Voyager 1: Earth's Farthest Spacecraft
Voyager 1 is one of two probes launched in 1977 to explore the outer planets in our solar system. The spacecraft and its twin, Voyager 2, made some surprising discoveries and have kept on going. Voyager 1 is about to become the first manmade object to travel into interstellar space.
Voyager 1 was actually the second of the twin spacecraft to launch, but it was the first to race by Jupiter and Saturn. The images it sent back have been used in schoolbooks and newspaper outlets for a generation. Also on board was a special record, carrying voices and music from Earth out into the cosmos.
Voyager 2 launched on Aug. 20, 1977, and Voyager 1 launched about two weeks later, on Sept. 5. Since then, the spacecraft have been traveling along different flight paths and at different speeds. The Voyager missions were intended to take advantage of a special alignment of the outer planets that happens every 176 years. It would allow a spacecraft to slingshot from one planet to the next, assisted by the first planet's gravity. [Infographic: How the Voyager Space Probes Work]
The Grand Tour
NASA originally planned to send two spacecraft past Jupiter, Saturn and Pluto and two other probes past Jupiter, Uranus and Neptune. Budgetary reasons forced the agency to scale back its plans, but NASA still got a lot out of the two Voyagers it launched. Voyager 2 flew past Jupiter, Saturn, Uranus and Neptune, while Voyager 1 focused on Jupiter and Saturn.
Recognizing that the Voyagers would fly out of the solar system, NASA authorized the production of two records to be placed on board the spacecraft. Sounds ranging from whale calls to the music of Chuck Berry were placed on board, as well as spoken greetings in 55 languages.
The 12-inch, gold-plated copper disks also included pictorials showing how to operate it, and the position of the sun among nearby pulsars in case extraterrestrials were wondering where the spacecraft came from.
Eye on Jupiter
Voyager 1 almost didn't get off the ground at its launch, as its rocket came within 3.5 seconds of running out of fuel on Sept. 5, 1977.
But it made it safely, and raced past its twin after launch, leaving the asteroid belt before Voyager 2 did. Voyager 1's first pictures of Jupiter beamed back to Earth in April 1978, when it was 165 million miles away.
To NASA's surprise, in March 1979 Voyager 1 spotted a thin ring circling the planet. It found two new moons as well – Thebe and Metis. Additionally, Voyager 1 sent back detailed pictures of the Galilean moons (Io, Europa, Ganymede and Callisto) as well as Amalthea.
Like the Pioneers before it, Voyager's look at Jupiter's moons revealed them to be active worlds of their own. Voyager 1 came out with some intriguing findings, as well. Io's volcanoes and mottled yellow-brown-orange surface were intriguing finds, proving that, like planets, moons could have active interiors.
Additionally, Voyager 1 sent back ephemeral pictures of Europa showing a smooth surface broken up by lines, hinting at ice and maybe even an ocean underneath.
Voyager 1's closest approach to Jupiter was on March 5, 1979, when it came within 174,000 miles of the turbulent cloud tops. Then it was time to aim for Saturn.
Saturnian rings and moons
Scientists only had to wait about a year, until 1980, to get close-up pictures of Saturn. The ringed planet turned out to be full of surprises.
One of Voyager 1's targets was the F ring, a thin ring only discovered the year previously by Pioneer 11. Voyager's higher-resolution camera spotted two new moons, Prometheus and Pandora, whose orbits keep the debris in the F ring in a defined orbit. It also discovered Atlas, and a new ring (called the "G" ring), and took images of several other Saturnian moons.
One puzzle for astronomers was the moon Titan. Close-up pictures of the moon showed nothing but orange haze, leading to years of speculation about what it was like underneath. It wouldn't be until the mid-2000s that humanity would send the probe Huygens into the haze.
With Voyager 1's primary mission over, the focus shifted on tracking the small probe as it sped out of the solar system.
Earth's most distant emissary
In 1998, Voyager 1 sped past Pioneer 10's distance to become the farthest machine humans have ever sent from Earth. As of September 2012, the spacecraft is 122 astronomical units (11.3 billion miles or 18.2 billion kilometers) from the sun. It is speeding away at about 11 miles per second (17 kilometers per second), rising above the elliptic plane at an angle of 35 degrees.
NASA's commands take more than 33 hours to get to the spacecraft and back. But the data that is coming back is indicating Voyager is on the verge of a new breakthrough.
The spacecraft is at a spot in the solar system where particles streaming out from the sun begin to slow as interstellar gases push against the particles. Called the heliosheath, it's the last major boundary before interstellar space.
Scientists estimate it will reach that point in 2017. NASA officials say Voyager 1 will have enough power to keep communicating with Earth until 2020, possibly 2025. Destined to wander the Milky Way, in about 40,000 years, Voyager 1 will come within 1.6 light-years of a star in the Camelopardalis constellation, designated AC+79 3888.
— Elizabeth Howell, SPACE.com Contributor