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

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).

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!

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).

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.

Look at the vertically-exaggerated image posted here.

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

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!

Jim Bell.....same question?

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

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.

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?

Seconded...

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?

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

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

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?

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

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.

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

Doug:

Here's a question: will they take suggestions for rock (etc) names?

Bob Shaw

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 whatonmars.com, but no longer available for free]

TTT

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

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?

Could we also please have a Jeffrey L. Bell Q and A??

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.

"MastCam also provides both natural color still and high definition video"

This one got done, as did the one regarding aging

Doug

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.

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

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

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

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.

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.

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.

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

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.

You have till 1700UT today for new questions - I'm doing another session with Jim later

Doug

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...

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

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...

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.

img2png



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.

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

You could just invite Jim Bell to join the arrival sol at Victoria lottery.

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

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

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

But some of them are rebuilt from an original that was compressed, right? like the 1bpp, 4bpp etc images?

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