Nasa has finally got back in contact with the Voyager 2 probe, which has been travelling through space since August 1977.
Engineers sent a series of commands to Voyager 2 via a huge radio antenna, which had been offline for repairs and upgrades since March.
Voyager 2 received the ‘call’ and executed the commands, despite being more than 11.6 billion miles (18.8 billion kilometers) from Earth.
It is so far away that engineers had to wait nearly 35 hours for a reply.
"What makes this task unique is that we're doing work at all levels of the antenna, from the pedestal at ground level all the way up to the feedcones at the center of the dish that extend above the rim," said Brad Arnold, the DSN project manager at Nasa’s Jet Propulsion Lab.
"This test communication with Voyager 2 definitely tells us that things are on track with the work we're doing."
Among the upgrades to the transmission dish, called DSS43 and located in Australia, are two new radio transmitters.
The transmitters have not been replaced in over 47 years, but it is expected that it will now come back online in February 2021.
Engineers also upgraded the heating and cooling, power supply equipment, and other electronics in order to make the transmitters work.
Since the dish went offline, operators have been able to receive health updates and science data from Voyager 2, but have not been able to send commands to it.
"The DSS43 antenna is a highly specialized system; there are only two other similar antennas in the world, so having the antenna down for one year is not an ideal situation for Voyager or for many other NASA missions," said Philip Baldwin, operations manager for Nasa's Space Communications and Navigation (SCaN) Program.
"The agency made the decision to conduct these upgrades to ensure that the antenna can continue to be used for current and future missions. For an antenna that is almost 50 years old, it's better to be proactive than reactive with critical maintenance."
As well as contact with Voyager 2, the repairs to the dish will have other benefits for future Mars missions.
It will be used for the Mars Perseverance mission, when the rover will land on the Red Planet in February 2021.
Nasa also said it will ensure communication for the Moon to Mars missions, supporting the Artemis mission which will send the first woman and the next man to the Moon in 2024.
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