Happy Carl Sagan Day — The Voyagers and the Pale Blue Dot
It was the year 1977 and just eight years after human beings had landed on the moon that another epic journey began. Voyager 1 and Voyager 2 are robotic probes launched in 1977, whose primary mission was to study the planetary systems of Jupiter and Saturn. After making game changing discoveries, such as the active volcanoes of Io and liquid water oceans on Europa (Jupiter’s moons), imaging the complexities of Saturn’s rings, as well as studying the atmosphere of Titan, the mission was extended — three times.
Voyager 2 went on to explore Uranus and Neptune and is still the only spacecraft to have visited the outer planets. On its 41st year, it is now studying the outer reaches of the Solar System, currently travelling through the heliosheath. Voyager 1 began its journey out of the Solar System in 1980 and crossed the heliopause in 2012, becoming the first spacecraft to enter interstellar space.
The extended mission of both spacecraft is called the Voyager Interstellar Mission (VIM) and its new objective is “to extend the NASA exploration of the solar system beyond the neighborhood of the outer planets to the outer limits of the Sun’s sphere of influence, and possibly beyond.”
As of today, November 2018, Voyager 1 was at a distance of 13.4 billion miles (144 AU) from the sun and Voyager 2 at a distance of 11 billion miles (119 AU).
The extended mission is expected to continue until 2025, when its radioisotope thermoelectric generators will no longer supply enough electric power to operate its scientific instruments. For now though, humanity’s farthest and longest-lived spacecraft are still in communication with Earth via a tracking station in Canberra, Australia.
Consider this for a moment though: the technology being used on both is from the seventies. Earlier, the two Voyagers transmitted photographs and scientific data from each planetary encounter. Now 40 years later, Nasa is still able to receive messages from 13 billion miles away, sent using a 40-year-old, 12-watt transmitter (around the same as the light bulb in your fridge). This technology is not even close to what we use in our cell phones.
And that’s not all, each space probe carries a Golden Record of sounds, pictures, music and messages from Earth, selected by a committee chaired by the brilliant Carl Sagan — as well as directions to Earth, using a pulsar map, in case some alien civilization happens upon it and wants to find us.
We continue to have spacecraft orbiting the two planets that the Voyagers visited all those years ago. On July 4, 2016, after 5 years of traveling 1.74 billion miles (2.7 billion km), spacecraft, Juno, entered into orbit around Jupiter. Juno has sent back never before seen picture of Jupiter’s North Pole, which show storm systems and weather activity unlike anything we have encountered before. More excitingly, instruments also captured ghostly sounding emissions from the planet. The main objective of the Juno mission is to study the formation and evolution of the planet and gain an understanding of our Solar System. The observations will also help scientists understand other planetary systems. The mission was supposed to end in February 2018 but Nasa has extended the mission until July 2021.
In 1997, we sent out Cassini, which reached the most beautiful planet in our Solar System — Saturn — in 2004. Cassini also had on board, a lander called Huygens, which landed on Titan, the largest of Saturn’s moons in 2005. It was the first landing ever on another planet and Huygens sent back important data from Titan, such as the existence of liquid hydrocarbon lakes.
After almost 20 years out there, the Cassini Mission plunged into Saturn on September 15, 2017.
Cassini ended in 2017 and Juno will in 2021. But the Voyagers, undoubtedly our greatest space mission, will continue their journey towards deep space. They have given us many moments of amazement. Perhaps the greatest one was when Voyager 1 turned its camera back towards the Earth to capture the entire Solar System — it was Carl Sagan’s idea — where Earth can be seen as a single pixel pale blue dot. Just a dot — in the entirety of the universe.
Who knows what new wonders they have in store for us?
Featured image: The Pale Blue Dot, NASA