DiscoverScroll article

The Voyager program is an American scientific program that employs two interstellar probes, Voyager 1 and Voyager 2.

They were launched in 1977 to take advantage of a favorable planetary alignment to explore the two gas giants Jupiter and Saturn and potentially also the ice giants, Uranus and Neptune—to fly near them while collecting data for transmission back to Earth. After Voyager 1 successfully completed its flyby of Saturn and its moon Titan, it was decided that Voyager 2 would continue on its pre-planned trajectory to fly by Uranus and Neptune. After the planetary flybys were complete, decisions were made to keep the probes in operation to explore interstellar space and the outer regions of the Solar System. On 25 August 2012, data from Voyager 1 indicated that it had entered interstellar space. On 5 November 2019, data from Voyager 2 indicated that it also had entered interstellar space. On 4 November 2019, scientists reported that on 5 November 2018, the Voyager 2 probe had officially reached the interstellar medium (ISM), a region of outer space beyond the influence of the solar wind, as did Voyager 1 in 2012. In August 2018, NASA confirmed, based on results by the New Horizons spacecraft, the existence of a "hydrogen wall" at the outer edges of the Solar System that was first detected in 1992 by the two Voyager spacecraft. As of 2026, both Voyagers are still in operation beyond the outer boundary of the heliosphere in interstellar space. At the same time, Voyager 2 was moving with a velocity of 55,000 kilometers per hour (34,000 mph), or 15 km/s, relative to the Sun, and was 20.4 billion kilometers (12.7×10^9 mi) from the Sun. The two Voyagers are the only human-made objects to date that have passed into interstellar space — a record they will hold until at least the 2040s — and Voyager 1 is the farthest human-made object from Earth.

The two Voyager space probes were originally conceived as part of the Planetary Grand Tour planned during the late 1960s and early 70s that aimed to explore Jupiter, Saturn, Saturn's moon Titan, Uranus, Neptune, and Pluto.

Due to the name change occurring close to launch, the probes were still occasionally referred to as Mariner 11 and Mariner 12, or even Voyager 11 and Voyager 12. Upon Voyager 1 completing its main objectives at Saturn, Voyager 2 received a mission extension, enabling it to proceed to Uranus and Neptune. Voyager 2 was the first to be launched. Had Voyager 1 been unable to perform the Titan flyby, the trajectory of Voyager 2 could have been altered to explore Titan, forgoing any visit to Uranus and Neptune. The New Horizons probe, which had a higher launch velocity than Voyager 1, is travelling more slowly due to the extra speed Voyager 1 gained from its flyby of Saturn. On 10 December 2007, Voyager 2 also reached the termination shock, about 1.6 billion kilometres (1 billion miles) closer to the Sun than from where Voyager 1 first crossed it, indicating that the Solar System is asymmetrical. As of 2017 Voyager 1 and Voyager 2 continued to monitor conditions in the outer expanses of the Solar System.

Voyager 1 and Voyager 2 have identical computer systems.

The Voyager primary mission was completed in 1989, with the close flyby of Neptune by Voyager 2. Voyager 1 crossed the heliopause boundary in 2012, followed by Voyager 2 in 2018.

By the start of VIM, Voyager 1 was at a distance of 40 AU from the Earth, while Voyager 2 was at 31 AU. Voyager 1 completed the phase of termination shock in December 2004 at a distance of 94 AU, while Voyager 2 completed it in August 2007 at a distance of 84 AU.

Quick Facts

• After Voyager 1 successfully completed its flyby of Saturn and its moon Titan, it was decided that Voyager 2 would continue on its pre-planned trajectory to fly by Uranus and Neptune.
• On 4 November 2019, scientists reported that on 5 November 2018, the Voyager 2 probe had officially reached the interstellar medium (ISM), a region of outer space beyond the influence of the solar wind, as did Voyager 1 in 2012.
• On 25 August 2012, data from Voyager 1 indicated that it had entered interstellar space.
• On 5 November 2019, data from Voyager 2 indicated that it also had entered interstellar space.
• At the same time, Voyager 2 was moving with a velocity of 55,000 kilometers per hour (34,000 mph), or 15 km/s, relative to the Sun, and was 20.4 billion kilometers (12.7×10^9 mi) from the Sun.

Source material: Wikipedia - "Voyager program". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.