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Unmanned Spaceflight.com _ Forum News _ Jim Bell Q'n'a
Posted by: djellison Jan 22 2006, 11:06 PM
Jim Bell's agreed to do a brief Q'n'A in a few days time, so similar to the one I did for Steve, I want your questions! Try and keep it quite 'current' if you can, as we're going to make this more a 'news' outlet than a look back type chat.
We're going to try, if this one works, to do these every couple of weeks or so, a bit of Rover news and a bit of Q'n'A each time, but we'll see how this one goes first!
Fire away people 
If they're all crap, don't worry, I've got LOADS in mind.
Doug
Posted by: CosmicRocker Jan 23 2006, 12:24 AM
Doug: I understand that Jim Bell is the Pancam expert, but also an integral part of the MER team. Do you expect questions to be mainly about imaging, or are any general MER questions acceptable? Any guidelines?
For an imagery question, I'd like to ask him to shed some light on the odd-looking luminosity histograms displayed by the raw jpegs (the weird stretching).
Posted by: Phillip Jan 23 2006, 01:34 AM
I would like to hear a current and honest diagnosis of Oppy -- will she be able to travel long distances again, so Victoria is even in the cards? What percent of her original travel capabilities remain? Is she at 100%, 80% what?? If no one knows yet, that is ok, but I would like to know what is the "best current estimate".
I miss Oppy's travels! 
Posted by: dot.dk Jan 23 2006, 01:40 AM
I miss Oppy's travels!
In relation to that question I would like to know how much testing went into the new stow position for the IDD. And how comfortable they are driving with it. Do they have to check the position after every stow now to make sure it is placed correctly?
I think Oppys wheels are as good to go as ever (apart from the steering actuator).
Posted by: Phillip Jan 23 2006, 02:06 AM
On the Spirit side, I would like to know:
1) Before Spirit gets there, what do the members of the MER team think, in their heart of hearts, that "homeplate" is? (And I would be interested in hearing what the UMSF community thinks too at this "last moment" before we are actually there); and
2) What is the current thinking (admittedly before peer reviewed papers can be published) of the significance of salts at Arad? I thought it had become pretty well acknowledged that Gusev, if it ever was a sea, has been buried by meters and meters of deposits -- how do salt evaporites fit into that "big picture"? (I think Sqyures agreed to that concept in your last Q&A) Did water seep UP into those deposits after the sea disappeared and deposits covered it over? I, for one, am confused.
PS Is the MER team as itchy as I am to finally get to homeplate after so many months (years?) of wondering what it is????? Do they view homeplate (as I do) as the scientific pinnacle of this mission to date?
PPS Does the MER team appreciate that they are joining the paragon of Lewis and Clarke in exploration??? (at least from a U.S. perspective). Do they realize that they rank in the tops of historical explorers and how does that make them feel (ok that may be too general of a question, but that is what I would ask). These guys rock and even if our media ignores them, they need to be reminded of the historical significance of what they are doing, from time to time.
Posted by: dvandorn Jan 23 2006, 03:57 AM
Look at the vertically-exaggerated image posted http://www.unmannedspaceflight.com/index.php?act=Attach&type=post&id=3572.
Home Plate seems very obviously, in this stretched image, to be the remnant of an impact crater. There are several impact crater remnants in the inner basin, here. Each seems to have been formed in a surface that was a good many meters higher than the present surface -- those missing several meters have been deflated from this terrain, by some process, leaving the shocked "pedestal" remnants of the deeper cratering forms.
Remember, when you make an impact crater, you don't just affect the surface. The disruption caused by the cratering event goes well under the surface, consisting of impact melt (if the impact is energetic enough) and shocked, brecciated rocks.
The crater remnants we're seeing on the surface look like the brecciated and shocked rocks that were originally created in a bowl-shaped lining beneath this cluster of impact craters. I can see traces of at least five different craters within the inner basin, here. (The ridge of rock Spirit is passing right now is, in fact, a small crater remnant.)
As for Home Plate, it sits within the largest and most well-defined of these crater remnants. Maybe such layers were exhumed in *all* of the craters here, and have since been completely eroded away -- but that doesn't seem right. We have traces of several craters, and in only one of them do we see any trace of this lighter-colored material.
I'd have to think that either the impact target composition was different where the Home Plate impact occurred -- which seems a little unlikely when you consider some of these impacts are only a few tens of meters apart -- or that some other substance was deposited in Home Plate crater that wasn't deposited in the other craters. (Or that has been completely deflated from the other craters, if it ever existed there.)
So, logic *seems* to point towards post-cratering material deposition accounting for the light-rock ring. Personally, I think it could have been water deposition. Home Plate could have been a puddle that was filled and dried thousands of times (maybe with an internal artesian spring) that resulted in aqueous transport and deposition.
Or, it could have just been a good wind trap and it trapped a lot of light-colored dust. Hard to say.
I'm not only interested in the light-rock ring's composition, I'm getting very curious about the erosion process that deflated the original surface. Could aeolian erosion have deflated *that* much surface, even over a few billion years? Do we need to postulate aqueous erosion, or even glacial erosion?
Maybe the specific composition and erosion patterns we see on the light-rock ring will help us puzzle that out.
-the other Doug
Posted by: edstrick Jan 23 2006, 06:08 AM
Question for Jim Bell:
The usual left cam 3-channel multispectal imaging is bands 2,5,7 <near-IR,green,violet> Sometimes we have other color combos like 2,5,6 or 2,4,7 or 3,5,7 (or some such.. I'd have to go back and check examples).
All of the alternate sequences seem to produce images with degraded color discrimination: two of the channels are too similar to each other, and you typically get images that are dominated by long-vs-short wavelength differences and the color differences due to the middle channel (reflecting curvature in the spectrum) are less discriminated.
What's the rationale behind some of these other filter sequences during only 3 filter color imaging?
Oh.. regarding HomePlate... it's obviously the fossilized pizza-crust of the gods. Heaven help us if Spirit finds 1 meter fossilized pepperoni, ...or anchovies!
Posted by: Toma B Jan 23 2006, 08:34 AM
Will Opportunity ever reach Victoria crater?
Jim Bell.....same question?
Posted by: djellison Jan 23 2006, 10:17 AM
Not sure exactly how we'll go, obviously Jim will know things outside the realm of just Pancam, but obviously, it'd be interesting to keep it imaging related. No strict rules though - we'll see how it goes
Doug
Posted by: paxdan Jan 23 2006, 11:45 AM
Next time they are doing earth observations can we get a little notice so i can go outside and wave 
I'm also curious about the scope of nightime observations possible. An update about the status of the meteor searches and if they have more than one unambiguous trail.
Also what about cometary or asteroid observations? Could the PMA be used like a star tracker during long PANCAM exposures.
Posted by: helvick Jan 23 2006, 02:11 PM
With regard to mission lifetime are there any indications that the cameras are degrading?
Do the "true colour on mars" claims annoy you as much as they annoy us?
If the rovers lose mobility but remain semi-operational what sort of imaging plans would be put in place?
What is the lowest power level the rovers can continue to operate on in that situation?
The rapid release PR images (the "Raw" data on the JPL and Exploratorium sites) are immensely popular with us amateur image nuts but their usefulness for more advanced processing is limited by the automatic contrast stretching that is applied when they are converted for release to these sites. Are there any plans to release actual "Raw" images more rapidly or would that be seen as a bad idea since they would be uncalibrated and would still be potentially unreliable data.
What (for you) was the biggest surprise of the MER mission?
Posted by: odave Jan 23 2006, 03:39 PM
Seconded...
Posted by: hendric Jan 23 2006, 04:18 PM
Obviously it's a little hard to tell from the preliminary models on the MSL website, but it looks like they don't have HAZCAMs or stereo capability on MSL. Is this accurate? How useful are the stereo cams on MER? MER used the same CCDs across all the cameras. Would you recommend MSL do the same?
Posted by: djellison Jan 23 2006, 04:29 PM
I believe MSL has Stereo imagery up on the mast http://www.msss.com/msl/mastcam/index.html - and it will obviously require some sort of Hazcam's for IDD work, but I'll try and ask about that one at some point. The more 'general' questions I'll save up, the one's that are a bit more 'here and now' are the sort I hope to ask.
Doug
Posted by: RNeuhaus Jan 23 2006, 08:43 PM
Will the MSL make short panoramic films on Mars? If not, why not? This will lead us to discover some strange movements.
Will incorporate some kind of special camera to take sky pictures in order to study the formation of dusts, clouds and meteorite phenomen?
Rodolfo
Posted by: The Messenger Jan 23 2006, 09:41 PM
Jim -
About a year ago, Oppy, spent a couple of days checking out her tattered heat shield...(It actually popped inside-out on landing.) Any feedback on the assessment? Did Oppy come in hot or cold?
Posted by: Bob Shaw Jan 23 2006, 11:46 PM
Home Plate seems very obviously, in this stretched image, to be the remnant of an impact crater. There are several impact crater remnants in the inner basin, here. Each seems to have been formed in a surface that was a good many meters higher than the present surface -- those missing several meters have been deflated from this terrain, by some process, leaving the shocked "pedestal" remnants of the deeper cratering forms.
Remember, when you make an impact crater, you don't just affect the surface. The disruption caused by the cratering event goes well under the surface, consisting of impact melt (if the impact is energetic enough) and shocked, brecciated rocks.
The crater remnants we're seeing on the surface look like the brecciated and shocked rocks that were originally created in a bowl-shaped lining beneath this cluster of impact craters. I can see traces of at least five different craters within the inner basin, here. (The ridge of rock Spirit is passing right now is, in fact, a small crater remnant.)
As for Home Plate, it sits within the largest and most well-defined of these crater remnants. Maybe such layers were exhumed in *all* of the craters here, and have since been completely eroded away -- but that doesn't seem right. We have traces of several craters, and in only one of them do we see any trace of this lighter-colored material.
I'd have to think that either the impact target composition was different where the Home Plate impact occurred -- which seems a little unlikely when you consider some of these impacts are only a few tens of meters apart -- or that some other substance was deposited in Home Plate crater that wasn't deposited in the other craters. (Or that has been completely deflated from the other craters, if it ever existed there.)
So, logic *seems* to point towards post-cratering material deposition accounting for the light-rock ring. Personally, I think it could have been water deposition. Home Plate could have been a puddle that was filled and dried thousands of times (maybe with an internal artesian spring) that resulted in aqueous transport and deposition.
Or, it could have just been a good wind trap and it trapped a lot of light-colored dust. Hard to say.
I'm not only interested in the light-rock ring's composition, I'm getting very curious about the erosion process that deflated the original surface. Could aeolian erosion have deflated *that* much surface, even over a few billion years? Do we need to postulate aqueous erosion, or even glacial erosion?
Maybe the specific composition and erosion patterns we see on the light-rock ring will help us puzzle that out.
-the other Doug
otherDoug:
I lean towards your interpretation in all regards, but confess that caution is whispering a big 'wait and see' in my ear - it could be simply an isolated and exposed unit of a more pervasive structure (as indicated by other, similar local landforms). However, I 'want' it to be some sort of exhumed crater, replete with shock cones, oh yes, I do! I sincerely hope that there'll be enough time for Spirit to thoroughly investigate Home Plate and that the desire to be pointing in the right direction when the depths of winter arrive won't cause our visit to be a short one.
Bob Shaw
Posted by: Phillip Jan 24 2006, 04:34 PM
I am afraid I do not have any imaging questions, but I would be curious to know what kind of debate surrounded the recent decision to have Spirit pass up the shelf/ledge, which looked to my untrained eyes as very interesting. Did they decide it was not very promising looking? Or that they will have a chance to study similar features later (maybe HP itself or on McCool Hill)? Or was it a regrettable but necessary result of the need to get to HP fast and then up the slopes? Depending on his answer, this may be good fodder for follow up questions giving interesting insights on the tough decisions MER team must have to make on a day to day basis.
Posted by: djellison Jan 24 2006, 10:14 PM
Quick update, Jim and I just tested Skype, and it worked great, so hopefully we're go for the first of these on Thursday Evening. More news soon.
Doug
Posted by: Bob Shaw Jan 24 2006, 11:27 PM
Doug:
Here's a question: will they take suggestions for rock (etc) names?
Bob Shaw
Posted by: Tom Tamlyn Jan 25 2006, 02:18 AM
1. Please discuss your reasons for being optimistic that the rovers have captured images of meteor trails.
2. Do the MER pancams share any significant systems with the "original" pancam discussed in Steve Squyres' book? Did the original pancam have any capabilities lacking in the MER pancams, or did subsequent advances in imaging technology result in the MER pancams being more capable all 'round. [Obviously No. 2 could also be a question for SS].
3. In a recent news article, Phil Christensen is quoted as saying that the same wind events which cleaned off the solar arrays left the mini-TES lenses filthy. Has pancam encountered similar problems? [I believe that this was a 1/9/2006 Arizona Republic article mirrored by http://www.whatonmars.com/, but no longer available for free]
TTT
Posted by: djellison Jan 25 2006, 02:43 AM
Oo - that's a GOOD one. I was going to ask about 'dirtyness' - but to have a comaprison with Mini TES is a news to me, a nice angle on it. It's IN.
Doug
Posted by: hendric Jan 25 2006, 07:11 AM
How does the team feel about posting the raw images on the web? Does it seem like us amateurs are stealing their thunder, a little? Would you do another public raw archive on your next mission? Do you read the various forums regularly?
Posted by: Canopus Jan 25 2006, 02:42 PM
Could we also please have a Jeffrey L. Bell Q and A?? 
Posted by: paxdan Jan 25 2006, 03:53 PM
Here's a question: will they take suggestions for rock (etc) names?
Bob Shaw
Yeah, a name a rock/feature on mars outreach project would be a great idea. Much in the same way the rovers were named e.g., get schoolkids to provide a name and reason.
Do it for a rock/feature at each site to commemerate an important milestone. (1k Sols) Give the winners a nice glossy print and you have yourself a nice PR opportunity.
Posted by: MahFL Feb 1 2006, 11:01 PM
"MastCam also provides both natural color still and high definition video"
Posted by: djellison Feb 14 2006, 10:09 PM
The usual left cam 3-channel multispectal imaging is bands 2,5,7 <near-IR,green,violet> Sometimes we have other color combos like 2,5,6 or 2,4,7 or 3,5,7 (or some such.. I'd have to go back and check examples).
All of the alternate sequences seem to produce images with degraded color discrimination: two of the channels are too similar to each other, and you typically get images that are dominated by long-vs-short wavelength differences and the color differences due to the middle channel (reflecting curvature in the spectrum) are less discriminated.
What's the rationale behind some of these other filter sequences during only 3 filter color imaging?
Oh.. regarding HomePlate... it's obviously the fossilized pizza-crust of the gods. Heaven help us if Spirit finds 1 meter fossilized pepperoni, ...or anchovies!
This one got done, as did the one regarding aging
Doug
Posted by: algorimancer Feb 16 2006, 06:00 PM
Here's a two part question for Jim Bell:
A) Why didn't the MER cameras use the Jpeg2000 file format specification (which is based on wavelet compression and an order of magnitude more efficient than standard jpegs) rather than using an in-house wavelet compression algorithm? Currently Nasa software must be used to view the raw image data, whereas with Jpeg2000 compression the raw images would have been immediately accessible with standard image editing/viewing software.
B) Would it be possible to post higher quality images to the exploratorium & jpl sites in Jpeg2000 format (same size, better quality) in addition to or instead of the currently used jpeg format?
Not only would use of Jpeg2000 for images in exploratorium provide better quality images, but it would also be a spur towards broader adoption of the format in browsers and other image software.
Posted by: djellison Feb 16 2006, 08:38 PM
Are you talking about the PDS IMG's - as the rules and regs for what you publish to the PDS are basically set in stone as I understand it.
I agree, better quality raw JPG's would be nice, but to be honest, so old and to date, fairly reliable is the system that's putting out the JPG's we see know, I'd not want to see it played with.
iirc, you'll get some Jpeg2000 goodness with HiRISE images though
Doug
Posted by: algorimancer Feb 17 2006, 12:30 AM
I agree, better quality raw JPG's would be nice, but to be honest, so old and to date, fairly reliable is the system that's putting out the JPG's we see know, I'd not want to see it played with.
iirc, you'll get some Jpeg2000 goodness with HiRISE images though
Doug
Fundamentally I was referring to the images comming out of the the MER. As I understand it the compression used prior to transmitting the files is a type of wavelet compression (which is good), however why they opted to "wing it" versus using an ISO standard is what I'm wondering about. My guess is that the standard wasn't finalized at the time they were building the hardware, but it's just a guess. As to the PDS rules... it has been a few years since I last looked at the requirements, but since HiRISE is apparently using Jpeg2000, I would guess that MER could as well. I wonder whether the compression scheme in MER overlaps with that in Jpeg2000 so that a direct conversion would be possible without any loss of quality.
Thanks for mentioning HiRISE, I hadn't looked closely at that mission but after having a look at the home page it looks pretty exciting, particularly from the perspective of the sort of people who hang-out at this site
Posted by: djellison Feb 17 2006, 09:50 AM
For the raw quick-look releases (like we get with MER at the Exp and JPL) HiRise will be J2K, but the calibrated published data down the line will be uncompressed IMG's or similar I'm fairly sure.
Doug
Posted by: ugordan Feb 17 2006, 10:26 AM
The main reason for developing a proprietary compression algorithm was better performace in regards to data transmission packet sizes and error resilience, both specific to the medium the data are transmitted along - radio waves over the DSN network. It was heavily influenced by Jpeg2000, only adapted to a very specific use. I have a PDF describing the MER algorithm somewhere, but can't seem to dig it up now.
While both standards are very similar in terms of compression principles, I don't believe they're that compatible. There are specifics to each algorithm that probably make a lossless conversion impossible.
Posted by: algorimancer Feb 17 2006, 01:55 PM
Doug
Actually it looks like you were correct the first time. I did some googling yesterday and came up with a justification to the PDS as to why Jpeg2000 was suitable (things like high compression quality and stable ISO standard, as well as the subsampling capability (you can pull a lowres thumbnail out of a j2k image without having to read or process the the entire image file). I gather it was approved and is being used. However it wouldn't surprise me if they downsampled/converted to regular Jpeg format for immediate release, while later posting to PDS in the original j2k format. Incidentally, while j2k has a lossless compression option, it would surprise me if they used it routinely. I gather, for instance, that MER occasionally returns lossless images, particularly with the MI, but otherwise some compression is routinely used. In my experience 99% quality compression is virtually indiscernable from lossless, and a fraction of the size ... meaning we get lot's more returned images than otherwise.
Posted by: algorimancer Feb 17 2006, 02:06 PM
While both standards are very similar in terms of compression principles, I don't believe they're that compatible. There are specifics to each algorithm that probably make a lossless conversion impossible.
This may well be that PDF, which describes the ICER compression scheme used by MER and compares it with j2k and others:
http://tmo.jpl.nasa.gov/progress_report/42-155/155J.pdf
As I read it, it rather sounds like it is using something like a subset of capabilities of j2k. While it is clear that a non-lossless j2k image could be losslessly converted to the ICER format, the reverse is not obvious.
Posted by: djellison Feb 17 2006, 02:09 PM
You average compression for 'earth' use isnt going to be robust enough to withstand a the odd bit error, so I image they do use a subset of j2k, but just modified for robustnes s:)
Doug
Posted by: ugordan Feb 17 2006, 02:31 PM
http://tmo.jpl.nasa.gov/progress_report/42-155/155J.pdf
Yes, that's exactly the one. Thanks for digging it up!
If the reverse is not possible, then the whole thing is useless in terms of releasing the PDS raw data as any recompression will make it less raw, and obviously not any different than regular JPEG. That's not to say it's impossible to repackage the bits and re-encode into J2000, as long as the wavelet coefficients aren't touched themselves.
Posted by: djellison Mar 22 2006, 12:04 PM
You have till 1700UT today for new questions - I'm doing another session with Jim later
Doug
Posted by: Toma B Mar 22 2006, 12:10 PM
Just one simple question...
When will Opportunity reach Victoria Crater...
I know that nobody knows that for sure but I would like to hear from someone as competent as Jim Bell is...
Thanks!
BTW, Doug, did you solve the problems with audio recorder...remember the last time... 
Posted by: djellison Mar 22 2006, 12:16 PM
That's one of those questions that's not worth asking, like the end of the Steve Q'n'A - I actually said I wouldnt ask how long they'll last - it's just one of those things you don't know.
When will Oppy reach Victoria Crater is like, how long's a piece of string.
I could ask how agressive they intend to be with driving, what sort of thing it would take to flag up a science stop, how the rover is in terms of health - But I don't think anyone knows how long it'll actually take.
I've tested Skype, and it's sounding much better now Still not perfect, but a lot better ( and infinitely cheaper ) than a phone call 
Things I intend to cover, some odd Pancam issues ( the white pixels down each side, the frames that are just noise etc ) - how was the resolving power of Pancam chosen - and the development of Pancam from way back in the pathfinder days.
And of course, their current status
Doug
Posted by: Toma B Mar 22 2006, 12:34 PM
Well, I’m not trying to be offensive but, if Jim Bell does know how aggressive they intend to drive and what sort of thing it would take to flag up a science stop, as you sad it then he CAN give approximate date when they will arrive...
Thank you anyway!
Just his opinion...
P.S.
That is whole other question. I think it would be unethical to ask that...
Posted by: algorimancer Mar 22 2006, 02:29 PM
As mentioned previously in this thread, I would be really interested to hear his take on the Jpeg2000 question, noting that HIRISE is apparently using it, and why they went with the proprietary ICER equivalent wavelet compression method instead. For that matter, could they send up a software patch and change to the more portable compression standard even now? Leading up to, it would be really nice to be able to download and view the raw MER images without the requirement of Nasa software.
Posted by: djellison Mar 22 2006, 02:37 PM
img2png
Doug
Posted by: algorimancer Mar 22 2006, 05:42 PM
Doug
Or for that matter, img2bmp or img2tiff, the problem is that while there is no loss in quality, the compression is lost (losing the benefit of the small file size), along with the possibility of various wavelet analyses which can be extracted from the original wavelet-based image; there is a LOT of interesting information in the raw data of a wavelet compression.
Posted by: djellison Mar 22 2006, 05:58 PM
You've lost me. The very best data is the RAD .img files as far as I know - what is it you're actually after instead of that?
Doug
Posted by: centsworth_II Mar 22 2006, 06:36 PM
You could just invite Jim Bell to join the arrival sol at Victoria lottery.
Posted by: djellison Mar 22 2006, 07:05 PM
OOops - too late
I got the JPEG2K question in, asked about the cloud pictures, the Spirit dragging, how agressive they intend to drive - will they stop for the dark cobbles or the baby craters, picking filters for end-of-drive imaging, and the history of pancam right back to the pushbroom jobbie in the early '90s.
AND....news just in. Odyssey safed yesterday, so no pretty pictures for a day or two.
Doug
Posted by: algorimancer Mar 22 2006, 07:34 PM
Doug
Fundamentally I'm after the best possible quality images in an international standard format. If the image is lossless, that would mean either PNG or Jpeg2000 (which has a lossless mode), though I'd settle for Tiff or Bmp (and happily convert to one of the others). If the image is compressed (most are), then wavelet compression yields the best quality with fewest artifacts (and is what they use on MER), and Jpeg2000 is the standard format. Admittedly Jpeg2000 involves additional processing overhead, but when dealing with limited bandwidth they seem the optimum solution.
There are just all sorts of benefits to wavelet-compressed images, completely aside from file size. Upon display they yield minimal artifacts, scale smoothly, and you can even pull an arbitrary resolution thumbnail out of one without having to read the entire file. Aside from that, there are a slew of papers out there on such topics as pattern recognition and texture analysis simply based upon the wavelet coeficients (similar things are possible with Jpeg images). I'm happy that they're using wavelet compression to begin with, I'm concerned that by choosing a non-standard format they have to some extent isolated the potential data analysis to within the JPL community.
My understanding of the .img file structure is that it contains a lot of useful header data plus a tag specifying the raw format of the image data, and then the actual image data is in the originally acquired format. For instance, the Hughens probe sent back Jpegs, so within the corresponding .img files there should be that raw Jpeg data, and likewise for the MER images in terms of the ICER format.
Anyway, I see that you've already done the interview and I look forward to hearing what he had to say
Posted by: djellison Mar 22 2006, 07:42 PM
That's not my understanding of it - I think the imagery data within an IMG is totally uncompressed (thus every full frame IMG is always 2mb. If they were in any way compressed, they would vary)
Doug
Posted by: helvick Mar 22 2006, 08:50 PM
But some of them are rebuilt from an original that was compressed, right? like the 1bpp, 4bpp etc images?
Posted by: djellison Mar 22 2006, 09:24 PM
Yes - a compressed image comes down, and they then rebuild a calibrated image from that, and all the other settings related to the camera at that time. Flatfield, Darkfield, Smear, temperature etc etc - to produced something calibrated.
Doug
Posted by: algorimancer Mar 22 2006, 09:57 PM
I stand corrected Surely they must archive the original raw images somewhere...
Posted by: djellison Mar 22 2006, 10:29 PM
Well - they must do somewhere, but the 'product' is something made from that data, not the data itself.
Doug
Posted by: Toma B Mar 23 2006, 06:30 AM
May I ask when (or where) will yesterday's Jim Bell's Q'n'a be posted?
Posted by: djellison Mar 23 2006, 07:46 AM
B)-->
The usual place ( http://www.planetary.org/explore/topics/mars_exploration_rovers/audio.html ) - and once Emily's had a chance to whack it up there, she'll post a thread in this sub-forum to say so
Doug
Posted by: edstrick Mar 23 2006, 09:57 AM
Bear in mind that the rovers have a 20 MhZ CPU, I believe. I think an important factor in their selection of compression methods is computing time required.
Posted by: djellison Mar 23 2006, 12:24 PM
Going on what Jim said yesterday - the most important thing is robustness. Your compression has to be able to withstand a lost bit or a lost packet, and not trash the whole image - hence why they developed something themselves. It's also highly tweakable and can compress things like the sky very very well, but still retain good detail in things like layering etc.
Doug
Posted by: odave Mar 24 2006, 03:03 PM
For the next time around - How often has autonav been used, percentage wise, and how well do they feel the autonav system has performed so far?
Posted by: djellison Mar 24 2006, 03:09 PM
See - I'd TOTALLY forget if you didn't put in here. I'm useless at things like that.
Things I want to get to next time include - autonav and visodom
Albedo measurements - what they actually achieve
How much of a mission could there be sans-Odyssey
and as an aside, CTX and MARCI performance with their test images.
and anything else you lot come up with
Doug
Posted by: alan Mar 27 2006, 03:57 AM
I'd like to know how much Spirit's stuck wheel will impair its ability to climb steep slopes. Of course with the varying traction I don't know if I should expect a very specific answer.
Posted by: Pertinax Mar 27 2006, 09:21 PM
Looking back in time a little bit: Has there been any sucess in creating an aprox. true color image of Spirit Sol 675's Phobos eclipse while Phobos was in Mars' umbra? If so, anything that can be shared at present?
-- Pertinax
Posted by: djellison Mar 27 2006, 09:45 PM
-- Pertinax
As I understand it - that imagery was just a movie in a single filter (L1), and even if it wasnt - then the subject of interest would have moved quite a lot between frames. If you've got another specific observation in mind thought, flag it up and I'll take a look and mention it - chances are if they're worked on it, then Jim will probably be able to share something.
Doug
Posted by: paxdan Mar 28 2006, 10:37 AM
Can you ask for an overview of Dark- and Flat-fields please. How often they are retaken etc... And if there are other techniques they use to compensate for degredation of the detectors/optics over time.
Posted by: Bob Shaw Mar 28 2006, 01:19 PM
Picking up on Bruce's comments in the Phobos and Deimos Origin thread (and previous discussions regarding man-made objects in orbit around Mars), could you ask about observations of the dusk/dawn sky seeking natural and man-made satellites. In particular, are (or will) such observations be possible on restricted sols this winter, or will be rovers simply be hunkered down against the chill?
Bob Shaw
Posted by: Pertinax Mar 28 2006, 01:27 PM
Doug
Well foo. That's the observation I was thinking of, but you are correct, only clear L1's apear to have been taken late on sol 675, and none early in 676. My confusion came from a portion of the press release from 15Nov05 (http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20051115a.html):
I remember seeing at least some of the raws, I just forgot that they were all L1s. Oh well. Maybe [hope, hope] they are just tagged at low priority and have not been transmitted yet.
For what it is worth, I don't think movement between frames would be a significant issue as long as the interest is only along the lines of 1) Is light of mars' umbra colorful, and 2) if yes, then roughly what color (hue) is it. The results would not exactly be representitive of a given location in mars' umbra, but it would get the general hue I think.
Thank you for the heads-up.
-- Pertinax
Posted by: algorimancer Aug 9 2006, 07:26 PM
For the next "Jim & Doug Show", questions for Jim...
I've been looking over the spec's of the equivalent of the pancam for the MSL,
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1214.pdf
These spec's are really exciting, but a few questions arise.
The MER pancams are separated by 30 cm, which makes for pretty good stereo imaging. On MSL this is only 20 cm. If anything, I would have been inclined to scale up to 40 or 50 cm, particularly on a larger vehicle. Curious as to what factors led to scaling this downwards rather than upwards (if it is indeed settled).
The MSL mast cameras include telephoto zoom (10X!) and focus capability. Whereas I really like the additional capability, I find I'm a bit concerned at the potential long term reliability, considering that MSL, like MER, may last for several martian years. I have dealt with a personal digital camera whose autofocus mechanism broke, and the same on Mars would be really irritating. Of course there're 2 cameras, so that helps. Safe to assume these will be tested to ridiculous extremes? There's mention of them using legacy actuators from MER.
Hi-def movies - considering how long it takes to get fixed images down currently, are we likely to see many of these? Not that I'm complaining or anything, quite the opposite. No Mars Telecommunications Orbiter
Have the flight cameras actually been constructed yet? Calibrated? Camera models generated - and if so, do they continue to use the CAHVOR model, and how will that cope with the zoom capability? [this latter may be a bit technical]
I see that the cams have a "Bayer Pattern Filter" ccd, which has red/green/blue filters overlaid on the ccd pixel sensors, as with typical personal digital cameras. Is this the only CCD, and if so are there any issues using it with the fixed wavelength filters?
Posted by: djellison Aug 9 2006, 07:48 PM
I was thinking of something along the lines of feeding forward for future missions
What would be the suggestions for someone designing cameras to fly on a future mission
What suggestions for operational protocol and commanding would you have
What ideas for outreach and press engagement would you suggest....
Phoenix and MSL camera's would fit into that general theme - so I'll see what I can do
Doug
Posted by: mcaplinger Aug 9 2006, 10:47 PM
You can ask Jim, but at this point I think I know more about the MSL cameras than he does.
Why, so your eyes would try to pop out of your head when you tried to fuse the stereo, like they do with the Viking cameras?
A 20 cm baseline was judged to be good enough for the near field. For the far field we will get stereo by moving the rover between frames, as no fixed baseline was large enough. And at any rate, I think the flight baseline will be a bit larger than 20 cm for reasons of the mast mechanical design.I'm concerned too, but those are the requirements the PI gave us. 3x mission life is the requirement, that's six years equivalent. And we are using slightly more robust materials than your digital camera.
No, of course not, not for a year or more. We'll use whatever camera model is appropriate. Zoomed in there is very little distortion; zoomed out there's a lot.
Yes, this is the only CCD. In some wavelengths (beyond 750 nm) the Bayer filter is essentially transparent anyway. In the visible wavelengths some of the pixels don't return usable signal levels and are discarded. If it were up to me I would leave the filter wheel off, but you can take that up with Jim.
Posted by: djellison Aug 9 2006, 11:01 PM
I was hoping you would pop in here MC
Doug
Posted by: algorimancer Aug 10 2006, 07:51 PM
Thanks for the detailed reply
Here's a related question for you: At least a decade ago there was a report in Science about a new CCD design in which each pixel could simultaneously detect multiple wavelengths, in fact my recollection of the paper was that each pixel could detect a pretty broad spectrum of colors. This was later commercialized by a company called Sigma, and they currently have a couple of cameras which use this type of sensor, called the SD10, and the sensor is called the "Foveon X3® direct image sensor".http://www.sigmaphoto.com/cameras/cameras_cameras_details.asp?id=3256&navigator=1
The obvious nice thing about this sensor is that you can at least triple your resolution per color channel for the same pixel count (and conceivably replace a whole stack of filters). When I first read the intial paper on this sensor my expectation was that it would be really useful for astronomy and spacecraft, but as far as I am aware it has never been used beyond the commercial market (though I understand it is highly regarded there). So, the obvious question is, are you aware of this type of sensor, does it have limitations which make it inappropriate for use as a rover camera, or is it simply a matter of too young a technology which has not been space-rated?
Posted by: mcaplinger Aug 10 2006, 08:22 PM
We have, of course, been tracking this technology since it was introduced (see http://www.foveon.com). There are two major issues: first, the company was not very forthcoming with samples of and details about the sensor in response to our inquiries initially (we haven't checked for several years, though; they initially were selling entire custom camera setups for studio use, not just the sensor) and the sensor isn't truly electronically shuttered (it's a CMOS rolling shutter design and is typically used with a mechanical shutter). Being CMOS, it is likely also susceptible to single-event latchup (CCDs aren't because they are NMOS). I don't know what the actual noise performance of these sensors is (all they appear willing to say is that they're "low noise"). And there really hasn't been a lot of commercial acceptance of this sensor technology yet; the Sigma SD9/10 is the only DSLR available that uses the sensor that I know of, and I've never seen one. For MSL, we believed that a CCD system was a better choice.
It's also not clear that you "triple" your resolution. A Bayer filter has two green and one each of red/blue for each 2x2 pixel group. With proper resampling, there is a fairly small impact on effective luminance resolution except for pathologically-color-patterned scenes. The MSL cameras will use good resampling and then compress in YUV space, so color artifacting should be pretty minimal for RGB color images. For narrowband color, we may take a resolution hit for some bands, but this mode is mostly only useful for fairly gross spatial characterization of color differences anyway.
Posted by: AlexBlackwell Aug 10 2006, 10:25 PM
Thanks for that link, Mike.
Posted by: helvick Aug 11 2006, 01:13 AM
I just love it when discussions here pass this far over my head. Sometimes I can converse and participate but more often I just have to think things like: These guys realy know their s**t and I should just remain thankful that I can just about follow the discussion.
What would (eventually) make my day is to have some one ask some techy question on the MSL cameras in October 2010 that has been preemptively answered in a thread like this.
Posted by: ElkGroveDan Aug 11 2006, 01:33 AM
But Joe many of us feel that way when you pull out your power charts and all that other "slide rule" stuff you do. And I'm sure there are people who are impressed that I can think up a wisecrack on nearly any topic being discussed.
Posted by: remcook Aug 11 2006, 10:00 AM
anything geology is over my head. as well as details on image processing really... (mmm..what am I doing here again?? ;-) ) One day someone should bring all the rovers work together in two big tomes with lots of pretty pictures and easy explanations... the updates from marsgeo look good, although I haven't had the patience to read them properly yet. anyway...enough rambling
Posted by: Bill Harris Aug 11 2006, 12:34 PM
Imaging technology has come a very long way within the last couple of years. It has matured a great deal for consumer products and has advanced over several orders of magnitude for technical applications.
We've come a long way since the Lunar Surveyor and the Mars Viking cameras. Attached is a link to an article on the http://history.nasa.gov/SP-425/contents.htm from the NASA archives.
--Bill
Posted by: algorimancer Aug 14 2006, 12:45 PM
Here's a quick question for Jim or anyone else who knows... when we see a series of pancam pics of the sun, followed by a regular series of pancam pics, while I assume that the pics of the sun are used to renormalize the rover orientation, is that renormalized orientation applied to the immediately following series of pancam images, or is the processing done on earth and sent back to Mars, so that the renormalized orientation applies to the NEXT series of images? Also, how accurate is the sun-based orientation (+/- degrees azimuth/elevation)?
Posted by: mcaplinger Aug 14 2006, 02:56 PM
I thought that most of the Sun images were being used only to estimate tau. I can't be sure from http://anserver1.eprsl.wustl.edu/anteam/mera/sis/Flight_School_coordinate_systems.ppt (page 13) if the processing is onboard or not, and I don't know the frequency with which they make these refinements. There has to be some onboard processing to provide coarse initial azimuth, but I'm not sure about fine adjustments.
There's a lot more information in http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/39648/1/05-0560.pdf but I haven't read through it yet.
Also see Eisenman, et al, "Sun sensing on the Mars exploration rovers", http://ieeexplore.ieee.org/xpl/abs_free.jsp?arNumber=1035391 if you have IEEE access.
Posted by: algorimancer Aug 14 2006, 03:59 PM
Thanks, those were exactly the references I was hoping to find. Trying to reconcile the site-to-site azimuth variation that I have encountered with the AlgorimancerPG utility.
(edit...)
After reading through the papers, it appears that the gist of it all (from my perspective) is that the rover orientations are calibrated to within 1.5 degrees, and recalibration is needed about every 20 Sols, quite possibly on the occasion of a major panorama acquisition. This is loosely in agreement with my own estimates based upon the apparent variation azimuth of the Twin Peaks (30-odd kilometers to the east) over some tens of Sols. Good to know. On the other hand, pancam orientation seems to be good to better than a tenth of a degree, but it is not clear to me what bearing this has on the rover orientation itelf, beyond assisting in its determination.
Posted by: Tesheiner Aug 24 2006, 08:06 AM
JB is in charge of Emily's blog this week, and posted this interesting article about their daily work on MER.
http://www.planetary.org/blog/article/00000679/
PS: Doug, if you find a better place for this post just move it there.
Posted by: remcook Aug 24 2006, 09:05 AM
it also gives some comments about the whole photography thing, the subtitle of his book. Jim Bell's blog entries have been quite good so far!
Posted by: djellison Aug 24 2006, 09:26 AM
My fav glogger to date - I must admit. But I'm loath to pass judgement on the 4 so far...because I'm ever aware that I'm only 5 weeks away.
Doug
Posted by: remcook Aug 24 2006, 10:08 AM
you'll do great, I'm sure. At least you've got a large fanbase :-)
Posted by: Pertinax Oct 12 2006, 02:22 PM
Another halo related question....
If I remember correctly, in the new software recently installed on the rovers recently there are improved provisions for auto cloud detection / imaging.
IF that is a fair statement, are there any plans to (or would it be difficult to) do any multispectral (L2,5,6 for ex) imaging of any clouds detected, particualry those within 05 to 50 degrees of the sun. Second and similarly, any possibility for high (temporal) resolution solar imagery when clouds are detected to be within say 05 degrees of the sun in order to learn more of the variable optical depth of the clouds? The first would further assist in halo element detection for H1, H2, and H4 type cirrus (http://www.srh.noaa.gov/jetstream/synoptic/h1.htm). The second would be nice just to better understand the observed clouds on mars.
-- Pertinax (the halo nut)
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