"pioneer anomaly" explained?

http://www.skyandtelescope.com/news/119226989.html

Tentatively, the sunward "drag" is explained as excess
energy radiating away from the Sun, off the back of the
satellite's radio dish. They don't have enough detailed
engineering data, so they had to use "plausible values"
of some parameters, but apparently their answer is of
the right order of magnitude.

--
Brian Tung (posting from Google Groups)
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"Brian Tung" wrote in message
...
| http://www.skyandtelescope.com/news/119226989.html
|
| Tentatively, the sunward "drag" is explained as excess
| energy radiating away from the Sun, off the back of the
| satellite's radio dish. They don't have enough detailed
| engineering data, so they had to use "plausible values"
| of some parameters, but apparently their answer is of
| the right order of magnitude.
|
| --
Since the position can only be the integral of the velocity,
it has to be a computed value and not a measured one
(unless parallax is used, and that isn't mentioned).

The only measurable quantity, then, is the doppler shift
of the signal radioed back. The correct computation of
that is f' = f * (c+v)/c, the anomaly could be an artefact
caused by using the wrong doppler equation, such as Einstein's,
and obtaining too low a velocity.

Androcles wrote:
Since the position can only be the integral of the velocity,
it has to be a computed value and not a measured one
(unless parallax is used, and that isn't mentioned).

I could be mistaken, but I seem to recall that the distance is
actually measured by pinging the satellite: We send a
message to it, and it replies right back, and the delay times
the speed of light gives us the distance. In which case there
is no need to track the instantaneous velocity and integrate,
which could only be done numerically and could easily result
in errors larger than the discrepancy they've measured, with
or without a relativistic adjustment.

--
Brian Tung (posting from Google Groups)
The Astronomy Corner at http://www.astronomycorner.net/
Unofficial C5+ Page at http://www.astronomycorner.net/c5plus/
My PleiadAtlas Page at http://www.astronomycorner.net/pleiadatlas/
My Own Personal FAQ at http://www.astronomycorner.net/reference/faq.html

"Brian Tung" wrote in message
...
| Androcles wrote:
| Since the position can only be the integral of the velocity,
| it has to be a computed value and not a measured one
| (unless parallax is used, and that isn't mentioned).
|
| I could be mistaken, but I seem to recall that the distance is
| actually measured by pinging the satellite: We send a
| message to it, and it replies right back, and the delay times
| the speed of light gives us the distance.

Ah...that's the anomaly, then: wrong theory, the domino effect
takes over.
http://www.androcles01.pwp.blueyonde...minoEffect.GIF

Your task is to find x on the assumption that the red slope has
the same magnitude as the black negative slope. If you make
the wrong assumption you'll get the wrong answer - which you
do, or it would not be called an anomaly.

Brian Tung wrote:

Androcles wrote:
Since the position can only be the integral of the velocity,
it has to be a computed value and not a measured one
(unless parallax is used, and that isn't mentioned).

I could be mistaken, but I seem to recall that the distance is
actually measured by pinging the satellite: We send a
message to it, and it replies right back, and the delay times
the speed of light gives us the distance. In which case there
is no need to track the instantaneous velocity and integrate,
which could only be done numerically and could easily result
in errors larger than the discrepancy they've measured, with
or without a relativistic adjustment.


nice post!




--
Brian Tung (posting from Google Groups)
The Astronomy Corner at http://www.astronomycorner.net/
Unofficial C5+ Page at http://www.astronomycorner.net/c5plus/
My PleiadAtlas Page at http://www.astronomycorner.net/pleiadatlas/
My Own Personal FAQ at http://www.astronomycorner.net/reference/faq.html