NASA launched the first of two identical probes designed to take advantage of planetary alignments in the outer portion of the solar system. Voyager 2 left the friendly confines of Earth Aug. 20, 1977. Its 35-year journey, along with Voyager 1, gave scientists unprecedented views of other planets. Popular Mechanics explains the longer the spacecraft journeys away from Earth, the more difficult its mission becomes. Current scientific thought believes the craft may be monitored for another 10 years.
Aug. 20, 1977: Launched
Voyager 2 launched from Cape Canaveral, Fla., in the late summer of 1977. Its twin went into space Sept. 5. Voyager 2's trajectory wasn't as fast as Voyager 1's, yet the probe took an incredible look at the outer planets. The craft's main scientific instruments were 1.78 meters (5.8 feet) across with an antenna 3.66 meters (12 feet) in diameter.
Dec. 15, 1977: In the asteroid belt
Voyager 2 was in the asteroid belt in December when Voyager 1 caught up to it. Despite being launched three weeks apart, Voyager 1 made it to Jupiter first after overtaking the initial launch in mid-December.
April 1979: Mission to Jupiter
Voyager 2 started photographing Jupiter as its primary mission around 20 months after it was launched. From April to August 1979, Voyager 2 snapped almost 18,000 pictures of the largest planet in the solar system.
July 9, 1979: Closest approach to Jupiter
The probe made its closest approach to Jupiter nearly two years into the mission. After this encounter, it would take another 10 years to meet the farthest planet reachable by Voyager 2.
Aug. 5, 1981: Saturn fly-by
Voyager 2 made its closest approach to Saturn more than two years after going to Jupiter. At this point, the twin spacecraft diverged. Voyager 2 explored Uranus and Neptune while Voyager 1's mission was finished.
Jan. 24, 1986: Uranus
The only man-made object to explore the planet Uranus made its closest encounter in January 1986. Adaptations had to be made for the extreme distances the craft traveled. Lower light levels and decreased communications capabilities meant the probe had to operate more efficiently. Voyager 2 captured around 8,000 images of Uranus. Previously unknown discoveries included 10 new moons, two new rings and a magnetic field stronger than Saturn.
Aug. 25, 1989: Neptune
Voyager 2 made its closest pass at Neptune more than three years after seeing Uranus. The craft discovered five new moons, four rings and a huge storm called the "Great Dark Spot." Triton, the largest moon of Neptune was touted as the coldest known planetary body with a volcano of icy nitrogen.
September 2007: Crossed into the heliosheath
A milestone was reached 30 years after launch when solar wind speeds around the craft were measured to be slower than the speed of sound. At this point, the influence of the sun became less of a factor and Voyager 2 came closer to interstellar space.
March 2012: Five teams still active
As of March, there are five scientific teams participating in the Voyager 2 mission. Although well past its primary goal, teams are assessing magnetic field strength, charged particles, cosmic rays, plasma and plasma waves in deep space. Voyager 2 is roughly 98.6 astronomical units (AUs) from Earth. That translates into 14.7 billion kilometers (9.134 billion miles). Fans of the deep space probe can follow daily updates on Voyager 2's Twitter presence. Thus far, it has transmitted more than 8,700 tweets.
William Browning is a research librarian.