The end of the 60s was marked by one of humanity’s most memorable achievements – the first manned mission to the Moon. In the wake of this accomplishment NASA turned its attention to the further reaches of our Solar System and the distant gas giants in orbit there. At first, they planned four separate missions – two were supposed to explore Jupiter, Saturn and Pluto and another two - Jupiter, Uranus and Neptune. However, now that the space race was over, the reduced budget did not allow for so many probes to be build and so they were forced to combine the two into the Voyager program.
Launched 42 years ago, on September 5, 1977, Voyager 1 took off, oddly enough, 16 days after its sister spacecraft, the Voyager 2. Both probes were meant to use a rare celestial occurrence, one that took place once every 175 years. Jupiter, Saturn, Uranus and Neptune were arrayed in such a way, that they would allow them to fly by and use their gravitational pull as a kind of slingshot, propelling them ever further. Voyager 2 would take a slower route, observing all four giant planets, while Voyager 1 was to visit only Jupiter and Saturn before it continued into deeper space. That meant that it would overtake its companion, which it did just before the Asteroid Belt, and so NASA named them appropriately.
Both probes are constructed identically and are truly incredible feats of engineering. Each contains about 65,000 parts and weighs roughly 680 kilograms. They are both equipped with special tools, allowing them to take pictures and measure different readings. Powered by special plutonium batteries, originally, they were supposed to last only five years, but both are still functioning and sending back signals to this day. As of today, the Voyager 1 has travelled more than 22 billion kilometers and it takes over 20 hours for its signals to reach Earth. This makes it the most distant man-made object in the universe. In 2004 it crossed the terminal shock – the distance, where solar particles become slower than the speed of sound and in 2012 it then traversed the heliopause. This is the boundary between matter originating from the Sun and matter from the rest of the galaxy, meaning that in that moment Voyager 1 became interstellar. Voyager 2 crossed these boundaries in 2007 and 2018 respectively.
There were many important discoveries made by the two spacecraft. For the first time scientist were able to observe a thin ring, circling around Jupiter as well as two previously undiscovered moons – Thebe and Metis. For the first time we saw the Io’s volcanos as well as pictures, hinting that Europa may be covered with ice and oceans. On Saturn they uncovered the moons Prometheus, Pandora and Atlas, as well as a new, previously unknown ring. After Saturn Nasa engineers turned off Voyager 1’s cameras to conserve energy, but on February 14, 1990 they went back on one final time. Pointed back, it took a series of photographs of the entire Solar System. On them we can see the Sun, Venus, Earth, Jupiter, Saturn and Uranus. On it our small planet is visible as less than a pixel, named by the famous Carl Sagan as a pale, blue dot, a mote of dust, suspended in a sunbeam.
As the final destination of both probes was the deep reaches of space, NASA created two very special discs for the spacecraft. Made out of copper and plated with gold, they carry a greeting on the off chance that they are ever discovered by extraterrestrial beings. They also carry 115 images and a collection of natural sounds and music from different cultures. Upon the disc they inscribed a kind of instruction manual on how to play it, as well as the position of the Sun in relation to nearby pulsars, in case they ever wanted to visit.