Anom Accel of Pioneer 10 for v>(GM/r)^1/2

In message , Igor
writes
On Mon, 24 Nov 2003 00:03:07 +0000, Jonathan Silverlight
wrote:

In message , Igor
writes

Apparently, the accepted explanation for the anomalous acceleration of
Pioneers 10 and 11 is that they're experiencing a larger gas and dust
density in the Kyper belt than was expected.


Interesting. Do you have a reference for that? I'd be surprised, because
the acceleration has been almost constant since about 15AU (inside the
orbit of Uranus) and if anything there is _less_ dust than expected in
the Kuiper belt..
Personally, I think it's looking more and more likely that Ned Wright is
correct and they hadn't modelled thermal emission from the RTGs
correctly. I haven't seen any evidence of an anomaly on Cassini.

Check out this link:

http://www.newtonphysics.on.ca/Anoma...eleration.html

Very interesting! It's somehow satisfying that the explanation is
conventional, not due to some boring property of the spacecraft, and
gives new information.
Presumably the reason Cassini hasn't seen an acceleration is that it's
more than 20 x as massive.
One thing does occur to me. Paul Marmet rather fancifully suggests that
the Pioneers will gather dust as they move. It seems to me that the dust
particles will actually be moving at very high speed relative to the
spacecraft and will vaporise. More to the point, that means they will
impart their kinetic energy to the spacecraft, which scales as V^2, not
V.
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Jonathan Silverlight writes:

In message , Igor
writes
Check out this link:

http://www.newtonphysics.on.ca/Anoma...eleration.html

Very interesting! It's somehow satisfying that the explanation is
conventional, not due to some boring property of the spacecraft, and
gives new information.
Presumably the reason Cassini hasn't seen an acceleration is that it's
more than 20 x as massive.
One thing does occur to me. Paul Marmet rather fancifully suggests that
the Pioneers will gather dust as they move. It seems to me that the dust
particles will actually be moving at very high speed relative to the
spacecraft and will vaporise. More to the point, that means they will
impart their kinetic energy to the spacecraft, which scales as V^2, not

Marmet's explanation is unconvincing. It depends entirely on the
density of dust in the outer solar system, which according to Marmet:

This amount of dust in the outer region of the solar system appears
quite reasonable remembering that the daily amount of dust falling
on Earth is reported as many tons of dust grains per day.

which is a completely fallacious argument. The number of "tons" of
dust falling on the earth has nothing to do with the dust conditions
in the outer solar system, because (a) one must normalize the captured
"tons" by the cross sectional area of the earth; and (b) the
conditions are different in the outer solar system. In particular,
the dust density drops of precipitously beyond Jupiter.

It is straightforward to show that the net acceleration due to dust
is:
a_dust = -2 (A/M) n V^2 m
where A/M is the area to mass ratio of the body, n is the dust
density, V is the body velocity, and m is the mean dust mass. This
conservatively assumes elastic scattering. It is likely that the dust
will be captured, in which case a_dust will be half the value quoted
above.

Dust properties in the outer solar system have been measured, in some
cases by quantitative dust instruments on Pioneers 10 and 11
themselves (Landgraf et al 2002; Gurnett et al 1997). The there is a
continuous density distribution. According to the above equation, the
acceleration is heavily weighted to large dust particles, but these
are extremely rare. The net densities are of order 2 x 10^{-17}
cm^{-3}, with dust masses ~0.1 ug, leaving the net acceleration due to
dust to be safely less than a few times 10^{-12} cm s^{-2}, far less
than the quoted anomalous acceleration.

Craig

References

D. A. Gurnett, J. A. Ansher, W. S. Kurth, and L. J. Granroth 1997,
Geophys. Res. Lett., 24, 3125
M. Landgraf, J.-C. Liou, H. A. Zook, and E. Gr\"un 2002,
Astrophys. J., 123, 2857

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In message , Craig Markwardt
writes

Jonathan Silverlight writes:

In message , Igor
writes
Check out this link:

http://www.newtonphysics.on.ca/Anoma...eleration.html

Very interesting! It's somehow satisfying that the explanation is
conventional, not due to some boring property of the spacecraft, and
gives new information.
Presumably the reason Cassini hasn't seen an acceleration is that it's
more than 20 x as massive.
One thing does occur to me. Paul Marmet rather fancifully suggests that
the Pioneers will gather dust as they move. It seems to me that the dust
particles will actually be moving at very high speed relative to the
spacecraft and will vaporise. More to the point, that means they will
impart their kinetic energy to the spacecraft, which scales as V^2, not

Marmet's explanation is unconvincing. It depends entirely on the
density of dust in the outer solar system, which according to Marmet:

This amount of dust in the outer region of the solar system appears
quite reasonable remembering that the daily amount of dust falling
on Earth is reported as many tons of dust grains per day.

which is a completely fallacious argument. The number of "tons" of
dust falling on the earth has nothing to do with the dust conditions
in the outer solar system, because (a) one must normalize the captured
"tons" by the cross sectional area of the earth; and (b) the
conditions are different in the outer solar system. In particular,
the dust density drops of precipitously beyond Jupiter.

It is straightforward to show that the net acceleration due to dust
is:
a_dust = -2 (A/M) n V^2 m
where A/M is the area to mass ratio of the body, n is the dust
density, V is the body velocity, and m is the mean dust mass. This
conservatively assumes elastic scattering. It is likely that the dust
will be captured, in which case a_dust will be half the value quoted
above.

I don't understand how the dust can be captured. Isn't it likely to be
hitting with a relative velocity of the order of Pioneer's own speed (12
km/sec)?
But is the question still open, or is anisotropic thermal emission still
the best candidate to explain the Pioneer effect? Marmet doesn't mention
the conventional explanations.
--
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Remove spam and invalid from address to reply.

Jonathan Silverlight writes:

I don't understand how the dust can be captured. Isn't it likely to be
hitting with a relative velocity of the order of Pioneer's own speed (12
km/sec)?

To be honest, I'm not sure. That's why I assumed the worst case of
elastic collisions, which maximize the momentum transfer to the
spacecraft. Since the dust particles are fluffy bodies, it is likely
that they will not elastically scatter, and so the momentum transfer
will be less.

But is the question still open, or is anisotropic thermal emission still
the best candidate to explain the Pioneer effect? Marmet doesn't mention
the conventional explanations.

I've looked into this a little more. From my analysis, there is some
evidence for a change in the acceleration over time. This is almost
enough to be consistent with the decrease in the amount of power
consumption in the Pioneer 10 equipment compartment. I think it is
quite possible there could be anisotropic emission from this
compartment, or via some other, similar means, which accounts for the
acceleration.

Craig

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Craig Markwardt replied to Jonathan Silverlight:

But is the question still open, or is anisotropic thermal
emission still the best candidate to explain the Pioneer
effect? Marmet doesn't mention the conventional explanations.

I've looked into this a little more. From my analysis, there is
some evidence for a change in the acceleration over time. This
is almost enough to be consistent with the decrease in the amount
of power consumption in the Pioneer 10 equipment compartment.
I think it is quite possible there could be anisotropic emission
from this compartment, or via some other, similar means, which
accounts for the acceleration.

Craig,

I posted this on February 22, 2002, here in sci.astro, in reply
to Bruce Sterling Woodcock:

Presently some 2000W of RTG heat must be dissipated,
so it would seem that would be enough. But the problem is the
RTGs are located at the ends of the booms, and they only see
the antenna "edge on", subtending an angle of about 1.5% of 4
steradians. That means at most 30W of power could be impacting
it. Moreover, every RTG is not a spherical black body, but
rather has fins that are "edge on" to the antenna, which means
only 2.5% of the surface area of the RTG is actually facing the
antenna. The RTG mechanism doesn't provide enough power to
explain the anomalous acceleration.

Looking at photographs of the spacecraft leads me to wonder
whether the analysis you quote is correct. First off, you said
"an angle of about 1.5% of 4 steradians". That was probably
intended to be "4 pi steradians", meaning the total sphere.
By eyeball estimate, I'd say that the antenna and other parts
of the spacecraft sunward of the RTGs subtend a solid angle of
about 5% of a sphere, rather than 1.5%. I estimate that 20%
of the RTGs are visible to the sunward parts of the spacecraft,
rather than 2.5%. Those are pretty big differences. Perhaps
my estimates are that far off, or perhaps someone fouled up
the analysis. Take a look at some photos of Pioneer, and see
if you don't agree that the figures you give seem way too low.

Maybe it still isn't enough to cause the anomaly. But it looks
like a very good possibility.

Bruce replied, in part:

The RTG's have fins on them that are "edge-on" to the antenna.
The actual surface area that faces the antenna is much smaller
because of it.

And I replied to Bruce:

Yes, I can see that. It is why I estimate that only 20% of
the RTG surface area is visible to the back side of the antenna
dish and other parts of the spacecraft sunward of the RTGs,
rather than the approximately 45% that would be visible if they
were plain cylinders.

Any comments?

-- Jeff, in Minneapolis

Subtract 1 from my e-mail address above for my real address.
..

(Jeff Root) writes:
And I replied to Bruce:

Yes, I can see that. It is why I estimate that only 20% of
the RTG surface area is visible to the back side of the antenna
dish and other parts of the spacecraft sunward of the RTGs,
rather than the approximately 45% that would be visible if they
were plain cylinders.

I think the fractional (i.e. edge-on) area that actually faces the
antenna is much smaller than the outward-facing area. How do you get
20%?

Craig

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Craig Markwardt replied to Jeff Root:

Yes, I can see that. It is why I estimate that only 20% of
the RTG surface area is visible to the back side of the antenna
dish and other parts of the spacecraft sunward of the RTGs,
rather than the approximately 45% that would be visible if they
were plain cylinders.

I think the fractional (i.e. edge-on) area that actually faces
the antenna is much smaller than the outward-facing area. How
do you get 20%?

Just from looking at photos and guessing. Nothing better.

Note that the 20% figure is for the area of the RTG which is
visible to the back of the dish, etc., and is not the most
important thing to measure here, but was a response to Bruce
Woodcock's assertion that:

every RTG is not a spherical black body, but rather has fins
that are "edge on" to the antenna, which means only 2.5% of
the surface area of the RTG is actually facing the antenna.

My 20% figure may be high, but Bruce's 2.5% figure has *got*
to be *way* too low. Or else he mis-stated what the figure
represented. As I said, if the RTGs were plain cylinders,
approximately 45% of their surfaces would be visible to the
back of the dish, etc. (Depending on how it is measured-- it
could be closer to 60%.) The fins reduce that greatly, but
not to 2.5%! Don't you agree?

The more important statement by Bruce was:

the RTGs are located at the ends of the booms, and they only
see the antenna "edge on", subtending an angle of about 1.5%
of 4 pi steradians.

This figure has also got to be way too low. Look at photos
or a model. No way can it be only 1.5%. My estimate was 5%.
Don't you agree that 5% looks more like it?

-- Jeff, in Minneapolis

..

Craig Markwardt wrote in message ...
Jonathan Silverlight writes:

I don't understand how the dust can be captured. Isn't it likely to be
hitting with a relative velocity of the order of Pioneer's own speed (12
km/sec)?

To be honest, I'm not sure. That's why I assumed the worst case of
elastic collisions, which maximize the momentum transfer to the
spacecraft. Since the dust particles are fluffy bodies, it is likely
that they will not elastically scatter, and so the momentum transfer
will be less.

But is the question still open, or is anisotropic thermal emission still
the best candidate to explain the Pioneer effect? Marmet doesn't mention
the conventional explanations.

I've looked into this a little more. From my analysis, there is some
evidence for a change in the acceleration over time. This is almost
enough to be consistent with the decrease in the amount of power
consumption in the Pioneer 10 equipment compartment. I think it is
quite possible there could be anisotropic emission from this
compartment, or via some other, similar means, which accounts for the
acceleration.

Craig

If I would not watch the Hystory Channel series of
Kennedy-assassination - I really would let it go to rest... But!

I still think that the Pioneer anomaly is the photon energy loss
accumulated over the photon progression time of up to 10 1/2 light
years. Conveniently covered-up in screwed-up records an explanatory
documentations...

And I believe in the Corsican team firing 4 shots... And Hg filled
bullet killing the President... Anyone could do that, who learned
about the contingency cover-up to avoid the thirld word war!

Cheers!
Aladar
http://www.stolmarphysics.com

It shows that the shift in wavelengths (redshift) is not due to acceleration
but is due to an interaction of waves with matter. See 'ashmore's paradox'
www.lyndonashmore.com where I show that the Hubble constant at 64 km/s per
Mpc is nothing more than a combination of the parameters of the electron
multiplied by the planck constant. Therefore redshift cannot be due to
expansion, it must be due to an interaction with electrons.
Lyndon.
"Aladar" wrote in message
om...
Craig Markwardt wrote in message
...
Jonathan Silverlight
writes:

I don't understand how the dust can be captured. Isn't it likely to be
hitting with a relative velocity of the order of Pioneer's own speed
(12
km/sec)?

To be honest, I'm not sure. That's why I assumed the worst case of
elastic collisions, which maximize the momentum transfer to the
spacecraft. Since the dust particles are fluffy bodies, it is likely
that they will not elastically scatter, and so the momentum transfer
will be less.

But is the question still open, or is anisotropic thermal emission
still
the best candidate to explain the Pioneer effect? Marmet doesn't
mention
the conventional explanations.

I've looked into this a little more. From my analysis, there is some
evidence for a change in the acceleration over time. This is almost
enough to be consistent with the decrease in the amount of power
consumption in the Pioneer 10 equipment compartment. I think it is
quite possible there could be anisotropic emission from this
compartment, or via some other, similar means, which accounts for the
acceleration.

Craig

If I would not watch the Hystory Channel series of
Kennedy-assassination - I really would let it go to rest... But!

I still think that the Pioneer anomaly is the photon energy loss
accumulated over the photon progression time of up to 10 1/2 light
years. Conveniently covered-up in screwed-up records an explanatory
documentations...

And I believe in the Corsican team firing 4 shots... And Hg filled
bullet killing the President... Anyone could do that, who learned
about the contingency cover-up to avoid the thirld word war!

Cheers!
Aladar
http://www.stolmarphysics.com

In message , Lyndon Ashmore
writes
It shows that the shift in wavelengths (redshift) is not due to acceleration
but is due to an interaction of waves with matter. See 'ashmore's paradox'
www.lyndonashmore.com where I show that the Hubble constant at 64 km/s per
Mpc is nothing more than a combination of the parameters of the electron
multiplied by the planck constant. Therefore redshift cannot be due to
expansion, it must be due to an interaction with electrons.

An interaction that is completely independent of wavelength would be
quite a trick. That's why it's not considered as a cause of the Pioneer
effect (or of red shifts, come to that)
Aladar is the _only_ person who thinks the Pioneer affect is an excess
red shift - and the only person who thinks it's travelled 10 1/2 light
years, apparently!
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Rabbit arithmetic - 1 plus 1 equals 10
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