When it was built 40 years ago, none of those involved in the Voyager mission expected it to be still working, let alone continue its journey and provide invaluable information. Through their four decades of operation, space probes Voyager 2 and Voyager 1, have racked up achievements that are likely beyond the reach of any other mission.
Though it might seem counter-intuitive, it was Voyager 2 that first took off, launched by NASA from Cape Canaveral on August 20, 1977. Voyager 1 would also be soon completing 40 years of operation, as it was launched on September 5, 1977. Their initial mission objective was to gather data on Jupiter and Saturn.
Voyager 1 took a trajectory that put it on a faster path, reaching Jupiter in March 1979. Voyager 2 made its way four months later and once the probes were done with their work pertaining to Jupiter, they sped by to Saturn, with a closest approach in August 1981.
Mission extended
Having reached their primary objective, the probes were still in great condition to continue on their journey. As they had been prepared for the radiation environment at Jupiter, which has the harshest conditions among planets in the solar system, they were well equipped for the extended mission as well.
While Voyager 1 made its way towards the edge of the solar system, Voyager 2 headed to make observations of Uranus and Neptune. Following its closest approach of Uranus in January 1986, Voyager 2 turned its gaze towards Neptune.
Twelve years and a day after its launch, Voyager 2 reached Triton, the largest of Neptune’s moons, on August 21, 1989. Triton is the coldest known object in the solar system with a mean surface temperature of minus 235 Celsius. It is also the only large satellite that orbits in the opposite direction of its planet’s rotation. Triton, which has a thin atmosphere unlike the Earth’s moon, was the last major heavenly body with which Voyager 2 had close contact.
On the next day, Voyager 2 found evidence for rings around Neptune, thus showing that all four gas giants – Jupiter, Saturn, Uranus and Neptune – in the solar system had rings. Three days later, Voyager 2 made its closest approach to Neptune, making precise measurements of the mass of the planet. When Pluto was demoted from its planetary status in 2006, this Neptune flyby by Voyager 2 in August 1989 marked the point when every planet in our solar system had been visited by a probe.
Ready for more
After Voyager 2 went past Triton and Neptune, the probes had once again outlived their mission objectives and were ready for more. As the mission’s planetary exploration phase had been successfully completed, NASA renamed it the Voyager Interstellar Mission.
As part of their ongoing missions, Voyager 1 is currently in interstellar space, while Voyager 2 is in heliosheath – the outermost layer of the heliosphere and a region where solar wind is slowed down by interstellar gas. While Voyager 1 became the first spacecraft to enter interstellar space in 2012, Voyager 2 will be joining it, albeit in a different location, in the next few years.
The probes are expected to continue working for over a decade, with their last science instrument to be turned off by 2030.
And after that, even though the spacecrafts might have stopped communicating with us, they will continue in their current trajectories at speeds over 48, 280 kilometres per hour.