August 20 marks the 40th anniversary of the launch of Voyager 2, now almost 11 billion miles away (AP)

Forty years after blasting off, Earth's most distant ambassadors - the twin Voyager spacecraft - are still going.

This Sunday marks the 40th anniversary of Nasa's launch of Voyager 2, now almost 11 billion miles distant.

It left Cape Canaveral, Florida, on August 20 1977 to explore Jupiter and Saturn.

Voyager 1 followed a few weeks later and is now ahead of Voyager 2.

It is humanity's farthest spacecraft at 13 billion miles away and is the world's only craft to reach interstellar space.

Each spacecraft carries a phonograph record containing messages from Earth.

Nasa is marking the anniversary on social media.

A TV documentary, The Farthest - Voyager in Space, is also due to air next Wednesday on PBS.

AP