Re: Ranging and Pioneer
- From: Oh No <NotI@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 25 Aug 2006 15:02:19 GMT
Thus spake George Dishman <gad@xxxxxxx>
<sent by email due to ISP problems>
The idea is that whenever a direct measurement of position is done (in
this instance ranging) the quantum theory gets renormalised.
How can the choice of what is done with data in a computer
which represents digitised samples of a sine wave from an
antenna affect whether that signal is a simple sine wave
or has phase discontinuities in it? You are saying that
the shape of the waveform out of the wavguide from the
dish is latered by the kind of program the user runs on
his computer to process that received waveform.
I don't mean to say that. This bears on the conditions under which
collapse of the wave function takes place in quantum theory. If data
exists which can be analysed in principle to give a direct measurement
of position, then collapse must have taken place and that will give one
result. If such data does not exist, then collapse has not taken place
and a different result is expected. To get the anomalous shift in
Pioneer transmissions I have to assume that collapse has not taken
place, and hence that there is no way to analyse the data so as to get
ranging information. The question is why, precisely, should this be the
case.
The reason
being that quantum theory is formulated between initial and final
states, and with each classical measurement a final state is
reinterpreted as an initial state in a quantum theory formulated on an
expanded universe. When measurement of position can be regarded
continuous the effect is a continuous renormalisation of the quantum
theory, which then yields classical results for Doppler. The "new
physics" stuff happens when measurement of position cannot be regarded
as continuous.
In an ideal measurement with instantaneous return of the ranging signal
the theory would effectively be renormalised more rapidly than one cycle
of the Doppler signal, giving the classical Doppler result. But for
Pioneer we do not have that. I feel handicapped by not understanding
enough of the practicalities of measurement to understand exactly how
when and why ranging for Pioneer breaks down.
I don't think anyone was sure why it failed, perhaps
radiation damage during the Jupiter flypast.
Really I am looking for some reason in principle why this should fail.
The reason should have to do with the quantum formulation, and would not
be apparent from a classical analysis.
However, so long as it
does break down and we cannot do a direct measurement of position I
think we are looking at Doppler between measurements, and therein lies
the source of the anomaly.
Assuming a carrier of 2.291GHz, the two-way Doppler
at 12.5km/s would be about 191048.836 Hz. An error
of 0.34m/s would produce a further shift of 5.196Hz
giving 191054.032 Hz.
Are you say that the signal would consist of short
sections at 191048.836 Hz separated by phase
discontinuities such that the mean phase rate was
191054.032 Hz ?
That is the idea.
OK so that would mean you need at least 11 discontinuities
per second to avoid continual cycle slips but occasionally
some larger jumps to create the observed blunders. Can you
calculate from your theory the mean magnitude and rate of
phase jumps and show they produce the required frequency
offset to explain the anomaly? That seems to be what you
are claiming.
To calculate the magnitude and rate of phase jumps I need information on
the accuracy to which the position of Pioneer can be measured directly
by ranging. As far as I can gather, we cannot measure the position of
Pioneer at all by ranging. I don't feel I understand why this is true,
but if it is true, then it is not possible to observe jumps.
I feel I am handicapped by a lack of knowledge
of the practical engineering principles according to which these things
work. Can you give me, or point me at, a simple explanation.
I can point you at an explanation, manual 207, section 4
from here:
http://deepspace.jpl.nasa.gov/dsndocs/810-005/stationdata.cfm
however it isn't what I would call simple.
No, it's not is it. Having no background in electrical engineering I
feel bamboozled by science.
I had assumed
you were sufficiently familiar with PLL behaviour when
you said your theory predicted that it would cycle slip.
Mea culpa. I think that was misinterpretation on my part. Better to
assume that I have a reasonable grasp of fundamental principles of
quantum theory, not much of practical electrical engineering.
And then how is the rate of slips influenced by the
theoretical resolution of a range measurement which
was not actually being performed at the time?
There is definitely an issue here to do with measurement in principle. I
don't think it is necessary that we actually take readings for a
measurement, but if it is possible to infer the results of a quantum
measurement in principle from readings which could be taken, that is
enough to cause wave function collapse and renormalisation of the
quantum theory.
Well the data was digitised so in theory could have been
written to file and an measurement imaginable applied at
a later date. In reality the frequency was computed and
stored but anything that can be calculated from those
numbers can be done. The files are freely available so
you can write a program to find the range from them now.
If that is true, then how come JPL have not written programs to find the
range of Pioneer and compared the results to the Doppler estimates of
position?
I'll carry on trying to read and absorb the information you have given
Sorry, I guess I have completely misunderstood your
explanation but hopefully you will see where I am
going wrong and point me in the right direction.
It may be the other way about. I would like to look more carefully at
what you mean by "sawtooth modulation on the PLL control voltage". Can
you put this in context.
There are lots of tutorials on PLLs on the web, this is
the first listed by Google and has a useful diagram in
Figure 7. Note this _isn't_ the sawtooth I mention above
but will help you understand how cycle slips originate.
http://www.uoguelph.ca/~antoon/gadgets/pll/pll.html
and pointed me at. There is a bit too much to comment on in one go.
Thus,
if we can measure Mars to an accuracy of 12m (Anderson's figure), then
intermediate positions calculated from high frequency Doppler (if we
could resolve them with sufficient accuracy) would have to be corrected
every 12/c secs.
Well the ranging system as I said was theoretically
capable of better than cm resolution, it just wasn't
working. For other spacecraft it did but why that
would create cycle slips in the frequency measuring
system is unclear to me.
I am unclear about this. Anderson talks of it taking minutes to resolve
and return a ranging signal. Does this time period not gradually
increase with distance, or is there something more fundamental I have
not understood?
The problem with Pioneer was that every time they sent the
modulation pattern the craft lost the uplink signal and all
they got back was the free-running craft oscillator.
This sounds critical. If it is stated in Anderson's paper I have missed
it. Can you point me to a reference. From Anderson I had thought that
the problem was to do with signal to noise ratio, but I don't see that
as a good answer because it is not a fundamental matter of principle -
one ought to be able to increase the power of the signal sent from
earth.
Well Charles, I hope that helped.
I think it has. But I have a lot to absorb.
It's not a simple system
Indeed.
and when you say your theory explains the Pioneer anomaly
I expect you to be able to show how this "renormalisation of
the quantum theory" produces a frequency measurement out of
the MDA that is quite different to the frequency of the sine
wave that is produced by applying the Doppler formula to the
frequency sent to the craft.
So far I can't follow how you
think that happens at all or why it would also produce blunder
points as well as a frequency error but only if a range
measurement was (wasn't?) being done simultaneously.
This is to do with the way in which the classical correspondence appears
from the quantum theory. If a range measurement is done simultaneously
then we are essentially dealing only with the classical theory. If that
were so we should get no anomalous acceleration or shift. If no such
range measurement is possible, then we need the quantum theory to model
transmissions from one reference frame to a remote reference frame.
Regards
--
Charles Francis
substitute charles for NotI to email
.
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