The Voyager probes are powered by radioisotope thermoelectric generators (RTGs) which convert heat from decaying Plutonium Pu-238 into electricity using thermocouples.
In 47 years, the power level has dropped by over 50% to ~223 watts.
Pu-238 has a half-life of 87.7 years, i.e., in 87.7 years, 50% of its atoms decay to uranium-234 and then to lead-206.
The bi-metallic thermocouples, which are quite inefficient to begin with, also degrade over time, leading to a net loss of ~4W per year.
2/n
Here are some key metrics on the twin Voyager spacecraft.
Let’s take a moment to marvel at the 1970s technology in these spacecraft - computing hardware/software, instruments, RTGs, thrusters, etc. - most of which are still operational after 47 years in the harsh environment of space, 22:53 and 19:04 light hours away resp., with no maintenance or repairs, just workarounds around few failures, quietly exploring where no spacecraft has explored before.
👏
https://science.nasa.gov/mission/voyager/where-are-they-now/
#Voyager
3/n