<p>The flyby anomaly is an occasional, unpredictable, and as yet unexplained discrepancy in acceleration of satellites when they pass close by the Earth.  It causes an increase of up to 13 mm/s during flybys but we have no understanding of it and how to predict it.</p>

<p>The laws of centripetal force predict that due to rotation, the more dense molten material within the Earth might accumulate at the equator, since there it can move further from the axis of rotation.  This will, of course be counteracted by gravity.  Nevertherless, it will be an effect present at the equator more so than at the poles.</p>

<p>This predicts that we should expect to see a flyby anomaly of some magnitude and that it will be correlated with proximity of a flyby to the equator.</p>

<p>Can anybody provide anomaly data and / or correlate it with angle of incidence in order to test this hypothesis?</p>

CC BY-SA 3.0
2016-07-15T20:16:47.283Z
I wish some expert here, would fix the weird typo or units here: https://en.wikipedia.org/wiki/Flyby_anomaly  - what does "400–1000 m" mean??
Fattie
CC BY-SA 3.0
2016-07-15T20:18:35.600Z
Say Robert, great question.  I personally would interpret your question thsi way:  the possible explanations listed on Wikipedia ... https://en.wikipedia.org/wiki/Flyby_anomaly#Possible_explanations ... are old, out of date, and poorly curated.  Would any experts in the field here have more up to date information about, what is currently considered the most likely cause?  Great question!
Fattie
CC BY-SA 3.0
2016-07-15T21:07:37.913Z
@JoeBlow I do actually think Wikipedia represents the current state of thinking. There's no known explanation so the opportunity exists for a bit of modeling and empirical testing. Brian Koberlein recently blogged that it's a mystery.
Robert Frost
CC BY-SA 3.0
2016-07-15T21:24:19.533Z
thanks for that @robertfrost!   i'm struggling to find that particular blog .. https://briankoberlein.com ???
Fattie
CC BY-SA 3.0
2016-07-15T21:29:18.580Z
@JoeBlow it's called one universe at a time. Also on Google Plus. The flyby post is probably quite a while ago though.
Robert Frost
CC BY-SA 3.0
2016-07-15T21:38:44.880Z
Ah - I had the idea of typing "Brian Koberlein flyby mystery" in to google, thanks  :)
Fattie
CC BY-SA 3.0
2016-07-15T21:40:17.303Z
For example, for anyone reading, here's commentary on a paper, https://briankoberlein.com/2015/10/04/the-flyby-mystery/ a paper which claims it's not an anomaly but just a "chirp" artifact in the radio communications technique used.
Fattie
CC BY-SA 4.0
2018-08-05T04:39:24.673Z
User [Hobbes at space.SE has an answer](https://space.stackexchange.com/a/23977/20766) which says it's an unsolved problem in physics.
Rob
CC BY-SA 4.0
2018-08-05T10:29:41.687Z
@Rob thank-you for that.  My reading of the answer is that inaccuracies in the geopotential model are the most likely scenario (which my suggestion falls into). My suggestion gives a specific possible shortcoming in the geopotential model whose impact could be calculated and compared with the anomaly.
Robert Frost
<gravity><earth><satellite><near-earth-object>
Do differentials in the Earth's density cause the flyby anomaly?
Robert Frost
# Do differentials in the Earth's density cause the flyby anomaly?

(Asked by: username_0 on 2016-07-15)

The flyby anomaly is an occasional, unpredictable, and as yet unexplained discrepancy in acceleration of satellites when they pass close by the Earth. It causes an increase of up to 13 mm/s during flybys but we have no understanding of it and how to predict it.

The laws of centripetal force predict that due to rotation, the more dense molten material within the Earth might accumulate at the equator, since there it can move further from the axis of rotation. This will, of course be counteracted by gravity. Nevertherless, it will be an effect present at the equator more so than at the poles.

This predicts that we should expect to see a flyby anomaly of some magnitude and that it will be correlated with proximity of a flyby to the equator.

Can anybody provide anomaly data and / or correlate it with angle of incidence in order to test this hypothesis?

**Tags:** gravity, earth, satellite, near-earth-object

> **Comments:**
> **username_1**: I wish some expert here, would fix the weird typo or units here: https://en.wikipedia.org/wiki/Flyby_anomaly  - what does "400–1000 m" mean??  
> **username_1**: Say username_2ert, great question.  I personally would interpret your question thsi way:  the possible explanations listed on Wikipedia ... https://en.wikipedia.org/wiki/Flyby_anomaly#Possible_explanations ... are old, out of date, and poorly curated.  Would any experts in the field here have more up to date information about, what is currently considered the most likely cause?  Great question!  
> **username_0**: @JoeBlow I do actually think Wikipedia represents the current state of thinking. There's no known explanation so the opportunity exists for a bit of modeling and empirical testing. Brian Koberlein recently blogged that it's a mystery.  
> **username_1**: thanks for that @robertfrost!   i'm struggling to find that particular blog .. https://briankoberlein.com ???  
> **username_0**: @JoeBlow it's called one universe at a time. Also on Google Plus. The flyby post is probably quite a while ago though.  
> **username_1**: Ah - I had the idea of typing "Brian Koberlein flyby mystery" in to google, thanks  :)  
> **username_1**: For example, for anyone reading, here's commentary on a paper, https://briankoberlein.com/2015/10/04/the-flyby-mystery/ a paper which claims it's not an anomaly but just a "chirp" artifact in the radio communications technique used.  
> **username_2**: User [Hobbes at space.SE has an answer](https://space.stackexchange.com/a/23977/20766) which says it's an unsolved problem in physics.  
> **username_0**: @username_2 thank-you for that.  My reading of the answer is that inaccuracies in the geopotential model are the most likely scenario (which my suggestion falls into). My suggestion gives a specific possible shortcoming in the geopotential model whose impact could be calculated and compared with the anomaly.  

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## 0 answers

