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New Horizons, Pluto and the Kuiper belt
ugordan
post Nov 9 2005, 03:16 PM
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QUOTE (john_s @ Nov 7 2005, 10:40 PM)
The data rate from Jupiter isn't our limiting factor on data storage, it's more to do with the complexity of managing our memory which means that we can only fill up one 32 Gbit section of the solid-state recorder once during the flyby.  Plus we won't be able to crop our images before storing them, so to image a 100-pixel-wide Galilean satellite with our color camera we will need to store the full 4000-pixel width of our CCD array.
*

Didn't you devise any smarter lossless image compression algorithm that would know black space when it sees it? IMO, that sort of thing was feasible probably even in the days Cassini was designed (as opposed to the lossless-although-line-truncating algorithm implemented) let alone today. Sort of like dividing the frame conceptually into two categories: empty space (which would be all low intensity background noise) and actual useful data. The encoding tables could be optimized for two extreme cases then. I read about even more advanced concepts, actually analyzing images taken through different filters and transmitting back only differences, this would be perfect for pushbroom cameras as there wouldn't be any alignment issues due to spacecraft attitude changes.

Hm, maybe I'm getting a wee bit too technical here rolleyes.gif


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Guest_Myran_*
post Nov 12 2005, 08:20 PM
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Transmitting the difference information was something used on Voyager for the Uranus & Neptune encounters, but this perhaps not the same as what you suggest ugordan.
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Decepticon
post Nov 12 2005, 08:23 PM
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QUOTE (ljk4-1 @ Nov 9 2005, 09:30 AM)
Go to this post for a response from the New Horizons team on their decision not to include any kind of message/information packet:

http://www.unmannedspaceflight.com/index.p...indpost&p=25901
*



This is very upsetting to me at least. I will email them telling them of my disappointment. sad.gif
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just-nick
post Nov 13 2005, 01:42 AM
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QUOTE (ugordan @ Nov 9 2005, 08:16 AM)
Didn't you devise any smarter lossless image compression algorithm that would know black space when it sees it?
*


I'm no compression expert, but unless you've got very fast algorithms working in some sort of swap space, you'll still need to stuff all the images into your main memory during the flyby. NH isn't packing a great deal of computing power, so I'd suspect that compression is happening offline, after the hectic time of the flyby so you avoid taxing the computing system any more than necessary. That means you're still maxed out by the capacity of your recorder.

But once all is said and done, I can't imagine some sort of lossless (or even lossy) compression isn't being used for transmission back to Earth.

Anyone in-the-know got anything to correct there?

--Nick

PS -- I'd also like to welcome myself to posting after a couple months of lurking and enjoying the best SNR on any Internet forum I've ever seen. Of course its all going downhill now...
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mcaplinger
post Nov 13 2005, 02:01 AM
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QUOTE (just-nick @ Nov 12 2005, 05:42 PM)
I'm no compression expert, but unless you've got very fast algorithms working in some sort of swap space, you'll still need to stuff all the images into your main memory during the flyby.  NH isn't packing a great deal of computing power, so I'd suspect that compression is happening offline...
*


Lossless compression algorithms can certainly be fast enough to be applied in real time, if that's desirable. For example, the MGS/MOC lossless compressor can compress the raw pixel rate of 5 megapixels/sec. I'm not certain, but I suspect that the NH camera pixel rate is less than that; it probably doesn't need to be more than a megapixel/sec or maybe even less. It would also surprise me if NH was using lossy compression; we certainly didn't propose that for our unselected PKB instruments.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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mcaplinger
post Nov 13 2005, 03:21 AM
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QUOTE (ugordan @ Nov 9 2005, 07:16 AM)
Didn't you devise any smarter lossless image compression algorithm that would know black space when it sees it?
*


If you are using a first-difference-based lossless compressor, you can get this for free depending on what encoding table you use and what your black-space noise level is. For example, on MGS/MOC, we use a table that compresses black space 8:1, and we occasionally use this for star calibration images.


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hendric
post Nov 13 2005, 07:49 AM
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QUOTE (john_s @ Nov 7 2005, 11:40 AM)
... and the fact that our cameras are designed to work at Pluto's dim illumination levels and thus will tend to give overexposed images at Jupiter
*


John,
How do you plan to commission the instruments after launch? Taking pictures of DSO's? I'm sure some amateur astronomers could recommend a few for you to try out...


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JRehling
post Nov 13 2005, 06:03 PM
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QUOTE (Decepticon @ Nov 12 2005, 01:23 PM)
This is very upsetting to me at least. I will email them telling them of my disappointment. sad.gif
*


Personally, I think an intricate spacecraft with nuclear power and state of the art computers on board, on a trajectory that will communicate its origin for at least tens of thousands of years is a pretty good message that doesn't need much elaboration.
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ljk4-1
post Nov 14 2005, 02:42 AM
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QUOTE (JRehling @ Nov 13 2005, 01:03 PM)
Personally, I think an intricate spacecraft with nuclear power and state of the art computers on board, on a trajectory that will communicate its origin for at least tens of thousands of years is a pretty good message that doesn't need much elaboration.
*


Any interstellar vessel crew, human or otherwise, that eventually finds NH is not going to find its technology, and certainly not its computers, to be very advanced.

It will say something about us, though, to be sure - mainly, why did they attach a data disc that apparently had its data wiped out by cosmic radiation so soon after it left? And what's that odd rectangular symbol with the bicolor stripes? Are those supposed to be stars in the upper left corner? Why didn't they give us some kind of detailed record about themselves, especially if they sent this robot probe into interstellar space? Were the beings who made this craft so primitive that they didn't even consider the rules of galactic ettiquite?

Just ten years after the Voyagers were launched, they kept saying how a home PC could do more than the combined might of the probes' computer systems.

As for messages and information packets on future interstellar probes - which I think should be mandatory, as we will be sending vessels into the greater galaxy - a committee independent of the mission teams, if necessary, needs to be formed to design and implement data records on the probes.

Carl Sagan and his team showed us the way, as they had to instigate and do almost all the work on the Pioneer Plaques and Voyager Records, as apparently almost no one at NASA seemed to show any real care or concern about the fact that those probes were going to exit our Sol system into the Milky Way for the first time in human history. Hardly an insignificant event.

If deep space mission teams are unable and unwilling to put data records on their probes, then they should let others handle that signficant detail. Anyone interested in helping to form a group on this matter?


--------------------
"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 Nov 14 2005, 06:27 AM
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Every probe we send into space is an expression of who we are. Any advanced alien species will be able to look at the instruments we included and the specific implementation of the craft and discern far more about the human species than you may imagine. If we were to put, say, images or videos of people dancing, dressed in particular cultural garb, the aliens may just ask themselves "Why did they put videos of people dancing on a probe designed to explore the universe?" Then, they would probably obliterate our entire galaxy, because dancing is against all that is Good.

I'm just not sure we can predict that any particular addition to the probe would have any particular effect whatsoever. Personally I'd rather we had more instrumentation to detect just what's out there than that we had a video of some sort of cultural activity. We can save that stuff for our diplomatic probes. If you want to throw on a CD with Bach, or Fifty Cent, or Coldplay, or a picture of people eating sushi, or curried rice, or a McDonald's hamburger, or the latest episode of 'Everybody Hates Chris', or whatever, then go for it, but only if it doesn't interfere with what we know will grant us something useful.

A purely 'diplomatic probe' would be fine with me, or maybe someday we'll be able to pack every instrument we could ever want on one platform and still have room left over, and hey, why not stick whatever you want on there (a piece of the World Trade Center, an unexploded suicide bomb, a Snickers bar, a copy of the UN charter, pictures of people playing jump rope, whatever ya want).
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ugordan
post Nov 14 2005, 08:21 AM
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QUOTE (mcaplinger @ Nov 13 2005, 05:21 AM)
If you are using a first-difference-based lossless compressor, you can get this for free depending on what encoding table you use and what your black-space noise level is.  For example, on MGS/MOC, we use a table that compresses black space 8:1, and we occasionally use this for star calibration images.
*

That's sort of what I was getting at. If the scan lines were encoded on the fly after being read out, there wouldn't even need to be a large memory buffer to store the whole image at first, like just-nick pointed out. I wonder if there would be a significant improvement if the image was processed in 2D, dividing it into variously sized blocks that are either black space or useful data. In any case, I'd think stating that you need to store the whole 5000 pixels to capture a Jovian moon can be a bit misleading in this perspective.
Then again, I really don't know about the inner workings of NH so I can't say anything for sure.


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ljk4-1
post Nov 14 2005, 02:01 PM
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QUOTE (mike @ Nov 14 2005, 01:27 AM)
Every probe we send into space is an expression of who we are.  Any advanced alien species will be able to look at the instruments we included and the specific implementation of the craft and discern far more about the human species than you may imagine.  If we were to put, say, images or videos of people dancing, dressed in particular cultural garb, the aliens may just ask themselves "Why did they put videos of people dancing on a probe designed to explore the universe?"  Then, they would probably obliterate our entire galaxy, because dancing is against all that is Good.

I'm just not sure we can predict that any particular addition to the probe would have any particular effect whatsoever.  Personally I'd rather we had more instrumentation to detect just what's out there than that we had a video of some sort of cultural activity.  We can save that stuff for our diplomatic probes.  If you want to throw on a CD with Bach, or Fifty Cent, or Coldplay, or a picture of people eating sushi, or curried rice, or a McDonald's hamburger, or the latest episode of 'Everybody Hates Chris', or whatever, then go for it, but only if it doesn't interfere with what we know will grant us something useful.

A purely 'diplomatic probe' would be fine with me, or maybe someday we'll be able to pack every instrument we could ever want on one platform and still have room left over, and hey, why not stick whatever you want on there (a piece of the World Trade Center, an unexploded suicide bomb, a Snickers bar, a copy of the UN charter, pictures of people playing jump rope, whatever ya want).
*


You seem to be equating data records on interstellar probes with poorly planned and stocked time capsules. No one is going to (or should not at least) just throw a bunch of random "junk" into such a record on such a vehicle. Though as any anthropologist will tell you, one often learns a lot more about a community through its refuse than its official records and monuments. But that doesn't mean we should just send whatever into the galaxy, at least not at this early stage.

I am well aware that much can be learned about our level of technology and other things just by examining a probe. But any probe by itself will leave quite a bit unanswered about us and our world. Adding information about us will not harm anything.

Any ETI that is bent on harming or destroying us will do so regardless of what may or may not be on such a data record. I also have my doubts about marauding aliens scouring the galaxy looking for worlds to conquer, but that is for another topic.

While I certainly would not oppose it, I also do not think at this stage we should build and launch a purely "diplomatic" probe, as you call it, unless we have an actual destination for it and some means of getting it there a bit faster than what we can muster at present.

You may find the ideas on this Web site of interest:

http://www.winlab.rutgers.edu/%7Ecrose/cgi-bin/cosmicB.html


--------------------
"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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john_s
post Nov 14 2005, 04:51 PM
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QUOTE (ugordan @ Nov 14 2005, 08:21 AM)
That's sort of what I was getting at. If the scan lines were encoded on the fly after being read out, there wouldn't even need to be a large memory buffer to store the whole image at first, like just-nick pointed out. I wonder if there would be a significant improvement if the image was processed in 2D, dividing it into variously sized blocks that are either black space or useful data. In any case, I'd think stating that you need to store the whole 5000 pixels to capture a Jovian moon can be a bit misleading in this perspective.
Then again, I really don't know about the inner workings of NH so I can't say anything for sure.
*


These are good suggestions, and indeed, there are many ways that on-the-fly compression could be enabled. But every feature that's added to the software carries the risk of adding bugs too, and more testing is needed to check everything out. Therefore we are keeping things very simple for the Jupiter flyby, so the flight software team can concentrate on the really crucial details that affect the health of the spacecraft.

So the plan is that we'll fill up one 32 Gbit buffer with uncompressed data (including all 5000 lines of every MVIC image), and use the second 32 Gbit buffer for compression of the data prior to downlink to Earth.
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ilbasso
post Nov 14 2005, 05:35 PM
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A prototype for a diplomatic probe exists already, one that is fluent in over 6 million forms of communication:


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mike
post Nov 14 2005, 06:49 PM
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My point in mentioning in all that 'junk' is that all those things are surely very popular - what makes them so horrible? What do you think we should place on a probe meant to inform an alien species just what we're all about? Personally, I haven't the vaguest idea.. a copy of the entire planet, miniaturized somehow, is all that currently comes to mind.
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