The Pioneer Anomaly Options

[Stephen]

Merek Chertkow's report on the 2005 Pioneer Anomaly Conference
"Turyshev and John Anderson, also of JPL, with financial support from The Planetary Society were able to save this additional information from simply being thrown in the dumpster! I know what you must be thinking! I can’t believe it either!"

That sounds just like the anecdote Don Wilhelms tells in "To a Rocky Moon"! When will NASA learn stop throwing its treasures out with the trash?

[Steffen]

Sorry, but what is this anomaly about?
( I'm a Newbie asking too many questions )

[elakdawalla]

Sorry, but what is this anomaly about?
( I'm a Newbie asking too many questions  )

Google searches will answer lots of questions -- try here for starters.
The Pioneer Anomaly

--Emily

[Planet X]

Another cool tidbit: there is one last opportunity to attempt to contact Pioneer 10, coming up in this February/March.  (They think that, just barely maybe there is enough power still now in the old RTGs...) The round-trip light-time is 25 hours, so the contact would proceed by sending out a signal from Goldstone, waiting a day while the earth spins around once and the radio waves make their merry way, and listening for a response again at Goldstone.  Somehow that image amuses me :^)

Cool! I hope they attempt it and it's successful. Later!

J P

[djellison]

I have an image in my head of driving around the M25 ( the london 'orbital' motorway ) and yelling at a service station "BIG MAC AND FRIES PLEASE"...then doing another lap of the motorway, only to have a burger land on my windscreen about 80 miles later once I was back in the same place

Doug

[The Messenger]

Sorry, but what is this anomaly about?
( I'm a Newbie asking too many questions  )

Here is a concise summary by the three principles:
http://arxiv.org/PS_cache/gr-qc/pdf/0411/0411077.pdf

And if you want to see how exhaustively this phenomena has been explored, here is another 55 pages:

http://arxiv.org/PS_cache/gr-qc/pdf/0104/0104064.pdf

NASA's unwillingness to fund a follow-up mission, or even preserve historical data that may shed additional light is disheartening. We know our physical models are close, and we also know exceptions that may require new models, if they exist, must be hiding in the fringes. Anderson & company have tried every avenue they can imagine to null this anomaly as an artifact, and have been unable to do so.

[JRehling]

NASA's unwillingness to fund a follow-up mission, or even preserve historical data that may shed additional light is disheartening.
[...]
Anderson & company have tried every avenue they can imagine to null this anomaly as an artifact, and have been unable to do so.

From a risk assessment basis, I don't find it disheartening that no dedicated mission is on the books. For one, it's possible (even if unlikely, and I mean no disrespect to Anderson et al) that future analysis will lead to a forehead-slapping resolution to the anomaly. That head-slap would be a lot harder if we had a $150 million mission already in interplanetary cruise for no good reason when the anomaly were understood. It's also possible that a future mission could investigate this completely in line with its other, primary goals.

There is no way we can investigate various outer solar system objects in great detail without visits from spacecraft. There's no chance that an ingenious look at old data will suddenly give us maps of the unseen hemispheres of the uranian moons. But in this case, there is a chance, and there's no urgency to resolving the mystery before the ground on which it rests has been plowed into dust by means much, much cheaper than a spacecraft.

The disregard for the existing data is rather more disheartening, but simply goes to show how things can be neglected for their due worth by a boxology-driven bureaucracy like NASA.

[Guest_Richard Trigaux_*]

From a risk assessment basis, I don't find it disheartening that no dedicated mission is on the books. For one, it's possible (even if unlikely, and I mean no disrespect to Anderson et al) that future analysis will lead to a forehead-slapping resolution to the anomaly. That head-slap would be a lot harder if we had a $150 million mission already in interplanetary cruise for no good reason when the anomaly were understood. It's also possible that a future mission could investigate this completely in line with its other, primary goals.

There is no way we can investigate various outer solar system objects in great detail without visits from spacecraft. There's no chance that an ingenious look at old data will suddenly give us maps of the unseen hemispheres of the uranian moons. But in this case, there is a chance, and there's no urgency to resolving the mystery before the ground on which it rests has been plowed into dust by means much, much cheaper than a spacecraft.

The disregard for the existing data is rather more disheartening, but simply goes to show how things can be neglected for their due worth by a boxology-driven bureaucracy like NASA.

I agree with this, especially with the conclusion. THE EXISTING DATA MUST BE KEPT SAFE and analyzed completelly. The results must be confirmed by other flights (of which it can be a secondary goal) before sending a dedicated mission.

[Mongo]

If the unmodeled acceleration is indeed, as the evidence suggests, about 0.00000008 cm-per-second per second, then since 1980 (when the effect first definitely appears) there would be a cumulative unmodeled delta-v of about 17 metres-per-second towards the Sun, and a cumulative unmodeled spatial displacement of about 269,000 km toward the Sun.

Given the upcoming opportunity for a com session with one of the Pioneers, this would result in a round-trip time almost two seconds shorter than what it 'should' be. Although it is still about 25 hours.

Bill

[ljk4-1]

If the unmodeled acceleration is indeed, as the evidence suggests, about 0.00000008 cm-per-second per second, then since 1980 (when the effect first definitely appears) there would be a cumulative unmodeled delta-v of about 17 metres-per-second towards the Sun, and a cumulative unmodeled spatial displacement of about 269,000 km toward the Sun.

Given the upcoming opportunity for a com session with one of the Pioneers, this would result in a round-trip time almost two seconds shorter than what it 'should' be.  Although it is still about 25 hours.

Bill

Is there any way to tell if small planetoids or comets are undergoing the same effect? Or are they just too big and their orbits - especially the ones farther out - just not known well enough?

Heck, while I'm at it - has anyone investigated to see if Dark Matter exists not just outside galaxies but in interstellar space as well? Perhaps closer than we think?

[Mongo]

Heck, while I'm at it - has anyone investigated to see if Dark Matter exists not just outside galaxies but in interstellar space as well?  Perhaps closer than we think?

I personally am less than convinced of the existence of so-called Dark Matter.

The problem for me is that:

1) New physics is needed to account for its existence.

2) In order for it to account for the observed galactic rotation curves (which is why it was originally proposed), the distribution of 'Dark Matter' in each galaxy must be carefully adjusted by radius from the galactic center in order to match the needed gravitational potentials. This distribution needs to vary wildly from one galaxy to the next, in order to produce rotation curves that are far more similar to each other than they 'should be'.

3) No candidate Dark Matter particles have ever been detected.

Compare this with Mordehai Milgrom's MOND theory, which was also designed to explain galactic rotation curves:

1) New physics is needed to account for the deviations from Newtonian physics. Okay, so far the two explanations are a wash.

2) MOND naturally explains galactic rotation curves with little or no special adjustment, by assuming that the visible matter (including gas and dust) is in fact all there is. The theory was used to make predictions of rotation curves for classes of galaxies (i.e. low surface-brightness galaxies) that were unknown when it was introduced, that have panned out exactly. Dark Matter, on the other hand, made wildly inaccurate predictions, that must be corrected ex post facto.

3) The same physics that seems to be behind MOND can also explain so-called 'Dark Energy' and, in certain formulations, even the Pioneer Effect,

Here are some papers about MOND:

The arXiv papers of the originator, Mordehai Milgrom, regarding MOND:

http://xxx.lanl.gov/find/astro-ph/1/AND+au...D/0/1/0/all/0/1

TeVeS, the currently most popular relativistic formulation of MOND:

http://xxx.lanl.gov/find/astro-ph/1/abs:+TeVeS/0/1/0/all/0/1

Bill

[ljk4-1]

This site gives the general history and background on MOND, including links to other sites:

http://en.wikipedia.org/wiki/MOND

[ljk4-1]

Astrophysics, abstract
astro-ph/0503368

From: Dario N\'u\~nez [view email]

Date (v1): Wed, 16 Mar 2005 19:54:33 GMT (409kb)
Date (revised v2): Mon, 9 Jan 2006 17:37:29 GMT (421kb)

Pioneer anomaly? Gravitational pull due to the Kuiper belt

Authors: Jose A. de Diego, Dario Nunez, Jesus Zavala

Comments: 5 figures, final version, accepted for publication at Int. J. of Mod. Phys. D

In this work we study the gravitational influence of the material extending from Uranus orbit to the Kuiper belt and beyond on objects moving within these regions. We conclude that a density distribution given by $\rho®=\frac{1}{r}$ (for $r\geq 20 UA$) generates a constant acceleration towards the Sun on those objects, which, with the proper amount of mass, accounts for the blue shift detected on the Pioneers space crafts. We also discuss the effect of this gravitational pull on Neptune, and comment on the possible origin of such a matter distribution.

http://arxiv.org/abs/astro-ph/0503368

[The Messenger]

Astrophysics, abstract
astro-ph/0503368

From: Dario N\'u\~nez [view email]

Date (v1): Wed, 16 Mar 2005 19:54:33 GMT  (409kb)
Date (revised v2): Mon, 9 Jan 2006 17:37:29 GMT  (421kb)

Pioneer anomaly? Gravitational pull due to the Kuiper belt

Authors: Jose A. de Diego, Dario Nunez, Jesus Zavala

Comments: 5 figures, final version, accepted for publication at Int. J. of Mod. Phys. D

In this work we study the gravitational influence of the material extending from Uranus orbit to the Kuiper belt and beyond on objects moving within these regions. We conclude that a density distribution given by $\rho®=\frac{1}{r}$ (for $r\geq 20 UA$) generates a constant acceleration towards the Sun on those objects, which, with the proper amount of mass, accounts for the blue shift detected on the Pioneers space crafts. We also discuss the effect of this gravitational pull on Neptune, and comment on the possible origin of such a matter distribution.

http://arxiv.org/abs/astro-ph/0503368

Anderson & Co. wrote a response to this - Essentially this type of mass could NOT produce the measured linearity - the probe should be accelerating at an increasing rate (if the Kuiper belt has a high enough density), and/or the density would have to extend to near the orbit of Saturn and therefore be easily be detectable.

MOND is not theoretically based - it is purely a phenomological explanation of a rather confusing family of observations.

http://arxiv.org/PS_cache/gr-qc/pdf/0104/0104064.pdf

Page 22: 

The Aerospace’s analysis of the Galileo data covered the same arc as JPL and a second arc from 2 December 1992 to 24 March 1993. The analysis of Doppler data
from the first arc resulted in a determination for aP of ∼ (8 ± 3) × 10−8 cm/s2, a value similar to that from Pioneer 10. But the correlation with solar pressure was
so high (0.99) that it is impossible to decide whether solar pressure is a contributing factor...

...So, by interpreting this time variation as a true r−2 solar
pressure plus a constant radial acceleration, we found that Ulysses was subjected to an unmodeled acceleration towards the Sun of (12 ± 3) ×10−8 cm/s2.
Note, however, that the determined constant aP(U) is highly correlated with solar radiation pressure (0.888).

This shows that the constant acceleration and the solar radiation acceleration are not independently determined, even over a heliocentric distance variation from 5.4 to 1.3 AU.

Four independent data point should lead to a little bit more than head scratching. True, an independent mission is prohibitively expensive, but piggy-backing a frizbee on the New Horizon's probe: spin stabilized, with a Doppler repeater similar to the Pioneer probes - that could have been a reasonably cheap and lightweight add-on with enough parametric control to nail this puppy down.

[Jeff7]

Concerning dark matter, I remembered some article that had a theory for why dark matter need not exist at all - that we only need to use relativity properly, and apply it to gravity. Something along those lines.
Link - it has a summary of this theory, and a link to the full abstract. It seems to say that, when looking at something small, like a single star, Newtonian physics may be an adequate approximation, but this doesn't work when you're looking at the way an entire galaxy behaves.