Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The Pioneer effect and Spacecraft flyby anomaly

  1. Feb 28, 2013 #1
    Does general relativity explain the Pioneer effect and the spacecraft flyby anomaly? I have seen several papers on those two topics but no GR explanation.
  2. jcsd
  3. Feb 28, 2013 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

  4. Feb 28, 2013 #3
    I will access the link, read, and come back to you.

    Meanwhile, have you read whether GRT explains either or both? Please be specific; will appreciate it.
  5. Feb 28, 2013 #4


    User Avatar
    Science Advisor

    SinghRP, I have read the link, and it gives a full explanation. Suggest you do too! :smile:
  6. Feb 28, 2013 #5


    User Avatar
    Science Advisor
    Gold Member

    I don't think the linked article/paper explains the Flyby anomaly, or does it?

    AFAIK, the flyby is still an open anomaly (e.g. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090010275_2009009651.pdf and http://arxiv.org/abs/1210.7333)
  7. Feb 28, 2013 #6


    User Avatar
    Science Advisor

    Yep, you're right. Sorry.
  8. Feb 28, 2013 #7
    This is what I know so far.
    1. The Pioneer anomaly is due to thermal (kinetic) effect. Probably heat is from the spacecraft itself.
    2. I believe only the NEAR spacecraft to an asteroid showed some significant flyby effect around Earth. At present they have fitted a curve with the data. They have accounted for Earth's varying gravitational filed. Etc., etc.
    GRT needs to explain it. It has not; I wonder why not. This could be a crucial test for GRT!

    A physicist friend thinks it is special-relativistic effect. But I can't say anymore here due to the Forum's rules. I will come back here after his paper is published.

    Thanks muchly.
  9. Feb 28, 2013 #8


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The Pioneer anomaly was completely bogus:

    Iorio, "Does the Neptunian system of satellites challenge a gravitational origin for the Pioneer anomaly?," http://arxiv.org/abs/0912.2947

    F. Francisco, O. Bertolami, P. J. S. Gil, J. Páramos, "Modelling the reflective thermal contribution to the acceleration of the Pioneer spacecraft," http://arxiv.org/abs/1103.5222

    Turyshev, Toth, et al. http://arxiv.org/abs/1204.2507

    The flyby anomaly is not as well understood, but Toth thinks it's just a data analysis artifact due to switching between solar-system barycentric coords and geocentric coords. Anderson had an empirical formula for the anomaly, but the formula predicted an anomaly for Rosetta, and in fact no anomaly was observed for Rosetta.
  10. Mar 1, 2013 #9
    Thank you all for your responses. I agree with bcrowell.

    1. Has someone investigated the effect of variations in the Earth's gravitational field or in the classical gravitational constant on the Pioneer effect and/or the Earth spacecraft-flyby effect?

    2. Can someone get me in contact with one at NASA who could provide me with related flyby data, particularly how the osculating orbit was determined?
  11. Mar 6, 2013 #10


    User Avatar
    Gold Member

    It is interesting to look at the actual data for the anomalous acceleration. it is available at:
    arXiv: gr-qc/0104064v5
    What one sees is three distinct signatures;
    (1) The effect gradually appears over a distance of about 5 AU or so reaching a maximum of about 10*10^-8 cm/sec^2 at 20 AU and staying more or less constant after that out to at least 70AU.
    (2) There is a definite yearly small variation in the magnitude at a certain position related to the earth's rotation around the sun in its orbit
    (3) There is a much larger (order of 100*10^-8 cm/sec^2) term with a period equal to the earth's period of rotation (24 hours)
    IN view of these facts, the thermal explanation does not seem valid: It should appear much sooner than 5 AU, more or less all the time; it does not address either the small annual term or the diurnal large term. I don't believe the thermal explanation.
  12. Mar 6, 2013 #11


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Then I look forward to reading your response in PRL to their paper.

  13. Mar 7, 2013 #12


    User Avatar
    2017 Award

    Staff: Mentor

    The error bars below 15 AU are so large, I would not trust those values.
    In short: If you don't know the exact position of the spacecraft, you get some wiggles due to the motion of earth. This does not influence the average, however.
  14. Mar 7, 2013 #13
    Thanks for your responses. I agree with those who pointed out that the Pioneer effect and the spacecraft flybys “mystery” are not clearly understood. They can’t be with our current knowledge of gravitation. I tried to explain the two effects with GRT – no success.

    I would not trust observations claiming accelerations as small as 10**-10 m/s/s. Also -- this is the acceleration they claim that the galaxies in the universe are accelerating at!

    Thanks to davidf32, who pointed out that the effects were gradual! I DID NOT KNOW THAT. Applying my physicist’s intuition, I think the effects could be due to variations in the classical gravitation constant G. Dirac said that a long, long time ago that G was not constant. Now, why and how G would be varying, I don’t know.

    How can I get the Pioneer and flyby data from NASA? So far, I have not succeeded.
  15. Mar 7, 2013 #14


    Staff: Mentor

    When you have published your idea in a mainstream physics journal then it can be discussed here. Until then it is unfounded and unsubstantiated speculation.

    Thread closed.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: The Pioneer effect and Spacecraft flyby anomaly
  1. Pioneer Spacecraft (Replies: 11)

  2. Pioneer 10 Anomaly (Replies: 7)

  3. Pioneer anomaly solved (Replies: 39)