"Craig Markwardt" wrote in
message news

"ralph sansbury" writes:
1)Re error: Craig,you say that the received frequency power
in
the FFT diagram is centered on the specific frequency of the
local oscillator frequency that most closely matches in phase
and
frequency the received frequency. You say it is by eyeball
estimation about 15 to 20db above the values at other
frequencies.

No, I did not say that. I said that there was a carrier peak
with
some breadth, bracketed by an overall noise level. I did not
say
anything about a local oscillator, or phase. The centering of
the
peak is merely a plotting convenience.

I realize but the whole point of doing this is to obtain a
frequency for the local oscillator
that is an accurate representation of the noisy received signal.
It is certainly not just a plotting convenience.


The FFT is an unbiased method for estimating the signal power
at many
frequencies simultaneously, not just a local oscillator
frequency.


Again I did not say that it wasn't.

For purposes of measuring signal strength, the FFT is just
fine. For
more detailed radiometric tracking, of course the phase must be
tracked, which is why the cycle counters are used.

That is why I said in the first paragraph that the FFT gives
the frequency
that the phase locked loop uses to obtain a local oscillator
frequency
that most closely matches the received noisy oscillations.


So, Craig, George, Is it unnecessary to reconcile this
error
estimate with the difference between the recieved
oscillations of
voltage and the oscillations produced by a local oscillator
at a
specifc rms amplitude at the selected frequency made to match
most closely in phase the received oscillations and then
modified
in frequency to maintain the close match?

This is a nonsensical paragraph. The FFT power density
spectrum is
not an error estimate, therefore the remainder of your question
is
irrelevant. Please keep this straight: the noise level is
completely
separate from the modeling error in the tracking analysis.

But what is the relationship? It sounds like you dont really
know the answer and you dont think it matters. I think it may
matter.


Perhaps so. But what about the degree of correspondence of
zero
crossings in the selected in phase local oscillator sequence
of
oscillating voltages and the corresponding sequence of zero
crossings in the reduced(intermediate)representation of the
received frequency?
I should think that this would be indicative of the
reliability of the 'detected' frequency and phase given to
the
local oscillator and would have some relationship to the
100db
Sig/Noise or whatever indicated FFT frequency with the most
power.??

The signal to noise level does indeed determine how well the
Doppler
cycle count (= phase) can be tracked. But that's nothing new,
from a
signal processing perspective. The Doppler cycle count
technique does
*not* require an exact correspondence between the reference
signal
(the local oscillator) and the received signal. It is the
difference
between these two signals which is accumulated in the counter,

What difference exactly and how is it "accumulated" and what
is
the relation between the degree of correspondence and the
signal/noise
figure and the accuracy in fractions of Hz of the specified
received frequency
as indicated by the local oscillator etc..?

and
then recorded for later analysis. There is enough information
to
reconstruct the received "sky" frequency from that.


2)Re transmitted frequency: For the nth time where is the
transmitted frequency or is this just something you make up
to
give the predicted Doppler result assuming the speed of light
delay?

And, for the N+1th time, the transmitted frequencies are
recorded and
stored with the Doppler count data as special "ramp" records,
with
timestamps. Again, you appear to be failing to pay attention.

Again is this item 112 in the tracking data logical record or
what other item number?



3)Re received frequencies.In the tracking data logical
record,
item 31 and 32 gives Doppler Count in units of 1000 time the
number of cycles. I gather this corresponds to Craig's
Doppler
count which is instead in units of cycles.
What item gives the FSKY minus 2292000000Hz?

Perhaps it is the output of my own program, which George may
have sent
to you. The "sky" frequency is computed in accord with the
recommendations of Moyer (2000), or Morabito & Asmar (1994).
Subtraction of 2.292 GHz is to avoid printing the same digits
over and
over again, it's as simple as that.


Understood. But what item number in the tracking data contains
the FSKY
in your program output?
I am looking at a Pioneer 10 cd with 21 files with a little
gnu c++ program on my laptop
and in the first 266 bytes am getting a lot of binary 00000000
bytes. This should be the file identification record where eg
bits 73 through 84 contain the last two digits of year.(which
should be 87 I think since file is named "87037.dat"
What is going on here?

4)re p6 of DSN 810-005 Rev.E/202,Rev.A
"The uplink carrier frequency is synthesized with the exciter
..... [at the receiver site] ...The uplink carrier may be
either
constant or varied in accord with a tuning plan. In either
case,
the phase of the[synthesized] uplink carrier is recorded for
use
in the computation of a Doppler effect."
This sounds to me like the transmitted frequency at the
assumed transmission site is simulated at the receiver site
and
used in computing the expected frequency.

What it sounds to you is irrelevant. Uplink and downlink
sessions can
overlap -- but not always --

For example and are these the times when there are a lot of
blanks in the received frequencies because of bad weather or
whatever other excuse is used?

so it is natural to have a single
reference signal, in this case from the uplink exciter. All of
the
Pioneer 10 uplinks were done at a constant transmitter
frequency. The
downlinks, on the other hand, will have the Doppler signatures
of
earth rotation and spacecraft motion imprinted on them. The
uplink
synthesizer cannot mimic these. Indeed, the synthesizer is
used only
as a reference frequency for Doppler counting. What the
reference
frequency actually is, is irrelevant (as long as it's within
the
counter's bandpass).

The comparison to a "predicted" frequency only happens hours,
months
or years later when the tracking analysis is performed in
software.


5)Thus unless it is possible to determine the transmit
frequency at the receiving site it will not be possible to
test
the hypothesis that light speed does not extrapolate beyond 1
second(ie beyond r for r/c1). If the transmit frequency at
the
receiving site is known to be the same as the transmit
frequency
at the assumed site then of course it would be possible to
test
this hypothesis.

The transmitted frequency is determined by solving the light
travel
time equations. Fortunately, there is only one solution
trajectory
(within an extremely tight confidence region) which agrees with
the
data. As I have mentioned several times in the past, changing
the
speed of light by even one part in one million ,destroys any
possible
solution.
If your suppositions about the motions of the earth site
and lines
between earth site and the craft at the time of transmission and
the time
of reception/transmission by the craft and the time of reception
by the
earth are correct. And then there are the fudge factors ascribed
to
atmospheric effects, relativity etc..

Therefore your supposition is completely erroneous.



Your phrase, "transmit frequency at the receiving site" is
nonsensical. *IF* the uplink transmitter is operating at the
receiving site, it would be for the *next* session, not the
current
one.
That is the hypothesis that is to be tested.

Furthermore, you have been provided with many examples where
the
receiving station is completely blocked from the line to the
spacecraft when the uplink occurs, or the transmitting station
is
blocked when the downlink occurs. In fact, blockage is far
more
common than not.

1)And the 87 87 and 89 files I have, have
lots of blank data which could account for this.

I am aware that you claim that somehow the transmitter's uplink
signal
is misinterpretted as the same station's downlink. But that
ignores
some very obvious and fatal issues like: if it were true, how
do the
signatures of spacecraft and earth motion get imprinted on the
signal?

2)If by signatures you mean time stamp, the reason is that
the
computer programs in the communication system erroneously assume
speed of light delay for the distance specified from Newtonian
calculations
of position independent of light speed delay.

(they wouldn't) or, how does *ANY* spacecraft telemetry get
detected
on the signal? (it wouldn't be) or, what happens when uplink
and
downlink are not always overlapping? (your supposition would
be
false)



or, how could any spacecraft be successfully navigated?
(they
couldn't be)

3The navigation depends on the Newtonian calculations
primarily
And to the extent erroneous modifications creep they may in
general
be too small to cause problems. But half of all spacecraft have
had
navigation problems.

And finally, how could the uplink be mistaken as
the
downlink when they are separated by over 200 MHz in frequency?
(they
couldn't be mistaken)

4)Your supposition here is nonsensical. The uplink is sent as
before
to the spacecraft where it is multiplied by 240/221 or whatever
and
send back to the receiver on earth two seconds about after the
uplink
was sent.

Your supposition is completely and
utterly
unfounded.

So let's test it.

Ralph