Flyby Anomaly


by ideasrule
Tags: anomaly, flyby
ideasrule
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Aug9-09, 06:43 AM
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One paper claims that the flyby anomaly only exists because NASA scientists forgot about the transverse Doppler effect. If that's true, why is it still called an anomaly? Why isn't everyone banging their heads on walls and thinking, "D'oh! I can't believe I forgot about that!"? If it's not true, did the paper's authors make a mistake?

According to the Wikipedia article on the flyby anomaly, under the "Possible explanations" section:

"Unaccounted Transverse Doppler effect, i.e. the redshift of light source with zero radial and non-zero tangential velocity[1]. However, this cannot explain the similar anomaly in the ranging data, or the possibly related Pioneer anomaly."

What ranging data? Why don't other websites mention it? I'm quite confused.
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fleem
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Aug9-09, 01:10 PM
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I'm surprised they consider a few mm/sec all that notable considering all the variables they can hardly predict well, like the charge of the Earth, the charge on the spacecraft, the current makeup of the ionosphere, solar wind, temperature of the ionosphere, induced currents in the spacecraft metal, etc. Granted most of these are probably negligible, but its just my first guess.
Bob S
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Aug9-09, 04:14 PM
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NASA's biggest anomaly was forgetting to use MKS units instead of English units in calculating thrust (Newtons instead of slugs or whatever) for the Mars Climate Orbiter in 1999. On this scale, a few mm/sec is in the noise.

ideasrule
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Aug9-09, 04:52 PM
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Flyby Anomaly


Quote Quote by fleem View Post
I'm surprised they consider a few mm/sec all that notable considering all the variables they can hardly predict well, like the charge of the Earth, the charge on the spacecraft, the current makeup of the ionosphere, solar wind, temperature of the ionosphere, induced currents in the spacecraft metal, etc. Granted most of these are probably negligible, but its just my first guess.
I think the data is good enough to suggest an anomaly exists. See these graphs:

http://en.wikipedia.org/wiki/File:An...inn199803b.jpg
http://en.wikipedia.org/wiki/File:An...inn199803a.jpg

which plot anomaly vs. time. Both unmistakably show an anomaly.
Creator
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Aug11-09, 08:07 PM
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Quote Quote by ideasrule View Post
One paper claims that the flyby anomaly only exists because NASA scientists forgot about the transverse Doppler effect. If that's true, why is it still called an anomaly? Why isn't everyone banging their heads on walls and thinking, "D'oh! I can't believe I forgot about that!"? If it's not true, did the paper's authors make a mistake?

According to the Wikipedia article on the flyby anomaly, under the "Possible explanations" section:

"Unaccounted Transverse Doppler effect, i.e. the redshift of light source with zero radial and non-zero tangential velocity[1]. However, this cannot explain the similar anomaly in the ranging data, or the possibly related Pioneer anomaly."

What ranging data? Why don't other websites mention it? I'm quite confused.

Apparently, this so called fly by 'anomaly' is NOT an anomaly after all, as long as you take into account the transverse doppler effect (which arises from the addition of velocities of earth and satellite.)

Initially the ranging data (derived from time delay measurements) also contained the 'anomalous" measurements....but BOTH velocity and ranging anomalies were resolved completely by J. Mbelek simply by including the transverse effect into the calculations....

See here: http://arxiv.org/ftp/arxiv/papers/0809/0809.1888.pdf

It is probably simply an oversight by Anderson et al, but....
Sometimes I think it may be easier to teach special relativity to 3rd graders than to get these 'anomaly guys' to admit their mistake.

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ideasrule
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Aug11-09, 09:05 PM
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Quote Quote by Creator View Post
Initially the ranging data (derived from time delay measurements) also contained the 'anomalous" measurements....but BOTH velocity and ranging anomalies were resolved completely by J. Mbelek simply by including the transverse effect into the calculations....

See here: http://arxiv.org/ftp/arxiv/papers/0809/0809.1888.pdf
OK, so the Wikipedia article is in need of fixing. Since you know more than I do, can you correct the article?
toftof
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Sep2-09, 12:56 PM
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I want to react about the transverse Doppler shift proposed by Mbelek. His explanation is rather naive. The JPL formulation of doppler and ranging "computed observables" takes into account already this effect and many more !

Read the book of Moyer where you can find all the explanations. The doppler shift is computed from the time derivative of the two-ways round-trip signal in a pure general relativistic way.

To see the explicit look of the formula used, see Linet & Teyssandier, Physical Review D, vol. 66, Issue 2, id. 024045, 2002
the Mbelek term is only "the second term" of these formula. So.....
Chronos
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Sep3-09, 01:07 AM
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I dont think the transverse doppler effect is sufficient to account for the flyby anomaly, nor does NASA - and trust me, NASA scientists are a pretty bright collection of guys and gals. It may, however, be a component of a larger set of error bars.


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