The 'old' ~2000m Geoid, based upon ~1500km Viking and Ranger missions is referenced in Lemoine 2000. The current, or a later Geoid, based upon Goddard Mars Model-1 data . If I am reading the colors correctly, the Geoid range is about 2800m, but I could be convinced otherwise.

Aharonson et al.2001 p 3. is a good article about the puzzling talus slope variance - Notice that the talus slopes of Venus are shallower than the talus slope for the Earth. In the article, they discuss these differences, and as I said, they can account for some but not all of the variance in terms of weathering:

I don't know if this trend could be explained by a non-Newtonian gravitational gradient - in fact, at first blush, it would seem like the effect should be just the opposite. But if static friction is lower, this might explain longer talus tails and steeper slopes. It does not explain why there is a polar orientation to the slopes.

Interesting place. Great puzzle.

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jwj

It's a big universe out there...is it really unwinding, really burning out?

It has everything to do with it!

If the planet or moon is more massive than analsysis of orbits predicts, any passes very close to the planet will result in an unexpected tug or roll on closest pass. This can be interpreted in a number of ways, depending upon flight software. If the probe is oriented so that only one reaction wheel is effected by the unexpected roll, the behavior of the reaction wheel would be most suspect.

The best example is in Cassini's close passes to Titan, where a 'drag' that cannot be attributed to atmospheric effects has been observed. Cassini was not using the reaction wheels to control the motion, (because of the bad experience near Jupiter), so the 'drag' resulted in an unexpected firing of thrusters. How many times this has occurred is not documented in the significant event logs, but as a precaution, they did raise the altitude of future passes.

Later, after reaction wheels were used to control altitude near Titan for the first time, the old nemises cropped up again.

There is another effect that could be buried in the reaction wheels and other inertial systems - this is the change in inertial energy Lunatik has proposed, but I think to be real, this should show up in all the wheels, and I don't think that current evidence supports this hypothesis.

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jwj

It's a big universe out there...is it really unwinding, really burning out?

Read Cassini's significant event longs for December 20, 2000 and January 7 2001, then tell me what is false about it.

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jwj

It's a big universe out there...is it really unwinding, really burning out?

I told you what was false about it three months ago when you unsuccessfully attempted to claim the fault was somehow due to gravity:

Your statement was and is an excellent example of your complete lack of scientific discipline and/or your willingness to be dishonest in attempting to support your failed pet "hypothesis".

You didn't read the fine print:

They quit turning Cassini to keep the instruments on a target! Without any slinging or momentum shifting, all the reaction wheels were doing was spinning! The loading would be trivial, compared to the force necessary to pivot Cassini towards Jupiter. As long as the pass was not close enough to create a big differential about Cassini's moment-of-inertia relative to the earth pointing mode, no significant anomolus forces would be present.

We don't know what would have happened if they would have continued the science run, but the reaction wheel event spooked mission controllers bad enough that they did not opt for reaction wheel control near a planet or moon again until March of 2005, the first reaction wheel controlled pass of Titan at a conservative distance of 200km. This was once again, a little shaky.

edit - quote brackets

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jwj

It's a big universe out there...is it really unwinding, really burning out?

Jerry,

I ask that you please stop characterizing science professionals as "spooked", "scared" or otherwise freaking out over alleged anomalous behavior they can't explain. Time and time again, you seem to imply that these are skittish, unprofessional, yahoos that are running around with arms akimbo, yelling "whaddowedo? whaddowedo?"

CJSF

__________________
Two years ago moved from my town
I was looking up past the city lights
But the city lights got in my way

See the constellation ride across the sky
No cigar, no lady on his arm
Just a guy made of dots and lines

-from "See The Constellation"
by They Might Be Giants

From the last link in your post Jerry:

Why, again, do you have reason to belive any different than this?

__________________

Feynman
>~~~~<
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.

Religion is a culture of faith; science is a culture of doubt.

Apparently not.

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In all fairness to Jerry, mainline scientists use terms like: "anomalous, unexplained, puzzling, unmodeled," and, dare I say it, "possible new physics." We obviously don't know everything, especially when it comes to cosmology, so it's an open playing field. Read any scientific paper dealing with black holes, dark matter, dark energy, quasar redshifts, or distant space probes acceleration towards the sun, and you will see what I mean. What Jerry is attempting to do is show that such anomalies may also exist in planet landings, which should bring pause to our understanding of what we think we know. There are a lot of things out there we don't know, and if we hope to figure them out, we have to ask hard questions rather than accept things without questioning. Then, maybe if we're smart and lucky, we'll find out. I don't see the need to beat up on someone asking questions. Isn't that what science should be? 8)

Naturally, I don't know if mission control was "spooked" or not, as I wasn't there. If things are not working to plan, there may be reason for alarm, especially since billions of bucks are riding on that thing out there, spinning up or down, etc. I'd be alarmed, if not outright spooked, especially if it was my job to make sure everything works.

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Credibility is simply incredible... sometimes even to me.
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No one is beating up on someone asking questions.

What is happening is someone is making claims, not backing them up with verifiable data, and sticking to those claims after they've been shown to contradict the verifiable data we've provided. That's not doing science, that's showing an inability to admit to having made mistakes, and not being able to learn from them.

Those non-scientific actions, repeated over and over (in some threads for 79 pages), are what the scientific people here are objecting to.

Based on that, I don't think you should pursue a career as a mission controller, or an engineer for that matter. When things go wrong is when a professional needs to have their wits about them, remain cool, and not let emotions get in the way of working on a solution to the pressing problem(s) at hand.

Once the problem is solved, then it's time to get emotional, usually a celebration of the success of the mission or project, due to its controllers or engineers remaining calm and rational during the crisis.


[edit/typo]

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Fear is a good thing, any wise man will recognize that, but a fool will not. How someone "spooked" reigns in that fear is a mark of his strength, and I fully trust the men and women who work the spaceprogram know how to handle this fear (of failure) with professional aplomb. I should hope that if it were my job, I would do the same.

I notice no one else has the courage to bring forth known cosmological anomalies. Why? Do you not think them important? If there are errors, then bring them out. If the errors belong to the person bringing them out, then show that. We can ask for no more. As geniuine seekers (mainstream or ATM) I am sure anyone who is wrong, including Jerry, will admit it and find a way to correct it. I personally appreciate the references listed, and from then I learned. I find a pursuit of pettiness, or blaming, serves no valuable cause. Wouldn't you agree?

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Credibility is simply incredible... sometimes even to me.
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Notice I didn't say not to have the emotions, but instead "a professional needs to have their wits about them, remain cool, and not let emotions get in the way of working on a solution to the pressing problem(s) at hand." Fear is not intrinsically a good thing. Acknowledgment and proper control of fear is a good thing.

Bringing forth "known" cosmological anomalies doesn't require courage here. Anyone can do it in ATM and if you read the history of threads here you'll find reams of material on those supposed anomalies.

What's missing from almost all those threads is a good basis for defining the described situation as an anomaly. When evidence and experimental data are requested, the poster usually creates a diversion, or claims his/her post is misunderstood, or beyond the ken of those who rely on the scientific method. Not one of those responses is going to favorably impress anyone here who knows how science works. Only a well-documented hypothesis with substantiating data will have a positive effect. Such things have been like hen's teeth here in ATM.

They're important if there's some substance to them which can be sustained with objective evidence. Claims of anomalies without data to back up such claims aren't really worth being bothered about.

It would be great if the various ATM post initiators would admit to errors and their speculations being wrong. That would certainly cut down on the length of some of these threads. BTW, Jerry has been wrong on minor points and on major points. He's admitted to his errors on some of the minor points, but has yet to acknowledge any error on his major points. Such admissions would destroy his primary speculations.

Re "...a pursuit of pettiness, or blaming, serves no valuable cause.", quite correct and I wish Jerry would lay off making such charges against the JPL, CICLOPS, and ESA scientists and engineers who are doing such wonderful and painstakingly scientific work with their respective missions.

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I read the fine print. Here's the full quote:
In any case, your response as to what the reaction wheels were used for over the next few days was irrelevant and an obvious attempt to change the subject. You asked me to tell you that your statement was false. I showed, again, that it was. Nothing in your response has made your original statement any less incorrect.

People can decide for themselves whether the false statements you have made while attempting to support your ideas are due to lack of research or understanding, or because you are being deliberately dishonest. The fact that you won't acknowledge and correct your mistakes speaks for itself.

Maksutov is right on the money. I couldn't have said it that well.

I'd like to add my "me too"...

edited to shorten...

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"The facts gentlemen, and nothing but the facts, for careful eyes are narrowly watching." Isaac Asimov

Come on! What the reaction wheels were doing is the subject!

Monitored, but not tested under the same conditions and constraints during which the anomaly emerged. If anything, the fact that the wheel continued to spin freely when it was not placed in a rigorous controlling mode indicates the sluggishness may be event related - Conversely, if the wheel would have slugged along while not under load, the 'bad lube job' hypothesis would have been confirmed:

Between Dec 19 and Dec 29 they cancelled activities that required reaction wheel control. This does not prove that the reaction wheels performed normally during this period: They weren't doing anything! In my original post I state that as Cassini neared Jupiter, the reaction wheel misbehaved. That is not false, and you are the one who won't admit it.

The reaction wheel reactions is not something I would have predicted: It is something I am trying to understand. Read through the event logs of the Galileo mission, and a definite pattern emerges: The Reaction wheels acted up when the probe was close to a moon and trying to track and make observations, they behaved quite normally between encounters - time and time and time again.

'Spooked' is the appropriate term for the Cassini navigators and mission planners. Redirecting an encounter planned for years to a higher altitude because of an unmodeled drag force that cannot be explained using known physical modeling should make any and every scientist shudder.

Edit: Bolding

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jwj

It's a big universe out there...is it really unwinding, really burning out?

I'll take a peice of that.

__________________

Feynman
>~~~~<
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.

Religion is a culture of faith; science is a culture of doubt.

Jerry, what's your obsession with malfunctioning reaction wheels? These thingies, though surprisingly reliable, make trouble every now and then in every place, like MIR, ISS and Hubble. IIRC, already Skylab had it's share.

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"Flying in space is risky business, but just staying on this planet is risky business too." - John Young, astronaut

OK let me put my question another way since I didn't ask the first one clearly enough

Jerry wrote:Where are your evidence, references and calculations used to back up these claims that a) Something is wrong, b) Non-Earth-based Newtonian gravitational gradient fits the bill?

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By asking questions we sometimes get the wrong answers, from wrong answers we learn to ask the right questions.

AS it approached Jupiter, NOT because it approached Jupiter.

CJSF

__________________
Two years ago moved from my town
I was looking up past the city lights
But the city lights got in my way

See the constellation ride across the sky
No cigar, no lady on his arm
Just a guy made of dots and lines

-from "See The Constellation"
by They Might Be Giants

This is a contradiction—orbits are the result of gravitational force, so any “unexpected tug” would be clearly visible in the ephemeris data for every object in the solar system. If we’re underestimating the mass of Mars (etc) and there is some compensating effect (variable G or “different path lengths”), the net result must be indistinguishable from conventional physics, because we have seen no anomalies in ephemeris data. For the probes to behave differently near the planet/moon, there would have to be a fairly major deviation from the inverse square law—and I’m pretty sure nobody has evidence of that.

For the reaction wheels to be a sign of any new physics, you’re going to have to model the unexpected behavior mathematically and prove it matches the prediction of your new physics. So far you’ve cataloged a list of single-event failures—if there was something gravitational affecting the reaction wheels, it would be a continuous effect that could be measured over time, particularly with probes in highly elliptical orbits. Any evidence of that?

My guess is, if the people looking at the reaction wheel problems noticed a continuous variation in angular velocity that coincided with the probes’ approach to a planet or moon, it would have been front page news on all the science and space websites and journals.

Is it not more likely that reaction wheel problems seem to occur during close approaches because that is when they use the reaction wheels the most? :wink:

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Do try not to take me too seriously.

Obviously what I'm getting at is not as clear as I think it is.

The problem with your statement is that the reaction wheel problem did not disappear "when the probe was no longer impacted by Jupiter and her moons", which is the rest of what you said:

Emphasis mine. It just didn't help your cause to say what really happened: Cassini had a minor problem with one reaction wheel when the probe was approaching Jupiter. The wheels were allowed to spin down, and when they were spun up again and tested, everything appeared normal. The reaction wheels were performing normally when Cassini made its closest pass to Jupiter and subsequently left the Jupiter system.

Oh really. Here's what you said at the time:

Emphasis mine. So, three months ago not only was it predictable, but you had a nice pseudoscience explanation for the effect. Now it's not something you would have predicted and are trying to understand. Fascinating. :roll:

The bottom line is that, like every other "anomaly" you can dig up, you wanted to somehow tie the reaction wheel problem to our alleged incorrect ideas about gravity, and Cassini's proximity to Jupiter. Forgetting for a moment that no reasonable person would conclude that the actual problem (increased friction) was caused in any way by gravity, it was better for you to say the problem appeared when Cassini neared Jupiter and "disappeared when the probe was no longer impacted by Jupiter and her moons". Even though that's not what happened.

It took about 5 minutes of research at the time to determine that Cassini's reaction wheels were performing quite normally for the vast majority of time spent in the proximity of Jupiter and were, in fact, performing normally during Cassini's closest approach to Jupiter. So the fact that you presented the reaction wheel problem as something that occurred when Cassini approached Jupiter and then mysteriously "disappeared" when Cassini left the proximity of Jupiter indicates, in my opinion, either a complete lack of research on your part, or dishonesty.

I must admit I too find the reasonable explanation in Cassini Problem near Jupiter as kind of hard to accept: Why did the problem disappear later, or "worked around" in the Status Report 4/2005? Different flight configurations? Does space dust get into the flywheel housing, or debris? From where? That's why something like this needs greater review. Though only one of the four wheels experienced this friction, it should not be let go too easily.

I have another question, not to beat the same dead horse all the time. Is there evidence of light redshift within the dimensions of our solar system, say by the Kuiper belt? Current theory would say not, since expansion of space is only supposed to happen between galaxies. Inside galaxy and solar system dimensions, ruled by internal gravity, expansion does not happen so exempt from redshift. But do we know they really are? Curious, if anyone knows the answer to this? :-?

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Credibility is simply incredible... sometimes even to me.
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IIRC something similar happened with Voyager. In this case a mechanism jammed, and the hypothesis was that a bit of swarf had jammed some gears. The fix was to cycle the spacecraft heating so that the alternating expansion and contraction could free up the bit of stray "stuff". Remember that the vast majority of spacecraft failures are due to mechanical problems, not electrical ones.

I mentioned gyroscopes used in airplanes by my boss before. I know this is exactly what happened, or something very simmilar:
Due to friction of the bearings in the track in which they ride, the lubricant will heat up, become viscous. Through a compressive action the fluid will be forced into said track and eventually, most of the fluid will be 'flung' toward the track and not be in contact with the frictional surfaces of the bearings themselves.
The solution aviators use for their gytoscopes is to turn them off for a while so the lubricant becomes solid and partially bonds with the bearing again. After being turned on a short while later the lubricant gets churned up and spread around once again.
I'm not sure how zero g or how much different a reaction wheel is compared to a gyroscope, but I think this is exactly what was done.

__________________

Feynman
>~~~~<
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.

Religion is a culture of faith; science is a culture of doubt.

Gravitational redishift has been measured on Earth: Wikipedia.

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papageno


"Why waste time learning, when ignorance is instantaneous?" - Hobbes (Calvin and Hobbes)

"It's all about context!" - Vince Noir (The Mighty Boosh)

"I've never heard of such a brutal and shocking injustice that I cared so little about!" - Zapp Brannigan (Futurama)

"...because the logic of the lines traced from reality is as poor of aesthetic value as it is strict in consistency. " - Paolo Bozzi (Naive Physics - free translation)

A couple of notes:

1. What you quoted was not the final explanation. This is what i believe they settled on:

This seems very reasonable to me. Certainly more reasonable than a failure of Newtonian physics being the problem. You should also bear in mind that we're not talking about a reaction wheel grinding away shooting sparks that suddenly healed itself. It required more energy to turn up until approximately 50rpm, at which point it spun freely. (Source)

2. The 4/2005 Status Report you linked to doesn't seem to relate to a problem with reaction wheels, so I'm not sure about that one...

3. I'm not arguing that the official explanation is perfectly correct or reasonable (even though I think it is quite reasonable and probably correct). I'm simply pointing out that Jerry has presented this problem..."creatively"...in an attempt to support his ideas. And the only reason I brought any of this up was because he started to use the same "creative presentation" of the problem, right here in this thread, even though it was pointed out to him months ago that his representation of the problem was inaccurate.

I'm not particularly interested in debating the cause of the problem or JPL's explanation. I'm simply asking for honest debate. If there's an anomaly to point out, great, but it ought to be presented objectively, with references. And it should be presented in an honest way, not distorted so that it better suits the needs of the poster.

Whatever the reason, Jerry did not present the problem with Cassini's reaction wheels correctly. He presented it in a factually incorrect manner that happened to better suit his needs.

I made the same point in the Huygens thread http://www.badastronomy.com/phpBB/vi...hlight=#458997 and Jerry didn't get it then either.

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"I come from London, a small village on Mars just outside the capital Wibble."
Captain Edmund Blackadder

=D> There is an excellent series of issues raised by the bloodhounds nipping at my heals, and I need to address all of them, but let me just start with Tassels, because it is a credibility issue, and his bone of contention is not without merit:


It is true, I did not provide a good answer before and in I was almost ready to dismiss the reaction wheel anomaly as a non-issue, but two new facts have raised their heads:

1) On ~Dec 16 Cassini went into a safing mode while approaching Jupiter due to a discrepancy in one of the reaction wheels. NASA did some trouble shooting, spun the wheel up to high speed, got it to work normally, hypothesized about lubrication and decided that they would keep the wheel running all the time at higher RPMs. This would mean the wheel would have to be unloaded more often, but if the diagnoses was right, there would be no more safe-moding.

But then they did a funny thing: They did not reinstate the testing program that lead to the discrepancy in the first place, but cancelled the science testing requiring reaction wheel control. I didn't know that.

This is like having your car overheat while climbing a hill, putting in a new water pump, driving around town and declaring victory. But what if the radiator was plugged, or the hill was just too steep for the car? NASA did not retest under the conditions that caused the safing mode and therefore did not resolve the issue in a competent manor. This was not a bad thing, because the prime objective was to get to Saturn, but I am not miss-representing the problem - I see this as ONE MORE CLUE.

2) In orbit about Saturn, NASA did not reattempt to use Reaction Wheels to control Cassini near one of Jupiters moons until about the fourth pass of Titan, at a very conservative altitude of ~200km.

It was just after this incident that NASA reported troubles with 'mirror flutter', and at least one other instrument that upon investigation, first showed up AT THE TIME OF ORBITAL INSERTION and may be related to a problem with one of Cassini's reaction wheels.

If spinning up the wheel fixed the problem in December of 2000, why did it not show up again for FIVE YEARS, and this time when Cassini tried to use the reaction wheels to AGAIN control an instrumental platform in close proximity to a very big planet? Am I the only person who sees a puzzling pattern here? Because this is what happened with Galileo: Every time the probe neared one of Jupiter's moons, one of the wheels behaved funky. When the probe backed away, the problem went away, too.

Tassel is correct: Before he pointed out that the reaction wheel behaved quite normally on closest approach, I was working with the hypothises that the error was mostly likely related to an apparent ‘drag force’ in one plane, but now it appears more likely that the error (if not random) is an interpretive error, generated when the reaction wheel does not correct for the anticipated amount of gravimetric force.

This possibility could be eliminated with the answer to a single question: Has the reaction wheel which has behaved badly (in the Galileo and Cassini missions ALWAYS been a wheel that was controlling motion in the same vector, relative to planet, or relative to the rotation of the probe? If so, did NASA try using different reaction wheels to execute similar manuvers? What were the results?

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jwj

It's a big universe out there...is it really unwinding, really burning out?

Let me se if I properly understood what are you saying: do you ask NASA to repeat a procedure (spinning a wheel at low rpm) that could damage the spacecraft? You've said already that NASA's scientists and engineers are puzzled, confused, that they don't know what's happening with Cassini and now you're saying that they should perform a potential dangerous manoeuver on purpose? If they'll do that I'll completely agree with you that they don't know their job... :wink:


Someone has already pointed that if the reaction wheels are used mostly near planets then is a higher probability to have malfunctions in a planetary environment (where the wheels are highly solicited) than in empty space (where they are less used).
So you'll have an evidence here if you'll prove that, in similar conditions (rpm, hours of continuous operation) the reaction wheels fail most often near a planet than in space.

Thanks for the reference link to Wikipedia's Redshift article. I answers a part of my question, but I may not have stated what was on my mind clearly: If a signal leaves Earth for let's say the Kiuper Belt, or far planets, for example, does it redshift within that short distance? (If it does, the wavelength at the receiving end would be longer?) By same token, does sunlight redshift within such a short distance? My understanding is no, it does not. The overlaid question then becomes: if light or signal did redshift, would we know it redshifted if it bounced back to us from those far away places (within our solar system)? I am assuming that the object from which such signal is bounced is stationary, which is unrealistic. The article did not address this, and I cannot find this answered anywhere, at least not where I looked for it, so asked it here.

Thanks.

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