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Juno - Jupiter Orbiter
helvick
post Apr 11 2006, 06:34 AM
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QUOTE (BruceMoomaw @ Apr 11 2006, 02:18 AM) *
The panels actually ARE somewhat bigger than those for the Mars missions.

At the risk of becoming permanantly tagged as "that Solar Power nut" I'd also add that Solar cell technology has progressed enormously since Viking days. I don't have the efficiency of the Viking orbiter arrays at hand but I'd be surprised if they were any better than 15% and were probably closer to 10%.
Similar improvements have been made in the remaining power management and distribution technologies (regulation and storage) so on a similar mass budget you can now generate 3-5x as much power using solar panels as was possible 30 years ago. Even within the time frame of the Cassini mission that increase is close to 2-3x.
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edstrick
post Apr 11 2006, 09:29 AM
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One thing's for sure... the increase in solar cell efficiency had better top out at 100% or a trace less..... or the free-energy psycho-ceramics will win!

It's sort of like Moore's law... unless you can start engineering with nuclear-matter, we're gonna bottom out with atom sized machinery components.
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edstrick
post Apr 11 2006, 09:43 AM
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"It describes an instrument for Juno..."

It looks to me like they're trying to persuade NASA to squeeze it on the mission. It would be much the same way the X-ray fluroescence instrument was added to the Viking's biology dominated payload after formal instrument selection was done, but Mariner 9 discovered an unexpectedly complicated and active geology. The instrument ended up with some significant compromizes from being squeezed onboard, but did a fine job anyway.

I really hope we do have good data from Junocam and / or that this proposed instrument flies. I've wanted to see more and better of the polar regions "boiling porridge" (as I call it) that we saw in Pioneer 11 data and get some good info on it's motions right up to the poles (impossible from equatorial missions).
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Guest_BruceMoomaw_*
post Apr 15 2006, 01:48 AM
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Slight historical correction: NASA decided to add an element analyzer to the Viking landers BEFORE Mariner 9's discoveries -- in summer 1971, when the science payload was being seriously shaken up anyway by cost and weight overruns, and scientists were complaining about the shortage of nonbiological experiments. There was a hasty competition between the XRS and Turkevich's Surveyor alpha-scatter spectrometer, which the XRS won.
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edstrick
post Apr 15 2006, 08:25 AM
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That's not what I recall.... but given "NASA-Speak" .... I would not be at all surprised if that was after-the-fact PR spin.

But again, my memory may be wrong... or it may have been prompted in part by the observations of "featureless terrain" and "chaotic terrain" in the Mariner 69 data instead.
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Guest_BruceMoomaw_*
post Apr 15 2006, 08:54 AM
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There was a very detailed "Science News" article in late spring 1971 on the overall changes in Viking's payload. At that time, the choice between the two element anal,yzers had not yet been made, but was called imminent. By early 1972, when Icarus did a whole special issue on the Viking science payload, it had been made.

(Not that this is exactly an earthshaking point -- but they definitely had an element analyzer of some type planned before Mariner 9's results. The official Viking history, "On Mars", can probably tell us more -- I have a copy.)
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edstrick
post Apr 15 2006, 10:10 AM
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I have an original copy of that Icarus special issue, but dragging them out of bookshelves 200 feet from here after I step over several boxes of books without breaking my legs.... inhibits a quick "lemme take a look"
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Guest_AlexBlackwell_*
post Jul 18 2006, 01:53 AM
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Again, I apologize for reviving a dormant thread; however, has anyone noticed this particular Juno website?
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JRehling
post Jul 18 2006, 02:50 PM
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QUOTE (AlexBlackwell @ Jul 17 2006, 06:53 PM) *
Again, I apologize for reviving a dormant thread; however, has anyone noticed this particular Juno website?


I crave good dormant-thread awakenings.

That site is incomplete, but apparently because they're putting very careful work into each section. In fact, it was the fact that the completed sections went so far over my head that I looked for explanations in the glossary section (which is incomplete).

The whole business with the gravitational mapping of Jupiter's interior is going to expand my math education before the mission's over.
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helvick
post Jul 18 2006, 04:05 PM
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QUOTE (JRehling @ Jul 18 2006, 03:50 PM) *
The whole business with the gravitational mapping of Jupiter's interior is going to expand my math education before the mission's over.

I was thinking the same thing - the topic of gravitional field mapping has come up here previously and it's one of those things that I'm intrigued by but I'm a bit concerned that the mathematics will be way too much for me.
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Mariner9
post Jul 18 2006, 06:39 PM
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I had a chance to talk to one of the engineers on the project at the JPL open house in May. It was fascinating stuff, particulalry the plan to use the radiometers to help determine if Jupiter's belt zones above and below the equator are linked to matching internal structures inside Jupiter.

It was so off the wall, I don't fully remember the specifics, and not even sure how to describe it properly. Essentially, there is a hypothosis that for each major atmospheric belt, there is a corresponding belt opposite the equator that is powered by the same internal dynamics. AKA ... if there is a belt at +33 degrees lattitude, then the belt at -33 degrees is part of the same structure. The belt at +42 degrees is connected to the belt at -42 degrees and so on. (I'm making up the numbers just for the example).

I was also able to confirm my suspicion that not every orbit will be devoted to gravity mapping. I asked the guy and he confirmed that the high gain antenna has to be pointed directly at Earth during the Periapsis pass of the orbit, and when that is being done the vehicle rotation axis will be such that the Junocam and radiometers are not pointing at Jupiter. So there are dedicated orbits for the gravity mapping, and other orbits for the radiometry.

He also said that just a single orbit would give them the data they need for the Radiometry experiment, but naturally they plan on at least 4-5 just to be sure their data is confirmed.

Juno is a fascinating mission.... but I'm not entirely sure how to explain it to the general public. Even my eyes partially glaze over when you start talking about exploration of the polar magnetosphere, and I at least have some idea what that means.
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Guest_AlexBlackwell_*
post Jul 18 2006, 09:07 PM
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QUOTE (Mariner9 @ Jul 18 2006, 08:39 AM) *
Juno is a fascinating mission.... but I'm not entirely sure how to explain it to the general public. Even my eyes partially glaze over when you start talking about exploration of the polar magnetosphere, and I at least have some idea what that means.

It'll be interesting to see if a fields and particles mission like Juno can capture the public's attention, but I agree that it's a fascinating mission. I'm sure that JunoCam will help in the PR department, assuming it stays on the payload.
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SFJCody
post Jul 18 2006, 10:07 PM
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QUOTE (AlexBlackwell @ Jul 18 2006, 10:07 PM) *
It'll be interesting to see if a fields and particles mission like Juno can capture the public's attention, but I agree that it's a fascinating mission. I'm sure that JunoCam will help in the PR department, assuming it stays on the payload.


I think it's fortunate that a mission of this type can be attempted through New Frontiers. If the Jupiter science required a Europa Orbiter level of expenditure this mission might be sitting on the back burner.
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Guest_AlexBlackwell_*
post Jul 18 2006, 10:13 PM
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QUOTE (SFJCody @ Jul 18 2006, 12:07 PM) *
I think it's fortunate that a mission of this type can be attempted through New Frontiers. If the Jupiter science required a Europa Orbiter level of expenditure this mission might be sitting on the back burner.

Juno still has to be confirmed for flight (i.e., pass its CDR). I guess we'll know then whether a Jupiter orbiter (even one sans probes) can be done on a New Frontiers budget, or at least whether such a mission isn't deemed not-doable prior to launch.

I remember that Dawn, too, looked pretty nice prior to the descopes/cancellation/re-start.
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JRehling
post Jul 19 2006, 06:12 PM
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QUOTE (Mariner9 @ Jul 18 2006, 11:39 AM) *
I had a chance to talk to one of the engineers on the project at the JPL open house in May. It was fascinating stuff, particulalry the plan to use the radiometers to help determine if Jupiter's belt zones above and below the equator are linked to matching internal structures inside Jupiter.

It was so off the wall, I don't fully remember the specifics, and not even sure how to describe it properly. Essentially, there is a hypothosis that for each major atmospheric belt, there is a corresponding belt opposite the equator that is powered by the same internal dynamics. AKA ... if there is a belt at +33 degrees lattitude, then the belt at -33 degrees is part of the same structure. The belt at +42 degrees is connected to the belt at -42 degrees and so on. (I'm making up the numbers just for the example).


If I match your description with what I have already read, I think the question is between two alternative hypotheses:

1) The belts are "surface" phenomena only, not penetrating very deeply into the atmosphere. The northern and southern hemispheres have similar patterns because they are similar structurally: two different examples of dynamics with similar parameters.

2) The belts are where deep concentric "cylinders" happen to intersect the surface. The belt at +33 is the ring where a north-south oriented internal cylinder slices into the upper clouds in the northern hemisphere; most of the cylinder is buried very deeply; the southern intersection of the cylinder and the "surface" is at -33.

I guess there's some complex integration of the gravitational data that can help settle the question. I can't picture that analysis, but there's plenty of time to read up on it before/if the data comes back.
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