|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Ranging and Pioneer
Thus spake "
Oh No wrote: Thus spake " Oh No wrote: The signal from Pioneer uses an effective Doppler frequency of 1MHz, equivalent to a distance scale of 300m. ... the MDA is capable of measuring phase to 1/256 of a cycle or about 0.5mm in range. ... This might be true if everything were perfect, but it is not. To interpolate higher frequencies than the 1MHz effective Doppler frequency one has to assume no such thing as cycle slip, for example. In fact even GPS systems are plagued with cycle slip. Surely the quantum effects are only affected by the equipment, not assumptions, but no matter, this was just FYI. Cycle slips were sufficiently infrequent that many were corrected by hand by the analysts going over the data. I believe Anderson et al may have excluded any measurement with a cycle slip from subsequent processing but I'm not sure on that without rechecking the paper. I don't think Anderson actually says how frequent cycle slips were, just that some were examined by an analyst. They did exclude the data. Anderson says: "If a blunder point is observed, the count is stopped and a Doppler point is generated by summing the preceding points. Otherwise the count is continued until a specified maximum duration is reached. Cases where this procedure detected the need for cycle corrections were flagged in the database and often individually examined by an analyst. Sometimes the data was corrected, but nominally the blunder point was just eliminated. This ensures that the data is consistent over a pass. However, it does not guarantee that the pass is good, because other errors can affect the whole pass and remain". I am not sure that that is what they are saying because I had been given to believe that the measurements of Mars are the most accurate within the Solar system. Perhaps in percentage terms, ranging using the corner refectors on the Moon achieves cm accuracy. Sorry, I overlook the obvious. ... The conventional linear Hubble law if applied to Pioneer 10 predicts an apparent acceleration some 15000 times smaller than the anomaly given by the equation a_H = 2 H v. I don't understand why you think your analysis produces a result four orders of magnitude larger than the normal Hubble Law under either of the regimes you explain above. Sorry if I'm being a bit slow but it is this factor of 15000 increase that I cannot fathom. I am not quite sure where the 15000 increase is, or what the equation a_H = 2 Hv refers to. Take the Hubble constant H as 71km/s per MPc. A parsec is 3.09e16 m and an AU is 1.5e11 m so changing units H = 3.44e-7 m/s per AU. In Jan 1987 the craft was at 40 AU so the signal had to travel 80 AU giving a redshift due to the Hubble constant equivalent to a speed of 2.75e-5 m/s. Similarly in Dec 1994 at the end of the period analysed for Pioneer 10, the range was 60 AU and the round trip 120 AU which gives an apparent speed from the Hubble Law of 4.13e-5 m/s. That's a change of 1.38e-5 m/s in a time of 2921 days or 2.51e8 s giving an apparent acceleration of 5.50e-14 m/s^2. Compare that with the anomaly of 8.74e-10 m/s^2. The equation that summarises that is a = 2 H v where H is the Hubble constant, v is the radial speed of the craft, a is the resulting apparent acceleration and the factor of 2 is due to the double trip. I have it that quantum coordinates introduce an acceleration in time which can be shown by a coordinate transformation equivalent to an acceleration Hc. If it is an effect in time, that could be quite different to the ranging analysis and might explain why the numbers differ so much. Of the phenomenological time models considered by Anderson et al, do any of their equations (60) through (65) match? See page 46 of gr-qc/0104064 for details. Equation 60 is the probably the best match, though I am not sure how different it is from 61 or 62. I used cosmic time, but in the quantum domain an "accelerating" time coordinate is used, proportional to the expansion parameter. This will affect Doppler, but not ranging which is based on cosmic time. Regards -- Charles Francis substitute charles for NotI to email |
#2
|
|||
|
|||
Ranging and Pioneer
Oh No wrote:
Thus spake " Oh No wrote: Thus spake " ..... I don't think Anderson actually says how frequent cycle slips were, just that some were examined by an analyst. They did exclude the data. The samples are generally once per minute and few are missing in the small sample of days I have examined. That may give you an upper limit of a few per hour at most, possibly much lower, that you could compare with your predicted rate. I am not quite sure where the 15000 increase is, or what the equation a_H = 2 Hv refers to. snip derivations ... giving an apparent acceleration of 5.50e-14 m/s^2. Compare that with the anomaly of 8.74e-10 m/s^2. Did that clarify my comment and show how the speed of the craft comes into the equation? Can you now explain why your result is so much higher for Pioneer yet that doesn't translate to extra-galactic redshift measurements? I have it that quantum coordinates introduce an acceleration in time which can be shown by a coordinate transformation equivalent to an acceleration Hc. What puzzles me here is that your anomalous acceleration is independent of the craft speed. If the craft were sitting at a fixed location with neither radial nor tangential velocity (e.g. station keeping with a solar sail), this implies you would still get a downlink frequency shift which increased linearly with time for a constant uplink frequency and it would also be independent of distance (as is observed) hence should apply to short range measurements over some spread of distance resolution. ... Of the phenomenological time models considered by Anderson et al, do any of their equations (60) through (65) match? ... Equation 60 is the probably the best match, though I am not sure how different it is from 61 or 62. I need to refresh my memory on the details. I used cosmic time, but in the quantum domain an "accelerating" time coordinate is used, proportional to the expansion parameter. This will affect Doppler, but not ranging which is based on cosmic time. Interesting, that might offer you another test as an inconsistency with other means of measuring the solar plasma. From page 10 of gr-qc/0104064: "Thus, the ranging data are independent of the Doppler data, which represents a frequency shift of the radio carrier wave without modulation. For example, solar plasma introduces a group delay in the ranging data but a phase advance in the Doppler data. Ranging data can also be used to distinguish an actual range change from a fictitious range change seen in Doppler data that is caused by a frequency error [39]. The Doppler frequency integrated over time (the accumulated phase) should equal the range change except for the difference introduced by charged particles." George |
#3
|
|||
|
|||
Ranging and Pioneer
In message , Oh No
writes Thus spake " Oh No wrote: I am not sure that that is what they are saying because I had been given to believe that the measurements of Mars are the most accurate within the Solar system. Perhaps in percentage terms, ranging using the corner refectors on the Moon achieves cm accuracy. Sorry, I overlook the obvious. Apache Point hopes to get millimeter accuracy but doesn't seem to have done so at the last update (June 2006) http://physics.ucsd.edu/~tmurphy/apollo/apollo.html |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Ranging and Pioneer | [email protected] | Research | 0 | August 13th 06 07:22 PM |
Ranging and Pioneer | Oh No | Research | 0 | August 13th 06 08:53 AM |
Ranging and Pioneer | [email protected] | Research | 0 | August 12th 06 01:25 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 |