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A Possible Answer to Flyby Anomalies

20 Jan , 2008 by

Strange things are happening to our robotic space explorers. Also known as the “Pioneer effect“ (the unexpected and sudden alterations to Pioneer 10 and Pioneer 11 trajectories measured as they continue their journey into the outer solar system), similar anomalies are being seen in flybys by modern space probes. Earth flybys by Galileo, Rosetta, NEAR and Cassini have all experienced a sudden boost in speed. After cancelling out all possible explanations, including leakage of fuel and velocity measurement error, a new study suggests the answer may lie in a bizarre characteristic of universal physics…

Planetary flybys are an essential aid to interplanetary missions to gain energy as they accelerate on their merry way to their destination. Gravity assists are accurately calculated by mission scientists so the time of arrival can be calculated down to the minute. Considering most missions take years to complete, this degree of accuracy is amazing, but essential.

So, when Galileo completed gravity assist past Earth on December 8, 1990, to speed it toward Jupiter, you can imagine NASA’s surprise to find that Galileo had accelerated suddenly, and for no apparent reason. This small boost was tiny, but through the use of the Deep Space Network, extremely accurate measurements of the speeding craft could be made. Galileo had accelerated 3.9 mm/s.

This isn’t an isolated case. During Earth flybys by the space probes NEAR, Cassini-Huygens and Rosetta, all experienced a unexplained boosts of 13 mm/s, 0.11 mm/s and 2 mm/s respectively. Once technical faults, observational errors, radiation pressure, magnetic instabilities and electrical charge build-up could be ruled out, focus is beginning to turn to more exotic explanations.

A recent study by Magic McCulloch suggests that “Unruh radiation” may be the culprit. The Unruh effect, put simply, suggests that accelerating bodies experience a type of electromagnetic radiation. At very low acceleration, the wavelength emitted will be so large that a whole wavelength will be longer than the dimensions of the Universe (otherwise known as the Hubble Distance). Low acceleration would therefore generate waves that have no effect on the body. However, should the accelerating body (i.e. Galileo getting accelerated by Earth’s gravity during the 1990 flyby) slowly exceed an acceleration threshold, the Unruh radiation will decrease in wavelength (smaller than the Hubble Distance), causing a tiny, but measurable “boost” to its increasing velocity.

Although complex, this theory is very interesting and proves that although we can calculate the arrival time of space probes down to the nearest minute, the Universe will continue to throw up some perplexing issues for a long time yet.

Sources: arXiv Blog, arXiv abstract and paper download


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Brian
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Brian
January 20, 2008 4:41 PM

Hmm…I was thinking it could have been some sort of stellar wind or current.

Did all of these happen near Earth? Maybe it could have been “pushed” by particles (dust, gas, or whatever) orbiting the planet? Might account for the small boost in acceleration.

Clint
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Clint
January 20, 2008 4:44 PM

Wow! Do we have any theory about how this effect behaves with increasing speed? Does it grow exponentially (that would be great for space flight, wouldn’t?) or just linear?

Sam Wise
Guest
January 20, 2008 8:29 PM

Just to pick a nit — the “Pioneer effect” doesn’t show up “suddenly.” It shows up as a REALLY subtle bias to the otherwise expected acceleration of the spacecraft during a flyby. I’m pretty sure it shows up in all flybys — but the ones at Earth can be more accurately measured. Build some DSN stations at Jupiter, and it could be more accurately measured there, too wink

Janus
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Janus
January 20, 2008 8:45 PM

Maybe it’s dark energy. wink

bryanthudson
Member
bryanthudson
January 20, 2008 8:45 PM

it must be cold fusion

Johnny Blues
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Johnny Blues
January 21, 2008 5:16 AM

Asa power boat on a breezy lake, the faster you go, the more skimming effect, further increasing speed capacity. In this case, would gravity waves work as the lake?

Tony
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Tony
January 20, 2008 10:24 PM

This seemingly very subtle observation and corresponding theory could have dramatic implications for the future of space travel…

actionforspace.com
Guest
January 21, 2008 6:56 AM

This is the kind of thing that NASA could figure out if they had more money. They could send probes specifically to measure this effect with sensors to corroborate the theory.

http://www.actionforspace.com is where you can tell the candidates to give NASA more money to study things like this.

go to http://www.actionforspace.com to send a fax to Romney, Clinton, and Obama all at the same time!

Chuck Lam
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Chuck Lam
January 21, 2008 7:06 AM

Perhaps the speed-up discussed here is related to a passing gravity wave. Compression then exxpansion might appear as a sudden increase in speed. As Eivind Lillevik suggests, “why not?”

Rod
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Rod
January 21, 2008 12:26 AM

Perhaps we only think we’re measuring that accurately . . .

TerryTrudgill
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TerryTrudgill
January 21, 2008 2:37 AM

The first indication of the effects of MOND pehaps?

ed hammer
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ed hammer
January 21, 2008 5:41 AM

The MOND special acceleration effect minimum value is related to the fundamental resonance of the universe. It is related to c*2/R. The precise value for the minimum acceleration value is 1.2345679 x 10*6 meters per second per second. It confirms the universe only has 3 spacial dimensions and one time dimension..

MeIdro
Member
MeIdro
January 21, 2008 5:46 AM

Could gravitational waves influence the speed of objects in space?
I know it should’t but then why not wink

ed hammer
Guest
ed hammer
January 21, 2008 5:51 AM

My value for the special acceleration is based on the alpha constant being precisely equal to 0.00729 and not the NIST accepted value of 0.007297352568

ed hammer
Guest
ed hammer
January 21, 2008 6:19 AM

My corrected value for the MOND special acceleration is 1.2345679 x 10*-10 meters per second per second.

Rmin
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Rmin
January 21, 2008 6:40 AM

We have calculated the expected acceleration using gravity law, we have calculated the mass of planets using gravity law too, but we have measured the space craft mass by accurate equipments in the earth so may be the error is in gravity law, when you are calculating acceleration of planets and stars you will not see the error because you have calculated the mass by the same law but in the case of space crafts you could see the error because we have measured the mass indipendently.

RoyWebb
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RoyWebb
January 21, 2008 6:52 AM

Could this be an effect of time dilation? The faster an object goes the slower time is for that object. Could we be seeing an example of this in action?

W. Scott
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W. Scott
January 21, 2008 6:58 AM
The Unru radiation hypothesis sounds flimsy. Remember, at the speeds we’re talking about, a couple of millimeters per second is NOT a lot of discrepency. It’s just as likely that we are failing to account for accelleration-affected time distortion. Einsteins equations describe universe-sized displacement effects at relativistic speeds, but we could be missing a scalar component of accelleration which affects the flow of time at far lower speeds. After all, we are talking about passing by a large, spinning gravity well. Consider that if the navigational thrusters were supposed to fire for a very small amount of time, but time is moving slightly more slowly for ground control than it is for the spacecraft (we have measured this… Read more »
Essel
Member
Essel
January 21, 2008 8:24 AM

Perhaps transfer of angular momentum is only calculated w.r.t. earth and actually the whole of solar system contributes at ecliptic.

JamesB
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JamesB
January 21, 2008 8:52 AM
This is worse than that magical “dark energy” they’ve conjured up (like “ether” was 150 years go). We simply do not understand gravity well enough. Newtonian gravity was a good approximation and General Relativity even better. The “ether” was a reasonable explanation back when physics was mechanical, but things like the Pioneer Anomaly tell us that we’re still lacking the understanding needed to “grok” gravity. I think Einstein was on the right track, that gravity a consequence of space, but that it and time are two ways of looking at the same thing (much as we now know there is 1 electro-weak force in quantum theory, rather than 2 forces at work). With one dimension you have neither… Read more »
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