Pioneer Anomaly Explained

  1. mathman

    mathman 6,395
    Science Advisor
    Gold Member

  2. jcsd
  3. berkeman

    Staff: Mentor

    From near the end of the long article:

     
  4. Drakkith

    Staff: Mentor

    Excellent!
     
  5. No mention was made of the criticism from Anderson & Morris; see
    J.D. Anderson and J.R. Morris, PRD 85, 0840817 (2012). A & M plotted
    the alleged "decay" of the anomaly as a function of the radius R from the sun
    and found that it goes almost exactly as 1/R^2. This behaviour makes it likely
    that the alleged decay is only an artefact due to a mismodelling of the solar
    radiation pressure on the spacecraft.

    With the "decay" of the anomaly removed, the claim that the thermal model agrees
    with the Doppler data to within 20% would hardly be valid. So I think that before
    they have explicitly refuted the criticism from Anderson & Morris, it would be
    unwise to draw any firm conclusions regarding the status of the anomaly.
     
  6. I'm extremely skeptical about this "explanation" since it was one of the first dismissed by the same authors in their original paper.

    Among the many dozens of explanations refuted then, thermal recoil was one of the simplest and the effect has been checked by so many people.
     
  7. Drakkith

    Staff: Mentor

    But not to the extent that this team did.
     
  8. Drakkith

    Staff: Mentor

    That article proposes a second gravitational constant.
    I'm going to stick with the heat dissipation theory for now. I believe it's far more likely than modifying gravity.
     
  9. The heat dissipation model was applied to the Pioneer 10 data, but not to the Pioneer 11 data set. Pioneer 11 exhibits a distinct variation with respect to heliocentric distance during the first 5 years of its mission (the onset of the Pioneer anomaly). The heat emission model proposed by Turyshev et. al. in their June 2012 paper is unable to account for it. They address this issue at the end of their paper by stating that “In closing, we must briefly mention additional avenues that may be explored in future studies. First, the case of Pioneer 11 was not analyzed at the same level of detail, albeit we note that spot analysis revealed no surprises for this spacecraft. Second, the question of the anomalous spin-down of both spacecraft remains unaddressed, even though it is plausible that the spin-down is due to heat that is reflected asymmetrically off instrument sunshades. Third, Fig. 2 is strongly suggestive that the previously reported “onset” of the Pioneer anomaly may in fact be a simple result of mismodeling of the solar thermal contribution; this question may be resolved with further analysis of early trajectory data.”

    In other words, since the data for Pioneer anomaly doesn’t fit their model, they claim that the data itself is wrong, not the model. Sounds a bit backwards, don’t you think?
     
  10. Drakkith

    Staff: Mentor

    Where did they claim the data was wrong? All I see is that they didn't analyze the data for Pioneer 11 in as much detail as they did for 10, and that they believe a previous model is incorrect.
     
  11. "Third, Fig. 2 is strongly suggestive that the previously reported “onset” of the Pioneer anomaly may in fact be a simple result of mismodeling of the solar thermal contribution; this question may be resolved with further analysis of early trajectory data.”

    Their model predicts that the heat dissipation should be at its greatest early in the mission, yet this is precisely where the anomalous acceleration is smallest. They attempt to reconcile this difference by stating that "mismodeling of the solar thermal contribution" is at fault, since the data disagrees with the predictions of their model.
     
  12. Drakkith

    Staff: Mentor

    And? So what? I see no problems with mentioning a possible reason that their model doesn't work. It appears they have at least some reason to believe mismodeling may have occurred.
     
  13. Based on what exactly?
     
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