Re: Pioneer Anomaly discussion continued


It' still ironic that you continue to delete the summary of previous
discussions, and yet, continue to make the same errors that have been
corrected multiple times. You could have corrected yourself, but
didn't.

Summary Points
1. Do you understand now that the Doppler data are *not* averaged (daily
or multi-day)? [ and thus, your claims about half-daily signals being
averaged are erroneous? ]

2. Do you understand now that a Fourier transform is *not* used in the
Pioneer Doppler analysis? [ and thus, your claims about a DC
"constant offset" frequency are erroneous? ]

3. Do you understand now that the "anomaly" was discovered a Doppler
frequency residual, and not as an "acceleration residual?"

4. Do you understand that varying the station positions produces no
improvement in the Doppler residuals, so your suppositions about
station position errors are incorrect? [Added 08 Apr: ] And further,
do you understand that when I allowed station positions to vary, they
varied less than 1 m? And that the algorithm alone is sensitive to
smaller changes (but the data are not)?

5. Do you understand that by introducing deliberate station position
errors -- such as 100 meters, which you yourself suggested -- no
linear Doppler frequency drift is produced?

6. Do you understand that your claims about the variations in earth
length of day are irrelevant? Namely that, while it is true that the
length of day varies over time, these are *measured* very precisely
and can be accounted for. Your concentration on the length of day
issue is a canard: underlying it, is your assumption that Doppler
analysis models the earth rotation rate as constant. But since this
is an erroneous assumption, your conclusions are irrelevant.

7. Do you understand that the UT1 "timescale" is *defined* by the
earth rotation angle? The only way to determine UT1 is to measure it.
These measurements are done via observations of a large ensemble of
known, distant radio quasars -- and also to a constellation of
orbiting satellites -- which firmly tie earth rotation to a fixed
inertial frame. [Added 14 Apr: ] These kinds of observations are
continuous throughout the day.

8. Do you understand that the contributors to the IERS earth
orientation conventions measure the earth orientation *angles* and not
the rotation rate?

9. Do you understand that the difference between clock time and earth
rotation angle, UT1-UTC, is routinely measureable, slowly varying, and
accounted for in the Pioneer analysis?

10. Do you understand that it's ludicrous to believe that two
discrepant spacecraft would somehow negate other earth orientation
observations? (which involve tens of satellites, hundreds of quasars,
and several observation techniques, including radio and optical)

11. Do you understand that your requirement that earth orientation be
"fully theoretically modeled" is a diversion? The implication is that
a lack of a complete analytical model for earth orientation somehow
prevents one from independently measuring the orientation, and then
using those measurements for spacecraft navigation, but this
implication is incorrect.

12. Do you understand that the result of a constant spacecraft
acceleration, and a station offset or a change to earth rotation,
produce completely different signatures in the Doppler residuals? In
fact the Doppler technique is sensitive enough to distinguish between
such signatures.


Thomas Smid <thomas.smid@xxxxxxxxx> writes:

On 8 Apr, 10:33, Craig Markwardt
<craigm...@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

Incidentally, your truncated sinusoid term, |sin(wt)|, is incorrect.
In terms of the earth motion, the spacecraft rises in the east
(station moving toward the spacecraft, so a blueshift), and then sets
in the west (station moving away from the spacecraft, so a redshift).

While the actual behavior of the Doppler signal during tracking passes
is indeed a "half" of a sine-wave, it is *not* just the positive half,
but rather the half from 90 to 270 degrees, which has both positive
and negative excursions. You erroneously took the absolute value
without considering the proper phasing.

The phasing is correct: x=x0*sin((w+dw)t) describes the location of
the spacecraft (defined as positive if the spacecraft is above the
horizon), which after differentiation, Taylor expansion, and
subtraction of the modelled oscillation leads to (see a couple of
posts above)

dx_r/dt = x0*[dw*cos(wt) -dw*w*t*sin(wt) ]

The first term in the bracket does indeed both result in a red- and
blue shift during a 'spacecraft day', but the second, with its phase
shifted by 90 deg, results only in either a redshift or a blueshift
(depending on the sign of dw).

As you wish.

It's not my wish. It's a hard fact that a small mismatch of the
earth's rotation rate will result in a term representing either a net
redshift or blueshift over the course of a day.

I note that the residuals you point out in Anderson et
al's Fig 18 (a) do not have a growing amplitude, and (b) are not the
sinusoidal "upper half" which you predicted, but rather both positive
and negative quadrants.

I note no response.

.... deleted text replaced ...
Finally, it's worth noting that the same Figure 18 you keep referring
to does *not* show sinusoidal residuals whose amplitude grows linearly
with time, but rather a sinusoid with a nearly constant amplitude.
Thus, your "derivation" does not match the data.

Yes, that's because evidently the long term drift has been subtracted
here. ...

It is impossible to compute (sinusoid with growing amplitude) minus
(linear drift) and arrive at (sinusoid with constant amplitude).
There is simply no way to do it. Thus, there is no way for your claim
to be correct, and any conclusions you draw from it are irrelevant.


There is no evidence in Anderson's paper to support your assumption
that a linear drift was subtracted to obtain this figure. It is only
clear that *something* must have been subtracted, as otherwise there
would be a large systematic drift of some sort over the 30 days.

Since the Figure you refer to shows residuals, the "something" that
was subtracted was the *best-fit model* -- which includes a linear
frequency drift. It is *you* that supposed that a long-term drift was
subtracted.

You conveniently deleted the original point, which I have replaced
above. Namely, if your "theory" were correct, then one would see a
(half)sinusoidal profile with *growing amplitude*, and that is not
seen. There is no "long term drift" that could change this fact.
(... unless you are suddenly changing the definition of "long term
drift" to mean "diurnal sinusoid," which would be silly.)


Furthermore, as a test, I can and did change the the earth rotation
"rate" in the Doppler analysis algorithm (by artificially adjusting
the formula for Greenwich Mean Sidereal Time by a small but
significant amount), and it does *not* produce a linear Doppler drift
in the Pioneer analysis.

Well, what does it produce then? It certainly must have produced
something, otherwise one would have to question your algorithm. So you
should substantiate this point with concrete data.

It produces exactly what was predicted, namely a residual sinusoidal
profile with growing amplitude. It does *not* produce a simple linear
frequency drift.



A fascinating claim, but since daily averages were *not* used in the
analysis (see point 1 above) your conclusions are irrelevant.

I would actually question this. I had another look at Anderson's
paper, and from what I understand, all plots displaying the long term
residuals (e.g. Fig. 8) where obtained by averaging the data over
blocks ranging from 1-200 days. ...

You understand incorrectly. See summary point 1 above. Neither least
squares (Anderson et al. or Markwardt) nor batch-sequential analysis
(Anderson et al.) involve averaging the Doppler data. I can tell you
umambiguously: I never averaged any Doppler data during my Pioneer analysis

Well, if you didn't average the data, then they must have been
averaged already when you received them. ...

You are incorrect. The raw data are ATDFs (Archival Tracking Data
Files), with typical sample periods of 60 seconds.

... Otherwise I can't see a way
how you get this small statistical error for the acceleration
residual, which is almost identical to that in Anderson's CHASMP
analysis. ...

Whether or not you can see "a way" is not relevant. What you are not
"seeing" is summarized in point 3 above.

The detection and characterization of the anomaly as a nearly linear
frequency drift, are separate from the *interpretation* as a constant
acceleration. Even before adding an acceleration component to the
model, the nature of the anomaly was clear (i.e. it does *not* have a
(half)sinusoidal profile).

Adding a constant acceleration to the model -- and thus solving for a
precise mean acceleration via least squares -- does *not* mean that
the original high resolution data had been lost due to averaging.

... And as mentioned on page 20 in Anderson's paper, for this
analysis the *raw data* where already averaged, not just the residuals
resulting from the difference with the model data. The possibility
that you used the same data set is also indicated by the fact that it
covers the same period (1987-1994).

You've discovered an ambiguity of passive voice in the English
language. The phrase in the Anderson paper, "[t]he raw data set was
averaged to 7560 data points..." is not a comment about the state of
the "raw" data, but rather a statement about how their data reduction
process operated on the raw data. It could be rephrased to the active
voice as, "we averaged the raw data to produce 7560 data points..."

If you had bothered to read the rest of the Anderson paper, you would
have found that their sample interval was 1980 seconds, which is *not*
a daily or multi-day averaging, and thus *would* see the effect you
have speculated about. (But they did not)

Finally, my own analysis preserved the data at a finer 60 second
sampling interval, with similar conclusions. Thus, your speculations
continue to be incorrect.



You can understand everything well if you don't bother about obvious
inconsistencies, and in case of ionospheric physics there are many. I
showed for instance by means of a detailed numerical model that
ionospheric photoelectrons can not possibly (as is generally assumed)
thermalize by means of elastic collisions with ions and neutrals, as
the energy transfer in an elastic collision is much too small (see
http://www.plasmaphysics.org.uk/research/elspec.htm). I have also
shown that the scattering (and refraction) or radio waves could (or
rather should) be due to high atomic Rydberg states rather than
electrons (see http://www.plasmaphysics.org.uk/papers/radscat2.htm).
There are about half a dozen other points I could address here. These
may not all be relevant in this context, but some may be, and there
may be other issues I have not considered in detail before, like the
suggested dragging of light by the earth's magnetic field. In any
case, the latter would only be a very small effect, and unlike some of
the other points addressed here, it would not imply a radically new
view of things.

You are making a mountain out of a mole-hill. The ionospheric effects
at the frequencies at issue (1.5-3 GHz) are small, and behave
predictably. Furthermore, they have been verified by measurement of
frequency-dependent phase and group delays, Faraday rotation, and
angular deflection; as measured by ionogram, sounding rocket, GPS
tomography, VLBI, radio astronomy observations, and radio occultation.
And of course those same observations have been combined into
successful models which can predict ionosphere and thermosphere
densities and behaviors (which, incidentally, also successfully
explain drag effects on orbiting spacecraft). The small effects
ionospheric are easily accounted for, and thus there is no need for a
"new" (and unsubstantiated) theory of the ionosphere by you.

I pointed out a number of inconsistencies in the theory of the
ionosphere above, so my suggestion isn't unsubstantiated. You are just
discrediting it as such without any concrete counter arguments.

Whether or not the "inconsistencies" you pointed out are valid or not
is immaterial. Recalling your original wording, you had some "vague
ideas" about the ionosphere. The problem is that there is nothing but
vagueness. There is no evidence that these "ideas" would have any
impact on how the ionosphere is understood to modify microwave
radiation. Furthermore, the host of observations and observational
techniques I mentioned above come to self-consistent conclusions about
the nature of the ionosphere. Finally, there is no evidence that
ionospheric corrections -- or the lack of ionospheric corrections --
could cause the earth rotation rate to be mis-measured.


Let's return to your original speculation that somehow the mean earth
rotation rate were relevant, and that it was mis-measured. According
to your inspection of the IERS website, the error in the mean rate is
about 1e-12 rad/s. Such an error would produce apparent shifts in
station positions in the East-West direction, with typical magnitudes
of about 200 meters per year. For the ~20-30 years that high
precision GPS and VLBI have been available, that would produce 4-5
kilometer shifts in station positions! Such shifts are simply not
occurring. Typical GPS and VLBI accuracies today are in the few
millimeter range. Thus, your speculation simply does not hold water.


Furthermore, as noted already, many of the earth orientation
observations are taken at similar wavelengths (microwave), with
similar receiver technologies, as spacecraft navigation techniques.
That your ionosphere "idea" would need to affect Pioneer and the earth
orientation observations dissimilarly is another strike against it.

You seem to be missing the point here. The Pioneer anomaly is so
miniscule that it can only be discovered if the spacecraft is far
enough from the sun (and earth) so that the physical influence of the
latter becomes secondary. At closer distance the effect will simply
disappear under the data noise (or be apparently absorbed into any
number of other physical forces).

Actually, the Pioneer anomaly is not *so* miniscule. An anomaly of
8e-8 cm/s^2 is equal to 2.4 cm/s per year. Such an acceleration would
produce 5-10 meter offsets in station positions over the 20-30 year
lifetimes of VLBI and GPS stations. These offsets are simply not
seen. GPS observations in particular are actually *more* sensitive
than deep space Doppler because the GPS signals are stronger.

Furthermore, distant quasars are far beyond the influences of the sun
or earth (or our galaxy!), so by your criteria VLBI observations are
sensitive to station motions.

The point of the Pioneer celestial mechanics experiment (as it was
originally designed) was to examine gravitational and
non-gravitational forces in the outer solar system. The DSN engineers
and technicians were well aware that station position and timing had
to be constrained to equivalent accuracy, which was done using various
observational and surveying techniques.

So, returning to the point that *you* are missing, is that somehow you
are supposing that GPS and VLBI observations would somehow miss
station location errors but spacecraft Doppler would not, when in fact
all the techniques are similar. That is simply one more of your
ludicrous suppositions.

CM
.

Relevant Pages

  • Re: Pioneer Anomaly discussion continued
    ... and that means that the Doppler shifts ... station positions in the East-West direction, ... consequence on station longitudes of *your* supposition that the earth ... I considered what effect the anomalous acceleration ...
    (sci.astro)
  • Re: Pioneer Anomaly discussion continued
    ... Pioneer Doppler analysis? ... Do you understand that your claims about the variations in earth ... analysis models the earth rotation rate as constant. ... discrepant spacecraft would somehow negate other earth orientation ...
    (sci.astro)
  • Re: Pioneer anomaly engineering questions
    ... you say Doppler radar was used.. ... from Earth, reflected off of the spacecraft and returned to Earth and ... way from the spacecraft? ...
    (sci.physics)
  • Re: Pioneer Anomaly discussion continued
    ... to does *not* show sinusoidal residuals whose amplitude grows linearly ... that my Doppler analysis did not perform daily or multi-day averaging. ... figures" do not suggest that the anomaly is due to earth rotation ...
    (sci.astro)
  • Re: NASA Loses Contact With Mars Global Surveyor
    ... It read, "Dummy to earth, Dummy to earth, what's this ... Maybe MGS came to the same realization, ... another Mars-orbiting spacecraft take pictures of MGS to assess its ... NASA will ask the Mars Reconnaissance Orbiter (MRO) ...
    (sci.astro.amateur)
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