The two Voyager probes, launched in 1977 to take advantage of a rare alignment of the planets Jupiter and Saturn, provided invaluable data on the gas giants. Voyager 2 even managed to perform a flyby of both Uranus and Neptune, near the outer portion of our Solar System. Both probes then took paths leading them towards interstellar space, and as of 2021, are still sending data back to Earth some 44 years after they left our planet.
Voyager 1 and Voyager 2 are more than 100 AU away from the Sun at this point, with an AU, or Astronomical Unit being roughly 92 million miles, or roughly the distance from the Sun to Earth.
Now, NASA is planning a mission to send an "Interstellar Probe" 1,000 AU from the Sun, more than six times as far out as the Voyage probes currently are.
The mission will be used to conduct data collection and research of the heliosphere, or the vast "bubble" around the Sun that is subject to solar wind. The two Voyager probes crossed the terminus of the heliosphere of the Sun but were not equipped with the instruments needed to properly study the transition to interstellar space.
The new probe will study how the Sun's plasma interacts with interstellar gas to possibly determine how the heliosphere is created. It could also help us determine how it is affected as the Sun travels in the Milky Way galaxy.
Other possible objectives for the mission include study of extragalactic background light, planetary science, and more.
The tentative plan is to launch the Interstellar Probe in the 2030s. From there, it would take around 15 years to reach the distance of 1,000 AU from the Sun.