Voyager 1 and Voyager 2 launched in 1977 and made a grand tour of the solar system's outer planets. They are the only functioning spacecraft in interstellar space, and they are still sending back measurements of the interstellar medium.
Tracking Molecules In the Interstellar Medium
How Astronomers Mapped the Interstellar Medium - And Discovered The Local Bubble
JWST Cycle 4 Spotlight, Part 4: Stellar Populations and the Interstellar Medium
