How far should Voyager 1 travel, before the earth loses contact, provided the power source does not die first?

5 September 2017, exactly 40 years after its launch, Voyager 1 was located at a distance of 20.88 billion kilometers from the earth.

The speed compared to the sun was at that time 17.00 km/sec.

For energy supply, Voyager 1 has three thermoelectric radioisotope generators on board.Each generator contains 24 bulbs of plutonium (IV) oxide, enriched with the isotope plutonium-238.At the time of the launch, the generators delivered 470 watts together. Because the fuel has a half-life of 87.7 years, the power continuously decreases. No instrument will be given more power by 2025.

When Voyager 1 cannot communicate directly with the Earth, the data is stored on a digital tape recorder with a capacity of 69.63 kilobytes.In 2013, a signal from Voyager 1 took 17 hours to reach the earth.

Voyager 1-Wikipedia

Voyager (for the current state of play for the Voyager 1 & 2 with the distance to the Earth and the Sun)

The signals from Voyager are captured by Nasa’s Deep Space Network (DSN).

The DSN does not consist of a single location, but spans multiple recipients spread across the US, Spain and Australia, grab it bite 120 degrees apart which allows us to always be able to “connect”, regardless of the rotation of the earth compared to the probe where We want to communicate with.The size of the largest receiver is such a sloppy 70 meters (in Pasadena, California).

The problem of reception is, however, in the power of the transmitter and the fact that the signal weakens over the distance causing a lot of noise which is to be filtered.There are numerous developments going on to be able to reach a higher bandwidth with future probes, but for Voyager 1 (launched in 1977) we will have to do it with the weak radio signal that it is broadcasting through its antenna of 3.7 diameter in size ( At the frequency of 2.3 GHz or 8.4 GHz). By the time this signal (almost a day later) is captured by the DSN, the measurable signal is 20 billion (!) times weaker than the battery of a wrist watch (10 to power-16 watts).

Nasa’s Jet Propulsion Laboratory claims that the Voyager would be reachable for 1 to (2!) centuries, but it was not expected that the probe would have no power in 2025 (see Karl’s answer).

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