Two sister probes
On August 20th, 1977 NASA launched Voyager 2 for a record flight that is still going. Shortly after, on September 5th, the identically built Voyager 1 followed. The initial aim of the mission was to obtain more information about Jupiter and Saturn — planets which were still largely unexplored at the time. Thanks to the long-lasting plutonium batteries, both spacecrafts are still active.