“The Voyager program is an American scientific program that employs two robotic probes, Voyager 1 and Voyager 2, to study the outer Solar System. The probes were launched in 1977 to take advantage of a favorable alignment of Jupiter, Saturn, Uranus and Neptune. Although their original mission was to study only the planetary systems of Jupiter and Saturn, Voyager 2 continued on to Uranus and Neptune. The Voyagers now explore the outer boundary of the heliosphere in interstellar space; their mission has been extended three times and they continue to transmit useful scientific data. Neither Uranus nor Neptune has been visited by a probe other than Voyager 2.
On 25 August 2012, data from Voyager 1 indicated that it had become the first human-made object to enter interstellar space, traveling “further than anyone, or anything, in history”. As of 2013, Voyager 1 was moving with a velocity of 17 kilometers per second (11 mi/s) relative to the Sun.
Data and photographs collected by the Voyagers’ cameras, magnetometers and other instruments, revealed unknown details about each of the four giant planets and their moons. Close-up images from the spacecraft charted Jupiter’s complex cloud forms, winds and ...