Voyager 1 has exited the Solar System?

[FighterJock]

That would be good news for Voyager 2's science mission if the engineers can prolong the mission for much longer than was originally thought possible, and another thing is there no news on Voyager 1's health Flyaway? It has been a long time since I had heard anything.

 

[Hobbes]

Voyager 1 is still operational. They shut down one of the instruments back in April.

 

[FighterJock]

Thanks Hobbes, I was beginning to think the worst about Voyager 1, not good that they have had to shut down another science instrument though.

 

[Hobbes]

Well, it's inevitable. As the power available from the RTG drops, they have to reduce the power demand.

 

[NMaude]

Well, it's inevitable. As the power available from the RTG drops, they have to reduce the power demand.

Even if its' RTGs last well it will eventually travel to a point where its' radio-signals are too weak to detect from Earth.

 

[Hobbes]

Even with the current DSN, that point is at about 200 AU. It could be extended farther by using the VLA radio telescope.

 

[FighterJock]

The VLA is indeed more powerful than NASAs deep space network and should be used to track the Voyager probes when the DSN cannot track them any more.

 

[Hobbes]

My mention of the VLA is theoretical. The Voyagers will run out of power long before they reach 200 AU.

 

[NMaude]

The Voyagers will run out of power long before they reach 200 AU.

The Voyager probes were launched 49 years ago and Pu-238 has a half-life of 87.7 years so a substantial portion of it will have decayed to U-234.

 

[FighterJock]

Interesting NMaude, so that means according to my maths which is not great at the best of times should be halfway through supply of Pu-238 so that would be more than enough for both Voyager probes to continue to communicate with the Earth, that is if they can transfer traking to the VLA quickly enough before they loose contact permanently.

 

[Hobbes]

1. the RTGs are losing power faster than the Pu-238 decay suggests: the thermoelectric generator elements in the RTG also degrade slowly. They're closer to 200 W than to 235 W (half of what the RTG supplied new).
2. the minimum power level needed to operate is higher than you think. The computers and transmitter draw a lot of power. There's also a bunch of heater that have to be kept on to prevent the fuel tank and lines from freezing.

Current estimates are that before 2030, both Voyagers will no longer produce enough power to run a single science instrument. The team is hoping to get to 2027, i.e fifty years after launch.

Edit:
Measurements from 2020 have the output of the RTGs at 48% of what they were new, so 225 W. The power is dropping by about 4 W/year, so it'll be 201 W now.

 

[zjz]

The reduction in power over the years is not only Pu decay, but the major cause is the thermocouple wires themselves have deteriorated faster than expected ......

 

[NMaude]

but the major cause is the thermocouple wires themselves have deteriorated faster than expected ......

Given the probes current positions they are no doubt exposed to higher levels of background radiation include cosmic-rays.

 

[Archibald]

Since I was a kid in the 1990s the red line was always 2025. Kudos to NASA having broken that date.

 

[Flyaway]

Voyager 1 is down to two working science instruments, and the fix that just bought its twin, Voyager 2, another year of power is now being tested on a probe NASA says no longer behaves quite like its sibling

 

[FighterJock]

Better that than letting the Voyagers die with the remaining instruments runing and using up the last available plutonium.