The longest-running missions in the illustrious space agency's history are Voyager 1 and 2. They have spent 45 years in space and have provided us with up-close pictures of Uranus and Neptune.
The "pale blue dot" photograph, which was captured by Voyager 1 at the urging of renowned scientist and science evangelist Carl Sagan, is its legacy. The legacy of the Voyager missions is summarized well by that image and Sagan's words (in the movie below).
They altered our perspective on our place in the universe and paved the way for following missions, such as the Jupiter Cassini mission and even this year's James Webb telescope observations. Pretty impressive for two space probes that, as NASA puts it, have about 3 million times less memory than modern smartphones.
Voyager 1 and 2: Humanity's two interstellar space probes
Voyager 2 was the first of NASA's two probes launched to investigate the outer planets of our Solar System. It launched on August 20, 1977, aboard a Titan IIIE-Centaur from Cape Canaveral Space Launch Complex 41. Voyager 1 was launched roughly two weeks later, on September 5.
The Voyager spacecraft launches were timed to take advantage of an alignment of the outer planets that only occurs once every 176 years. The alignment would allow the probes to hop from one planet to the next with the help of a gravity boost.
Jupiter and Saturn imaging and analysis were tasks for Voyager 1. The Voyager team was getting ready to turn off the imaging technology in 1990, after the spacecraft had passed by Jupiter and Saturn. Carl Sagan advised they train the machinery back on Earth just before they did. The above video shows the outcomes.
Voyager 2 also took images of Saturn and Jupiter, but it then moved on towards Uranus and Neptune. Voyager 2 is currently about 12 billion miles (19 billion kilometers) away from Earth. Voyager 1 crossed the boundary into interstellar space in 2012, while Voyager 2 crossed the outer edge of our solar system in 2018.
The Voyager team planned for the interstellar phase of the mission — using the probes' Plasma Science Subsystem instruments, they were able to measure the drop in solar wind when each of the spacecraft left the outer edges of the Solar System.
Voyager 2 photographed Jupiter's Great Red Spot during its approach and also got in-depth pictures of the planet's satellites. Thebe, Metis, and Adrastea were among the moons orbiting Jupiter that were found by Voyagers 1 and 2. Only roughly 19 miles (30.5 kilometres) are thought to make up the diameter of Adrastea.
Voyager 2: The only human spacecraft to visit Neptune
After also capturing many images of Saturn and taking in new details of its icy moons and its rings, Voyager 2 used a gravity assist to travel on to Uranus. This is where its path altered from Voyager 1, which was to focus on Jupiter and Saturn before traveling, making its way to the boundary of our solar system.
Voyager 2 became the first spacecraft to visit the ice giant Uranus when it made a close approach on January 24, 1986. The spacecraft's readings showed that Uranus' atmosphere is roughly 85% hydrogen and 15% helium. It also discovered 10 moons orbiting Uranus as well as a magnetic field that was, strangely, 55 degrees off the planet's axis — scientists are still unsure today why Uranus' magnetic field is off kilter. Voyager 2 also captured impressive images of Uranus' moon Miranda, revealing its strikingly uneven surface.
On August 25, 1989, Voyager 2 made its next closest flyby of Neptune after Uranus, travelling about 3,000 miles over the planet's surface. The probe found four rings, five new moons, and what is today thought to be our solar system's most distant planet from the sun - Pluto hadn't been eliminated yet. Since Voyager 2 is the only human-built spacecraft to have passed Neptune, its data is still very useful.
Surprisingly, according to NASA, Voyager 2 will continue to operate until around 2025, when it will be 11.4 billion miles (18.4 billion kilometres) beyond Earth. Even after it is unable to transmit signals to Earth, it will continue to move farther into the Milky Way. For instance, NASA predicts that in 40,000 years, Voyager 2 will pass within 1.7 light-years (9.7 trillion miles) of the star Ross 248. a relic of humanity, marking the start of its attempts to explore the cosmos, floating across space for aeons to come.
Referenec(s): NASA