New theory proposed to explain Pioneer probe gravitational anomaly

April 27, 2011 by Bob Yirka, report

Schematics of the configuration of Lambertian sources used to model the lateral walls of the main equipment compartment. Image credit: arXiv:1103.5222v1 []
( -- Portuguese physicists might have finally solved the decades old mystery of why the Pioneer probes, launched in the early 70’s, haven’t been decelerating from the Sun’s gravitational pull at the rate expected; it seems it might be something as mundane as adding in the tiny forces that occur when minute traces of heat from the plutonium on board the probes bounce off their receiving dishes, creating a counterforce, which in turn, causes the craft to slow; if ever so slightly.

The Pioneer anomaly, as it’s come to be known, has had physicists scratching their heads ever since an astronomer by the name of John Anderson, working for NASA’s Jet Propulsion Laboratory, back in 1980, noticed a discrepancy between the slowdown rate projections for the craft and the rates they were actually experiencing, which led to the basic question, how could both probes be slowing down faster than the laws of physics projected? Possible explanations ranged from unknown mechanical issues with both craft, to dark matter pushing back, to possible flaws in the physics theories themselves.

But now, Frederico Francisco of the Instituto de Plasmas e Fusao Nuclear, Lisbon Portugal and colleagues, as they describe in their paper published in arXiv, seem to have solved the problem using a simple old technology. Suspecting that heat was involved, they started with follow-up work by Anderson in 2002 and Slava Turyshev in 2006, also from NASA’s Jet Propulsion Laboratories, who both showed that heat released from the plutonium onboard the spacecraft could very well explain a slowdown. Unfortunately, both concluded that such heat emissions could not possibly account for the amount of slowdown seen. But this was because neither man thought to consider the impact of heat hitting the backside of the satellite dish (antennae) and then bouncing back. Francisco and his team used a computer modeling technique called Phong shading to show how the flow of as it was emitted from the main equipment compartment could emanate outwards, eventually bouncing off the back of the dish, resulting in just enough counterforce to explain the gravitational discrepancy.

Case closed, as far as Francisco et al are concerned, but of course this being science, others will have to replicate the results before any sort of consensus can be found.

Explore further: TPS Enables Study Of Mysterious Pioneer Anomaly

More information: Modelling the reflective thermal contribution to the acceleration of the Pioneer spacecraft, arXiv:1103.5222v1 []

We present an improved method to compute the radiative momentum transfer in the Pioneer 10 & 11 spacecraft that takes into account both diffusive and specular reflection. The method allows for more reliable results regarding the thermal acceleration of the deep-space probes, confirming previous findings. A parametric analysis is performed in order to set an upper and lower-bound for the thermal acceleration and its evolution with time.

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Display comments: newest first

3.7 / 5 (12) Apr 27, 2011
^ Reported 37 seconds after posting...damn I'm good :)
5 / 5 (1) Apr 27, 2011
WTG !! Now, if only removal could be streamlined.
not rated yet Apr 27, 2011
Maybe Physorg has a case for charging advertising fees against the spammer. That would be an interesting "negative reinforcement" mechanism.
1 / 5 (1) Apr 27, 2011
Does anyone here actually visit that jerks website or be dumb enough to actually buy something?

physorg seems to be completely unresponsive. I sent a PM to them weeks ago and it hasn't been read. I have also been unable to rate articles for months. I am going to report abuse this post, maybe they will see that.
not rated yet Apr 27, 2011
while the rest of the scientific community read this article weeks ago when the new model was tested it is good to see physorg finally caught up.
2.5 / 5 (4) Apr 28, 2011
This doesn't seem right to me ~ it is like placing a fan on the deck of a sailing ship on a windless day: it doesn't work.
Is their no recoil when particles are emitted???
2.3 / 5 (9) Apr 28, 2011

Is there no recoil when particles are emitted???

Yes there is - but consider the reverse thrusters on a landing jet aircraft - although the "recoil" acts against the engines according to Newton's laws, or just like a rocket exhaust during takeoff, the thrust is reversed in direction so as to cause a slowing in the forward direction of landing.
The backside of the radio-dishes act like reverse thrusters.
3 / 5 (2) Apr 28, 2011
Most excellent Tachyon8491.
1 / 5 (1) Apr 28, 2011
yes, that would explain it if the particles bounce off the dish.

An alternative explanation assumes that particles are equally emitted in all directions but only those projected backward are absorbed by the trailing dish.

That would mean that the recoil is absorbed for rearward projected particles but not forward projected particles giving an overall braking effect.

Either solution would work, but which one is right (which one did they actual model?)
3.7 / 5 (3) Apr 28, 2011
Hopefully they finally put this stupid thing (Pioneer anomoly) to bed now. By nature of being the only craft experiencing it, occams razor says it has specifically to do with the craft, and not some new or unproven form or interaction of cosmological physics.

With such a minute amount of force, you bet your sweet momma that every bit of geometry should be considered. Case closed, put it in the textbook for engineers and budding physicists, and lets start arguing over more important scientific conundrums and disagreements.

and a note for mr oliver k manuel: I told you neutrons had nothing to do with the pioneer anomoly.
1 / 5 (1) Apr 29, 2011
^ Reported 37 seconds after posting...damn I'm good :)

Got him 7sec after Posting ;)
1 / 5 (2) May 06, 2011
Plain old elementary stardrive in reverse. The metal elements of the spacecraft (which is being overtaken by solar electrons) are conducting those captured electrons to the outbound side which is overtaking ionized nuclei of the solar wind and a force of 1/2m deltaV*2 created by the colision and the perfect mirror effect from the release of energy from the recombination causes a 100% reflection of the overtaken particles. and decelerating energy of 2 x 1/2mv*2.
No problem releasing the info as the venculum is closed.
1 / 5 (1) Jun 03, 2011
ound side which is overtaking ionized nuclei
Do you have a clue as to the velocity of the Solar wind? It is MUCH higher than the Pioneer's velocity. The Solar wind is overtaking the Pioneers and not the other way around.


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