The Voyager program is a space exploration program of the United States' NASA agency. It consists of a pair of unmanned scientific probes, Voyager 1 and Voyager 2. They were launched in 1977 to take advantage of a favorable planetary alignment of the late 1970s. Although they were officially used to study just Jupiter and Saturn, the two probes were able to continue their mission into the outer solar system. They have since continued out and exited the solar system. These probes were built at JPL and were funded by NASA.
Both missions have gathered large amounts of data about the gas giants of the solar system, of which little was known before. In addition, the spacecraft paths have been used to place limits on the existence of Planet X, a planet believed by some people to be farther from the Sun than Pluto.
In 2013, NASA announced that Voyager 1 had left the solar system (Heliosphere) on 25 August 2012. It is the first man-made object to enter interstellar space. In 2018, NASA announced that Voyager 2 had reached the heliopause on 5 November of that year.  Both of them are now in travelling in the interstellar space.
- "NASA Spacecraft Embarks on Historic Journey Into Interstellar Space". NASA. 12 September 2013. Retrieved 8 March 2016.
- "NASA's Voyager 2 Probe Enters Interstellar Space". NASA Jet Propulsion Laboratory. 10 December 2018. Retrieved 14 December 2018.
- NASA Voyager website - Main source of information.
- Voyager Spacecraft Lifetime
- Space Exploration - Robotic Missions
- NASA Facts - Voyager Mission to the Outer Planets (PDF format)
- Spacecraft Escaping the Solar System - current positions and diagrams
- Voyager 1 and 2 atlas of six Saturnian satellites (PDF format) 1984
- Mission state