 1.) Voyager 1 was launched on September 5, 1977. This spacecraft followed the

same trajectory as its Voyager 2 twin and overtook its sister ship just after entering the asteroid belt in mid-December 1977.

Voyager 1 made its closest approach to the Gaseous giant, Jupiter on March 5, 1979, and then used Jupiter’s gravity to swing itself to Saturn. On November 12, 1980, Voyager 1 successfully encountered the Saturnian system and then was flung out of the ecliptic plane on an interstellar trajectory. The Voyager 2 spacecraft successfully encountered the Jovian system on July 9, 1979 (closest approach), and then used the gravity assist technique to follow Voyager 1 to Saturn. On August 25, 1981, Voyager 2 encountered Saturn and then went on to successfully encounter both Uranus (January 24, 1986) and Neptune (August 25, 1989). Space scientists consider the end of Voyager 2’s encounter with the Neptunian system as the end of a truly extraordinary epoch in planetary exploration. In the first 12 years after they were launched from Cape Canaveral, these incredible spacecraft contributed more to our understanding of the giant outer planets of our solar system than was accomplished in more than three millennia of Earth-based observations. Following its encounter with the Neptunian system, Voyager 2 also was placed on an interstellar trajectory and, like its Voyager 1 twin, now continues to travel away from the Sun.

Questions to Ponder

• What were the key accomplishments of the Voyager Mission?
• Why the first Voyager to be launched was called Voyager-2?