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As we've already determined, Curiosity should last about 14 years on its nuclear power.

What happens near that timeframe? Will NASA start to manage the rover's use of power by shutting down unused tools?

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It will survive the way that pretty much all space missions survive.

First of all, most space missions are speced such that the power at the end of the mission will meet 100% of the demand of the spacecraft. The mission of Curiosity is 2 years, thus, the spacecraft will have 100% of required power after 2 years.

Beyond that, its power will decrease. However, Curiosity has two batteries which will allow it to store charge, allowing it to still perform high power tasks, just for less time than it otherwise would be able to. So what will happen is the amount of moving, science, etc will be decreased over time.

The half life of the Plutonium 238 is 87.7 years. In effect, that means that the amount of power will only be halved every 87 years.

In practice, the limiting factor will probably be the lithium ion batteries, and not the RTG. But the effect will still be the same, you can't use your instruments as much, or move as far, but you can still do science to some extent, as time continues.

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    $\begingroup$ The available power will drop faster than the decay would suggest: the thermocouples become less efficient over time. $\endgroup$
    – Hobbes
    Commented Feb 10, 2014 at 13:47
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    $\begingroup$ Not so sure about the batteries being the limiting factor. MER's Li-ion batteries have shown almost no degradation in ten years. I don't think that we understand why. More degradation was predicted. At this point, I would guess that the wheels will be the limiting factor, perhaps followed by the moving parts -- actuators and joints. $\endgroup$
    – Mark Adler
    Commented Feb 10, 2014 at 20:22
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    $\begingroup$ @Hobbes is there something out there we can read about thermocouple degradation? Is it radiation damage primarily? $\endgroup$
    – uhoh
    Commented Dec 27, 2015 at 14:39
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    $\begingroup$ this book says it's due to precipitation of the phosphorous doping in the n-type leg of the thermocouple, leading to a 1.5%/year decay in capacity. $\endgroup$
    – Hobbes
    Commented Dec 27, 2015 at 17:31
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    $\begingroup$ The go-to source for this kind of information is the NTRS, but unfortunately the studies into RTG degradation (search result 1-5) are not available as PDFs there: ntrs.nasa.gov/… $\endgroup$
    – Hobbes
    Commented Dec 27, 2015 at 17:36

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