Sunday marks the 40th anniversary of Voyager's launch

Tom Hinde

40 years ago today NASA launched Voyager 2. Now almost 11 billion miles from Earth, it departed from Cape Canaveral on August 20, 1977. Its mission was to explore the planets of Jupiter and Saturn.

Voyager 1 followed a few weeks later and is ahead of Voyager 2. It's humanity's farthest spacecraft at 13 billion miles away and is the world's only craft to reach interstellar space, the vast mostly emptiness between star systems. Voyager 2 is expected to cross that boundary during the next few years. Each carries a 12-inch, gold-plated copper phonograph record containing messages from Earth. There were no CDs or MP3s back then.

Both missions are considered wildly successful offering scientists the opportunity to explore our solar system's outer planets and beyond. Public television is paying tribute with a documentary, "The Farthest - Voyager in Space," airing Wednesday on PBS at 8:00 p.m. CDT.