On 1 Jun 2006 08:20:37 -0700, "George Dishman"
<[email protected]> wrote:
>John C. Polasek wrote:
>> On 1 Jun 2006 06:16:57 -0700, "George Dishman"
>> <[email protected]> wrote:
>> >John C. Polasek wrote:
>> >> On 31 May 2006 10:52:02 -0500, Craig Markwardt
>> >> <[email protected]> wrote:
>> >> >
>> >> >John C. Polasek <[email protected]> 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,
Wait right here. How do you record the transmitted frequency? You mean
that the clock that was always regarded as 2.11 Ghz is assigned a new
and improved frequency with each shot? How do you measure the
frequency, by comparison to a similar clock or a maser? If all clocks
advance secularly, then your comparison is moot, and so after a few of
these antiseptic efforts, finding it's still 2.11Ghz, then it seems
acceptable to just take the book value and work from there. I cannot
conceive of a mechanism to check the clock for a new rate, unless the
clock becomes defective for example.
>> >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,
>> >> and that ftran
>> >> was likewise subjected to 240/211 so as to match frequencies,
>> >Pardon, ftran was the uplink frequency wasn't it?
George, George, when fdown was modified by 240/221 from 2.11GHz, it
seems only logical to take the reference ftran at 2.11 and similarly
multiply it by 240/221 so the modified ftran and fdown would match.
The diagram shows this
2.11as ref x 240/221--in lab to match down----->
There's nothing here to talk about except to express a measure of
dismay at your thinking I don't know 1 frequency from another. The
Lissajous remark below still applies; the diagram shows the separate X
and Y inputs to the scope.
>> No George, what I meant was that in order to subtract frequencies or
>> make a Lissajous on a scope, ftran was likewise boosted by the 240/211
>> before a comparison could be made.
>No, you said below "the whole thing was heterodyned
>down to 1 Mhz" which is correct. The returned frequency
>is predicted based on the modelled velocity at that time
>and the heterodyne reference chosen to be about 1MHz
>away from the expected receive frequency.
>> But you knew that.
>I have no idea what you are talking about John. There is
>a signal sent to the craft at a frequency near 2.11 GHz
>which we call the "uplink". If that isn't what you mean
>when you say "ftran", to which frequency are you referring?
This is tedious. Let's get on with the world's work.
>I spent some considerable effort writing a long paragraph
>to explain how it works above from which you should have
>been able to understand the process so it would help if you
>could refer your answer to that but if you are describin
>something you think I missed, please explain where you
>think it fits in
>> >> 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.