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Computer Forensics to Help Solve Pioneer Mystery
Posted by
Hemos
on Mon Mar 05, 2007 08:37 AM
from the deconstructing-the-past dept.
from the deconstructing-the-past dept.
Matthew Sparkes writes "Launched 35 years ago on Friday, Pioneer 10 was the first spacecraft to reach the outer Solar System and return pictures of Jupiter, closely followed by Pioneer 11. However, the twin Pioneer spacecraft drifted off course (see number 8) by hundreds of thousands of kilometres during their three-decade mission, and NASA eventually lost contact with them. An international team of scientists, including many amatuer hobbyists, are re-analysing the tracking and telemetry data in the hope of discovering the reason."
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not bad (Score:2)
Oblig. Simpsons (Score:2, Funny)
Yeah, but it's hundreds of thousands of kilometers.
[french guy]Sacre bleu!![/]
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Yeah, but it's hundreds of thousands of kilometers.
Even better!
Not Really a True "Solution" (Score:5, Informative)
As the article states: So if the direction of deceleration is towards Earth, then you might be able to consider the mystery solved and blame it on the process of collecting the data. But if the deceleration is towards the sun or another direction, we have an observation of an unknown effect in physics. If the latter is the case, I think the mystery is just starting to be understood--with a long ways to go and many more observations before we can consider it solved.
Re:Not Really a True "Solution" (Score:4, Informative)
Parent
Re:Not Really a True "Solution" (Score:4, Informative)
No, we may have an observation of unknown physics. We may also have an observation of well-known physics which nobody has been able to quantify. The acceleration is sufficiently small and the two Pioneer craft so similar (virtually identical, in fact) that nobody has conclusively ruled out such trivialities as the colour of the paint having changed or a thicker-than-expected layer of dust having formed - effects like these could be sufficient to cause the observed anomalous acceleration (think 'solar sails' for similar physics, but with the Pioneers emitting radiation as well as reflecting it). It really is a tiny effect.
The problem with ruling these kinds of effects out is that the Pioneers are the only suitable craft we have which have been going far enough for long enough to provide good data. The Voyager craft have gone a long way too, but they aren't spin-stabilised (like a bullet from a rifled firearm) like the Pioneers; they are stabilized by thrusters and firing the thrusters causes sufficient uncertainty that the anomalous acceleration is lost in noise. I recall a paper which looked at other spin-stabilised craft during their cruise phase to other planets which also reported the anomaly, but again the data was too noisy to be entirely convincing. We really need a new mission to test this anomaly properly before we can say there is any new physics.Parent
Pioneer anomaly (Score:5, Interesting)
Strangest of all:
Data from the Galileo and Ulysses spacecraft indicate a similar effect
Do they have all the original calculations? (Score:2)
Seriously, though, how likely is it that the gravitational and orbital calculations were just not quite as precise when they did them 35 years ago?
Despite a highly rigorous formula for determining this stuff, I can imagine that there could have been a few unknowns that affected such an enormously complex calculation.
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And another guess, but surely the gentlest squirrel's fart as the craft left Earth could translate to huge discrepancies by the time they get to the other side of the solar system?
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Or, of course, as it swung by Uranus.
Re:Do they have all the original calculations? (Score:4, Informative)
> the craft left Earth could translate to huge discrepancies by
> the time they get to the other side of the solar system?
Yes, a one-off measurement error at launch would turn into hundreds of thousands of miles difference years later. However, the positions of the craft all along the way show it is still slowing down too fast.
In your terms, the squirrel must be hiding on board and farting from time to time on a reqular basis and in the direction of travel, slowing it.
Parent
Re:Your sig (off topic) (Score:4, Informative)
It is not that modern proportional typefaces have extra space after the period, it is that typewriters' fixed-fonts padded the period with extra space to make it take up the same space as a 'W', for example. Therefore, if you didn't hit the spacebar twice, it became somewhat difficult, optically, to discern where sentences began and ended.
Since modern typefaces no longer have to pad the period with extra space, the single space is more than sufficient for discerning sentence beginnings and endings.
Note that it has always been AP and Chicago style to put only one space after each sentence-ending character (. ? !).
Parent
Re:Do they have all the original calculations? (Score:4, Interesting)
The codes used took into account all the major sources of gravity, including all the planets and major asteroids. These are some of the same codes that have been used to place many, many other probes in proper orbits around planetary bodies as far away as Saturn, and land on tiny things like asteroids and comets.
The damned thing about the Pioneer anomaly is that the acceleration is constant and the measurement is exceedingly simple. It's just position vs. time. There isn't much that can mess with that, and since individual communications with the craft are uncorrelated with each other, there shouldn't be any kind of drift (relativistic clock drifts are taken into account). Since the acceleration is constant over a distance from roughly Jupiter to well past Pluto, and gravity follows a force law that goes like 1/r^2, you can't add a single source of gravity (e.g. a new planet) -- the force wouldn't be constant. You can't make the sun slightly heavier. You can't add dark matter to do it: the dark matter would have to conspire to have a density as a function of distance from the sun that mimicked the constant acceleration. Such a density profile has more dark matter at the edges of the solar system, which would not be stable. It should collapse and concentrate near the sun. The acceleration is approximately the same magnitude as the expansion of the universe, but it's in the wrong direction, and our current understanding of dark energy wouldn't cause such an effect anyway.
Personally, I think we've got gravity totally wrong.
-- Bob
Parent
Re:Do they have all the original calculations? (Score:4, Informative)
Do you think the calculation was done only once? No. It's pretty much a continuous process. While the calculation would have been as accurate 35 years ago as today. (People have known how to multiply and divide out to many decimal places for century's now) What's changes and what limits our ability is that we don't exactly know the exact mass and location of every object in the Solar System. But if you track the spacecraft you can deduce forces acting on it by where it goes. The anomaly here is that we know the force but can't explain it in terms of gravity. The most likely thing is a small leak in the plumbing that acts like a weak jet. It could also be explained by some revolutionary physics. But if you look back in history and count the number of time plumbing has leaked vs. the number of times physics hes been re-written. My money is on the 30 year old plumbing.
It's not a case of not hitting the spot that was aimed for but of watching a curve develop over decades and seeing the curve be a shape that is not quite what one would expect if only gravity were the cause.
Parent
Don't start off with any assumptions (Score:2)
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However, gravity is still not fully understood, and it could well be that the gravitational laws are wrong. This could provide an indication of that.
Why not start with assumptions? (Score:3, Insightful)
This doesn't mean that I'm advocating ignoring re-investigating things from fairly basic principles, but at the same time I think that it would be foolish to immediately assume that something that we haven't yet had any notion of is the culprit.
Drift? In Space? (Score:2)
I hope they fail. (Score:5, Insightful)
One word.. (Score:5, Funny)
I suppose it would actually be P'neer, but that just doesn't sound right somehow.
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Re:One word.. (Score:5, Funny)
Parent
Re:One word.. (Score:4, Funny)
Parent
P'neer (Score:2)
I thought you'd (Score:2)
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Dammit. (Score:2)
Ambiguous summary (Score:4, Informative)
This seems to imply that NASA lost contact because the spacecraft drifted off-course. AIU, they lost contact because the signals became too weak to be readable (due to distance and/or degradation of the RTG).
the story that keeps on giving (Score:3, Interesting)
Gravity: 1/r^2.0000001??? (Score:2, Interesting)
IANAP, but as an engineer I've learned that so-called "constants" seldom are.
What of Other Craft? (Score:5, Interesting)
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True enough, but 3-axis stabilization (not spinning) implies some kind of reaction control system (*) that may be cancelling this unknown effect as it stabilizes the spacecraft, i.e. it also corrects the course.
(* Even if the primary attitude control is via momentum wheel, you still some kind of thruster-based RCS system to periodically dump the momentum you're building up in those wheels.)
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Smells like a big coincidence that a mechanism that stabilises the attitude of the spacecraft happens to exactly balance out, in every case, the effect of some unknown error in the laws of gravity (or whatever). And, given that the cause of the effect on Pioneer is unknown, why pick on spin stabilisation as the thing that is preventing it from happening to other craft?
What really happened to the Pioneer (Score:3, Funny)
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It's turtles all the way down.
Ive never seen the big mystery with this ... (Score:5, Interesting)
Re:Ive never seen the big mystery with this ... (Score:4, Informative)
Note that this argument also gives a pretty clear idea of why most scientists don't seriously think that there is new physics involved here -- if (say) gravity operated differently at extreme distances, it would already have shown up in the orbits of the outer planets. Instead we see all of the outer planets in precise agreement about all of the forces, and then Pioneer having a dissenting opinion for some reason. So most of the searching is for Pioneer-specific effects, like dust (which wouldn't measurably slow down somethng the size of a planet) or gas leakages.
Parent
You forgot to say... (Score:3, Informative)
FDIV? (Score:3, Funny)
Oh. (Score:2)
We weren't supposed to do that?
With all this evidence for weirdness, why. . . (Score:3, Interesting)
The Kuiper Cliff (#10) fascinates me. I'd not heard about that, but I was aware that a peculiar wobble in the orbits of all the planets suggested that a very large object was orbiting in the distance. The Twin Sun theories are very interesting, especially in how they link to cyclical comet clusters bombarding the earth into the stone age every few thousand years. We're due right now, according to some.
I also find #12 interesting. (The not-so-constant constants). At first glance, it appears to fit well with the idea that there are various levels of energy 'density', providing different levels of reality in which beings can exist. One idea posits that UFOs are visitors from a higher level of reality which is constantly around us.
#13 is funny. (Cold Fusion), --Largely because the editor used pissy wording to describe Pons & Fleischmann's work, probably because he was numbered among those who scoffed at the pair and would prefer to believe that it was somehow the two researcher's faults that he wasn't smart or brave enough to give them more credit.)
And of course #4. (Homeopathy). The solution to accepting that homeopathy works links nicely with many other theories considered bunkish, but which also "somehow" carry weight. Basically, it's not the molecule as much as it is the energetic vibration of the molecule which carries information, and which responds to the body. This is Chi in a nutshell; a whole layer of energetic reality which affects pretty much everything in our universe, upon which astrology, awareness and the spirit, (among other things) are based, but which nobody wants to look at. Except the dark corners of the military, which know how to manipulate aspects of it. CFL's produce how much radio interference? More than cell phones and microwaves and TV's? Hmm.
-FL
If you're really interested in this... (Score:4, Informative)
Also, if you're interested, and in the New York area, some of the scientists who've been working on this are speaking at the Hayden planetarium in a few weeks: http://haydenplanetarium.org/programs/asimov/ [haydenplanetarium.org]
Just to give a feel for what obsessive level of detail we're dealing with, here's a list of the possible causes considered in the paper above. The numbers after each listing are the bias and uncertainty in units of 10^-8 cm/sec^2. Listings with only one number only have an uncertainity, not a bias.
1 Systematics generated external to the spacecraft:
a) Solar radiation pressure and mass +0.03 ±0.01
b) Solar wind ± 10^-5
c) Solar corona ±0.02
d) Electro-magnetic Lorentz forces ± 10^-4
e) Influence of the Kuiper belt's gravity ±0.03
f) Influence of the Earth orientation ±0.001
g) Mechanical and phase stability of DSN antennae ± 0.001
h) Phase stability and clocks ± 0.001
i) DSN station location ± 10^-5
j) Troposphere and ionosphere ± 0.001
2 On-board generated systematics:
a) Radio beam reaction force +1.10 ±0.11
b) RTG heat reflected off the craft -0.55 ±0.55
c) Differential emissivity of the RTGs ±0.85
d) Non-isotropic radiative cooling of the spacecraft ±0.48
e) Expelled Helium produced within the RTGs +0.15 ±0.16
f) Gas leakage ±0.56
g) Variation between spacecraft determinations +0.17 ±0.17
3 Computational systematics:
a) Numerical stability of least-squares estimation ±0.02
b) Accuracy of consistency/model tests ±0.13
c) Mismodeling of maneuvers ±0.01
d) Mismodeling of the solar corona ±0.02
e) Annual/diurnal terms ±0.32
Re: (Score:2, Informative)
I have a reletive who is a CSI guy. I get the impression that 95% of there work is dusting for prints where there was some petty theft then all the paperwork that involves. When there is a major crime they mostly gather the physical evedence then move on to the next crime scene,
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I really can't believe you seem to
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I know I shouldn't reply to this but... it can't be. A red shift means acceleration (we see a red shift in galaxies because they accelerate away from us). However, the Pioneers are slowing down, so we should see a blue shift (purple shift?)