Nasa spacecraft just days away from reaching historic milestone: ‘Astonishing!’

Voyager 1 is expected to become the first human-made object to reach a distance of one light-day from Earth, a milestone that illustrates the scale of interstellar space and the challenge of communicating across it. Nasa is inviting people around the world to mark the occasion with a symbolic Morse-code greeting, celebrating a spacecraft that has continued operating far longer than its original mission.

The probe will be about 16 billion miles away, so a signal from Earth takes 24 hours to reach it. The public transmission of its call sign, “VGR”, is scheduled for 17 November, a day before the milestone; Voyager 1 cannot see the display because its cameras were switched off in 1990. Launched 48 years ago, it is powered by generators that convert heat from decaying plutonium into electricity.