The Pioneer Missions. March 26, 2007

PIONEER 10 SPACECRAFT SENDS LAST SIGNAL - After more than 30 years, it appears the venerable Pioneer 10 spacecraft has sent its last signal to Earth. Pioneer's last, very weak signal was received on 23 January 2003.

A little about Pioneer 11:

The Earth's motion has carried it out of the view of the spacecraft antenna. The spacecraft cannot be maneuvered to point back at the Earth.

Why didn't Pioneer 10 (as well as its twin probe Pioneer 11) keep up communications with Earth as the Voyagers do? As Pioneers and Voyagers were all launched in the 70's, presumably they all shared the similar technologies. Is it due to engineering failure or some other reason?

  • Pioneer 10 will continue to coast silently as a ghost ship through deep space into interstellar space, heading generally for the red star Aldebaran, which forms the eye of Taurus (The Bull). Aldebaran is about 68 light years away and it will take Pioneer over 2 million years to reach it.
  • The spacecraft is headed toward the constellation of Aquila (The Eagle), Northwest of the constellation of Sagittarius. Pioneer 11 will pass near one of the stars in the constellation in about 4 million years.

NASA already lost connection with the Pioneers, so are they still on their way into deep space without NASA's acknowledgement? How can scientists determine that? Is there any scientific purpose for the Pioneers to reach their respective so-called "destination"? Cause if they do, I can't figure out the purpose of having to wait for millions of years; humanity probably would no longer exist anymore. Or they simply wander around deep space for no specific purpose and act as a "time capsule" for the existence of humanity on Earth along with The Pioneer Plaque?

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    $\begingroup$ Pioneer 10 was planned for 21 months of operation. It did work 31 years, that is 16 times longer. We should be very happy about such a reliable space probe. $\endgroup$
    – Uwe
    Nov 23, 2018 at 12:23
  • 4
    $\begingroup$ Voyager 1 and 2 were designed for 5 years of operation: They work 41 years now, about 8 times longer. So Pioneer 10 did work 16 times longer than planned, much longer than the Voyagers. If the Voyagers work till 2025, it will be only about 10 times longer than planned. $\endgroup$
    – Uwe
    Nov 23, 2018 at 17:29
  • $\begingroup$ @Uwe Shocking facts! Can't believe the Pioneer and Voyager probes would decently keep operating for much longer than expected. Since those probes were launched in 70's, it was over two decades before I was born! $\endgroup$
    – not_Prince
    Nov 26, 2018 at 0:45
  • $\begingroup$ Relatable popular question $\endgroup$
    – not_Prince
    Nov 27, 2018 at 8:41

1 Answer 1


Why the Pioneers didn't last as long:

  • The Pioneers were a low-budget mission just to test if flying to the outer planets was feasible
  • They used a smaller radio transmitter (8 W vs. 23 W) and antenna (2.7 vs 3.6 m diameter) so their signals are weaker
  • The Pioneers used a smaller, earlier design Radioisotope thermoelectric generator as their power source (155 W at launch vs 470 W). By 2003 (date of last contact) the RTG had decayed to the point where its power output was barely enough to power the transmitter. The Voyagers have a bigger RTG with more margin before that point is reached.

Despite NASA already lost connection with the Pioneers, are they still on its way into deep space without NASA's acknowledgement

Yes. These deep space probes follow a very predictable trajectory: they keep going in a straight line. There are no planets nearby that can change that trajectory.

It is possible one of the Pioneers has collided with a small Kuiper Belt Object we haven't detected yet, but that region of space is really empty so chances of a collision are tiny.

Is there any scientific research purpose for the Pioneers to reach its respective so-called "destination"?

No. Their instruments don't work anymore, the Pioneers are just inert objects now. The only purpose they still have is carrying a plaque that describes our location.

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    $\begingroup$ And the only reason they tried one last time in 2007 to talk to Pioneer 10 is they wanted to firm-up its position for studying the Pioneer Anomaly. $\endgroup$
    – Joshua
    Nov 23, 2018 at 16:28
  • 1
    $\begingroup$ And there are actually 4 RTGs (mounted on 2 booms) which heat the leading side more, which explained the anomalous sun-ward acceleration. $\endgroup$
    – amI
    Nov 23, 2018 at 18:19
  • $\begingroup$ The pioneers were designed for 21 months of operation but the Voyagers for 5 years, 2.8 times longer. $\endgroup$
    – Uwe
    Nov 24, 2018 at 14:57
  • $\begingroup$ The official requirement was for 5 years. The engineers did everything they could to ensure the longest possible lifespan. $\endgroup$
    – Hobbes
    Nov 24, 2018 at 17:54
  • $\begingroup$ I'm surprised that a slight difference of 2.7 vs 3.6 m diameter would ended up in such big consequences. $\endgroup$
    – not_Prince
    Nov 26, 2018 at 0:27

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