NASA communicates with all its space probes, including Voyager 2, with the Deep Space Network (DSN), a set of radio dishes at three sites around the world; Goldstone in California, Robledo near Madrid and Tidbinbilla near Canberra.
Since Voyager 2 is only visible from the southern hemisphere, an antenna called DSS-43, at the Australian site, is the only antenna on Earth that can send and receive signals to/from the probe.
The transmitter on Voyager 2 – currently more than 20 billion km from Earth – has a power of about 23 Watts (about eight times that of a typical mobile phone). By the time the radio signal reaches Earth, it has about one-tenth of a billion-trillionth of this power.
In order to detect this extremely faint signal, DSS-43 and the transmitter on Voyager 2 are highly directional and use narrow-band, high-frequency signals transmitted at a slow bit-rate.
Complex signal processing techniques, a lack of interference and the fact that radio signals travel almost unimpeded through space means the vast distance is no obstacle for DSS-43.
The antenna transmits signals to Voyager 2 at much higher power than it receives – up to about 400,000 Watts – easily heard by the distant probe.
This article is an answer to the question (asked by Elouise Pace) 'How can we still talk to Voyager 2 when it's billions of miles away?'
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