In the 1960s, astronomers noted that in just a few years, Jupiter, Saturn, Uranus, and Neptune would all come into alignment so that a spacecraft could use “gravity assist” to whirl from one planet to the next with minimal fuel. This alignment occurs only once every 175 years. Normally it would take a spacecraft 30 years to fly past all four planets, but the gravity assist reduced travel time to 12 years.    NASA began to prepare.

The result was two identical spacecraft dubbed Voyager 1 and Voyager 2.  Voyager 2 was launched first, on August 20, 1977; Voyager 1 followed about two weeks later on a different trajectory.    Voyager I reached Jupiter in March of 1979, while Voyager 2 arrived in July.

Voyager 1 flew by all of Jupiter’s moons and found two new ones. One remarkable discovery was that the moon called Io has extremely active volcanoes.

Next Voyager 1 examined Saturn’s moons, finding three new moons. Images of the moon Titan showed a thick atmosphere composed of 90% nitrogen. Titan might be the first body in the solar system, apart from Earth, where liquid might exist on the surface.

The Boot Shop Outlet

From there, Voyager 1 headed for the outer reaches of the solar system. In 1998, Voyager 1 became the most distant human-made object in existence when it overtook Pioneer 10. In August of 2012, it became the first spacecraft to cross the heliosphere, the boundary where the influences outside our solar system are stronger than those from our Sun.

Meanwhile, Voyager 2 made a study of Uranus and Neptune before also heading out towards interstellar regions. In November of 2019, it also crossed the heliosphere.

On Feb. 14, 1990, when the Voyager 1 was 3.7 billion miles (6 billion km) from Earth,    its cameras captured about 60 images of the Sun and planets, the first pictures of our solar system as seen from the outside. This became known as the “Solar System Family Portrait” even though Mercury and Mars can’t be seen. Mercury was too close to the Sun to be seen, and Mars was on the same side of the Sun as Voyager 1, so only its dark side faced the cameras. A single pixel of the 640,000 pixels contained a photo of Earth, which became known as “The Pale Blue Dot” made famous by Carl Sagan. These images were the last of 67,000 images taken by the two Voyager spacecraft. Their cameras were turned off to save power and memory for the interstellar mission.

Each Voyager carries a message, prepared by a team headed by Carl Sagan, in the form of a 12 inch (30-cm) gold-plated disc for extraterrestrials who might find the spacecraft. It has symbols to show the location of Earth relative to several pulsars.

The two craft have now been travelling through space for over 44 years, longer than any other spacecraft in history. Voyager I is currently about 14.5 billion miles away from Earth, making it the most distant artificial object away from the planet. VoIt travels at about 38,000 mph    (61,155 kph). Voyager 2 is traveling at 34,000 mph (55,150 kph) and is about 12 billion miles from Earth.

They continue to receive and transmit data. Signals from Voyager 1 take over 20 hours to reach Earth.

Both spacecraft will continue operating until around 2025, after which there may not be enough power to support them. They will continue flying through space forever at the rate of about a million miles per day.