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"Pioneer anomalous acceleration" and Cassini



 
 
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  #11  
Old October 29th 03, 11:40 AM
Volker Hetzer
external usenet poster
 
Posts: n/a
Default "Pioneer anomalous acceleration" and Cassini


"Jonathan Silverlight" schrieb im Newsbeitrag
...
In message , greywolf42
writes
Jonathan Silverlight
wrote in message
conjunction.

There are no modelling of forces on the spacecraft in the paper -- construct
or otherwise.

Have you actually looked at the paper??


Yes.

They wouldn't be able to see anything without accurate modelling of the
gravitational and non-gravitational forces on the spacecraft.


You are incorrect. The paper does not deal with forces on the
spacecraft at all. Please read it.


Which part of "An important contribution to the frequency shift is due
to non-gravitational forces acting on the spacecraft" do you have a
problem reading?

Maybe my english isn'g good enough but the sentence "However, the uncertainty
in the thermal model overwhelms any plausible application of the pioneer
anomaly to Cassini." seems to me that they couldn't model arrurately enough
for the checking of the "pioneer anomaly". Thermal seems to refer to the
thermal radiation of the isotope batteries.

Lots of Greetings!
Volker

  #12  
Old October 29th 03, 10:05 PM
Jonathan Silverlight
external usenet poster
 
Posts: n/a
Default "Pioneer anomalous acceleration" and Cassini

In message , Volker Hetzer
writes

"Jonathan Silverlight"
schrieb im Newsbeitrag
...
In message , greywolf42
writes
Jonathan Silverlight
wrote in message
conjunction.

There are no modelling of forces on the spacecraft in the paper
-- construct
or otherwise.

Have you actually looked at the paper??

Yes.

They wouldn't be able to see anything without accurate modelling of the
gravitational and non-gravitational forces on the spacecraft.

You are incorrect. The paper does not deal with forces on the
spacecraft at all. Please read it.


Which part of "An important contribution to the frequency shift is due
to non-gravitational forces acting on the spacecraft" do you have a
problem reading?

Maybe my english isn'g good enough but the sentence "However, the uncertainty
in the thermal model overwhelms any plausible application of the pioneer
anomaly to Cassini." seems to me that they couldn't model arrurately enough
for the checking of the "pioneer anomaly". Thermal seems to refer to the
thermal radiation of the isotope batteries.


That's _very_ interesting. Thanks! I assume you're quoting "Improved
Test of General Relativity with Radio Doppler Data from the Cassini
Spacecraft" by Anderson et al., as that's the only hit I get doing a
search for "application of the pioneer anomaly to Cassini".
It's at http://www.arxiv.org/abs/gr-qc/0308010v1, but there's a note
that "This paper was withdrawn at the recommendation of the Cassini
Radio Science Team."
Version 1 is still available, and they quote a radial acceleration of
-26.7 x 10^-8 cm s^2 and note that "unlike Pioneer, the result is not
anomalous".
--
Rabbit arithmetic - 1 plus 1 equals 10
Remove spam and invalid from address to reply.
  #13  
Old October 31st 03, 11:18 AM
Volker Hetzer
external usenet poster
 
Posts: n/a
Default "Pioneer anomalous acceleration" and Cassini


"Jonathan Silverlight" schrieb im Newsbeitrag
...
In message , Volker Hetzer
writes

"Jonathan Silverlight"
schrieb im Newsbeitrag
...
In message , greywolf42
writes
Jonathan Silverlight
wrote in message
conjunction.

There are no modelling of forces on the spacecraft in the paper
-- construct
or otherwise.

Have you actually looked at the paper??

Yes.

They wouldn't be able to see anything without accurate modelling of the
gravitational and non-gravitational forces on the spacecraft.

You are incorrect. The paper does not deal with forces on the
spacecraft at all. Please read it.


Which part of "An important contribution to the frequency shift is due
to non-gravitational forces acting on the spacecraft" do you have a
problem reading?

Maybe my english isn'g good enough but the sentence "However, the uncertainty
in the thermal model overwhelms any plausible application of the pioneer
anomaly to Cassini." seems to me that they couldn't model arrurately enough
for the checking of the "pioneer anomaly". Thermal seems to refer to the
thermal radiation of the isotope batteries.


That's _very_ interesting. Thanks! I assume you're quoting "Improved
Test of General Relativity with Radio Doppler Data from the Cassini
Spacecraft" by Anderson et al., as that's the only hit I get doing a
search for "application of the pioneer anomaly to Cassini".
It's at http://www.arxiv.org/abs/gr-qc/0308010v1, but there's a note
that "This paper was withdrawn at the recommendation of the Cassini
Radio Science Team."

Yep. That's the one.

Version 1 is still available, and they quote a radial acceleration of
-26.7 x 10^-8 cm s^2 and note that "unlike Pioneer, the result is not
anomalous".

Hm. Sounds like a contradiction to me. First they say that they don't
have an anomaly and then they say they couldn't check for it.

Lots of Greetings!
Volker

  #14  
Old November 1st 03, 09:18 PM
ralph sansbury
external usenet poster
 
Posts: n/a
Default "Pioneer anomalous acceleration" and Cassini

You are all blithely assuming that the low amplitude
oscillations of charge around some
average that are received when the receiving antenna is pointing
in the region of the
sky containing the spacecraft show a clear frequency over a
period of four hours or
so when the receiver antenna is so positioned and constantly
readjusted to point
to the spacecraft as the earth moves.
This may be a perfectly correct assumption on your part
and Anderson et al.; parts of the Anderson paper and others
describing the method of amplifying and detecting the expected
doppler shifted frequency are hard to decipher though
George Dishman has been helpful in translating some of the
FFT and PLL jargon.
If the reception was perfectly clear then one would see every
(1/2.11.....) times 10^-9 seconds a crossing at zero ( average
value) of the oscillating voltage.
But because of thermal noise and other radiation other
voltages
are added to this expected set of voltages and so to those at the
zero crossings every (1/2.11.....) times 10^-9 seconds
obscuring|
the zero and to other voltages making zero crossings appear which
are not part of the systematic pattern.
Using phase locked loops one could find a first true zero
and then one could take a second or billions of successive
voltage values
and add them to the next second or billion etc for 60 seconds and
the
random obscuring voltages would cancel out.
Apparently they have done so until recently for Pioneer 10 but
I
imagine there had been a steady degradation and I would like
to know from a radio astronomer what form this degradation
takes??
eg How many regularly spaced zeros do you have to miss before
you decide the data is too noisy to establish a specific
frequency?



"Volker Hetzer" wrote in message
...

"Jonathan Silverlight"

schrieb im
Newsbeitrag
...
In message , Volker

Hetzer
writes

"Jonathan Silverlight"


schrieb im Newsbeitrag
...
In message

, greywolf42
writes
Jonathan Silverlight


wrote in message


conjunction.

There are no modelling of forces on the spacecraft in

the paper
-- construct
or otherwise.

Have you actually looked at the paper??

Yes.

They wouldn't be able to see anything without accurate

modelling of the
gravitational and non-gravitational forces on the

spacecraft.

You are incorrect. The paper does not deal with forces

on the
spacecraft at all. Please read it.


Which part of "An important contribution to the frequency

shift is due
to non-gravitational forces acting on the spacecraft" do

you have a
problem reading?
Maybe my english isn'g good enough but the sentence

"However, the uncertainty
in the thermal model overwhelms any plausible application of

the pioneer
anomaly to Cassini." seems to me that they couldn't model

arrurately enough
for the checking of the "pioneer anomaly". Thermal seems to

refer to the
thermal radiation of the isotope batteries.


That's _very_ interesting. Thanks! I assume you're quoting

"Improved
Test of General Relativity with Radio Doppler Data from the

Cassini
Spacecraft" by Anderson et al., as that's the only hit I get

doing a
search for "application of the pioneer anomaly to Cassini".
It's at http://www.arxiv.org/abs/gr-qc/0308010v1, but there's

a note
that "This paper was withdrawn at the recommendation of the

Cassini
Radio Science Team."

Yep. That's the one.

Version 1 is still available, and they quote a radial

acceleration of
-26.7 x 10^-8 cm s^2 and note that "unlike Pioneer, the

result is not
anomalous".

Hm. Sounds like a contradiction to me. First they say that they

don't
have an anomaly and then they say they couldn't check for it.

Lots of Greetings!
Volker



  #15  
Old November 4th 03, 11:24 AM
kurtan
external usenet poster
 
Posts: n/a
Default "Pioneer anomalous acceleration"

Perhaps some of you clever guys could care to bestow an opinion on findings
at www.estfound.org/pioneer.htm . Is it go again for "Tired Light"
redshift?
/kgb

"ralph sansbury" wrote in message
...
You are all blithely assuming that the low amplitude
oscillations of charge around some
average that are received when the receiving antenna is pointing
in the region of the
sky containing the spacecraft show a clear frequency over a
period of four hours or
so when the receiver antenna is so positioned and constantly
readjusted to point
to the spacecraft as the earth moves.
This may be a perfectly correct assumption on your part
and Anderson et al.; parts of the Anderson paper and others
describing the method of amplifying and detecting the expected
doppler shifted frequency are hard to decipher though
George Dishman has been helpful in translating some of the
FFT and PLL jargon.
If the reception was perfectly clear then one would see every
(1/2.11.....) times 10^-9 seconds a crossing at zero ( average
value) of the oscillating voltage.
But because of thermal noise and other radiation other
voltages
are added to this expected set of voltages and so to those at the
zero crossings every (1/2.11.....) times 10^-9 seconds
obscuring|
the zero and to other voltages making zero crossings appear which
are not part of the systematic pattern.
Using phase locked loops one could find a first true zero
and then one could take a second or billions of successive
voltage values
and add them to the next second or billion etc for 60 seconds and
the
random obscuring voltages would cancel out.
Apparently they have done so until recently for Pioneer 10 but
I
imagine there had been a steady degradation and I would like
to know from a radio astronomer what form this degradation
takes??
eg How many regularly spaced zeros do you have to miss before
you decide the data is too noisy to establish a specific
frequency?

"Volker Hetzer" wrote in message
...

"Jonathan Silverlight"

schrieb im
Newsbeitrag
...






  #16  
Old November 4th 03, 05:55 PM
greywolf42
external usenet poster
 
Posts: n/a
Default "Pioneer anomalous acceleration" and Cassini

Jonathan Silverlight wrote
in message ...
In message , Volker Hetzer
writes

"Jonathan Silverlight"
schrieb im Newsbeitrag
...
In message ,

greywolf42
writes
Jonathan Silverlight
wrote in message


{snip}

Which part of "An important contribution to the frequency shift is due
to non-gravitational forces acting on the spacecraft" do you have a
problem reading?


Maybe my english isn'g good enough but the sentence "However, the
uncertainty in the thermal model overwhelms any plausible application
of the pioneer anomaly to Cassini." seems to me that they couldn't
model arrurately enough for the checking of the "pioneer anomaly".
Thermal seems to refer to the thermal radiation of the isotope batteries.


That's _very_ interesting. Thanks! I assume you're quoting "Improved
Test of General Relativity with Radio Doppler Data from the Cassini
Spacecraft" by Anderson et al., as that's the only hit I get doing a
search for "application of the pioneer anomaly to Cassini".


Yes, that was the reference.

It's at http://www.arxiv.org/abs/gr-qc/0308010v1, but there's a note
that "This paper was withdrawn at the recommendation of the Cassini
Radio Science Team."


Fascinating.

Version 1 is still available, and they quote a radial acceleration of
-26.7 x 10^-8 cm s^2 and note that "unlike Pioneer, the result is not
anomalous".


Well, the complete abstract is:
"Radio Doppler data from the Cassini spacecraft during its solar conjunction
in June 2002 can be used to test General Relativity. In terms of the
standard post-Newtonian parameter , the result is gamma - 1 = (-4.8 +- 5.7)
x 10^-5, including both random and systematic error (sic). Einstein's
theory has survived yet another test."

There are two mentions of the Pioneer effect in this paper:

"We include eight parameters in the weighted-least-squares solution: first,
the six initial conditions (state) for the spacecraft trajectory; secondly,
a constant radial acceleration a_r, primarily to account for the spacecraft'
s thermal emission, but also for smaller effects such as unmodeled
solar-pressure, beamed radio emission, and a possible contribution from the
Pioneer anomaly [12]; and finally the relativity parameter gamma."

And:

"Finally, the error in a_r from 27 days of Cassini Doppler data is about two
times better than the result from 11 years of Pioneer 10 Doppler data [12].
However, unlike Pioneer, the result is not anomalous. Both Pioneer and
Cassini are powered by radioisotope thermoelectric generators (RTG), but on
Pioneer they are mounted on booms and radiate the bulk of their thermal
output isotropically into space without reaching the spacecraft. On the
other hand for Cassini, the RTG's are mounted on the spacecraft bus beneath
the high-gain parabolic dish antenna. Their thermal output is controlled by
refection and absorption by the antenna and other spacecraft parts. It is
difficult to model, although it should be directed toward the Earth, as
confirmed by the negative sign in the solution for a_r. However, the
uncertainty in the thermal model overwhelms any plausible application of the
Pioneer anomaly to Cassini."


In short, there is no way Cassini can be used for evaluation of the Pioneer
effect. This is because the thermal emissions from Cassini are
non-isotropic, and far greater in magnitude than the expected Pioneer
effect. The statement the Cassini "result is not anomalous" is completely
misleading. And completely wrong when taken out of context. The result is
not anomalous only because the Pionner effect cannot be observed by Cassini,
due to the effect being swamped by difficult-to-model thermal emissions.

Again, the purpose of this measurement was validation of GR's gamma -- not
the Pioneer effect.

--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}



  #17  
Old November 5th 03, 12:16 AM
Jonathan Silverlight
external usenet poster
 
Posts: n/a
Default "Pioneer anomalous acceleration" and Cassini

In message , greywolf42
writes

In short, there is no way Cassini can be used for evaluation of the Pioneer
effect. This is because the thermal emissions from Cassini are
non-isotropic, and far greater in magnitude than the expected Pioneer
effect. The statement the Cassini "result is not anomalous" is completely
misleading. And completely wrong when taken out of context. The result is
not anomalous only because the Pionner effect cannot be observed by Cassini,
due to the effect being swamped by difficult-to-model thermal emissions.

Again, the purpose of this measurement was validation of GR's gamma -- not
the Pioneer effect.


I know that.
I don't know if the solar opposition experiment has been published, but
the point is that Bertotti et al. quote a figure for the acceleration
from the RTGs of 3 x 10^-9 m s^-2, with an error of 9 x 10^-11 m s^-2.
That error is about "an order of magnitude" less than the Pioneer
effect.
Anderson et al. quote a figure for a_r (the radial acceleration, mostly
due to the RTGs) of -26.7 x 10^-8 cm s^-2, which is essentially the same
when you convert.
As Volker Hetzer says, there's a contradiction between the statements
that "the result is not anomalous" and "the uncertainty in the thermal
model overwhelms any plausible application of the Pioneer anomaly to
Cassini". The new measurements are much more accurate than the Pioneer
ones (compare the residuals) and the Pioneer effect doesn't appear.
--
Rabbit arithmetic - 1 plus 1 equals 10
Remove spam and invalid from address to reply.
  #18  
Old November 5th 03, 08:57 AM
Jim Greenfield
external usenet poster
 
Posts: n/a
Default "Pioneer anomalous acceleration" and Cassini

"greywolf42" wrote in message ...
Jonathan Silverlight wrote
in message ...


There's an article in the current issue of Nature that seems relevant to
the Pioneer anomalous acceleration question ("A test of general
relativity using radio links with the Cassini spacecraft" B Bertotti, L
Iess and P Tortora, Nature vol 425. No. 6956 p. 374,
doi:10.1038/nature01997)
AFAICS they have accurately modelled emission from the RTGs and they
don't see any unexplained acceleration.


They haven't looked for anomalous acceleration with this experiment. The
referenced experiment measures the time-delay of the signal in a
gravitational field. Nothing more.

Does that mean the question is settled, or isn't their measurement
sufficiently sensitive?


The question was settled years ago. There *is* definitive anomalous
acceleration in pioneer and the voyagers. No theoretical explanation has
yet been settled on.


Finally gathered the courage to tentatively suggest that when photons
are emmitted, they give a 'recoil' against the source. If radiation
from within the craft is directed in a particular direction, a thrust
might occur. (I thought that this would be so insignificant as to be
immesurable and undetectable, but maybe not)
What would happen to a high-power laser carefully suspended- any
chance of detecting an observable thrust counter to beam direction???

Jim G
  #19  
Old November 5th 03, 09:12 AM
greywolf42
external usenet poster
 
Posts: n/a
Default "Pioneer anomalous acceleration" and Cassini

Jonathan Silverlight wrote
in message ...
In message , greywolf42
writes


{replaced invisibly snipped quote from paper}
==========================
Well, the complete abstract is:
"Radio Doppler data from the Cassini spacecraft during its solar conjunction
in June 2002 can be used to test General Relativity. In terms of the
standard post-Newtonian parameter , the result is gamma - 1 = (-4.8 +- 5.7)
x 10^-5, including both random and systematic error (sic). Einstein's
theory has survived yet another test."

There are two mentions of the Pioneer effect in this paper:

"We include eight parameters in the weighted-least-squares solution: first,
the six initial conditions (state) for the spacecraft trajectory; secondly,
a constant radial acceleration a_r, primarily to account for the spacecraft'
s thermal emission, but also for smaller effects such as unmodeled
solar-pressure, beamed radio emission, and a possible contribution from the
Pioneer anomaly [12]; and finally the relativity parameter gamma."

And:

"Finally, the error in a_r from 27 days of Cassini Doppler data is about two
times better than the result from 11 years of Pioneer 10 Doppler data [12].
However, unlike Pioneer, the result is not anomalous. Both Pioneer and
Cassini are powered by radioisotope thermoelectric generators (RTG), but on
Pioneer they are mounted on booms and radiate the bulk of their thermal
output isotropically into space without reaching the spacecraft. On the
other hand for Cassini, the RTG's are mounted on the spacecraft bus beneath
the high-gain parabolic dish antenna. Their thermal output is controlled by
refection and absorption by the antenna and other spacecraft parts. It is
difficult to model, although it should be directed toward the Earth, as
confirmed by the negative sign in the solution for a_r. However, the
uncertainty in the thermal model overwhelms any plausible application of the
Pioneer anomaly to Cassini."
==========================

In short, there is no way Cassini can be used for evaluation of the

Pioneer
effect. This is because the thermal emissions from Cassini are
non-isotropic, and far greater in magnitude than the expected Pioneer
effect. The statement the Cassini "result is not anomalous" is

completely
misleading. And completely wrong when taken out of context. The result

is
not anomalous only because the Pionner effect cannot be observed by

Cassini,
due to the effect being swamped by difficult-to-model thermal emissions.

Again, the purpose of this measurement was validation of GR's gamma --

not
the Pioneer effect.


I know that.


Then why are you attempting to claim results other than what the paper and
observations were about?

I don't know if the solar opposition experiment has been published, but
the point is that Bertotti et al.


Horsefeathers. The reference under discussion was Anderson and Lau -- not
Bertotti. And the difficulty of modelling the emission is not physically
different for Bertotti than four Anderson and Lau.

But I guess that's why you snipped the quotes from your own reference (for
the second time):

quote a figure for the acceleration
from the RTGs of 3 x 10^-9 m s^-2, with an error of 9 x 10^-11 m s^-2.
That error is about "an order of magnitude" less than the Pioneer
effect.


Not according to Anderson and Lau.

Anderson et al. quote a figure for a_r (the radial acceleration, mostly
due to the RTGs) of -26.7 x 10^-8 cm s^-2, which is essentially the same
when you convert.


Yes. And Anderson and Lau mention that "the uncertainty in the thermal
model overwhelms any plausible application of the Pioneer anomaly to
Cassini."

As Volker Hetzer says, there's a contradiction between the statements
that "the result is not anomalous" and "the uncertainty in the thermal
model overwhelms any plausible application of the Pioneer anomaly to
Cassini". The new measurements are much more accurate than the Pioneer
ones (compare the residuals) and the Pioneer effect doesn't appear.


How are they more accurate? According to Anderson, the measurements
of 'anomalous accelerations' would are 10 times less precise than the gross
effect measured to 2 sig figs on Pioneer. Due to "the uncertainty in the
thermal model" of Cassini.

--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}


  #20  
Old November 5th 03, 02:28 PM
George Dishman
external usenet poster
 
Posts: n/a
Default "Pioneer anomalous acceleration" and Cassini


"Jim Greenfield" wrote in message
om...
"greywolf42" wrote in message

...

The question was settled years ago. There *is* definitive anomalous
acceleration in pioneer and the voyagers. No theoretical explanation

has
yet been settled on.


Finally gathered the courage to tentatively suggest that when photons
are emmitted, they give a 'recoil' against the source.


Yes, each photon carries a momentum proportional to
its frequency.

If radiation
from within the craft is directed in a particular direction, a thrust
might occur. (I thought that this would be so insignificant as to be
immesurable and undetectable, but maybe not)


The data from Pioneer is sent back by radio. The power is
nominally 8W, a little more than a mobile phone. The radiation
pressure from the beam is about 13% of the magnitude of the
anomaly but the beam pushes the craft away from the Earth while
the anomaly is an acceleration towards the Earth. This is why
asymmetric thermal radiation from the RTGs was looked at as a
possible explanation, they emit a couple of kW altogether. The
trouble was that nobody could figure out how to explain the
asymmetry.

What would happen to a high-power laser carefully suspended- any
chance of detecting an observable thrust counter to beam direction???


Yes, or turned around, shining a laser on a solar sail can give
it thrust. The effect can also be used to suspend individual
atoms in a laser beam.

George


 




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