Over 45 years ago, NASA’s Voyager 2 spacecraft left Earth to embark on a journey to the outer planets and beyond; a journey that continues to this day. Voyager 2, the first of two spacecraft part of the mission, lifted off on August 20, 1977, taking advantage of a rare planetary alignment to use the gravity of one planet to propel itself to another. Even though the Voyager mission only targeted Jupiter and Saturn, Voyager 2 went on to explore Uranus and Neptune as well. Voyager 1 was launched on September 5 of the same year.
The pair of spacecraft carry sophisticated instruments for the in-depth exploration of outer planets. They both continue to return data as they are heading out of the solar system and into interstellar space.
Voyager mission: Origin
The Voyager mission has its origins in the 1960s when mission designers at NASA’s Jet Propulsion Laboratory observed that the next alignment of outer planets, a rare event that occurs only once every 175 years, would happen in the late 1970s. At the time, technology was advanced enough to take advantage of this alignment to fly a spacecraft by Jupiter and use its gravity to visit Saturn as well, to then repeat the process to visit Uranus, Neptune and Pluto.
This was an ideal scenario since launching several missions to each planet individually would have been an expensive affair that also took much more time. The space agency developed a plan to send two pairs of “Thermoelectric Outer Planet Spacecraft” on these Grand Tours. But that plan was cancelled in 1971 as it proved too costly.
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The very next year, NASA approved a scaled-down version of the project, which involved launching two spacecraft in 1977 to explore just Jupiter and Saturn. NASA Administrator Jame C. Fletcher announced on March 7, 1977, the renaming of two Mariner spacecraft to Voyager 1 and Voyager 2. At the time, scientists held out hope that one of them could eventually visit Uranus and Neptune, fulfilling the original objectives of the cancelled Grand Tour mission.
Voyager mission launch
Voyager 2 was the first to leave the planet and was launched on a Titan IIIE-Centaur rocket from Launch Complex 21 at the Cape Canaveral Space Force Station (then the Cape Canaveral Air Force Station) in Florida. Even though Voyager 1 was launched two weeks later, it travelled on a faster trajectory and arrived at Jupiter four months earlier than Voyager 2.
Between December 10, 1977, and October 21, 1978, Voyager 2 successfully crossed the asteroid belt. However, its primary radio failed in April 1978 and it has been operating on its backup receiver ever since then.
Voyager 2: Observing Jupiter and Saturn
Between April 24 and August 5, 1959, Voyager 2 conducted observations of Jupiter, with its closest approach of around 563,000 kilometres above the gas giant’s cloud tops on July 9. Voyager 2 returned 17,000 images of Jupiter and its satellites and also helped confirm Voyager 1’s discovery of a thin ring encircling the planet. The spacecraft also returned information about the planet’s atmospheric and magnetic field. It then used Jupiter’s gravity to bend its trajectory and accelerate towards Saturn.
On June 5, 1981, Voyager 2 began its long-range observations of Saturn and passed within 41,000 kilometres of the planet’s cloud tops on August 26 before concluding its observations on September 4. It captured 16,000 photographs of Saturn, its rings and many of its satellites. Apart from discovering many new satellites, Voyager 2’s instruments also returned data about the ringed planet’s atmosphere. The planet’s gravity then sent the spacecraft on its journey to Uranus.
Going beyond: Uranus and Neptune
Between November 4, 1985, and February 25, 1986, Voyager 2 conducted close-up observations of Uranus, making its closest approach of around 81,500 kilometres above the planet’s cloud tops on January 25, 1986. The spacecraft returned over 7,000 photos of the planet, its ring and moons. It also discovered two new rings and 11 new moons. Voyager 2’s instruments also returned data concerning the planet’s atmosphere and its unusual magnetic field.
The spacecraft then used Uranus’ gravity to launch itself towards its last planetary stop, Neptune. Between June 5 and October 2, 1989, it conducted close-up observations of the planet, flying as close as around 5,400 kilometres above the north pole of the eighth planet on August 25. On this trajectory, it also observed Neptune’s largest moon Triton, the last solid object it explored.
During its observation of Uranus, Voyager 2 returned more than 9,000 images of the planet, its atmosphere, dark rings, and moons. It also discovered six new moons. The spacecraft helped discover that Neptune also had an unusual magnetic field like Uranus.; tilted 47 degrees from the planet’s axis and significantly offset from its centre.
Voyager 2’s interstellar journey
After its observation of Neptune, the spacecraft began its interstellar mission that continues to this day. Over the years, many of Voyager 2’s instruments had to be turned off to conserve power, starting with the imaging system in 1998. Currently, the spacecraft is more than 19 billion kilometres away from Earth. In fact, it is so far away that it takes 18 hours for radio signals from the spacecraft to reach here. With it being so far away from the Sun, it is a remarkable scientific achievement that it can continue to return data.
Over 45 years ago, NASA engineers had prepared for the possibility that an alien intelligence finds the space crafts. Voyager 2, just like Voyager 1, carries a gold-plated record that contains information about Earth including recordings of sounds, music, and greetings in 55 languages. Engineers also included instructions on how to play the record.