The Pioneer Anomaly |
The Pioneer Anomaly |
Aug 16 2005, 04:27 PM
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#1
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Rover Driver Group: Members Posts: 1015 Joined: 4-March 04 Member No.: 47 |
http://www.planetary.org/news/2005/pioneer_anomaly_faq.html
The planetary society may be checking it out... QUOTE 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 The Pioneer data exists on a few hundred ancient 7- and 9-track magnetic tapes, which can only be read on "antique" outdated computers.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! |
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Aug 30 2005, 08:52 AM
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#2
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Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
Climate orbiter was not radar tracked, it was transponder tracked. You get precise distance, but have to model angular position on the sky from indirect data. One way to get precise relative position in the sky is differential interferometry, where one vehicle, say a mars orbiter, is a reference source, and the approaching vehicle's position relative to the reference can be measured.
The problem with Climate orbiter was not with the tracking data, it was modelling the trajectory based on that data when bogus information <incorrect spacecraft peturbation values from the momentum wheel offloading with thruster firing) was included in the solution. The nav team had recognized and been bothered the entire flight by considerably (several times?) larger trajectory calculation variations than normal, but not been able to find a cause of the error with available time and resource. Polar Lander wiped out due to either 1.) a programming error in the descent software that was almost guaranteed to eat their lunch. or 2.) any of considerable number of design defects that added risk to the landing but weren't "smoking gun" errors. The Pioneer anomaly is just that.. it's a departure of observations from very precise, but known imperfect calculations. We don't know if there's a physical something based on "deep" important physics, or if our engineering models of non-gravitational forces on the spacecraft are subtly wrong. It will cost at least a few hundred million dollars to fly a mission that will convincingly and unambiguously prove an "important" physics cause is either present or not, and *PRECISELY* measure that effect if it exists as a function of distance from the sun. *** NOT TRIVIAL ***. There are a lot of other research proposals and proposed space missions with equal or greater chances of testing and getting an important answer to "deep" physics questions that would cost the same or less than a Pioneer Anomaly mission. The best strategy is to pick the strongest tests with the greatest likelyhood of surprise, for the least amount of money and do or fly those..... and to pick tests that test fundamentally different possible suprises in deep physics. Things like dark matter detection experiments, gravity wave observatories, Dark energy investigations have far more chance per doller of real surprises than a pioneer anomaly mission. We need to keep it as an open question with the possibility of a mission, but right now, it seems a high risk, probably low yield mission for the money. |
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Aug 30 2005, 07:12 PM
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#3
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Member Group: Members Posts: 723 Joined: 13-June 04 Member No.: 82 |
QUOTE (edstrick @ Aug 30 2005, 08:52 AM) There are a lot of other research proposals and proposed space missions with equal or greater chances of testing and getting an important answer to "deep" physics questions that would cost the same or less than a Pioneer Anomaly mission. The best strategy is to pick the strongest tests with the greatest likelyhood of surprise, for the least amount of money and do or fly those..... and to pick tests that test fundamentally different possible suprises in deep physics. Things like dark matter detection experiments, gravity wave observatories, Dark energy investigations have far more chance per doller of real surprises than a pioneer anomaly mission. We need to keep it as an open question with the possibility of a mission, but right now, it seems a high risk, probably low yield mission for the money. The problem with a 'dark matter' mission is that the putative dark matter is entirely hypothetical, and may not (I would say probably doesn't) exist. Stanley Milgrom's MOND theory or Jakob Bekenstein's TeVeS theory seems to me to explain the observations in question much more easily than any dark matter theory does. There are also indications that the effects ascribed to 'dark energy' may also be a natural result of a full MOND or TeVeS theory. http://xxx.lanl.gov/abs/astro-ph/0504130 On the other hand, the so-called 'Pioneer Anomaly' appears to be genuine. The alternative explanations (solar wind, asymmetrical thermal radiation, etc.) appear to be several orders of magnitude too small to adequately explain the observed acceleration. I personally would say that a proper investigation of the 'Pioneer Anomaly' would be at least as important as Gravity Probe B, and could be mounted at a reasonable cost too. The spacecraft itself would be relatively inexpensive; the biggest cost would be the launch vehicle. Here are links to papers discussing possible approaches to a mission: http://xxx.lanl.gov/abs/astro-ph/0504634 http://xxx.lanl.gov/abs/astro-ph/0409373 http://xxx.lanl.gov/abs/gr-qc/0409117 Bill |
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Aug 31 2005, 11:28 AM
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#4
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Senior Member Group: Members Posts: 2488 Joined: 17-April 05 From: Glasgow, Scotland, UK Member No.: 239 |
Bill:
Your links, er, don't! Bob Shaw -------------------- Remember: Time Flies like the wind - but Fruit Flies like bananas!
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Aug 31 2005, 02:45 PM
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#5
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Member Group: Members Posts: 723 Joined: 13-June 04 Member No.: 82 |
That's strange; I just clicked on them and they sent me to the reports that I had referenced...
If they still don't work, I suppose that you can just go to http://xxx.lanl.gov/find/astro-ph and do a search for 'Pioneer Anomaly'. Or else just type out the links on your address bar. Bill |
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