|
|
John C. Polasek wrote:
> On 31 May 2006 10:52:02 -0500, Craig Markwardt
> <craigmnet@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> >
> >John C. Polasek <jpolasek@xxxxxxxxxx> writes:
> >> But we are neglecting another reference frequency, nu_87 that is built
> >> into the model. ...
> >
> >No. Despite multiple corrections, and extensive discussions of the
> >actual procedures, you persist with this delusion. As the thread is
> >purely based on speculation, I no longer care to be involved.
> >
> >CM
> It would be helpfulif you would illuminate us on what steps were
> followed to generate nu_model ...
The process is slightly iterative however the end
result is as follows:
For any measurement of the received frequency,
the time of receipt is recorded in the data files.
Having an estimate of the trajectory of the craft,
the time at which the signal was transmitted can
be deduced together with the location of the craft
at that time. That also corresponds to the receipt
of the uplink by the craft. From those and the
known rotation and orbital parameters of the Earth,
the time of transmission of the uplink from the
DSN site can be calculated. The frequency which
was transmitted during that period is also recorded
in the data files. nu_model is then calculated by
taking the recorded uplink transmit frequency,
applying Doppler to deal with the motion of the
planet relative to the solar system barycentre.
That signal travels to the craft and is changed by
the Doppler effect due to the motion of the craft
relative to the barycentre. The frequency is
increased by 240/221 and retransmitted from the
craft. Allowance is then made for the Doppler
effect on the path to the receiving site in a similar
fashion to the uplink.
> ... is so it could be subtracted from
> nu_observed to get
> (f_observ - f_model)DSN = -2fP*t (2)
> Is this all mathematical or is the computer model made to operate a
> charge pump to create real frequency f_model to beat against
> f_observed?
The data files were recorded thirty years ago! It
is all mathematical and if you get a copy of
the files you can do it yourself.
> Or is f_observ reduced to a numeric for comparison with a numeric
> value from f_model?
> This subtraction operation is at the crux of the Pioneer observation,
> but as an outsider I can't be sure how it was done, just that it must
> have been done, but how?
Craig used IDL. The details are on his web site.
> But don't patronize me about definition of nu_0 etc. I know the signal
> went up as 2.11 Ghz, ...
Yes, you are calling that "ftran".
> ... was transformed down by 240/211,
Right.
> and that ftran
> was likewise subjected to 240/211 so as to match frequencies,
Pardon, ftran was the uplink frequency wasn't it?
> and that
> the whole thing was heterodyned down to 1 Mhz and that they were able
> with a phase lock loop to interpolate 256 Mhz into the 1 Mhz for fine
> readings.
Not quite, the system made measurements in steps
of 1/256 of a cycle so for a 60s sample, they could
measure with a resolution of 65 micro Hz.
> By what means was Eq. (2) mechanized? When this matter is clarified
> maybe we can make some progress.
If you know f_model then an Excel spreadsheet is
adequate to do the simple subtraction. That's not
really what you are asking though.
George
|
|