What could be more ambitious than a lunar landing? How about a tour of the outer solar system? Realizing that a once-every-176-years alignment of the planets would occur in the late 1970s, NASA planners conceived a “grand tour” of the four planets farthest from the sun (minus Pluto), settling on a two-spacecraft scheme after determining it would be more cost effective than building one spacecraft to observe all the worlds. Voyager 2 launched from the Kennedy Space Center on August 20, 1977; Voyager 1, 16 days later. Both spacecraft carried TV cameras, ultraviolet and infrared spectrometers, and photopolarimeters to determine the physical properties of the atmospheres of their target planets. Voyager 1 observed Jupiter, Saturn, and Saturn’s moon Titan before becoming the first human-made object to reach interstellar space.
Voyager 2 gave scientists second looks at Jupiter and Saturn before proceeding to capture the first photos of Uranus and Neptune. Among its most surprising discoveries was the revelation that Jupiter’s mysterious red spot was in fact a massive storm. Scientists were stunned by the detection of volcanic activity, as the twin probes documented nine eruptions on Jupiter’s moon Io.
The Voyager Development Test Model entered the National Air and Space Museum collection in 1977. Both spacecraft are still transmitting.