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The main issue with communication with Voyager is power available on the spacecraft to operate instruments or power the comms system. The radio-isotope thermal generator does not have an infinite lifespan, mainly due to degradation of the thermocouples rather than half-life of the plutonium core, and is expected to be unable to power any one science instrument by about 2025.
The comms system has a 22.4W transmitter which is the highest load (but runs intermittently). The DSN uses a 400kW transmitter to communicate with Voyager on S-band.
Voyager 2 should be more than 150 AU from the sun by 2025. Thats about 0.00237 light years.
https://en.wikipedia.org/wiki/Voyage...e_of_the_probe
https://en.wikipedia.org/wiki/Voyager_program#Power
https://en.wikipedia.org/wiki/List_o...e_from_the_Sun
http://deepspace.jpl.nasa.gov/dsndoc...5/101/101E.pdf
Regards,
Tony Barry
WSAAG