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#11
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"Pioneer anomalous acceleration" and Cassini
"Jonathan Silverlight" schrieb im Newsbeitrag ... In message , greywolf42 writes Jonathan Silverlight wrote in message conjunction. There are no modelling of forces on the spacecraft in the paper -- construct or otherwise. Have you actually looked at the paper?? Yes. They wouldn't be able to see anything without accurate modelling of the gravitational and non-gravitational forces on the spacecraft. You are incorrect. The paper does not deal with forces on the spacecraft at all. Please read it. Which part of "An important contribution to the frequency shift is due to non-gravitational forces acting on the spacecraft" do you have a problem reading? Maybe my english isn'g good enough but the sentence "However, the uncertainty in the thermal model overwhelms any plausible application of the pioneer anomaly to Cassini." seems to me that they couldn't model arrurately enough for the checking of the "pioneer anomaly". Thermal seems to refer to the thermal radiation of the isotope batteries. Lots of Greetings! Volker |
#12
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"Pioneer anomalous acceleration" and Cassini
In message , Volker Hetzer
writes "Jonathan Silverlight" schrieb im Newsbeitrag ... In message , greywolf42 writes Jonathan Silverlight wrote in message conjunction. There are no modelling of forces on the spacecraft in the paper -- construct or otherwise. Have you actually looked at the paper?? Yes. They wouldn't be able to see anything without accurate modelling of the gravitational and non-gravitational forces on the spacecraft. You are incorrect. The paper does not deal with forces on the spacecraft at all. Please read it. Which part of "An important contribution to the frequency shift is due to non-gravitational forces acting on the spacecraft" do you have a problem reading? Maybe my english isn'g good enough but the sentence "However, the uncertainty in the thermal model overwhelms any plausible application of the pioneer anomaly to Cassini." seems to me that they couldn't model arrurately enough for the checking of the "pioneer anomaly". Thermal seems to refer to the thermal radiation of the isotope batteries. That's _very_ interesting. Thanks! I assume you're quoting "Improved Test of General Relativity with Radio Doppler Data from the Cassini Spacecraft" by Anderson et al., as that's the only hit I get doing a search for "application of the pioneer anomaly to Cassini". It's at http://www.arxiv.org/abs/gr-qc/0308010v1, but there's a note that "This paper was withdrawn at the recommendation of the Cassini Radio Science Team." Version 1 is still available, and they quote a radial acceleration of -26.7 x 10^-8 cm s^2 and note that "unlike Pioneer, the result is not anomalous". -- Rabbit arithmetic - 1 plus 1 equals 10 Remove spam and invalid from address to reply. |
#13
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"Pioneer anomalous acceleration" and Cassini
"Jonathan Silverlight" schrieb im Newsbeitrag ... In message , Volker Hetzer writes "Jonathan Silverlight" schrieb im Newsbeitrag ... In message , greywolf42 writes Jonathan Silverlight wrote in message conjunction. There are no modelling of forces on the spacecraft in the paper -- construct or otherwise. Have you actually looked at the paper?? Yes. They wouldn't be able to see anything without accurate modelling of the gravitational and non-gravitational forces on the spacecraft. You are incorrect. The paper does not deal with forces on the spacecraft at all. Please read it. Which part of "An important contribution to the frequency shift is due to non-gravitational forces acting on the spacecraft" do you have a problem reading? Maybe my english isn'g good enough but the sentence "However, the uncertainty in the thermal model overwhelms any plausible application of the pioneer anomaly to Cassini." seems to me that they couldn't model arrurately enough for the checking of the "pioneer anomaly". Thermal seems to refer to the thermal radiation of the isotope batteries. That's _very_ interesting. Thanks! I assume you're quoting "Improved Test of General Relativity with Radio Doppler Data from the Cassini Spacecraft" by Anderson et al., as that's the only hit I get doing a search for "application of the pioneer anomaly to Cassini". It's at http://www.arxiv.org/abs/gr-qc/0308010v1, but there's a note that "This paper was withdrawn at the recommendation of the Cassini Radio Science Team." Yep. That's the one. Version 1 is still available, and they quote a radial acceleration of -26.7 x 10^-8 cm s^2 and note that "unlike Pioneer, the result is not anomalous". Hm. Sounds like a contradiction to me. First they say that they don't have an anomaly and then they say they couldn't check for it. Lots of Greetings! Volker |
#14
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"Pioneer anomalous acceleration" and Cassini
You are all blithely assuming that the low amplitude
oscillations of charge around some average that are received when the receiving antenna is pointing in the region of the sky containing the spacecraft show a clear frequency over a period of four hours or so when the receiver antenna is so positioned and constantly readjusted to point to the spacecraft as the earth moves. This may be a perfectly correct assumption on your part and Anderson et al.; parts of the Anderson paper and others describing the method of amplifying and detecting the expected doppler shifted frequency are hard to decipher though George Dishman has been helpful in translating some of the FFT and PLL jargon. If the reception was perfectly clear then one would see every (1/2.11.....) times 10^-9 seconds a crossing at zero ( average value) of the oscillating voltage. But because of thermal noise and other radiation other voltages are added to this expected set of voltages and so to those at the zero crossings every (1/2.11.....) times 10^-9 seconds obscuring| the zero and to other voltages making zero crossings appear which are not part of the systematic pattern. Using phase locked loops one could find a first true zero and then one could take a second or billions of successive voltage values and add them to the next second or billion etc for 60 seconds and the random obscuring voltages would cancel out. Apparently they have done so until recently for Pioneer 10 but I imagine there had been a steady degradation and I would like to know from a radio astronomer what form this degradation takes?? eg How many regularly spaced zeros do you have to miss before you decide the data is too noisy to establish a specific frequency? "Volker Hetzer" wrote in message ... "Jonathan Silverlight" schrieb im Newsbeitrag ... In message , Volker Hetzer writes "Jonathan Silverlight" schrieb im Newsbeitrag ... In message , greywolf42 writes Jonathan Silverlight wrote in message conjunction. There are no modelling of forces on the spacecraft in the paper -- construct or otherwise. Have you actually looked at the paper?? Yes. They wouldn't be able to see anything without accurate modelling of the gravitational and non-gravitational forces on the spacecraft. You are incorrect. The paper does not deal with forces on the spacecraft at all. Please read it. Which part of "An important contribution to the frequency shift is due to non-gravitational forces acting on the spacecraft" do you have a problem reading? Maybe my english isn'g good enough but the sentence "However, the uncertainty in the thermal model overwhelms any plausible application of the pioneer anomaly to Cassini." seems to me that they couldn't model arrurately enough for the checking of the "pioneer anomaly". Thermal seems to refer to the thermal radiation of the isotope batteries. That's _very_ interesting. Thanks! I assume you're quoting "Improved Test of General Relativity with Radio Doppler Data from the Cassini Spacecraft" by Anderson et al., as that's the only hit I get doing a search for "application of the pioneer anomaly to Cassini". It's at http://www.arxiv.org/abs/gr-qc/0308010v1, but there's a note that "This paper was withdrawn at the recommendation of the Cassini Radio Science Team." Yep. That's the one. Version 1 is still available, and they quote a radial acceleration of -26.7 x 10^-8 cm s^2 and note that "unlike Pioneer, the result is not anomalous". Hm. Sounds like a contradiction to me. First they say that they don't have an anomaly and then they say they couldn't check for it. Lots of Greetings! Volker |
#15
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"Pioneer anomalous acceleration"
Perhaps some of you clever guys could care to bestow an opinion on findings
at www.estfound.org/pioneer.htm . Is it go again for "Tired Light" redshift? /kgb "ralph sansbury" wrote in message ... You are all blithely assuming that the low amplitude oscillations of charge around some average that are received when the receiving antenna is pointing in the region of the sky containing the spacecraft show a clear frequency over a period of four hours or so when the receiver antenna is so positioned and constantly readjusted to point to the spacecraft as the earth moves. This may be a perfectly correct assumption on your part and Anderson et al.; parts of the Anderson paper and others describing the method of amplifying and detecting the expected doppler shifted frequency are hard to decipher though George Dishman has been helpful in translating some of the FFT and PLL jargon. If the reception was perfectly clear then one would see every (1/2.11.....) times 10^-9 seconds a crossing at zero ( average value) of the oscillating voltage. But because of thermal noise and other radiation other voltages are added to this expected set of voltages and so to those at the zero crossings every (1/2.11.....) times 10^-9 seconds obscuring| the zero and to other voltages making zero crossings appear which are not part of the systematic pattern. Using phase locked loops one could find a first true zero and then one could take a second or billions of successive voltage values and add them to the next second or billion etc for 60 seconds and the random obscuring voltages would cancel out. Apparently they have done so until recently for Pioneer 10 but I imagine there had been a steady degradation and I would like to know from a radio astronomer what form this degradation takes?? eg How many regularly spaced zeros do you have to miss before you decide the data is too noisy to establish a specific frequency? "Volker Hetzer" wrote in message ... "Jonathan Silverlight" schrieb im Newsbeitrag ... |
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"Pioneer anomalous acceleration" and Cassini
Jonathan Silverlight wrote
in message ... In message , Volker Hetzer writes "Jonathan Silverlight" schrieb im Newsbeitrag ... In message , greywolf42 writes Jonathan Silverlight wrote in message {snip} Which part of "An important contribution to the frequency shift is due to non-gravitational forces acting on the spacecraft" do you have a problem reading? Maybe my english isn'g good enough but the sentence "However, the uncertainty in the thermal model overwhelms any plausible application of the pioneer anomaly to Cassini." seems to me that they couldn't model arrurately enough for the checking of the "pioneer anomaly". Thermal seems to refer to the thermal radiation of the isotope batteries. That's _very_ interesting. Thanks! I assume you're quoting "Improved Test of General Relativity with Radio Doppler Data from the Cassini Spacecraft" by Anderson et al., as that's the only hit I get doing a search for "application of the pioneer anomaly to Cassini". Yes, that was the reference. It's at http://www.arxiv.org/abs/gr-qc/0308010v1, but there's a note that "This paper was withdrawn at the recommendation of the Cassini Radio Science Team." Fascinating. Version 1 is still available, and they quote a radial acceleration of -26.7 x 10^-8 cm s^2 and note that "unlike Pioneer, the result is not anomalous". Well, the complete abstract is: "Radio Doppler data from the Cassini spacecraft during its solar conjunction in June 2002 can be used to test General Relativity. In terms of the standard post-Newtonian parameter , the result is gamma - 1 = (-4.8 +- 5.7) x 10^-5, including both random and systematic error (sic). Einstein's theory has survived yet another test." There are two mentions of the Pioneer effect in this paper: "We include eight parameters in the weighted-least-squares solution: first, the six initial conditions (state) for the spacecraft trajectory; secondly, a constant radial acceleration a_r, primarily to account for the spacecraft' s thermal emission, but also for smaller effects such as unmodeled solar-pressure, beamed radio emission, and a possible contribution from the Pioneer anomaly [12]; and finally the relativity parameter gamma." And: "Finally, the error in a_r from 27 days of Cassini Doppler data is about two times better than the result from 11 years of Pioneer 10 Doppler data [12]. However, unlike Pioneer, the result is not anomalous. Both Pioneer and Cassini are powered by radioisotope thermoelectric generators (RTG), but on Pioneer they are mounted on booms and radiate the bulk of their thermal output isotropically into space without reaching the spacecraft. On the other hand for Cassini, the RTG's are mounted on the spacecraft bus beneath the high-gain parabolic dish antenna. Their thermal output is controlled by refection and absorption by the antenna and other spacecraft parts. It is difficult to model, although it should be directed toward the Earth, as confirmed by the negative sign in the solution for a_r. However, the uncertainty in the thermal model overwhelms any plausible application of the Pioneer anomaly to Cassini." In short, there is no way Cassini can be used for evaluation of the Pioneer effect. This is because the thermal emissions from Cassini are non-isotropic, and far greater in magnitude than the expected Pioneer effect. The statement the Cassini "result is not anomalous" is completely misleading. And completely wrong when taken out of context. The result is not anomalous only because the Pionner effect cannot be observed by Cassini, due to the effect being swamped by difficult-to-model thermal emissions. Again, the purpose of this measurement was validation of GR's gamma -- not the Pioneer effect. -- greywolf42 ubi dubium ibi libertas {remove planet for return e-mail} |
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"Pioneer anomalous acceleration" and Cassini
In message , greywolf42
writes In short, there is no way Cassini can be used for evaluation of the Pioneer effect. This is because the thermal emissions from Cassini are non-isotropic, and far greater in magnitude than the expected Pioneer effect. The statement the Cassini "result is not anomalous" is completely misleading. And completely wrong when taken out of context. The result is not anomalous only because the Pionner effect cannot be observed by Cassini, due to the effect being swamped by difficult-to-model thermal emissions. Again, the purpose of this measurement was validation of GR's gamma -- not the Pioneer effect. I know that. I don't know if the solar opposition experiment has been published, but the point is that Bertotti et al. quote a figure for the acceleration from the RTGs of 3 x 10^-9 m s^-2, with an error of 9 x 10^-11 m s^-2. That error is about "an order of magnitude" less than the Pioneer effect. Anderson et al. quote a figure for a_r (the radial acceleration, mostly due to the RTGs) of -26.7 x 10^-8 cm s^-2, which is essentially the same when you convert. As Volker Hetzer says, there's a contradiction between the statements that "the result is not anomalous" and "the uncertainty in the thermal model overwhelms any plausible application of the Pioneer anomaly to Cassini". The new measurements are much more accurate than the Pioneer ones (compare the residuals) and the Pioneer effect doesn't appear. -- Rabbit arithmetic - 1 plus 1 equals 10 Remove spam and invalid from address to reply. |
#18
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"Pioneer anomalous acceleration" and Cassini
"greywolf42" wrote in message ...
Jonathan Silverlight wrote in message ... There's an article in the current issue of Nature that seems relevant to the Pioneer anomalous acceleration question ("A test of general relativity using radio links with the Cassini spacecraft" B Bertotti, L Iess and P Tortora, Nature vol 425. No. 6956 p. 374, doi:10.1038/nature01997) AFAICS they have accurately modelled emission from the RTGs and they don't see any unexplained acceleration. They haven't looked for anomalous acceleration with this experiment. The referenced experiment measures the time-delay of the signal in a gravitational field. Nothing more. Does that mean the question is settled, or isn't their measurement sufficiently sensitive? The question was settled years ago. There *is* definitive anomalous acceleration in pioneer and the voyagers. No theoretical explanation has yet been settled on. Finally gathered the courage to tentatively suggest that when photons are emmitted, they give a 'recoil' against the source. If radiation from within the craft is directed in a particular direction, a thrust might occur. (I thought that this would be so insignificant as to be immesurable and undetectable, but maybe not) What would happen to a high-power laser carefully suspended- any chance of detecting an observable thrust counter to beam direction??? Jim G |
#19
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"Pioneer anomalous acceleration" and Cassini
Jonathan Silverlight wrote
in message ... In message , greywolf42 writes {replaced invisibly snipped quote from paper} ========================== Well, the complete abstract is: "Radio Doppler data from the Cassini spacecraft during its solar conjunction in June 2002 can be used to test General Relativity. In terms of the standard post-Newtonian parameter , the result is gamma - 1 = (-4.8 +- 5.7) x 10^-5, including both random and systematic error (sic). Einstein's theory has survived yet another test." There are two mentions of the Pioneer effect in this paper: "We include eight parameters in the weighted-least-squares solution: first, the six initial conditions (state) for the spacecraft trajectory; secondly, a constant radial acceleration a_r, primarily to account for the spacecraft' s thermal emission, but also for smaller effects such as unmodeled solar-pressure, beamed radio emission, and a possible contribution from the Pioneer anomaly [12]; and finally the relativity parameter gamma." And: "Finally, the error in a_r from 27 days of Cassini Doppler data is about two times better than the result from 11 years of Pioneer 10 Doppler data [12]. However, unlike Pioneer, the result is not anomalous. Both Pioneer and Cassini are powered by radioisotope thermoelectric generators (RTG), but on Pioneer they are mounted on booms and radiate the bulk of their thermal output isotropically into space without reaching the spacecraft. On the other hand for Cassini, the RTG's are mounted on the spacecraft bus beneath the high-gain parabolic dish antenna. Their thermal output is controlled by refection and absorption by the antenna and other spacecraft parts. It is difficult to model, although it should be directed toward the Earth, as confirmed by the negative sign in the solution for a_r. However, the uncertainty in the thermal model overwhelms any plausible application of the Pioneer anomaly to Cassini." ========================== In short, there is no way Cassini can be used for evaluation of the Pioneer effect. This is because the thermal emissions from Cassini are non-isotropic, and far greater in magnitude than the expected Pioneer effect. The statement the Cassini "result is not anomalous" is completely misleading. And completely wrong when taken out of context. The result is not anomalous only because the Pionner effect cannot be observed by Cassini, due to the effect being swamped by difficult-to-model thermal emissions. Again, the purpose of this measurement was validation of GR's gamma -- not the Pioneer effect. I know that. Then why are you attempting to claim results other than what the paper and observations were about? I don't know if the solar opposition experiment has been published, but the point is that Bertotti et al. Horsefeathers. The reference under discussion was Anderson and Lau -- not Bertotti. And the difficulty of modelling the emission is not physically different for Bertotti than four Anderson and Lau. But I guess that's why you snipped the quotes from your own reference (for the second time): quote a figure for the acceleration from the RTGs of 3 x 10^-9 m s^-2, with an error of 9 x 10^-11 m s^-2. That error is about "an order of magnitude" less than the Pioneer effect. Not according to Anderson and Lau. Anderson et al. quote a figure for a_r (the radial acceleration, mostly due to the RTGs) of -26.7 x 10^-8 cm s^-2, which is essentially the same when you convert. Yes. And Anderson and Lau mention that "the uncertainty in the thermal model overwhelms any plausible application of the Pioneer anomaly to Cassini." As Volker Hetzer says, there's a contradiction between the statements that "the result is not anomalous" and "the uncertainty in the thermal model overwhelms any plausible application of the Pioneer anomaly to Cassini". The new measurements are much more accurate than the Pioneer ones (compare the residuals) and the Pioneer effect doesn't appear. How are they more accurate? According to Anderson, the measurements of 'anomalous accelerations' would are 10 times less precise than the gross effect measured to 2 sig figs on Pioneer. Due to "the uncertainty in the thermal model" of Cassini. -- greywolf42 ubi dubium ibi libertas {remove planet for return e-mail} |
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"Pioneer anomalous acceleration" and Cassini
"Jim Greenfield" wrote in message om... "greywolf42" wrote in message ... The question was settled years ago. There *is* definitive anomalous acceleration in pioneer and the voyagers. No theoretical explanation has yet been settled on. Finally gathered the courage to tentatively suggest that when photons are emmitted, they give a 'recoil' against the source. Yes, each photon carries a momentum proportional to its frequency. If radiation from within the craft is directed in a particular direction, a thrust might occur. (I thought that this would be so insignificant as to be immesurable and undetectable, but maybe not) The data from Pioneer is sent back by radio. The power is nominally 8W, a little more than a mobile phone. The radiation pressure from the beam is about 13% of the magnitude of the anomaly but the beam pushes the craft away from the Earth while the anomaly is an acceleration towards the Earth. This is why asymmetric thermal radiation from the RTGs was looked at as a possible explanation, they emit a couple of kW altogether. The trouble was that nobody could figure out how to explain the asymmetry. What would happen to a high-power laser carefully suspended- any chance of detecting an observable thrust counter to beam direction??? Yes, or turned around, shining a laser on a solar sail can give it thrust. The effect can also be used to suspend individual atoms in a laser beam. George |
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