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More Spacecraft Velocity Anomalies

  1. Mar 17, 2008 #1
    Number 857 #2, February 28, 2008 by Phil Schewe

    More Spacecraft Velocity Anomalies

    A new look at the trajectories for various spacecraft as they fly past the Earth finds in each case a tiny amount of surplus velocity. For craft that pursue a path mostly symmetrical with respect to the equator, the effect is minimal. For craft that pursue a more unsymmetrical path, the effect is larger. In the case of the NEAR asteroid rendevous craft (<http://near.jhuapl.edu/>), for instance, the velocity anomaly amounts to 13 mm/sec. Although this is only one-millionth of the total velocity, the precision of the velocity measurements, carried out by looking at the Doppler shift in radio waves bounced off the craft, is 0.1 mm/sec, and this suggests that the anomaly represents a real effect, one needing an explanation.

    Some ten years ago another anomaly was identified for the Pioneer 10 spacecraft (see http://www.aip.org/pnu/1998/split/pnu391-1.htm) and a certain amount of controversy has clung to the subject since then. One of the researchers on that earlier measurement is part of the new study, conducted by Jet Propulsion Lab scientists. John D. Anderson (jdandy@earthlink.net, 626-449-0102) says that the JPL scientists are now working with German colleagues to search for possible velocity anomalies in the recent flyby of the Rosetta spacecraft. (Anderson et al., Physical Review Letters, upcoming article; designated as an editor’s suggested articlePhysical Review Letters)

    My fd said.. They forgot to account for EM force. It is quite possible that the craft is charged. The Magnetic pole.... etc, explains what there's no acceleration when travelling around the equator. What do u think?
  2. jcsd
  3. Mar 24, 2008 #2
    do you have any ideas?
  4. Mar 24, 2008 #3
    Number 391 (Story #1), September 15, 1998 by Phillip F. Schewe and Ben Stein

    ANOMALOUS ACCELERATION. Data from several spacecraft, including Pioneer 10 and 11, Galileo, and Ulysses, provide evidence for an unexplained, weak, long-range acceleration, a new report shows. Position and velocity information is derived from radio signals sent from the craft to the Deep Space Network back on Earth. Any change in velocity over time can be ascribed to a variety of known sources: the sun and planets, the solar wind, the Milky Way, the Kuiper belt, etc. But even after taking this all into account, as well as other possibilities such as the presence of dark matter in the solar system (only a millionth of a solar mass of dark matter could reside within the orbit of Uranus, it is estimated) or gas leakage from the vehicles themselves, a small acceleration in the direction of the Sun---8 x 10-8 cm/sec2 for Pioneer 10---remains unaccounted for. Signs of this anomaly first appeared in the Pioneer tracking as long ago as 1980; Pioneer 10 was launched in 1972 and is presently 70 astronomical units from Earth. Now six space scientists, armed with many years of Pioneer data, supplemented with trajectory information from Galileo and Ulysses, have carried out the first thorough analysis of the problem and find the anomaly to be as persistent as ever. (The Voyager spacecraft are less useful for determining acceleration anomalies.) The researchers doubt but do not rule out the possibility of a novel gravitational effect or other kind of new physics. Alternative explanations include subtle systematic errors in the data analysis or unexpected aspects of space navigation. Further work on this problem may extend to the observed motions of planets, comets, and the proposed Pluto Express craft. (John D. Anderson et al., Physical Review Letters, 5 October 1998; contact John Anderson at JPL, 818-354-3956, john.d.anderson@jpl.nasa.gov; or Michael Nieto at Los Alamos, 505-667-6127, mmn@mmn.lanl.gov; journalists can obtain copies of the article from AIP Public Information.)
  5. Mar 24, 2008 #4


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    One has to admire the analysts for getting the anomaly down to O(10^-8) cm/sec^2. It is small enough to have an explanation without invoking new physics, so it's not earth shattering is it ? On the other hand, that probably was said of the perihelion precession of Mercury ...
  6. Mar 24, 2008 #5


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    For an anomaly that small, couldn't it just be a very very tiny error in the accepted mass of the solar system?
  7. Mar 24, 2008 #6
    If that were true then the orbits of the planets would also be off from our expected calculations.
  8. Mar 24, 2008 #7
    No because any acceleration as a result of solar system mass would still produce a predictable acceleration curve. It's not the acceleration but the way the acceleration evolved over time that allowed the anomalous acceleration to be defined.
  9. Mar 24, 2008 #8


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    There is another factor, though. Craft on fly-by paths that are symmetrical with respect to the equator show little, if any, of the anomaly. Craft on paths that are not symmetrical WRT the equator show more of the effect.
  10. Mar 24, 2008 #9


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  11. Mar 24, 2008 #10
    That's pretty spooky. Sounds like a good bet the error is with our knowledge of gravity (which wouldn't exactly be a shock!)
  12. Mar 24, 2008 #11
    Turbo, I am interested in more detail on the flyby anomaly. What data we have seems to have relatively large variations and the equatorial null effect seemed to be assumed from the MESSENGER spacecraft. Do you know of any published work that attempts to analyze these orbital trajectories of the various space-craft wrt the anomalous accelerations?
  13. Mar 24, 2008 #12


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    Last edited: Mar 24, 2008
  14. Mar 24, 2008 #13
    Yes perfect, thanks turbo. Don't worry about access cost. It doesn't cost me anything but a little trouble.
  15. Mar 24, 2008 #14


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    I know we can measure doppler shift to the level of precision stated in the Anderson paper but comparing it to the expected trajectory has to be done on a computer. Isn't the drift reported (10^-18 s/s2) of a similar magnitude to the rounding error of the IEEE math co-processor? Isn't that maybe the place to look for the Pioneer (and other) trajectory anomaly?
  16. Mar 24, 2008 #15
    frame dragging due to the earth's rotation?
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