|
|
Thread Tools | Display Modes |
#41
|
|||
|
|||
Pioneer Anomaly 2017
On Tuesday, May 9, 2017 at 7:27:45 AM UTC+10, Craig Markwardt wrote:
On Friday, May 5, 2017 at 8:08:05 PM UTC-4, wrote: On Tuesday, May 2, 2017 at 6:52:52 AM UTC+10, Craig Markwardt wrote: On Monday, May 1, 2017 at 8:25:16 AM UTC-4, wrote: --- --- Your comments were noted, but you were referring to the wrong paper. This is the exact wording from the 2012 version linked above: Third, Fig. 2 is strongly suggestive that the previously reported "onset" of the Pioneer anomaly may in fact be a simple result of mismodeling of the solar thermal contribution; this question may be resolved with further analysis of early trajectory data. Nope, you are incorrect. The 2012 paper concludes that "thermal recoil" is the explanation for the Pioneer anomaly. But not *solar* thermal. Or rather, the *new* thing of that paper is that by including the *internal* thermal effects (RTGs and electrical compartment dissipation) the anomaly is resolved. My paragraph above is exactly as presented in Turyshev's paper. You will find it in the conclusion section. OK, I acknowledge that quote now, but you are still incorrect. The conclusion of the paper is that *internally generated* thermal recoil force is a signifcant effect that has to be newly reckoned. The quote you are referring to is a single sentence in the entire paper. It *SUGGESTS* that the "early data" points in the chart you like to refer to, *may* be because the early analysts erroneously did not account for internal heat generation. Not the entire anomaly, as you originally stated, but the early data. But Anderson did include a fairly convincing argument in his analysis which demonstrated that internally generated heat could not cause the Pioneer anomaly. https://arxiv.org/pdf/gr-qc/0104064v5 "V111. SOURCES OF SYSTEMATIC ERROR INTERNAL TO THE SPACECRAFT" I can't imagine how the anomaly could be generated within the scope of the possible errors he could have made. I certainly can't see this. And in this following paragraph, what exactly "tipped the balance" ? I'm still lost here. --- --- Previous work *ALWAYS* considered solar thermal recoil forces, and could not explain the anomaly. Again, the new thing in the Turyshev et al 2012 paper was inclusion of internally-generated thermal terms, and this is what "tipped the balance." What exactly are the physical properties of these thermal terms? Do they represent new physics that Anderson was unaware of back in 2002? Hey, you asked this question, I responded that you could read Turyshev et al's 2012 paper for details, and you conveniently deleted that response. Why do you ask again? And, if you had bothered to read my other responses, you would be aware that (a) Anderson et al in 2002 did a more simplified modeling analysis (i.e. it was not "new physics," but rather model fidelity) (b) Anderson did not have access to temperature and other thermal data during the actual mission, that did become available later (Viktor Toth spent a large amount of time recovering old data disks with mission data). (c) The team "discovered" or at least had more time to consider pre-launch thermal engineering documents that Anderson did not. And (d) there was time to develop a high fidelity thermal model of the Pioneer spacecraft and validate it against actual mission temperature data. None of that can override Anderson's very fundamental logic. It's not handwaving by any means. So which part did he get wrong?? "V111. SOURCES OF SYSTEMATIC ERROR INTERNAL TO THE SPACECRAFT" --- --- Almost all known thermal coatings degrade w.r.t. the optical properties (the "alpha" coefficient), but do *not* significantly change w.r.t the infrared emission properties (the "epsilon" coefficient), including the coatings used on Pioneer. Therefore, your assumptions are irrelevant. However you wish to define "optical properties", one thing that's certain is that if a paint surface deteriorates and becomes more absorptive, it will also become equally more emissive. ... Incorrect. Optical (reflective) properties of most thermal coatings, including the coatings in question for Pioneer, do degrade. But the infrared emissivity properties do *NOT* change significantly. I referred you to a textbook on the matter, but you ignored it. Here, let me quote for you, "Thermal-control finishes are affected in orbit by charged particles, ultraviolet (UV) radiation, high vacuum, and the contaminant films that deposit out on almost all spacecraft surfaces. The general result of these processes is an increase in solar absorptivity with little or no effect on IR emittance." That makes no sense. If energy is continually pumped in through increased solar absorptivity, there's no doubt at all that the energy must come out again. Otherwise the temperature of the affected object will increase forever. Or is the reference to an onboard energy source, where the emittance remains constant as the surfaces degrade? I'll assume this to be the case. (Spacecraft Thermal Control Handbook, 2002, p. 143) But if you read onward, there are like twenty pages about degradation, why it occurs, etc. There have been long-term studies of degradation on the International space station (Fig 4.12) which show optical but not infrared degradation. Why would anyone expect anything else in these or any other circumstances? Let's bring it all back to the earth's surface and apply normal physical principles. My solar hot water system provides a proper insight into the consequences of the principles involved. It's a "stand alone" system which consists of an array of six solar panels connected in parallel, giving a maximum total output of 50 amps at 32 volts (1600 watts). The heating element wire diameter is 2.57mm and that's formed into a coil which is 2mm diameter less than the bore of the tube into which it's fitted. Earlier elements failed because they were placed inside a ceramic tube, which obviously required a much greater core temperature so that the 1600 watt input could be transferred to the water. They failed because the required core temperature was too high. **There's no doubt that if 1600 watts is put in, 1600 watts will eventually come out**. If the element tube is placed in an open air environment the tube temperature will rise until 1600 watts of thermal energy is transferred at the tube/air interface. Temperature sensors placed around the tube would all read the same. If (e.g.) 1/2 of the element circumference is shielded by a long ceramic insulator, placed inside the tube, a lesser temperature will be recorded adjacent to the insulator. But the total must still add up to 1600 watts. Now place the part shielded element tube in a vacuum. The only means of transferring the thermal energy is via radiation. The whole assembly would of course melt long before 1600 watts could be transferred via the vacuum. But now there's a significant time delay involved in the process of pumping the temperature up to the required level. Thermal conduction around the tube housing would quickly smooth out the temperature asymmetries. So it really doesn't matter where the sun is relative to a Pioneer spacecraft. All absorbed solar thermal energy will conduct throughout all contacting surfaces, adding to the general temperature. It would take some time before full emissive capability could be achieved. In the meantime, thermal energy is conducting to the lower temperature areas, ironing out the bumps. The ratio of conducted thermal energy per radiative thermal energy for a given temperature is not 1/1. Nothing like it. The temperature differential between the two means of transferring energy vastly favors conduction, so the temperature will continue to rise fairly uniformly throughout all contacting parts of the spacecraft until the absorbed energy rate is matched by the emission rate. And it will be emitted globally from all parts of the spacecraft at roughly the same rate. So, apart from a reduced solar radiation pressure, the drive from absorbed solar thermal energy is virtually zero. These two statements were derived from chapter V111 in the above link; (1) The RTG coating was designed to give .9 emissivity and .2 absorptivity. (2) The fore and aft emissivity would need to change by 10% to account for the Pioneer anomaly. So all that's left to drive the spacecraft inward are, the RTG reflections off the back of the HGA dish which diminish in power as the rear surfaces deteriorate, a solar radiation pressure error which becomes less significant with distance, and an emissivity difference between the fore and aft faces of the RTG's, even though your earlier quote appears to reject such a thing; "contaminant films deposit out on almost all spacecraft surfaces. The general result of these processes is an increase in solar absorptivity with little or no effect on IR emittance". Changing the absorptivity of any RTG face isn't going to affect the emissive power generated from within the RTG's. Decreasing IR emittance from the front face of the RTG's is the only way to cancel the anomaly. And solar radiation is all that's left to do the job. The rate of degradation of the RTG sun facing surfaces would then follow a solar radiation pressure style curve. But that doesn't compare with the Pioneer anomaly at all. Even if the front face of the HGA dish was affected by solar radiation in a manner that would increase solar thermal absorptivity the same curve would result. The reflective surface of the HGA dish was also covered in the same contaminates as the rest of the spacecraft yet it was still capable of reflecting audible signals to the onboard receiver at distances beyond 80 AU. The reflective surface certainly hadn't deteriorated too much. ----- Max Keon |
#42
|
|||
|
|||
Pioneer Anomaly 2017
On Sunday, May 14, 2017 at 3:50:09 AM UTC-4, wrote:
... are you again there ? .... consider the point of max anomaly or the point of max changement of anomaly ! .. and so you understand the uselessness to discuss around the RTG or similar things for resolving the Pioneer anomaly .. i think .. Not really. From the best available Doppler tracking data, dating from about 1980 and onward, the "anomaly" is quite constant. But also, the generated heat is rather constant as well, so it is difficult to disentangle these two effects. Turyshev's 2012 work showed that the emissive heat is compatible with the Doppler tracking data. CM |
#43
|
|||
|
|||
Pioneer Anomaly 2017
But Anderson did include a fairly convincing argument in his analysis which demonstrated that internally generated heat could not cause the Pioneer anomaly. https://arxiv.org/pdf/gr-qc/0104064v5 "V111. SOURCES OF SYSTEMATIC ERROR INTERNAL TO THE SPACECRAFT" I can't imagine how the anomaly could be generated within the scope of the possible errors he could have made. I certainly can't see this. And in this following paragraph, what exactly "tipped the balance" ? I'm still lost here. Actually, you are right, Anderson’s arguments were fairly convincing FOR THE TIME. What happened is that the Turyshev et al 2012 work came up with *more convincing* evidence of what’s going on. Heck, the section you quote says, “a complete thermal/physical model of the spacecraft might be able to ascertain if there are any other unsuspected heat systematics,” but then dismisses it. It turns out that was a premature dismissal. It doesn’t take much to see that Anderson did a very crude estimate using simple geometry, when it is now clear a higher fidelity approach was required. I think the key thing that Anderson’s discussion could not have known at the time, is that whether or not the equipment compartment louvers are open or closed, most of the heat generated inside the compartment escapes out the fore platform surface, and that is enough to account for much of the anomaly. Here, let me quote for you, "Thermal-control finishes are affected in orbit by charged particles, ultraviolet (UV) radiation, high vacuum, and the contaminant films that deposit out on almost all spacecraft surfaces. The general result of these processes is an increase in solar absorptivity with little or no effect on IR emittance." That makes no sense. If energy is continually pumped in through increased solar absorptivity, there's no doubt at all that the energy must come out again. Otherwise the temperature of the affected object will increase forever. … It’s unfortunate it doesn’t make sense to you. Yes, there is a thermal balance between energy received (related to optical absorptance alpha), energy emitted (related to infrared emittance epsilon) and temperature. If alpha increases while epsilon is constant, then yes, the temperature increases. So it really doesn't matter where the sun is relative to a Pioneer spacecraft. All absorbed solar thermal energy will conduct throughout all contacting surfaces, adding to the general temperature. Nope, that’s mostly incorrect. The sun-absorbing face of the spacecraft is the high-gain antenna, plus some of the RTGs. These bodies are thermally insulated from the rest of the spacecraft, so they do not “conduct.” The HGA primarily comes to thermal equilibrium via emission. It’s true that non-sun-facing (fore) side of the HGA which is adjacent to the equipment compartment, and is the same temperature as the sun-facing side because of conduction. But since the emissivity of the sun-facing side is 10-20x more than the fore side, most of the solar heating is re-emitted toward the sun. Very little of it is emitted toward the direction of the anomaly. But let’s summarize the issues you seem to be “lost” about. 1. You continue to mention that somehow Turyshev’s 2012 work is about “solar thermal” when that is incorrect. It is about solar thermal yes, but mostly about internally-generated thermal. When noted, you ignore or distract. 2. You continue to ask about what is in the Turyshev 2012 paper. I continue to refer you to it, but you ignore or distract. 3. You continue to ask about what is different between the Anderson 2001 and Turyshev 2012 works. I reply with detailed points, but you ignore or distract. 4. You continue to appeal to authority of Anderson’s work for thermal aspects. However, Anderson’s work in this topic is rather crude, and limited to point-like and plate-like approximations. Even Anderson noted that a higher fidelity model could be useful and Turyshev’s 2012 work accomplished it! You continue to ignore or distract from this point. |
#44
|
|||
|
|||
Pioneer Anomaly 2017
Il giorno domenica 14 maggio 2017 09:50:09 UTC+2, ha scritto:
Il giorno venerdì 5 maggio 2017 10:07:49 UTC+2, ha scritto: Il giorno lunedì 1 maggio 2017 22:52:52 UTC+2, Craig Markwardt ha scritto: Opening note... Don't tell me it won't. Hey bud, this is an open discussion forum. Whatever you think I should or should not say is completely irrelevant. On Monday, May 1, 2017 at 8:25:16 AM UTC-4, wrote: On Wednesday, April 26, 2017 at 3:15:29 AM UTC+10, Craig Markwardt wrote: On Monday, April 24, 2017 at 7:17:03 AM UTC-4, wrote: On Thursday, April 20, 2017 at 7:36:10 AM UTC+10, Craig Markwardt wrote: On Wednesday, April 19, 2017 at 5:50:36 AM UTC-4, wrote: --- --- Fig.2 from this link https://arxiv.org/pdf/1204.2507v1 apparently suggests that the Pioneer anomaly may only be the result of mismodelling of the solar thermal contribution. Your interpretation of this paper is incorrect. This paper (Turyshev et al 2002) demonstrates that most if not all of the "anomalous" acceleration can be attributed to *internal* thermal emission, generated by the RTGs and internal electronics. I note no response. Your comments were noted, but you were referring to the wrong paper. This is the exact wording from the 2012 version linked above: Third, Fig. 2 is strongly suggestive that the previously reported "onset" of the Pioneer anomaly may in fact be a simple result of mismodeling of the solar thermal contribution; this question may be resolved with further analysis of early trajectory data. Nope, you are incorrect. The 2012 paper concludes that "thermal recoil" is the explanation for the Pioneer anomaly. But not *solar* thermal. Or rather, the *new* thing of that paper is that by including the *internal* thermal effects (RTGs and electrical compartment dissipation) the anomaly is resolved. Previous work *ALWAYS* considered solar thermal recoil forces, and could not explain the anomaly. Again, the new thing in the Turyshev et al 2012 paper was inclusion of internally-generated thermal terms, and this is what "tipped the balance." But such an error can't reside in the mismodelling of the solar reflection/absorption characteristics of the HGA dish because that was accurately determined prior to launch, Just a side note, but thermal coatings do degrade over time, due to exposure to solar UV as well as ionizing radiation (white coatings become darker). So one can't be so certain about these properties. That was one of the aspects covered by the thermal analysis reported in Turyshev et al's 2012 paper. You apparently agree that the RTG surface coating becomes darker over time due to both solar radiation and radiation from within the RTG's. ... The pressure gradient will follow the RTG line, **not the solar radiation pressure curve.** .... Your writing appears to be motivated by intuition, but that is not the case. You can find a more correct and physics- and engineering-motivated discussion in books like "Spacecraft Thermal Control Handbook." Also, there are quite a few reference books on the degradation of thermal coatings from the time in the public domain. Almost all known thermal coatings degrade w.r.t. the optical properties (the "alpha" coefficient), but do *not* significantly change w.r.t the infrared emission properties (the "epsilon" coefficient), including the coatings used on Pioneer. Therefore, your assumptions are irrelevant. But bringing back to your original point before you distracted... you wondered why analysts could not know the thermal/optical properties of the Pioneer coatings exactly today. I guess you concede now that it's more difficult than you first wondered. It's obvious that either Turyshev or Anderson made a fairly significant error. But it's strange that Anderson is deemed wrong when a significant number of others also demonstrated the existence of the anomaly, including yourself (2002)? Why should this new result override all others when the average result from all contributors well and truly favors the anomaly's existence? That's a funny way to do physics. What would be funny is to ALWAYS assume that the "average" of some papers is relevant. ... I note no response. Still no response. But actually it's not true to say no one else was considering thermal. ... I note no response. Most folk can understand that the thermal solution doesn't work. "Most folk?" That's a rather unsubstantiated throwaway claim. It was *you* who claimed that everybody except for Turyshev et al 2012 had ignored the thermal origin, and I had to point out the error of your statement. You act as though analysts from the 1970's were using a set of physical laws that analysts of today are not familiar with. But that's not the case at all. Even if modifications have been made to some of the physical laws the analysts of today would still know exactly how the first data points showing the onset of the anomaly were derived. This is unsubstantiated. I am an analyst today of the Pioneer doppler data, and I do not have enough information from that one "onset" chart to understand how it was derived. But a discrepancy between observation and what was expected according to the prevailing physics at the time was clearly noted, and it continued to increase until the spacecraft reached the 20 AU mark. ... Non-sequitur. Your statement doesn't make it any easier for a Doppler analyst to reconstruct how the data analysis was done with early data. And... if you read Anderson's paper, the discrepancy was clearly noted... in the 1980s far after the spacecraft had passed 20AU. There is nothing in the paper that I can find which references earlier times, aside from the figures you point out of unknown provenance. Furthermore, let's be clear what was happening in the early 1970s. The Pioneer spacecraft were the first spacecraft to be sent to the outer solar system, with long cruise phases. Earlier spacecraft were kept inside the Earth-Moon system, or directed to the inner solar system. This new direction required new attention to detail and modeling of the physical effects of the space environment. No, the physical laws did not change, but the modeling capability within the software that was used did not capture all of the physics with the same fidelity. Effects such as spacecraft spin and new relativistic physics were being incorporated at that time. You can read the paper of Wong & Lubeley from 1974 (AIAA Paper No. 74-845) which demonstrates how the orbit determination groups were incorporating new software with better capabilities. Effects such as spacecraft propellant valve leaks were harder to understand, and navigation analysts had to make do. What physical laws does one apply to a valve that is leaky??? Before encountering Jupiter, both Pioneer spacecraft performed frequent maneuvers (every few weeks), which disturbed the orbit determination process, and also introduced more possibilities for leaks. Within the first 20 AU, the solar system radiation pressure is significant. In fact, before Jupiter approach, the radiation pressure is dominant over most of the force terms and is many times the "anomalous" acceleration. You pointed out thermal coatings, but let us not forget that the exact geometry of the spacecraft has an effect. Is the antenna treated as parabolic or flat-plate? What about the cut-outs and antenna feeds, how are those treated? These are not simple "physical law" issues. They have to do with how accurately the spacecraft systems can be modeled. Early in the mission, with computing power limited, some short cuts were inevitably taken. Each component would need to be analyzed properly, with a fairly in depth description of the processes involved if the analysis was expected to be taken seriously. Exactly. In the early 1970s, the computing power did not exist to do the in-depth analysis required. The operational need did not exist either.. But I see now that you understand that the process is not just about physical laws, but something more. Which raises some questions here. What data was plugged into the 2012 Turyshev computer simulation? The answers are in the Turyshev 2012 paper and its predecessors. Were the RTG emissions and solar radiation pressures correctly represented? Discussed in the Turyshev 2012 paper. "Correct" is a matter of tolerance. Or were they in fact mismodeled as was the assumption regarding Anderson's work? Thanks for the loaded question. Anderson et al did not "mismodel" anything intentionally. The level of fidelity was lower and they did not have the thermal data available at the time required to check, which Turyshev et al did have by 2012. Does the simulation software contribute toward the outcome? If so, what was the programmer's information source? The software is validated against all the missions supported by JPL for radiometric navigation, and the thermal modeling software is standard in the industry. That's why I say it has been validated: it has successfully been used thousands of times to correctly predict temperatures and emission profiles of equipment under test. And, let's not forget that Anderson et al 2002 compared multiple independent software suites, to guard against software errors. Thermal modeling software also has many inputs. All the inputs for thermal/optical properties were taken from Pioneer engineering documentation, but error tolerances were also considered. *AND*, then the simulations were validated against actual spacecraft measured temperatures. This temperature record was not readily available for Anderson et al to use in 2001, but was for later work. In the end it comes down to unconditional belief. Please. It comes down to a consideration of an analysis using established techniques, which has been validated against known data (both other spacecraft and Pioneer itself). There are mountains of documentation on this, which you ignored or barely skimmed over. It's easy for you to just cast out that claim without substantiation, and I reject it. So, please do not pretend that the state of affairs in the early 1970s can really be compared to the state today. Again, no response. The figure which you have referred to which shows the "onset" of the acceleration, you have replotted. What you failed to show was the uncertainty range (error bars) of the points. If you had displayed those as well, you would have seen that the bars are very large and that early data is not necessarily as stringent as you say. Again, no response. ... First of all, the quote is actually what Anderson et al. said in their paper, not me. And second of all, what is your point? If the goal is to accurately measure the "onset" of the anomaly, then the early data which would or could have shown that is largely lost forever. If the goal is to get an accurate measure of the anomaly in late days (20 AU) then the Anderson et al 2002 paper is just fine... but it doesn't prove or disprove any of your claims then. Anderson's paper claims the acceleration is consistent with being constant, quite the opposite of your claim! But he does acknowledge that there was an observed onset of the anomaly which indicated a deviation from well known standard physics at the time. Who acknowledges it? As I noted above, aside from the figures from unknown sources which you care to reproduce deceptively (see above), Anderson et al 2002 do not mention an "onset" in the paper. Again, I note that Anderson's claim is that the Pioneer anomaly is consistent with being constant. There was no evidence in the data available for something varying with time. This completely undercuts your own conclusion. CM PS.: .. could somebody give to me the email address of Mauro De Benedetto , rocket trajectory 'analist ? ... are you again there ? .... consider the point of max anomaly or the point of max changement of anomaly ! .. and so you understand the uselessness to discuss around the RTG or similar things for resolving the Pioneer anomaly .. i think .. .... ohoo .. ohooo ..is somebody hearing ? may i do a rererephrasation and try to do a little step for the science , and a big step for the anomaly' Pioneer ? The anomaly has yearly some changements ... changements of the 10-15% ..: the sun can stay between the earth and the Pioneer or the earth can look directly the rocket without the sun interposition ... so the difference in the anomaly'value becomes the 20-30% ... conclusion : if the earth should remain fixed in special positions , we should have differences in the anomaly of the 20-30% ... without discussing of RTG or interior leakages , can we do an hipothesis ? : the anomaly should be given by the distances that the rocket is marking .. and that is so true that the larger increasing (changement) of the anomaly'value is just when the earth is changing the speed relatively to the rochet of 30 km/s (sinusoidal inflection) ... hypothesis in the hypothesis : it is the Raman effect ( scattering ) aging in the distance and vacuum differences ... nope, nope ... yespe , yespe ... |
#45
|
|||
|
|||
Pioneer Anomaly 2017
On Monday, May 22, 2017 at 4:01:01 AM UTC-4, wrote:
Il giorno domenica 14 maggio 2017 09:50:09 UTC+2, ha scritto: Il giorno venerdì 5 maggio 2017 10:07:49 UTC+2, ha scritto: Il giorno lunedì 1 maggio 2017 22:52:52 UTC+2, Craig Markwardt ha scritto: Opening note... Don't tell me it won't. Hey bud, this is an open discussion forum. Whatever you think I should or should not say is completely irrelevant. On Monday, May 1, 2017 at 8:25:16 AM UTC-4, wrote: On Wednesday, April 26, 2017 at 3:15:29 AM UTC+10, Craig Markwardt wrote: On Monday, April 24, 2017 at 7:17:03 AM UTC-4, wrote: On Thursday, April 20, 2017 at 7:36:10 AM UTC+10, Craig Markwardt wrote: On Wednesday, April 19, 2017 at 5:50:36 AM UTC-4, wrote: --- --- Fig.2 from this link https://arxiv.org/pdf/1204.2507v1 apparently suggests that the Pioneer anomaly may only be the result of mismodelling of the solar thermal contribution. Your interpretation of this paper is incorrect. This paper (Turyshev et al 2002) demonstrates that most if not all of the "anomalous" acceleration can be attributed to *internal* thermal emission, generated by the RTGs and internal electronics. I note no response. Your comments were noted, but you were referring to the wrong paper. This is the exact wording from the 2012 version linked above: Third, Fig. 2 is strongly suggestive that the previously reported "onset" of the Pioneer anomaly may in fact be a simple result of mismodeling of the solar thermal contribution; this question may be resolved with further analysis of early trajectory data. Nope, you are incorrect. The 2012 paper concludes that "thermal recoil" is the explanation for the Pioneer anomaly. But not *solar* thermal. Or rather, the *new* thing of that paper is that by including the *internal* thermal effects (RTGs and electrical compartment dissipation) the anomaly is resolved. Previous work *ALWAYS* considered solar thermal recoil forces, and could not explain the anomaly. Again, the new thing in the Turyshev et al 2012 paper was inclusion of internally-generated thermal terms, and this is what "tipped the balance." But such an error can't reside in the mismodelling of the solar reflection/absorption characteristics of the HGA dish because that was accurately determined prior to launch, Just a side note, but thermal coatings do degrade over time, due to exposure to solar UV as well as ionizing radiation (white coatings become darker). So one can't be so certain about these properties. That was one of the aspects covered by the thermal analysis reported in Turyshev et al's 2012 paper. You apparently agree that the RTG surface coating becomes darker over time due to both solar radiation and radiation from within the RTG's. ... The pressure gradient will follow the RTG line, **not the solar radiation pressure curve.** ... Your writing appears to be motivated by intuition, but that is not the case. You can find a more correct and physics- and engineering-motivated discussion in books like "Spacecraft Thermal Control Handbook." Also, there are quite a few reference books on the degradation of thermal coatings from the time in the public domain. Almost all known thermal coatings degrade w.r.t. the optical properties (the "alpha" coefficient), but do *not* significantly change w.r.t the infrared emission properties (the "epsilon" coefficient), including the coatings used on Pioneer. Therefore, your assumptions are irrelevant. But bringing back to your original point before you distracted... you wondered why analysts could not know the thermal/optical properties of the Pioneer coatings exactly today. I guess you concede now that it's more difficult than you first wondered. It's obvious that either Turyshev or Anderson made a fairly significant error. But it's strange that Anderson is deemed wrong when a significant number of others also demonstrated the existence of the anomaly, including yourself (2002)? Why should this new result override all others when the average result from all contributors well and truly favors the anomaly's existence? That's a funny way to do physics. What would be funny is to ALWAYS assume that the "average" of some papers is relevant. ... I note no response. Still no response. But actually it's not true to say no one else was considering thermal. ... I note no response. Most folk can understand that the thermal solution doesn't work. "Most folk?" That's a rather unsubstantiated throwaway claim. It was *you* who claimed that everybody except for Turyshev et al 2012 had ignored the thermal origin, and I had to point out the error of your statement.. You act as though analysts from the 1970's were using a set of physical laws that analysts of today are not familiar with. But that's not the case at all. Even if modifications have been made to some of the physical laws the analysts of today would still know exactly how the first data points showing the onset of the anomaly were derived. This is unsubstantiated. I am an analyst today of the Pioneer doppler data, and I do not have enough information from that one "onset" chart to understand how it was derived. But a discrepancy between observation and what was expected according to the prevailing physics at the time was clearly noted, and it continued to increase until the spacecraft reached the 20 AU mark. ... Non-sequitur. Your statement doesn't make it any easier for a Doppler analyst to reconstruct how the data analysis was done with early data. And... if you read Anderson's paper, the discrepancy was clearly noted... in the 1980s far after the spacecraft had passed 20AU. There is nothing in the paper that I can find which references earlier times, aside from the figures you point out of unknown provenance. Furthermore, let's be clear what was happening in the early 1970s. The Pioneer spacecraft were the first spacecraft to be sent to the outer solar system, with long cruise phases. Earlier spacecraft were kept inside the Earth-Moon system, or directed to the inner solar system. This new direction required new attention to detail and modeling of the physical effects of the space environment. No, the physical laws did not change, but the modeling capability within the software that was used did not capture all of the physics with the same fidelity. Effects such as spacecraft spin and new relativistic physics were being incorporated at that time. You can read the paper of Wong & Lubeley from 1974 (AIAA Paper No. 74-845) which demonstrates how the orbit determination groups were incorporating new software with better capabilities. Effects such as spacecraft propellant valve leaks were harder to understand, and navigation analysts had to make do. What physical laws does one apply to a valve that is leaky??? Before encountering Jupiter, both Pioneer spacecraft performed frequent maneuvers (every few weeks), which disturbed the orbit determination process, and also introduced more possibilities for leaks. Within the first 20 AU, the solar system radiation pressure is significant. In fact, before Jupiter approach, the radiation pressure is dominant over most of the force terms and is many times the "anomalous" acceleration. You pointed out thermal coatings, but let us not forget that the exact geometry of the spacecraft has an effect. Is the antenna treated as parabolic or flat-plate? What about the cut-outs and antenna feeds, how are those treated? These are not simple "physical law" issues. They have to do with how accurately the spacecraft systems can be modeled.. Early in the mission, with computing power limited, some short cuts were inevitably taken. Each component would need to be analyzed properly, with a fairly in depth description of the processes involved if the analysis was expected to be taken seriously. Exactly. In the early 1970s, the computing power did not exist to do the in-depth analysis required. The operational need did not exist either. But I see now that you understand that the process is not just about physical laws, but something more. Which raises some questions here. What data was plugged into the 2012 Turyshev computer simulation? The answers are in the Turyshev 2012 paper and its predecessors. Were the RTG emissions and solar radiation pressures correctly represented? Discussed in the Turyshev 2012 paper. "Correct" is a matter of tolerance. Or were they in fact mismodeled as was the assumption regarding Anderson's work? Thanks for the loaded question. Anderson et al did not "mismodel" anything intentionally. The level of fidelity was lower and they did not have the thermal data available at the time required to check, which Turyshev et al did have by 2012. Does the simulation software contribute toward the outcome? If so, what was the programmer's information source? The software is validated against all the missions supported by JPL for radiometric navigation, and the thermal modeling software is standard in the industry. That's why I say it has been validated: it has successfully been used thousands of times to correctly predict temperatures and emission profiles of equipment under test. And, let's not forget that Anderson et al 2002 compared multiple independent software suites, to guard against software errors. Thermal modeling software also has many inputs. All the inputs for thermal/optical properties were taken from Pioneer engineering documentation, but error tolerances were also considered. *AND*, then the simulations were validated against actual spacecraft measured temperatures. This temperature record was not readily available for Anderson et al to use in 2001, but was for later work. In the end it comes down to unconditional belief. Please. It comes down to a consideration of an analysis using established techniques, which has been validated against known data (both other spacecraft and Pioneer itself). There are mountains of documentation on this, which you ignored or barely skimmed over. It's easy for you to just cast out that claim without substantiation, and I reject it. So, please do not pretend that the state of affairs in the early 1970s can really be compared to the state today. Again, no response. The figure which you have referred to which shows the "onset" of the acceleration, you have replotted. What you failed to show was the uncertainty range (error bars) of the points. If you had displayed those as well, you would have seen that the bars are very large and that early data is not necessarily as stringent as you say. Again, no response. ... First of all, the quote is actually what Anderson et al. said in their paper, not me. And second of all, what is your point? If the goal is to accurately measure the "onset" of the anomaly, then the early data which would or could have shown that is largely lost forever. If the goal is to get an accurate measure of the anomaly in late days (20 AU) then the Anderson et al 2002 paper is just fine... but it doesn't prove or disprove any of your claims then. Anderson's paper claims the acceleration is consistent with being constant, quite the opposite of your claim! But he does acknowledge that there was an observed onset of the anomaly which indicated a deviation from well known standard physics at the time. Who acknowledges it? As I noted above, aside from the figures from unknown sources which you care to reproduce deceptively (see above), Anderson et al 2002 do not mention an "onset" in the paper. Again, I note that Anderson's claim is that the Pioneer anomaly is consistent with being constant. There was no evidence in the data available for something varying with time. This completely undercuts your own conclusion. CM PS.: .. could somebody give to me the email address of Mauro De Benedetto , rocket trajectory 'analist ? ... are you again there ? .... consider the point of max anomaly or the point of max changement of anomaly ! .. and so you understand the uselessness to discuss around the RTG or similar things for resolving the Pioneer anomaly .. i think .. .... The anomaly has yearly some changements ... changements of the 10-15% ...: the sun can stay between the earth and the Pioneer or the earth can look directly the rocket without the sun interposition ... so the difference in the anomaly'value becomes the 20-30% This is not a correct assessment of the Pioneer "anomaly." There are no such changes of the magnitude of the anomaly with sun-earth-probe angle. What is the basis for your supposition? CM |
#46
|
|||
|
|||
Pioneer Anomaly 2017
Il giorno lunedì 22 maggio 2017 16:28:56 UTC+2, Craig Markwardt ha scritto:
On Monday, May 22, 2017 at 4:01:01 AM UTC-4, wrote: Il giorno domenica 14 maggio 2017 09:50:09 UTC+2, ha scritto: Il giorno venerdì 5 maggio 2017 10:07:49 UTC+2, ha scritto: Il giorno lunedì 1 maggio 2017 22:52:52 UTC+2, Craig Markwardt ha scritto: Opening note... Don't tell me it won't. Hey bud, this is an open discussion forum. Whatever you think I should or should not say is completely irrelevant. On Monday, May 1, 2017 at 8:25:16 AM UTC-4, wrote: On Wednesday, April 26, 2017 at 3:15:29 AM UTC+10, Craig Markwardt wrote: On Monday, April 24, 2017 at 7:17:03 AM UTC-4, wrote: On Thursday, April 20, 2017 at 7:36:10 AM UTC+10, Craig Markwardt wrote: On Wednesday, April 19, 2017 at 5:50:36 AM UTC-4, wrote: --- --- Fig.2 from this link https://arxiv.org/pdf/1204.2507v1 apparently suggests that the Pioneer anomaly may only be the result of mismodelling of the solar thermal contribution. Your interpretation of this paper is incorrect. This paper (Turyshev et al 2002) demonstrates that most if not all of the "anomalous" acceleration can be attributed to *internal* thermal emission, generated by the RTGs and internal electronics. I note no response. Your comments were noted, but you were referring to the wrong paper. This is the exact wording from the 2012 version linked above: Third, Fig. 2 is strongly suggestive that the previously reported "onset" of the Pioneer anomaly may in fact be a simple result of mismodeling of the solar thermal contribution; this question may be resolved with further analysis of early trajectory data. Nope, you are incorrect. The 2012 paper concludes that "thermal recoil" is the explanation for the Pioneer anomaly. But not *solar* thermal. Or rather, the *new* thing of that paper is that by including the *internal* thermal effects (RTGs and electrical compartment dissipation) the anomaly is resolved. Previous work *ALWAYS* considered solar thermal recoil forces, and could not explain the anomaly. Again, the new thing in the Turyshev et al 2012 paper was inclusion of internally-generated thermal terms, and this is what "tipped the balance." But such an error can't reside in the mismodelling of the solar reflection/absorption characteristics of the HGA dish because that was accurately determined prior to launch, Just a side note, but thermal coatings do degrade over time, due to exposure to solar UV as well as ionizing radiation (white coatings become darker). So one can't be so certain about these properties. That was one of the aspects covered by the thermal analysis reported in Turyshev et al's 2012 paper. You apparently agree that the RTG surface coating becomes darker over time due to both solar radiation and radiation from within the RTG's. ... The pressure gradient will follow the RTG line, **not the solar radiation pressure curve.** ... Your writing appears to be motivated by intuition, but that is not the case. You can find a more correct and physics- and engineering-motivated discussion in books like "Spacecraft Thermal Control Handbook." Also, there are quite a few reference books on the degradation of thermal coatings from the time in the public domain. Almost all known thermal coatings degrade w.r.t. the optical properties (the "alpha" coefficient), but do *not* significantly change w.r.t the infrared emission properties (the "epsilon" coefficient), including the coatings used on Pioneer. Therefore, your assumptions are irrelevant. But bringing back to your original point before you distracted... you wondered why analysts could not know the thermal/optical properties of the Pioneer coatings exactly today. I guess you concede now that it's more difficult than you first wondered. It's obvious that either Turyshev or Anderson made a fairly significant error. But it's strange that Anderson is deemed wrong when a significant number of others also demonstrated the existence of the anomaly, including yourself (2002)? Why should this new result override all others when the average result from all contributors well and truly favors the anomaly's existence? That's a funny way to do physics. What would be funny is to ALWAYS assume that the "average" of some papers is relevant. ... I note no response. Still no response. But actually it's not true to say no one else was considering thermal. ... I note no response. Most folk can understand that the thermal solution doesn't work.. "Most folk?" That's a rather unsubstantiated throwaway claim. It was *you* who claimed that everybody except for Turyshev et al 2012 had ignored the thermal origin, and I had to point out the error of your statement. |
#47
|
|||
|
|||
Pioneer Anomaly 2017
On Tuesday, May 23, 2017 at 6:36:48 AM UTC-4, wrote:
Il giorno lunedì 22 maggio 2017 16:28:56 UTC+2, Craig Markwardt ha scritto: On Monday, May 22, 2017 at 4:01:01 AM UTC-4, wrote: Il giorno domenica 14 maggio 2017 09:50:09 UTC+2, ha scritto: Il giorno venerdì 5 maggio 2017 10:07:49 UTC+2, ha scritto: Il giorno lunedì 1 maggio 2017 22:52:52 UTC+2, Craig Markwardt ha scritto: Opening note... Don't tell me it won't. Hey bud, this is an open discussion forum. Whatever you think I should or should not say is completely irrelevant. On Monday, May 1, 2017 at 8:25:16 AM UTC-4, wrote: On Wednesday, April 26, 2017 at 3:15:29 AM UTC+10, Craig Markwardt wrote: On Monday, April 24, 2017 at 7:17:03 AM UTC-4, wrote: On Thursday, April 20, 2017 at 7:36:10 AM UTC+10, Craig Markwardt wrote: On Wednesday, April 19, 2017 at 5:50:36 AM UTC-4, wrote: --- --- Fig.2 from this link https://arxiv.org/pdf/1204.2507v1 apparently suggests that the Pioneer anomaly may only be the result of mismodelling of the solar thermal contribution.. Your interpretation of this paper is incorrect. This paper (Turyshev et al 2002) demonstrates that most if not all of the "anomalous" acceleration can be attributed to *internal* thermal emission, generated by the RTGs and internal electronics. I note no response. Your comments were noted, but you were referring to the wrong paper. This is the exact wording from the 2012 version linked above: Third, Fig. 2 is strongly suggestive that the previously reported "onset" of the Pioneer anomaly may in fact be a simple result of mismodeling of the solar thermal contribution; this question may be resolved with further analysis of early trajectory data. Nope, you are incorrect. The 2012 paper concludes that "thermal recoil" is the explanation for the Pioneer anomaly. But not *solar* thermal. Or rather, the *new* thing of that paper is that by including the *internal* thermal effects (RTGs and electrical compartment dissipation) the anomaly is resolved. Previous work *ALWAYS* considered solar thermal recoil forces, and could not explain the anomaly. Again, the new thing in the Turyshev et al 2012 paper was inclusion of internally-generated thermal terms, and this is what "tipped the balance." But such an error can't reside in the mismodelling of the solar reflection/absorption characteristics of the HGA dish because that was accurately determined prior to launch, Just a side note, but thermal coatings do degrade over time, due to exposure to solar UV as well as ionizing radiation (white coatings become darker). So one can't be so certain about these properties. That was one of the aspects covered by the thermal analysis reported in Turyshev et al's 2012 paper. You apparently agree that the RTG surface coating becomes darker over time due to both solar radiation and radiation from within the RTG's. ... The pressure gradient will follow the RTG line, **not the solar radiation pressure curve..** ... Your writing appears to be motivated by intuition, but that is not the case. You can find a more correct and physics- and engineering-motivated discussion in books like "Spacecraft Thermal Control Handbook." Also, there are quite a few reference books on the degradation of thermal coatings from the time in the public domain. Almost all known thermal coatings degrade w.r.t. the optical properties (the "alpha" coefficient), but do *not* significantly change w.r.t the infrared emission properties (the "epsilon" coefficient), including the coatings used on Pioneer. Therefore, your assumptions are irrelevant. But bringing back to your original point before you distracted.... you wondered why analysts could not know the thermal/optical properties of the Pioneer coatings exactly today. I guess you concede now that it's more difficult than you first wondered. It's obvious that either Turyshev or Anderson made a fairly significant error. But it's strange that Anderson is deemed wrong when a significant number of others also demonstrated the existence of the anomaly, including yourself (2002)? Why should this new result override all others when the average result from all contributors well and truly favors the anomaly's existence? That's a funny way to do physics. What would be funny is to ALWAYS assume that the "average" of some papers is relevant. ... I note no response. Still no response. But actually it's not true to say no one else was considering thermal. ... I note no response. Most folk can understand that the thermal solution doesn't work. "Most folk?" That's a rather unsubstantiated throwaway claim. It was *you* who claimed that everybody except for Turyshev et al 2012 had ignored the thermal origin, and I had to point out the error of your statement. You act as though analysts from the 1970's were using a set of physical laws that analysts of today are not familiar with.. But that's not the case at all. Even if modifications have been made to some of the physical laws the analysts of today would still know exactly how the first data points showing the onset of the anomaly were derived. This is unsubstantiated. I am an analyst today of the Pioneer doppler data, and I do not have enough information from that one "onset" chart to understand how it was derived. But a discrepancy between observation and what was expected according to the prevailing physics at the time was clearly noted, and it continued to increase until the spacecraft reached the 20 AU mark. ... Non-sequitur. Your statement doesn't make it any easier for a Doppler analyst to reconstruct how the data analysis was done with early data. And... if you read Anderson's paper, the discrepancy was clearly noted... in the 1980s far after the spacecraft had passed 20AU. There is nothing in the paper that I can find which references earlier times, aside from the figures you point out of unknown provenance. Furthermore, let's be clear what was happening in the early 1970s. The Pioneer spacecraft were the first spacecraft to be sent to the outer solar system, with long cruise phases. Earlier spacecraft were kept inside the Earth-Moon system, or directed to the inner solar system. This new direction required new attention to detail and modeling of the physical effects of the space environment. No, the physical laws did not change, but the modeling capability within the software that was used did not capture all of the physics with the same fidelity. Effects such as spacecraft spin and new relativistic physics were being incorporated at that time. You can read the paper of Wong & Lubeley from 1974 (AIAA Paper No. 74-845) which demonstrates how the orbit determination groups were incorporating new software with better capabilities. Effects such as spacecraft propellant valve leaks were harder to understand, and navigation analysts had to make do. What physical laws does one apply to a valve that is leaky??? Before encountering Jupiter, both Pioneer spacecraft performed frequent maneuvers (every few weeks), which disturbed the orbit determination process, and also introduced more possibilities for leaks. Within the first 20 AU, the solar system radiation pressure is significant. In fact, before Jupiter approach, the radiation pressure is dominant over most of the force terms and is many times the "anomalous" acceleration. You pointed out thermal coatings, but let us not forget that the exact geometry of the spacecraft has an effect. Is the antenna treated as parabolic or flat-plate? What about the cut-outs and antenna feeds, how are those treated? These are not simple "physical law" issues. They have to do with how accurately the spacecraft systems can be modeled. Early in the mission, with computing power limited, some short cuts were inevitably taken. Each component would need to be analyzed properly, with a fairly in depth description of the processes involved if the analysis was expected to be taken seriously. Exactly. In the early 1970s, the computing power did not exist to do the in-depth analysis required. The operational need did not exist either. But I see now that you understand that the process is not just about physical laws, but something more. Which raises some questions here. What data was plugged into the 2012 Turyshev computer simulation? The answers are in the Turyshev 2012 paper and its predecessors.. Were the RTG emissions and solar radiation pressures correctly represented? Discussed in the Turyshev 2012 paper. "Correct" is a matter of tolerance. Or were they in fact mismodeled as was the assumption regarding Anderson's work? Thanks for the loaded question. Anderson et al did not "mismodel" anything intentionally. The level of fidelity was lower and they did not have the thermal data available at the time required to check, which Turyshev et al did have by 2012. Does the simulation software contribute toward the outcome? If so, what was the programmer's information source? The software is validated against all the missions supported by JPL for radiometric navigation, and the thermal modeling software is standard in the industry. That's why I say it has been validated: it has successfully been used thousands of times to correctly predict temperatures and emission profiles of equipment under test. And, let's not forget that Anderson et al 2002 compared multiple independent software suites, to guard against software errors. Thermal modeling software also has many inputs. All the inputs for thermal/optical properties were taken from Pioneer engineering documentation, but error tolerances were also considered. *AND*, then the simulations were validated against actual spacecraft measured temperatures. This temperature record was not readily available for Anderson et al to use in 2001, but was for later work. In the end it comes down to unconditional belief. Please. It comes down to a consideration of an analysis using established techniques, which has been validated against known data (both other spacecraft and Pioneer itself). There are mountains of documentation on this, which you ignored or barely skimmed over. It's easy for you to just cast out that claim without substantiation, and I reject it. So, please do not pretend that the state of affairs in the early 1970s can really be compared to the state today. Again, no response. The figure which you have referred to which shows the "onset" of the acceleration, you have replotted. What you failed to show was the uncertainty range (error bars) of the points. If you had displayed those as well, you would have seen that the bars are very large and that early data is not necessarily as stringent as you say. Again, no response. ... First of all, the quote is actually what Anderson et al. said in their paper, not me. And second of all, what is your point? If the goal is to accurately measure the "onset" of the anomaly, then the early data which would or could have shown that is largely lost forever. If the goal is to get an accurate measure of the anomaly in late days (20 AU) then the Anderson et al 2002 paper is just fine... but it doesn't prove or disprove any of your claims then. Anderson's paper claims the acceleration is consistent with being constant, quite the opposite of your claim! But he does acknowledge that there was an observed onset of the anomaly which indicated a deviation from well known standard physics at the time. Who acknowledges it? As I noted above, aside from the figures from unknown sources which you care to reproduce deceptively (see above), Anderson et al 2002 do not mention an "onset" in the paper. Again, I note that Anderson's claim is that the Pioneer anomaly is consistent with being constant. There was no evidence in the data available for something varying with time. This completely undercuts your own conclusion. CM PS.: .. could somebody give to me the email address of Mauro De Benedetto , rocket trajectory 'analist ? ... are you again there ? .... consider the point of max anomaly or the point of max changement of anomaly ! .. and so you understand the uselessness to discuss around the RTG or similar things for resolving the Pioneer anomaly .. i think .. ... The anomaly has yearly some changements ... changements of the 10-15% ..: the sun can stay between the earth and the Pioneer or the earth can look directly the rocket without the sun interposition ... so the difference in the anomaly'value becomes the 20-30% This is not a correct assessment of the Pioneer "anomaly." There are no such changes of the magnitude of the anomaly with sun-earth-probe angle. What is the basis for your supposition? CM The Anderson et al paper did not find evidence of a different amplitude of acceleration depending on sun-earth-probe angle. Figure 6 is actually historical, but is not the result of Anderson et al's work. Figure 18 is a *daily* variation of Dopppler residuals which is not an acceleration. The conclusion of the Anderson et al work is that the anomaly was constant to within the measurement tolerances. However, after the thermal result, the Turyshev et al work in 2012 concluded that the small variations in the measured "anomaly" were consistent with the thermal origin. CM |
#48
|
|||
|
|||
Pioneer Anomaly 2017
On Tuesday, May 16, 2017 at 4:36:17 AM UTC+10, Craig Markwardt wrote:
But Anderson did include a fairly convincing argument in his analysis which demonstrated that internally generated heat could not cause the Pioneer anomaly. https://arxiv.org/pdf/gr-qc/0104064v5 "V111. SOURCES OF SYSTEMATIC ERROR INTERNAL TO THE SPACECRAFT" I can't imagine how the anomaly could be generated within the scope of the possible errors he could have made. I certainly can't see this. And in this following paragraph, what exactly "tipped the balance" ? I'm still lost here. Actually, you are right, Anderson's arguments were fairly convincing FOR THE TIME. What happened is that the Turyshev et al 2012 work came up with *more convincing* evidence of what's going on. Heck, the section you quote says, "complete thermal/physical model of the spacecraft might be able to ascertain if there are any other unsuspected heat systematics," but then dismisses it. It turns out that was a premature dismissal. It doesn't take much to see that Anderson did a very crude estimate using simple geometry, when it is now clear a higher fidelity approach was required. That's not so at all. Anderson dismissed the idea because it was **CLEARLY** incapable of generating the Pioneer anomaly. Perhaps you should read it again. https://arxiv.org/pdf/gr-qc/0104064v5 "V111. SOURCES OF SYSTEMATIC ERROR INTERNAL TO THE SPACECRAFT" It's very clear that the key to Turyshev's success is in his determination of the error margins relating to the RTG surface coatings because the uncertainty provides 20% of the total error budget. In section X1 of Anderson's paper; POSSIBLE ORIGINS OF THE SIGNAL; he lists many theories, ranging from slight variations to known physics to completely new physics which attempt to explain the anomaly, and they all get the thumbs down. Turyshev's analysis is seriously flawed as well. --- I've reinstalled the following three paragraphs from your previous reply. There have been long-term studies of degradation on the International space station (Fig 4.12) which show optical but not infrared degradation. "Optical but not infrared degradation"? What kind of test would be relevant here? i.e. If the amount of solar thermal energy reflected off the ISS surfaces reduces, absorbed thermal energy must increase by that amount. Otherwise where has the missing thermal energy gone? If all surfaces have degraded equally and the added thermal energy isn't freely emitted from the surfaces the internal temperature will rise until it is. Infrared emissions will always be exactly as expected. Even if a local thermal energy source is absorbed into the degraded surface it will still be immediately emitted because the internal temperature is already altered to accommodate the degraded emissive properties. There have been detailed studies of the reflective properties of the Cassini high gain reflector (which has temperature sensing; di Bennetto, "The non-gravitational accelerations of the Cassini spacecraft ..." 2001) which show the same. The non-gravitational accelerations of the Cassini spacecraft demonstrate a major flaw in Turyshev's analysis. The Cassini mission parameters didn't include extended flight times beyond Saturn. But that's irrelevant to the proposal that the Pioneer anomaly is generated by mismodelling of the thermal characteristics of the onboard power sources. Radial velocity is of no consequence either. So if Turyshev is right, the same anomaly should be noted for Cassini, **at very least**. From Anderson's paper the Cassini RTG's are much closer to the spacecraft body than for Pioneer. If that distance is halved, the consequences of reflection off the rear of the HGA dish will be four times greater. So how do you explain the non-gravitational acceleration of Cassini ??? My proposal isn't related to radial velocity either. But the Cassini mission is confirmation that it's correct. Run the application file and you will notice that the anomaly is only just beginning to really make its presence known at 9.5 AU. http://members.optusnet.com.au/maxkeon/pneer-fh.exe The Pioneer anomaly onset is very obvious. And it's nothing like the sun focused curve Turyshev's analysis would generate. There was work in the late 1960s and early 1970s which showed the same for the exact thermal coatings used by Pioneer (e.g. Mayer et al. 1969, "Investigation of Spacecraft Coatings," NASA CR-61267; Broadway 1971, "Radiation Effects Design Handbook, Section 2. Thermal-Control Coatings"). "exact thermal coatings used by Pioneer"? Did they know something Turyshev didn't? --- I think the key thing that Anderson's discussion could not have known at the time, is that whether or not the equipment compartment louvers are open or closed, most of the heat generated inside the compartment escapes out the fore platform surface, and that is enough to account for much of the anomaly. If that info has recently become available the question of how much has been answered. So how much does it contribute toward removing the anomaly? In which direction did the error bars shrink? Here, let me quote for you, "Thermal-control finishes are affected in orbit by charged particles, ultraviolet (UV) radiation, high vacuum, and the contaminant films that deposit out on almost all spacecraft surfaces. The general result of these processes is an increase in solar absorptivity with little or no effect on IR emittance." That makes no sense. If energy is continually pumped in through increased solar absorptivity, there's no doubt at all that the energy must come out again. Otherwise the temperature of the affected object will increase forever. It's unfortunate it doesn't make sense to you. Yes, there is a thermal balance between energy received (related to optical absorptance alpha), energy emitted (related to infrared emittance epsilon) and temperature. If alpha increases while epsilon is constant, then yes, the temperature increases. So it really doesn't matter where the sun is relative to a Pioneer spacecraft. All absorbed solar thermal energy will conduct throughout all contacting surfaces, adding to the general temperature. Nope, that's mostly incorrect. The sun-absorbing face of the spacecraft is the high-gain antenna, plus some of the RTGs. These bodies are thermally insulated from the rest of the spacecraft, so they do not "conduct". So the anomaly canceling effect from a hotter than expected HGA dish can't be considered. i.e. If the fore/aft surfaces of the dish were identical the added thermal energy would be emitted equally in opposite directions, but because the aft (reflective surface) is known to be much less emissive than the fore surface a substantial inward drive would be expected. Your claim that the anomaly has been explained would have a lot more credibility if it could be shown that Anderson had overlooked something like this. A discrepancy between current theory and my theory is guaranteed. The difference is determined by how inaccurate current theory is, or by how inaccurate my theory is. The Pioneer anomaly, fact or fiction, is the key to truth. Either way, I don't care. I would be over the moon if my theory could be proven wrong. Reality according to current theory and my theory is vastly different. You wouldn't like mine. The HGA primarily comes to thermal equilibrium via emission. It's true that non-sun-facing (fore) side of the HGA which is adjacent to the equipment compartment, and is the same temperature as the sun-facing side because of conduction. But since the emissivity of the sun-facing side is 10-20x more than the fore side, most of the solar heating is re-emitted toward the sun. Very little of it is emitted toward the direction of the anomaly. Why do you say "re-emitted" ??? Absorption doesn't precede reflection. Anyway all of the above was tested prior to launch and has obviously been considered in Anderson analysis. --- If the sun facing RTG coating has degraded to the point where the internally generated heat emission is at the error bar limit while all other anomaly negatives have been set at their most negative limits, some error bars overlap and the anomaly is proclaimed dead. You're a scientist, what do you think of that proclamation? Do you honestly believe it's justified? I say it's absolutely ridiculous. My conclusion: The cards just keep on falling into place. ----- Max Keon |
#49
|
|||
|
|||
Pioneer Anomaly 2017
On Wednesday, May 24, 2017 at 11:42:40 PM UTC-4, wrote:
On Tuesday, May 16, 2017 at 4:36:17 AM UTC+10, Craig Markwardt wrote: But Anderson did include a fairly convincing argument in his analysis which demonstrated that internally generated heat could not cause the Pioneer anomaly. https://arxiv.org/pdf/gr-qc/0104064v5 "V111. SOURCES OF SYSTEMATIC ERROR INTERNAL TO THE SPACECRAFT" I can't imagine how the anomaly could be generated within the scope of the possible errors he could have made. I certainly can't see this. And in this following paragraph, what exactly "tipped the balance" ? I'm still lost here. Actually, you are right, Anderson's arguments were fairly convincing FOR THE TIME. What happened is that the Turyshev et al 2012 work came up with *more convincing* evidence of what's going on. Heck, the section you quote says, "complete thermal/physical model of the spacecraft might be able to ascertain if there are any other unsuspected heat systematics," but then dismisses it. It turns out that was a premature dismissal. It doesn't take much to see that Anderson did a very crude estimate using simple geometry, when it is now clear a higher fidelity approach was required. That's not so at all. Anderson dismissed the idea because it was **CLEARLY** incapable of generating the Pioneer anomaly. Perhaps you should read it again. Again, your appeal to authority. See #2 below. You don't deny that Anderson's work was simplistic and crude compared to Turyshev's. In section X1 of Anderson's paper; POSSIBLE ORIGINS OF THE SIGNAL; he lists many theories, ranging from slight variations to known physics to completely new physics which attempt to explain the anomaly, and they all get the thumbs down. Turyshev's analysis is seriously flawed as well. So far you haven't been able to bring up a clear or quantitative reason why Turyshev's *much more detailed* analysis is flawed. ..... If all surfaces have degraded equally and the added thermal energy isn't freely emitted from the surfaces the internal temperature will rise until it is. Infrared emissions will always be exactly as expected. Please learn about the difference between thermal emission and thermal emissivity. (#5 below) It is the emissivity which changes. There have been detailed studies of the reflective properties of the Cassini high gain reflector (which has temperature sensing; di Bennetto, "The non-gravitational accelerations of the Cassini spacecraft ..." 2001) which show the same. The non-gravitational accelerations of the Cassini spacecraft demonstrate a major flaw in Turyshev's analysis. ... ... So if Turyshev is right, the same anomaly should be noted for Cassini, **at very least**. From Anderson's paper the Cassini RTG's are much closer to the spacecraft body than for Pioneer. If that distance is halved, the consequences of reflection off the rear of the HGA dish will be four times greater. So how do you explain the non-gravitational acceleration of Cassini ??? Why are you asking me when you could read de Bennedetto's work yourself? If you had bothered to, you would find that de Bennedetto has a very careful discussion of thermal effects, including RTGs and the HGA. In other words, a fairly detailed thermal analysis... just as Turyshev was able to accomplish for the Pioneers. There was work in the late 1960s and early 1970s which showed the same for the exact thermal coatings used by Pioneer (e.g. Mayer et al. 1969, "Investigation of Spacecraft Coatings," NASA CR-61267; Broadway 1971, "Radiation Effects Design Handbook, Section 2. Thermal-Control Coatings"). "exact thermal coatings used by Pioneer"? Did they know something Turyshev didn't? Cute. Rather that learning about thermal emissivity properties, you instead decide to invent a conspiracy theory (see #5 below). The thermal coatings were documented, and *some* UV and radiation tests were performed on those coatings in laboratories, but they did not mimic the exact space environment the Pioneers experienced. So do we really know the amount of degradation experienced? What we do know is that most thermal coatings degrade by changing their optical reflectivity (absorptivity) but have very little change to the infrared emissivity. You could have read about this but did not. I think the key thing that Anderson's discussion could not have known at the time, is that whether or not the equipment compartment louvers are open or closed, most of the heat generated inside the compartment escapes out the fore platform surface, and that is enough to account for much of the anomaly. If that info has recently become available the question of how much has been answered. So how much does it contribute toward removing the anomaly? In which direction did the error bars shrink? I note you keep asking this question, I keep responding, and you ignore (#2 below) Nope, that's mostly incorrect. The sun-absorbing face of the spacecraft is the high-gain antenna, plus some of the RTGs. These bodies are thermally insulated from the rest of the spacecraft, so they do not "conduct". So the anomaly canceling effect from a hotter than expected HGA dish can't be considered. I see you finally understand that. Neither Anderson et al (2002) nor Turyshev et al (2012) claimed that degradation of the HGA could "account" for the anomaly. You could have read this but did not (see #2 below). However, the *uncertainty* in the thermal properties of the HGA does contribute an uncertainty of the thermal effects, which is what Turyshev et al considered. If the sun facing RTG coating has degraded to the point where the internally generated heat emission is at the error bar limit while all other anomaly negatives have been set at their most negative limits, some error bars overlap and the anomaly is proclaimed dead. That's kind of how science works. Compare the tolerances of the experiment with the tolerances of the theory, and if they overlap, then we cannot reject the theory. In this case we cannot reject the thermal origin theory. And by the principle of Occam's razor, if we have a "new physics" theory and a "basic physics" theory which are both consistent with the data, then we choose the basic physics. This is basic science. Why would we pick new physics when mundane physics will suffice? But let’s summarize the issues you seem to be willfully ignoring. 1. You continue to mention that somehow Turyshev’s 2012 work is about “solar thermal” when that is incorrect. It is about solar thermal yes, but mostly about internally-generated thermal. When noted, you ignore or distract. 2. You continue to ask about what is in the Turyshev 2012 paper. I continue to refer you to it, but you ignore or distract. 3. You continue to ask about what is different between the Anderson 2001 and Turyshev 2012 works. I reply with detailed points, but you ignore or distract. 4. You continue to appeal to authority of Anderson’s work for thermal aspects. However, Anderson’s work in this topic is rather crude, and limited to point-like and plate-like approximations. Even Anderson noted that a higher fidelity model could be useful and Turyshev’s 2012 work accomplished it! You continue to ignore or distract from this point. |
#50
|
|||
|
|||
Pioneer Anomaly 2017
Il giorno martedì 23 maggio 2017 12:36:48 UTC+2, ha scritto:
Il giorno lunedì 22 maggio 2017 16:28:56 UTC+2, Craig Markwardt ha scritto: On Monday, May 22, 2017 at 4:01:01 AM UTC-4, wrote: Il giorno domenica 14 maggio 2017 09:50:09 UTC+2, ha scritto: Il giorno venerdì 5 maggio 2017 10:07:49 UTC+2, ha scritto: Il giorno lunedì 1 maggio 2017 22:52:52 UTC+2, Craig Markwardt ha scritto: Opening note... Don't tell me it won't. Hey bud, this is an open discussion forum. Whatever you think I should or should not say is completely irrelevant. On Monday, May 1, 2017 at 8:25:16 AM UTC-4, wrote: On Wednesday, April 26, 2017 at 3:15:29 AM UTC+10, Craig Markwardt wrote: On Monday, April 24, 2017 at 7:17:03 AM UTC-4, wrote: On Thursday, April 20, 2017 at 7:36:10 AM UTC+10, Craig Markwardt wrote: On Wednesday, April 19, 2017 at 5:50:36 AM UTC-4, wrote: --- --- Fig.2 from this link https://arxiv.org/pdf/1204.2507v1 apparently suggests that the Pioneer anomaly may only be the result of mismodelling of the solar thermal contribution.. Your interpretation of this paper is incorrect. This paper (Turyshev et al 2002) demonstrates that most if not all of the "anomalous" acceleration can be attributed to *internal* thermal emission, generated by the RTGs and internal electronics. I note no response. Your comments were noted, but you were referring to the wrong paper. This is the exact wording from the 2012 version linked above: Third, Fig. 2 is strongly suggestive that the previously reported "onset" of the Pioneer anomaly may in fact be a simple result of mismodeling of the solar thermal contribution; this question may be resolved with further analysis of early trajectory data. Nope, you are incorrect. The 2012 paper concludes that "thermal recoil" is the explanation for the Pioneer anomaly. But not *solar* thermal. Or rather, the *new* thing of that paper is that by including the *internal* thermal effects (RTGs and electrical compartment dissipation) the anomaly is resolved. Previous work *ALWAYS* considered solar thermal recoil forces, and could not explain the anomaly. Again, the new thing in the Turyshev et al 2012 paper was inclusion of internally-generated thermal terms, and this is what "tipped the balance." But such an error can't reside in the mismodelling of the solar reflection/absorption characteristics of the HGA dish because that was accurately determined prior to launch, Just a side note, but thermal coatings do degrade over time, due to exposure to solar UV as well as ionizing radiation (white coatings become darker). So one can't be so certain about these properties. That was one of the aspects covered by the thermal analysis reported in Turyshev et al's 2012 paper. You apparently agree that the RTG surface coating becomes darker over time due to both solar radiation and radiation from within the RTG's. ... The pressure gradient will follow the RTG line, **not the solar radiation pressure curve..** ... Your writing appears to be motivated by intuition, but that is not the case. You can find a more correct and physics- and engineering-motivated discussion in books like "Spacecraft Thermal Control Handbook." Also, there are quite a few reference books on the degradation of thermal coatings from the time in the public domain. Almost all known thermal coatings degrade w.r.t. the optical properties (the "alpha" coefficient), but do *not* significantly change w.r.t the infrared emission properties (the "epsilon" coefficient), including the coatings used on Pioneer. Therefore, your assumptions are irrelevant. But bringing back to your original point before you distracted.... you wondered why analysts could not know the thermal/optical properties of the Pioneer coatings exactly today. I guess you concede now that it's more difficult than you first wondered. It's obvious that either Turyshev or Anderson made a fairly significant error. But it's strange that Anderson is deemed wrong when a significant number of others also demonstrated the existence of the anomaly, including yourself (2002)? Why should this new result override all others when the average result from all contributors well and truly favors the anomaly's existence? That's a funny way to do physics. What would be funny is to ALWAYS assume that the "average" of some papers is relevant. ... I note no response. Still no response. But actually it's not true to say no one else was considering thermal. ... I note no response. Most folk can understand that the thermal solution doesn't work. "Most folk?" That's a rather unsubstantiated throwaway claim. It was *you* who claimed that everybody except for Turyshev et al 2012 had ignored the thermal origin, and I had to point out the error of your statement. You act as though analysts from the 1970's were using a set of physical laws that analysts of today are not familiar with.. But that's not the case at all. Even if modifications have been made to some of the physical laws the analysts of today would still know exactly how the first data points showing the onset of the anomaly were derived. This is unsubstantiated. I am an analyst today of the Pioneer doppler data, and I do not have enough information from that one "onset" chart to understand how it was derived. But a discrepancy between observation and what was expected according to the prevailing physics at the time was clearly noted, and it continued to increase until the spacecraft reached the 20 AU mark. ... Non-sequitur. Your statement doesn't make it any easier for a Doppler analyst to reconstruct how the data analysis was done with early data. And... if you read Anderson's paper, the discrepancy was clearly noted... in the 1980s far after the spacecraft had passed 20AU. There is nothing in the paper that I can find which references earlier times, aside from the figures you point out of unknown provenance. Furthermore, let's be clear what was happening in the early 1970s. The Pioneer spacecraft were the first spacecraft to be sent to the outer solar system, with long cruise phases. Earlier spacecraft were kept inside the Earth-Moon system, or directed to the inner solar system. This new direction required new attention to detail and modeling of the physical effects of the space environment. No, the physical laws did not change, but the modeling capability within the software that was used did not capture all of the physics with the same fidelity. Effects such as spacecraft spin and new relativistic physics were being incorporated at that time. You can read the paper of Wong & Lubeley from 1974 (AIAA Paper No. 74-845) which demonstrates how the orbit determination groups were incorporating new software with better capabilities. Effects such as spacecraft propellant valve leaks were harder to understand, and navigation analysts had to make do. What physical laws does one apply to a valve that is leaky??? Before encountering Jupiter, both Pioneer spacecraft performed frequent maneuvers (every few weeks), which disturbed the orbit determination process, and also introduced more possibilities for leaks. Within the first 20 AU, the solar system radiation pressure is significant. In fact, before Jupiter approach, the radiation pressure is dominant over most of the force terms and is many times the "anomalous" acceleration. You pointed out thermal coatings, but let us not forget that the exact geometry of the spacecraft has an effect. Is the antenna treated as parabolic or flat-plate? What about the cut-outs and antenna feeds, how are those treated? These are not simple "physical law" issues. They have to do with how accurately the spacecraft systems can be modeled. Early in the mission, with computing power limited, some short cuts were inevitably taken. Each component would need to be analyzed properly, with a fairly in depth description of the processes involved if the analysis was expected to be taken seriously. Exactly. In the early 1970s, the computing power did not exist to do the in-depth analysis required. The operational need did not exist either. But I see now that you understand that the process is not just about physical laws, but something more. Which raises some questions here. What data was plugged into the 2012 Turyshev computer simulation? The answers are in the Turyshev 2012 paper and its predecessors.. Were the RTG emissions and solar radiation pressures correctly represented? Discussed in the Turyshev 2012 paper. "Correct" is a matter of tolerance. Or were they in fact mismodeled as was the assumption regarding Anderson's work? Thanks for the loaded question. Anderson et al did not "mismodel" anything intentionally. The level of fidelity was lower and they did not have the thermal data available at the time required to check, which Turyshev et al did have by 2012. Does the simulation software contribute toward the outcome? If so, what was the programmer's information source? The software is validated against all the missions supported by JPL for radiometric navigation, and the thermal modeling software is standard in the industry. That's why I say it has been validated: it has successfully been used thousands of times to correctly predict temperatures and emission profiles of equipment under test. And, let's not forget that Anderson et al 2002 compared multiple independent software suites, to guard against software errors. Thermal modeling software also has many inputs. All the inputs for thermal/optical properties were taken from Pioneer engineering documentation, but error tolerances were also considered. *AND*, then the simulations were validated against actual spacecraft measured temperatures. This temperature record was not readily available for Anderson et al to use in 2001, but was for later work. In the end it comes down to unconditional belief. Please. It comes down to a consideration of an analysis using established techniques, which has been validated against known data (both other spacecraft and Pioneer itself). There are mountains of documentation on this, which you ignored or barely skimmed over. It's easy for you to just cast out that claim without substantiation, and I reject it. So, please do not pretend that the state of affairs in the early 1970s can really be compared to the state today. Again, no response. The figure which you have referred to which shows the "onset" of the acceleration, you have replotted. What you failed to show was the uncertainty range (error bars) of the points. If you had displayed those as well, you would have seen that the bars are very large and that early data is not necessarily as stringent as you say. Again, no response. ... First of all, the quote is actually what Anderson et al. said in their paper, not me. And second of all, what is your point? If the goal is to accurately measure the "onset" of the anomaly, then the early data which would or could have shown that is largely lost forever. If the goal is to get an accurate measure of the anomaly in late days (20 AU) then the Anderson et al 2002 paper is just fine... but it doesn't prove or disprove any of your claims then. Anderson's paper claims the acceleration is consistent with being constant, quite the opposite of your claim! But he does acknowledge that there was an observed onset of the anomaly which indicated a deviation from well known standard physics at the time. Who acknowledges it? As I noted above, aside from the figures from unknown sources which you care to reproduce deceptively (see above), Anderson et al 2002 do not mention an "onset" in the paper. Again, I note that Anderson's claim is that the Pioneer anomaly is consistent with being constant. There was no evidence in the data available for something varying with time. This completely undercuts your own conclusion. CM PS.: .. could somebody give to me the email address of Mauro De Benedetto , rocket trajectory 'analist ? ... are you again there ? .... consider the point of max anomaly or the point of max changement of anomaly ! .. and so you understand the uselessness to discuss around the RTG or similar things for resolving the Pioneer anomaly .. i think .. ... The anomaly has yearly some changements ... changements of the 10-15% ..: the sun can stay between the earth and the Pioneer or the earth can look directly the rocket without the sun interposition ... so the difference in the anomaly'value becomes the 20-30% This is not a correct assessment of the Pioneer "anomaly." There are no such changes of the magnitude of the anomaly with sun-earth-probe angle. What is the basis for your supposition? CM ..many years ago , i read queekly the referement'paper of the anomaly arxiv gr-qc/0104064 19 apr 2001 and searched inside it the confirmation to a kind of personal theory of the Bigbang ... effectively the things are more complicated around the anomaly : somebody thought also to a sinusoid of 200 days 'period ; often , or yearly fit'manouvres were made ; the points 'averages for building curves were along few days (much better mounthly ?!); Pioneer 10 and 11 had almost opposite directions , but the datas were furnished sometime overposed ; the fig. 6 at page 33 could clear , but nothing is really sure ; it is difficult also clarify the question 'toward' the sun because in the fig. 6 the solar'pressure is diminuishing the anomaly'value , but at page 72-73 the same strenght , jointed to the 'radio beam reaction force' have the same positive sign = are its increasing the anomaly with its components? ... Benedetto , quoted by you , was thinking that Cassini had an anomaly 'away from the sun' , not 'towards'(did i undestood well?!) ... Craig - msk.. you are much higther than me in the cohomprension of the Pioneer 'anomaly .. at this point , i go back home near the fire ,.. i have only one question : why in the historical figure 6 , the sun 'pressure is of opposite sign ( + sun'pressure and - the anomaly'acceleration ) regards to the anomaly and in the last pages of the same report , the 'sun'pressure' and the 'radio beam reaction force' have , ofcourse , the same sign + , but -there- also the anomaly has their same sign + ( also in the precedent page , their quantities are added to the anomaly ) ? ..thanks .. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Pioneer Anomaly | [email protected] | Policy | 7 | July 21st 07 09:44 PM |
30 Years of Pioneer Spacecraft Data Rescued: The Planetary Society Enables Study of the Mysterious Pioneer Anomaly | [email protected] | News | 0 | June 6th 06 05:35 PM |
Pioneer anomaly | Oz | Research | 10 | October 1st 05 09:40 AM |
The Pioneer Anomaly | Mark F. | Amateur Astronomy | 4 | December 25th 04 02:30 PM |