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 volcanos 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 40th 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 February 2017, Voyager 1 was at a distance of 20. 6 Billion Kilometers (138 AU) from the sun and Voyager 2 at a distance of 17 Billion kilometers (114 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 20 billion kilometres away, sent using a 40-year-old, 12-watt transmitter (around the same as the lightbulb in your fridge).
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 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.
In addition to getting some awesome pictures, Juno is observing Jupiter’s magnetosphere; measuring water, gases and other elements in its atmosphere; and studying the very bright auroras at its poles, as well as its giant red spot. Jupiter’s core is still a mystery because we do not know whether it is a solid or a gas and it is helping us understand that as well.
Juno is in a slowly degrading orbit (it will undertake 37 in total), till it fails completely due to Jupiter’s destructive atmosphere, at which time it will be plunged into Jupiter in February 2018.
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.
Now after almost 20 years out there, the Cassini Mission is nearing its grand finale. Starting in April 2017, Cassini has been undertaking daring orbits around Saturn. Now, after a few close flybys of Titan, it has begun weekly dives into the inner fringes of Saturn’s rings. On September 11, 2017, Cassini will have a last close encounter with Titan and on September 15, 2017, it will plunge into Saturn’s atmosphere. And like a trooper that it has been, it will continue to send back data till the very end, until it loses contact with Earth and burns up to become part of Saturn itself.
The reason for this dramatic ending is that Cassini is running low on rocket fuel used to adjust it course. And its data has revealed that two of Saturn’s moons: Enceladus and Titan have the potential to contain habitable environments. If the spacecraft runs out of fuel, it will not be possible for mission control to adjust its course and there is a possibility that it may collide with one of these two moons, thus contaminating them for future missions. In order to avoid the possibility, Nasa has chosen to safely crash it into Saturn.
Cassini will reach its end this year and Juno, the next. 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 2 turned its camera back towards the Earth to capture the entire Solar System, 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?