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The images taken by Pioneer 10 and 11 were of much lower quality than those of later planetary probes. I wonder if this is representative also for their other instruments. For example, they don't seem to have discovered volcanism on Io or any rings.

Should the Pioneer 10 & 11 be considered as disappointments or poorly designed missions (maybe prematurely rushed for prestige in the space race)? Or were they the necessary groundbreakers which made the Voyagers so successful? Was there really a big gap in science results (and interplanetary probe technology) between Pioneer and Voyager in the mid-70s and if so, was the reasons for it just general technological maturity, or some change in mission design philosophy at NASA?

I rarely see the Pioneers mentioned, while Voyager is still often admired even after the Galileo and Cassini orbiters. The first two (out of only seven to date) probes to the outer planets seem to have missed the spotlight in space exploration history.

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2 Answers 2

Yes, Pioneer 10 and 11 each carried a 0.000001 megapixel camera. The single pixel was scanned over the body by the constant spin of the spacecraft in one direction and a slew of the spacecraft in the other. Building up one image took a long time, over which the relative position of the spacecraft and the body changed quite a bit, distorting the image.

That does not mean that the missions were "poorly designed". They were launched in the early 70's, so all of the planning and payload selection was in the 60's. Each had one-third the mass to work with as Voyager did, and much less power. The science objectives were focused on fields and particle experiments, which were considered more scientific at the time than taking "pretty pictures". Later the science value of really good images was better appreciated. (The science definition was led by James Van Allen, who was a fields and particles guy.) Even if they wanted to make it an imaging mission, Pioneer had nowhere near the resources that Voyager did to accomplish that. Nor did they have the technology. With the mass they had, they did what they could to maximize the science return.

The Pioneers really did pioneer, and provided important data on radiation and micrometeoroids that was used in the design of the Voyagers.

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Now with Juno on its way without any science camera, do you think it's fair to say that the visual imaging exploration is over for good reasons and that other kinds of detectors are more interesting? Such as magnetic fields to learn about the core of Jupiter, or chemical detectors to capture volatiles thrown out from Europa's inner ocean, or a seismometer on a tidally massaged moon. Rather than another optical camera. –  LocalFluff Mar 26 at 16:22
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No, it just depends on your science objectives. The science objectives in the New Frontiers announcement of opportunity that Juno responded to do not benefit from a camera. –  Mark Adler Mar 26 at 16:41
    
@LocalFluff Juno does have a camera onboard called JunoCam. While it perhaps can't be considered a science camera (depends on your definition), and it's not in any way mission critical, it's described as education and public outreach visible-light camera. It's expected to function for up to 7 orbits, mostly because it can't be powered while other, primary science equipment is active. –  Noordung Mar 26 at 17:07
    
It is not a science camera, so @LocalFluff was correct in the characterization "without any science camera". –  Mark Adler Mar 26 at 18:11

Pioneer 10 and 11 were built to gain experience in sending probes to the outer solar system. NASA had no experience at all of space outside Mars' orbit. The opportunity for a Grand Tour (one probe could cover all 4 of the outer planets) was recognized early enough to do some experiments. There wasn't much of a budget though, so the scientific payload was limited. Remember that the Pioneers were built in the middle of the eyewateringly-expensive Apollo program.
The Pioneer 5-9 series of spacecraft were all focused on measuring fields and particles. It made sense to do environmental measurements so they could prepare later space probes for the circumstances they'd be likely to encounter.

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