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The Voyager 1 spacecraft is the virtual twin of the Voyager 2 spacecraft. This pair was launched into space in 1977, to travel to the outer planets. Voyager 1 only made stops at Jupiter and Saturn, while Voyager 2 went on to explore Uranus and Neptune as well.
Voyager 1 was launched on September 5th, 1977 aboard a Titan III rocket. It was originally supposed to be the 11th spacecraft in the Mariner program, but mission planners decided to call it Voyager 1, because of the unique destination its partner would make – being the first spacecraft to reach Uranus and Neptune.
Even though it was launched after Voyager 2, Voyager 1 was given a more direct trajectory, so it was the first to reach Jupiter and Saturn. It flew past Jupiter on March 5th, 1979, and helped make several important discoveries about the Jovian system. The Voyagers turned up volcanic activity on Jupiter’s moon Io, and the presence of large cracks in the surface of Europa, indicating the moon might have a large ocean under a shell of water ice.
Voyager 1 used the gravity of Jupiter to increase its velocity, and made a flyby of Saturn on November 12, 1980. It came within 124,000 km of the cloud tops of Saturn. NASA scientists wanted to gather detailed information about the atmosphere of Saturn’s moon Titan, so they put it into a trajectory that brought it close to the moon. Unfortunately, this trajectory stopped it from being able to reach the outer planets Uranus and Neptune.
Now Voyager 1 is speeding out of the plane of the ecliptic, with enough velocity to escape the Solar System. It’s now the most distant man-made object in the Solar System. It’s still able to send faint signals back to Earth, and is expected to continue transmitting until 2025, when it finally runs out of power.
We’ve recorded an episode of Astronomy Cast all about Interstellar Travel. Listen here, Episode 145: Interstellar Travel.