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Ranging and Pioneer
The position of Pioneer was calculated from Doppler information. Ranging
was not available. Can anyone explain why ranging could not be used? Is this just a limit on available technology, or is there a more fundamental reason? Regards -- Charles Francis substitute charles for NotI to email |
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Ranging and Pioneer
Oh No wrote: The position of Pioneer was calculated from Doppler information. Ranging was not available. Can anyone explain why ranging could not be used? Is this just a limit on available technology, or is there a more fundamental reason? gr-qc/0104064 Spud |
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Ranging and Pioneer
Thus spake Spud
Oh No wrote: The position of Pioneer was calculated from Doppler information. Ranging was not available. Can anyone explain why ranging could not be used? Is this just a limit on available technology, or is there a more fundamental reason? gr-qc/0104064 Many thanks. If I understand Anderson correctly it is merely an engineering constraint. With a (perhaps greatly) amplified signal it should be possible to reduce integration times to achieve correlation so that the signal can be returned without a substantial range delay. Anyway that is the basis on which I am working at the moment. But I am not an engineer, and I was hoping this might be confirmed. My arguments would take quite a different form if this was a fundamental constraint. Regards -- Charles Francis substitute charles for NotI to email |
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Ranging and Pioneer
Oh No wrote:
Thus spake Spud Oh No wrote: The position of Pioneer was calculated from Doppler information. Ranging was not available. Can anyone explain why ranging could not be used? Is this just a limit on available technology, or is there a more fundamental reason? gr-qc/0104064 Many thanks. If I understand Anderson correctly it is merely an engineering constraint. With a (perhaps greatly) amplified signal it should be possible to reduce integration times to achieve correlation so that the signal can be returned without a substantial range delay. Anyway that is the basis on which I am working at the moment. But I am not an engineer, and I was hoping this might be confirmed. My arguments would take quite a different form if this was a fundamental constraint. http://arxiv.org/abs/gr-qc/0205059 Pioneer anomaly http://arXiv.org/abs/gr-qc/0307042 Rationalized Pioneer anomaly http://arXiv.org/abs/gr-qc/9810085 Believable rationalized Pioneer anomaly http://arXiv.org/abs/gr-qc/gr-qc/0310088 Believable Pioneer anomaly updated http://www.arxiv.org/abs/gr-qc/0411020 Pioneer anomaly http://arXiv.org/abs/physics/0502123 Commentary on Pioneer anomaly minutia http://arXiv.org/abs/gr-qc/0506139 http://math.ucr.edu/home/baez/open.questions.html -- Uncle Al http://www.mazepath.com/uncleal/ (Toxic URL! Unsafe for children and most mammals) http://www.mazepath.com/uncleal/qz3.pdf |
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Ranging and Pioneer
Oh No wrote:
The position of Pioneer was calculated from Doppler information. Ranging was not available. Can anyone explain why ranging could not be used? Is this just a limit on available technology, or is there a more fundamental reason? Regards Here is an extreme case in terms of Beta Pictoris at many light years distance arXiv:astro-ph/0601244 v1 11 Jan 2006 Dynamic motions are inferred from atomic molecular quantum transitions. The time (frequency) of such transitions are assumed the same there and here from which observed differences in frequencies are related to dynamic motions. The problem is the same as you identify. How does one "range" the motions of Asteroid size objects (which do not have quantum transitions) in Beta Pictoris other than observing the gross newtonian gravity motions of the system as a whole. The problem could be solved if only a radar signal could be sent, reflected for obtaining active ranging information. Such a procedure is performed with the earth's moon which is aided by a corner reflector positioned there. Moon position is ranged from earth within centimeters. Could such a ranging procedure be conducted on a Pioneer size object at 10 AU. If so, then a dedicated spacecraft mission would not be necessary. One would only have track various objects of Pioneer size and smaller that are at 10 AU. (area to mass ratio may be a very important parameter) Such questions are important. It could be the reason that our solar system is essentially dust free at 5 billion years old and Beta Pictoris has lots of dust at ~10 million years old. Richard |
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Ranging and Pioneer
Oh No wrote: The position of Pioneer was calculated from Doppler information. Ranging was not available. Can anyone explain why ranging could not be used? Is this just a limit on available technology, or is there a more fundamental reason? Interesting astro-ph/0501626 Spud |
#7
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Ranging and Pioneer
In article .com, Spud writes:
Oh No wrote: The position of Pioneer was calculated from Doppler information. Ranging was not available. Can anyone explain why ranging could not be used? Is this just a limit on available technology, or is there a more fundamental reason? gr-qc/0104064 Spud Just wanted to ask something about this. In order to measure Doppler shift, you need to measure frequency accurately right? And in order to measure frequency accurately you have to have an accurate clock. I founded an IRC network (Newnet Internet Relay Chat). We had a problem with servers being out of sync, clocks didn't agree. Part of our network was using national institute of standards and technologies NIST time server, others were using a time server at Nasa. The root of the problem turned out that NASA's time server was about five seconds off of NIST's. Now I thought NIST was supposed to be THE gold standard, which would mean that NASA's clock is off. And if NASA's clock isn't accurate, then by extension neither is the precise measure of frequency and thus Doppler shift. So I can't help but wonder while we're re-writing the laws of cosmology on the basis of the unexpected Doppler shift of Pioneer I and II, if we might be really doing so on the basis of an incorrectly calibrated clock at NASA. -- -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_- Eskimo North Linux Friendly Internet Access, Shell Accounts, and Hosting. Knowledgable human assistance, not telephone trees or script readers. See our web site: http://www.eskimo.com/ (206) 812-0051 or (800) 246-6874. |
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Ranging and Pioneer
In article , Nanook wrote:
Part of our network was using national institute of standards and technologies NIST time server, others were using a time server at Nasa. The root of the problem turned out that NASA's time server was about five seconds off of NIST's. Now I thought NIST was supposed to be THE gold standard, which would mean that NASA's clock is off. And if NASA's clock isn't accurate, then by extension neither is the precise measure of frequency and thus Doppler shift. I was under the impression that the "gold standard" for time is a collaborative thing between a number of national and international time services, not tied to any one machine or even site. A five *second* difference between clocks that are meant to be accurate to microseconds per year/ millennium (I can't remember which) I don't think is credible. More credible would be that your network topology either had some sort of horrible delay-inducing asymmetric loop in it to one of the time sources, or that you were asking the wrong questions of one of the machines. E.g., getting time according to UTC from one machine, but something corrected to local noon from the other (that would give time differences of up to several minutes a day, if I remember my horology correctly, but variable at different times of the year). -- Aidan Karley, FGS Aberdeen, Scotland Written at Tue, 11 Jul 2006 03:13 +0100, but posted later. |
#9
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Ranging and Pioneer
In article , Nanook
wrote: The root of the problem turned out that NASA's time server was about five seconds off of NIST's. Now I thought NIST was supposed to be THE gold standard, which would mean that NASA's clock is off. And if NASA's clock isn't accurate, then by extension neither is the precise measure of frequency and thus Doppler shift. NASA is a big organization. They don't have 'a clock'. Are the timeservers you were using supposed to be public timeservers? What stratum are they? If you are setting up a large IRC network, you shouldn't be hitting high level time servers. Get one of your machines to be the only one to contact a good server (or some other source like a cheap GPS clock) and have others contact that machine. Anyway, when I got to my current job, I pointed my NTP client at time.where.I.work , which worked as an NTP server. When I noticed that the time on my computer was way off, I tracked down the owner of that machine. He didn't know his computer's NTP server port was active, he just had a desktop computer named 'time' and a laptop named 'space'. So anyway, it is unlikely that the Pioneer anomaly is due to an inaccurate NTP server. -- David M. Palmer (formerly @clark.net, @ematic.com) |
#10
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Ranging and Pioneer
In article , David M. Palmer
wrote: So anyway, it is unlikely that the Pioneer anomaly is due to an inaccurate NTP server. Doesn't the Pioneer anomaly predate the development of NTP anyway? -- Aidan Karley, FGS Aberdeen, Scotland Written at Wed, 12 Jul 2006 09:30 +0100, but posted later. |
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