NASA's Voyager 1 spacecraft, the most distant human-made object from Earth, will on 18 November be one light day from our planet — approximately 26 billion km.
After that, a radio signal will take around 24 hours to reach the spacecraft, and the same again for the reply to return to Earth.
“The most exciting thing is to receive a reply signal from Voyager when it is one light day away,” said Jamie Rankin, NASA's deputy project scientist.
Voyager 1 was launched in 1977. Since 2012 the spacecraft has been in interstellar space. Contact with it is maintained via a 23-watt transmitter on board and the 70-metre antennas of the ground-based Deep Space Network. Contact with the probe is expected to be lost around 2036.
Ahead of the historic milestone, NASA is inviting anyone who wishes to send the spacecraft a symbolic message after sunset on 17 November using phones, torches and even building lights. The aim is to create a “wave of golden light” that will sweep across the planet in succession.
Voyager 2, launched in 1977 along with the first spacecraft, is forecast to reach a distance of one light day from Earth in November 2035.
