The Pioneer Anomaly Options

[remcook]

http://www.planetary.org/news/2005/pioneer_anomaly_faq.html

The planetary society may be checking it out...

The Planetary Society has committed to raise the funds to preserve the priceless Pioneer data from destruction.


After years of analysis, but without a final conclusion, NASA, astonishingly, gave up trying to solve the "Pioneer Anomaly" and provided no funds to analyze the data. The Pioneer data exists on a few hundred ancient 7- and 9-track magnetic tapes, which can only be read on "antique" outdated computers. The agency is going to scrap, literally demolish, the only computers able to access and process that data in the next few months!

[The Messenger]

I am at least as interested in the flight path eccentricities of Odysseus, Galileo and Pioneer 6 as the Pioneer 10 and 11. While the Pioneer probes indicate an acceleration towards the sun, an unsolicited acceleration away from the sun had to be used to model the paths of Odysseus and Galileo, and one of a greater magnitude: ~1x10^-8m/s^2.

Likewise, I mentioned the navigational problems associated with the Polar Lander and Climate orbiter, not because of the failure modes, but because of the difficulty navigators had both predicting and tracking the probes – with or without a unit conversion error.

After the Climate Orbiter failed to achieve a non-intersecting orbit, two teams of navigators worked on the flight path of the Polar Lander. Each time they tried to model and predict solar wind effects, they were frustrated – they could not correlate the small force corrections due to the solar wind with the path of the probe.

On both missions, NASA tried to use triangulation as well as the Doppler ranging data, and triangulation yielded surprisingly unsatisfactory results.

Please allow me enough latitude to use a hypothetical to demonstrate why I think we must track down the exact causes of these small force and/or navigational errors. Assume the forces are real, and assume they are caused by a gravitational equivalent to a change in the permeability-of-free-space that is a function of mass. This would mean that a probe moving towards the sun would be slowed as more energy is stored in a stronger ‘mass field’ nearer the sun.

The Newtonian equation for velocity then becomes a function of total proximal mass, not just the mass of the object in motion (Ek=Mv^2/2f(x) where f(x) @ 1 AU = 1, and becomes larger as the object approaches the sun, leaving more energy in the potential energy pool (Remember, this is ALL HYPOTHETICAL and the force changes are very small and tightly constrained.)

Look what would happen: As a probe approaches the sun, less potential energy is 'released' as kinetic. The velocity increases at a slightly slower rate than Newtonian predictions. Leaving close proximity to the Sun, the probe would require slightly less energy to achieve a greater acceleration, returning the probe to the predicted path. This is EXACTLY what the residuals look like in the Pioneer 6 pass near the limb of the sun, peaking (slowing) at closest proximity to the sun. Likewise, the 1/r ‘spring constant’ Anderson used to model the Solar wind effects upon Odysseus and Galileo follow this model.

There is more: If more potential energy is stored in a more massive environment, probes to Venus are proportionally slowed, while probes to Mars would experience a slight acceleration, achieve a slightly different orbit. This would cause us to overestimate the mass of Venue, and underestimate the mass of Mars. When we interpret the orbital gravimetric data, the smaller accelerations near the mountain peaks on Venus would then appear as negative gravity anomalies, and likewise, valley floors would appear as positive anomalies. This is what we observe.

On Mars, the situation is exactly opposite: The increase in the transfer to kinetic energy would cause us to underestimate the mass of Mars from orbiters, so the mountain peaks would be interpreted as positive gravity anomalies while valley floors would appear negative. This is also precisely what we observe.

There is more.

We now have gravity maps of Mars from distances varying from 300 to 800 km, but the 800 km data cannot be reconciled with the 300 km maps. The 300km data showing greater anomalies. The moment of inertia for Mars appears to be different if ranging data to the surface probes (Pathfinder and Viking) is used than the inertial moment necessary to explain the orbital gravity anomalies.

All of the Martian probes have landed at higher velocities than expected and, entered at higher attitudes. All descent trajectory models have required a thinner-than-expected upper atmosphere, and high surface winds.

I can go on and on, but I think that you get my point: It would not take a major change in solar dynamics to produce surprising errors. I have been arguing with Jason and Bruce that the rocks, the craters, the strata, and the Doppler descent data from Huygens could be better modeled with less shear wind and more mass.

Fortunately, missions are already in progress that can disprove this hypothesis: Messenger will pass close enough to the sun that the ‘limb effect’ observed by Pioneer 6 could be repeated. MRO will provide gravity maps at 150 km – if this hypothesis is true, MRO will map greater gravity anomalies than prior orbiters that cannot be fit with harmonic extrapolations. MCO will also provide us with a good average atmospheric gradient, one that will be steeper than expected if the planet is more massive.

Finally, careful mapping of the effects of Saturn’s moons on Cassini should reveal ‘unmodelable drag’ forces and even greater gravity anomalies than Galileo found on Ganymede.

I don’t expect any degree of agreement with this assessment, but I hope I have peaked your interest in the manifold scientific data returning from the robotic planetary missions; and there just might be more to learn than mission planners dreamed, a truly revolutionary prospective of the cosmos, one just as foreign to scientific thinking today as the Ptolemic model.