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Space Science

Pioneer Anomaly Solved 147

First time accepted submitter gstrickler writes "After years of work recovering and analyzing old mission data and vehicle schematics, a just published analysis(Pdf) provides strong evidence for anisotropic thermal radiation being the source of the slowing of the Pioneer 10 and 11 spacecraft. The theory isn't new, but the recovered data and new analysis provide solid evidence that at least 80% of the deceleration is accounted for by anisotropic thermal radiation. Members of The Planetary Society were instrumental in recovering the data and helping fund the analysis. The lesson is, in space, it matters what direction your heat radiating surfaces point."
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Pioneer Anomaly Solved

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  • by Banichi ( 1255242 ) on Thursday April 19, 2012 @07:03PM (#39740289)

    Does this discovery have a relationship (however distant or inefficient) to Nuclear Lightbulb or Nuclear Photonic propulsion? []

  • Re:This just in (Score:4, Interesting)

    by l0ungeb0y ( 442022 ) on Thursday April 19, 2012 @07:09PM (#39740355) Homepage Journal

    Well actually, if they'd anticipated this and pointed the heat dissipating surfaces to the rear, Pioneer would be going faster.
    What the article did not state was how long it would take for these forces to cease forward momentum -- or if that is an issue.

  • Re:This just in (Score:5, Interesting)

    by Chris Burke ( 6130 ) on Thursday April 19, 2012 @07:30PM (#39740545) Homepage

    Well actually, if they'd anticipated this and pointed the heat dissipating surfaces to the rear, Pioneer would be going faster.

    I'm not sure they'd have done anything... the effect is so small, completely irrelevant for the main part of the missions, and they might have other reasons for orienting the craft a certain way -- maybe to maximize cooling. As a rule the side that emits the most photons would also be absorbing the most from the sun. I realize the situation could be more complicated than this; if it was simple the result would have been calculated a long time ago.

    What I'm wondering is how many people will remove this from their "these handful of unexplained results in not fully understood circumstances mean all of physics are wrong (and my pet theory is right)" lists?

  • by careysub ( 976506 ) on Thursday April 19, 2012 @08:05PM (#39740873)

    Not exactly.

    Numerous investigators have been strengthening the case for thermal radiation as the cause for nearly a decade. The work of Bertolami, Francisco, et al in Portugal in 2008-2009 accounted for 67% of the acceleration, a then-new high point in this reckoning. This was a notable result, but they didn't "figure it out" or "solve" it, they strengthened the case that was by then widely believed to be correct. For an account of the whole story up through 2010 see: [] .

    The new study raises the level of confirmation to 80%, using data that they newly recovered, and further shows that the remaining 20% is not statistically significant. It is this study that deserves to be regarded as having "solved" the problem: accounting essentially for the full anomalous acceleration, and leaving no residual anomaly.

  • by slashmydots ( 2189826 ) on Thursday April 19, 2012 @08:58PM (#39741279)
    If I understand ion thrusters correctly (that's a big if), a big tank of neutral atoms are bombarded by electrons to knock other electrons out of orbit around those atoms, creating positive particles, which are electrostatically accelerated out a big metal screen thing and the motion of them going the opposite way makes your spaceship go the correct way.
    I believe thermal radiation in this article's context means heat being turned into infrared light, that means photons going the opposite direction can have a noticeable impact on an existing spaceship in a real world text over a relatively short distance in space. I would think a gigantic atom nucleus has thousands of times more mass than a photon so ion thrusters would be pretty effective over time. Now of course the opposite "kick back" reaction is proportionate to the amount of energy you're putting into the ions and their speed is ohhhhh just a hair slower than a photon (lol) but at least we can say the theory should work in real space based on this experience.

Don't tell me how hard you work. Tell me how much you get done. -- James J. Ling