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Complete Science Data Of Galileo Probe Mission?
um3k
post Sep 8 2005, 07:39 PM
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QUOTE (ljk4-1 @ Sep 8 2005, 03:13 PM)
As for a camera on an Jupiter atmosphere probe, how about an infrared one for cutting through the haze and clouds?
*

But then what would there be to look at? huh.gif
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ljk4-1
post Sep 8 2005, 07:45 PM
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QUOTE (um3k @ Sep 8 2005, 02:39 PM)
But then what would there be to look at? huh.gif
*


The, uh... alien invasion fleet hiding in the clouds?

The big jellyfish AC Clarke and Sagan and Salpeter wrote about?

A McDonald's?


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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mike
post Sep 8 2005, 10:06 PM
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QUOTE (um3k @ Sep 8 2005, 11:39 AM)
But then what would there be to look at? huh.gif
*


Who knows. That's the idea, to find out what is under there. Maybe nothing, probably something. I'm not knowledgeable on whether it's possible to have an IR probe that cuts through cloud and haze but bounces off of more solid matter, but the basic idea makes sense, RADAR or whatever.

Surely you agree that gravity causes things to coalesce, and that therefore if Jupiter is gas so far away from the core, the (massive) core must be rather more dense?
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JRehling
post Sep 8 2005, 11:15 PM
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QUOTE (DDAVIS @ Sep 8 2005, 10:18 AM)
  Well, future probes may well have better data bandwidth than what you are used to. I don't see uncertainty about what a camera would see as good reason to assume a camera isn't desirable.

this may be apocrophal but I recall in my USGS days hearing talk about a debate on whether the Pioneer F abd G spacecraft should have any imaging capability at all, after all, what could possibly be interesting about cloud tops? As it was the imaging Photopolerimeter was a cheap crappy substitute for a camera which was better than nothing, but outclassed by the real cameras the Voyagerws later carried.
  Don
*


In itself, uncertainty about what the camera would see is not a reason to scratch it from the payload list, but when mass is also an issue, we'd have to opt for an instrument that definitely has a point over one that merely might.

We can say with certainty that some images in a jovian descent would occur inside clouds and therefore be blank. Others would almost certainly have to look like Earthly cloud formations (as jovian clouds do from orbit) -- sometimes showing structure, sometimes just a blank wall. Indeed, I can imagine we would learn something from an image snapped at the right place and time, but flying through terrestrial clouds shows us how time/location-varying that will be, information-wise.

Bandwidth ought to follow Moore's Law, and with Galileo designed 30 years prior to any followup, we can expect the bandwidth issue to go away, but not the mass issue. Given that, the middling probability of getting *any* result is pertinent. I look at expected value, and a middling probability of something useful loses to a sure probability of something else useful.

Simply put, a camera is going to add to the cost of an entry probe, so we have to see how the expected science gain would fare as a function of cost. I'd love to see the pictures -- believe me, I enhanced one of those simulated images to make it look more realistic and made it my wallpaper -- but it's going to be a while before that wins out as a priority.

I wish they had tried something like the following with the Galileo *orbiter*: create a mode of turning off all safe modes; design a super close flyby of the cloud tops on a *penultimate* pass of Jupiter; transmit the resulting image(s) to Earth before the final plunge. If this failed (and I could well imagine that it would), at least we tried.
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JRehling
post Sep 8 2005, 11:22 PM
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QUOTE (mike @ Sep 8 2005, 03:06 PM)
Who knows.  That's the idea, to find out what is under there.  Maybe nothing, probably something.  I'm not knowledgeable on whether it's possible to have an IR probe that cuts through cloud and haze but bounces off of more solid matter, but the basic idea makes sense, RADAR or whatever.

Surely you agree that gravity causes things to coalesce, and that therefore if Jupiter is gas so far away from the core, the (massive) core must be rather more dense?
*


There should be no doubt that Jupiter has interesting "stuff" in its depths, but probing it from point-blank electromagnetic sensing (IR, microwave, radar, whatever) may not perform particular explorations the way we wish.

It is very unlikely that *any* EM sensing will penetrate more than a small fraction of the planet's depth. A few thousand km of air will still block light. We'd likely see an isotropic (ie, blank) field in most any wavelength. Exceptions would be:

1) Thermal wavelengths: We could see heat and cooling in updrafts, but really this sort of thing is more appropriately done from orbit. The intricacy of the structure of such updrafts and downdrafts is unlikely to be featured well from inside the atmosphere. You might see one or two "features" in the immediate vicinity, but if the atmosphere is heterogeneous in this respect, you wouldn't see very much, very far.

2) Unusual "clouds", deeper down, of compounds that we don't think of as volatiles. There could be sulfur, or even iron (etc) clouds at great depth. I don't know -- possibly a probe could go deep enough to radar scan for those? The feasability is questionable.
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Guest_Sunspot_*
post Sep 8 2005, 11:41 PM
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Guests






There were also problems with the Galileo orbiter not too long before it arrived. The tape recorder got stuck, and I believe they cancelled all the probe entry site observations. No one knows for sure what the area the probe came down into looked like.
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Dominik
post Sep 9 2005, 05:23 AM
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QUOTE (Sunspot @ Sep 9 2005, 12:41 AM)
There were also problems with the Galileo orbiter not too long before it arrived.  The tape recorder got stuck, and I believe they cancelled all the probe entry site observations.  No one knows for sure what the area the probe came down into looked like.
*



I remember, that there was a picture of jupiter, that shows the entry point of the galileo probe...

EDIT: I've found it.



Hi-Res:
Click

But this picture is from hubble...


--------------------
--- Under Construction ---
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edstrick
post Sep 9 2005, 07:59 AM
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"Bandwidth ought to follow Moore's Law, and with Galileo designed 30 years prior to any followup, we can expect the bandwidth issue to go away, "

Bandwidth is not determined by mass, power requirements and cpu speed of electronics but by frequency, transmitted power, directionality of transmission, area of receiving antenna and sensativity / signal to noise of receivers, including encoding of the signal to make it noise resistant. There were rapid improvements in receivers and encoding from the early 60's to the mid 70's but improvements since then have mostly been done by upping the frequency of signals to make transmitters more directional. Back in late 70's, they were doing usable telemetry with a signal to noise level rather less than 1.0, and were and are pretty much at theoretical limts set by physics.
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mike
post Sep 9 2005, 05:14 PM
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QUOTE (JRehling @ Sep 8 2005, 03:22 PM)
It is very unlikely that *any* EM sensing will penetrate more than a small fraction of the planet's depth. A few thousand km of air will still block light. We'd likely see an isotropic (ie, blank) field in most any wavelength.
*


That doesn't seem fair, to have a huge ball of matter floating nearby and no way to examine most of it. Surely there's some way to take a look, perhaps with methods we haven't yet discovered/devised.. Maybe Jupiter will just have to wait a while.

I'd personally like to see a camera-equipped probe descend into Jupiter, just because the pictures would be utterly unique if nothing else - even if they are just undifferentiable walls of white, they're undifferentiable walls of white from Jupiter. We'd have to see something, and I think that something would be worth the effort. I'll pony up the $300 kajillion myself. If that's not enough, we can use some of that 'blowing people up' money of which we possess so much...
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JRehling
post Sep 9 2005, 06:45 PM
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QUOTE (mike @ Sep 9 2005, 10:14 AM)
That doesn't seem fair, to have a huge ball of matter floating nearby and no way to examine most of it.  Surely there's some way to take a look, perhaps with methods we haven't yet discovered/devised..  Maybe Jupiter will just have to wait a while.
*


I would liken the problem to seeing the core of the Earth. Can't be done. The only two ways to probe that are with thumps and gravity. Sensing the gravitational field is part of the Juno mission, so look forward to it! Thumping a gas is harder than thumping a solid. I suppose we could "sound" Jupiter by setting off a hydrogen bomb and listening for the sound reflection at a second site, separated by some fraction of Jupiter's circumference away. If we had the capability, it would be ideal to have a probe (or more than one!) listening at the same time as another comet hits the planet, but those events are few and far between. You can't really count on an entry probe being timed precisely enough (the margins are very tight), so a dirigible would be necessary. Maybe a long-lived nuclear powered hot air balloon would be possible -- but the hazards are innumerable. Remember that Jupiter's atmosphere has a tiny molecular weight (lower than helium!), so that only heated H2 could float in it, and provide meager buoyancy per volume of balloon.

Once you had something long-lived, a camera would seem a lot more worthwhile, as the high probability of getting a bland image would eventually give way to a good side-looking shot of a cloud formation. But it would still have to fit into the mass margins of what would have to be a small payload once you had a balloon big enough to loft a nuclear reactor, and this large and therefore flimsy balloon would have to face incredible wind shear sooner or later. I don't know if it's even possible to hope for a lifespan beyond hours. Surviving one rotation of the planet would be fantastic.

Given another comet strike with enough advance warning, we could hope to plop a dirigible or two in there and get the sounding data, maybe even several distinct ones if the impactor is fragmented like Shoemaker-Levy was. Nature is not forced to cooperate with this plan, however, which is already baroque.

QUOTE (mike @ Sep 9 2005, 10:14 AM)
I'd personally like to see a camera-equipped probe descend into Jupiter, just because the pictures would be utterly unique if nothing else - even if they are just undifferentiable walls of white, they're undifferentiable walls of white from Jupiter.  We'd have to see something, and I think that something would be worth the effort.  I'll pony up the $300 kajillion myself.  If that's not enough, we can use some of that 'blowing people up' money of which we possess so much...
*


You can pretend these are from Jupiter: tongue.gif

http://www.backgroundcity.com/groups/g7.html
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mike
post Sep 9 2005, 07:34 PM
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I think we, or something we create, will eventually go to the core of the Earth. I also think we'll somehow get something or other into Jupiter. Of course, by the time we can do these things they may seem rather trivial and meaningless..

And those clouds don't count, sorry. smile.gif
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DDAVIS
post Sep 9 2005, 08:35 PM
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I'd personally like to see a camera-equipped probe descend into Jupiter, just because the pictures would be utterly unique if nothing else - even if they are just undifferentiable walls of white, they're undifferentiable walls of white from Jupiter. We'd have to see something, and I think that something would be worth the effort.

Obviously I agree, because of the PR value of a good image we might get. Cameras can be made quite small these days, and in the years ahead they can be made lighter and smaller. Images are worth far more in stimulating public interest than many volumes of 'squiggly line science'. Again, I ask people to look at the SRB descent videos and imagine seeing similar sequences from other worlds!
Here is a composite image from a panning scene in my Galileo animation for Ames showing probe sunset during its descent:
Attached thumbnail(s)
Attached Image
 
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mike
post Sep 9 2005, 09:47 PM
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Striking. Jupiter is so huge I'm not sure I can really comprehend it.. Pictures would help.
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David
post Sep 9 2005, 10:05 PM
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QUOTE (JRehling @ Sep 9 2005, 06:45 PM)
You can't really count on an entry probe being timed precisely enough (the margins are very tight), so a dirigible would be necessary. Maybe a long-lived nuclear powered hot air balloon would be possible -- but the hazards are innumerable. Remember that Jupiter's atmosphere has a tiny molecular weight (lower than helium!), so that only heated H2 could float in it, and provide meager buoyancy per volume of balloon.


And given that, at Jupiter's cloudtops, everything weighs more than two and a half times what it does no earth, you'd need something extraordinarily light. The task might be more practical on Saturn, where the gravity is less than earth's.

QUOTE
Once you had something long-lived, a camera would seem a lot more worthwhile, as the high probability of getting a bland image would eventually give way to a good side-looking shot of a cloud formation.
*


I wouldn't expect that an entry-probe with an imager would provide very spectacular images from inside the clouds (though I'd be happy to be wrong); but if one had a downward-pointing camera, you could get invaluable images from the approach to the cloudtops, at much higher resolution than anything we have now, something like the approach images from Titan. Obviously they'd be more interesting if you dropped the probe into a raging storm, instead of a bland cloud-band!
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JRehling
post Sep 9 2005, 10:20 PM
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QUOTE (David @ Sep 9 2005, 03:05 PM)
And given that, at Jupiter's cloudtops, everything weighs more than two and a half times what it does no earth, you'd need something extraordinarily light.  The task might be more practical on Saturn, where the gravity is less than earth's.
*


That also means the buoyancy is less. Hint: If you had a bathtub on Jupiter (filled with water and surrounded by STP air!), the same things would float there as on Saturn/Earth/Moon/Phobos/etc.
Unless you're worried about the thing falling apart under its own weight, the local g divides out.
In fact, Saturn's atmosphere is slightly lower in molecular weight than Jupiter's, making buoyancy there a bit harder.

QUOTE (David @ Sep 9 2005, 03:05 PM)
  I wouldn't expect that an entry-probe with an imager would provide very spectacular images from inside the clouds (though I'd be happy to be wrong); but if one had a downward-pointing camera, you could get invaluable images from the approach to the cloudtops, at much higher resolution than anything we have now, something like the approach images from Titan.  Obviously they'd be more interesting if you dropped the probe into a raging storm, instead of a bland cloud-band!
*


My own terrestrial experience is that side-looking views of cloud formations can be pretty striking as you see the topside profile of them against the sky. One difficulty on Jupiter would be that there might be similarly-hued clouds behind those (there are layers on layers). Another thought is that the clear air above and between layers would still have some humidity (from various species), and even on a clear day, you can't see forever. A couple of hundred kms' line of sight would probably yield blankness no matter what cloud/sky mix were behind it -- although the "humidity" of a parcel of Jupiter air would have to vary depending upon... many things. A view might show the tops of local fluffy cumulus in front of what seems to be a blue sky that actually has lots more clouds behind it, but too far away to see through the vast distances of "air".

Another thought on in-cloud imaging is that onboard processing might be used to choose which of many images are worth sending up (the less blank the better). Thus, a probe might take dozens of images, then send one or a few later, before it dies.

Personally, the thing I'd most like to "see" from a dirigible would be mass spectrometry from cloud particles at all heights, and to find out what the coloring agents are in the clouds.
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