Voyagers

The Voyager 1 and Voyager 2 interstellar probes are part of NASA's Voyager program launched in 1977 to take advantage of a rare planetary alignment that occurs every 175 years and allows a spacecraft to reach all outer planets using gravitational assists.

Learn more: https://en.wikipedia.org/wiki/Voyager_program and https://science.nasa.gov/mission/voyager/.

Voyager 1 approaching 1 light day distance from Earth: https://science.nasa.gov/mission/voyager/where-are-voyager-1-and-voyager-2-now/