Mercury mosaics from January 2008 Flyby Options

[volcanopele]

The raw data from MESSENGER's January 14, 2008 flyby of the planet Mercury are now online on NASA Planetary Data Service's website:

http://pds-imaging.jpl.nasa.gov/data/messe...grmds_1001_new/

As such, I am proud to present a series of mosaics I have created using these raw images. These use the mosaic designs shown on the MESSENGER project's Mercury Flyby 1 Visualization Tool webpage. These mosaics were created in either Photoshop CS3 (using the Photomerge tool) or PTGui Pro (particularly for the two MASSIVE mosaics).

Keep in mind that these mosaics are quite large in most cases, and it may be better just to right-click and save them to your hard drive to view them separately, rather than viewing them in your browser.

[volcanopele]

Global Mosaic - January 14, 2008



http://pirlwww.lpl.arizona.edu/~perry/Mess...bal_mosaic1.png - PNG, 8145x9305, 24.0 MB
http://pirlwww.lpl.arizona.edu/~perry/Mess...bal_mosaic1.jpg - JPEG, 8145x9305, 6.2 MB

This global mosaic of Mercury consists of 87 MDIS Narrow-angle Camera images acquired during the MESSENGER spacecraft's January 14, 2008 flyby of Mercury. These images were acquired when MESSENGER was between 17,484 and 20,790 km from Mercury or between 53 and 63 minutes after closest approach. This mosaic has a resolution of 550 m/pixel. This mosaic uses calibrated MDIS images and the brightness was adjusted to improve the visibility of surface features. The features seen in this mosaic cover a significant portion of the terrain not seen by Mariner 10 during its three flybys in the 1970s.

[volcanopele]

Northern Hemisphere Mosaic



http://pirlwww.lpl.arizona.edu/~perry/Nort...here_mosaic.png - PNG, 10548x8558, 35.1 MB
http://pirlwww.lpl.arizona.edu/~perry/Nort...here_mosaic.jpg - JPEG, 10548x8558, 9.35 MB

This regional mosaic showcasing Mercury's northern hemisphere consists of 96 MDIS Narrow-angle Camera images acquired during the MESSENGER spacecraft's January 14, 2008 flyby of Mercury. These images were acquired when MESSENGER was between 8,148 and 11,516 km from Mercury or between 27.5 and 37 minutes after closest approach. This mosaic has a resolution of 309 m/pixel. This mosaic uses calibrated MDIS images and the brightness was adjusted to improve the visibility of surface features. The features seen in this mosaic cover a significant portion of the terrain not seen by Mariner 10 during its three flybys in the 1970s including a number of features that have been recently named. The Caloris impact, the largest and most recent large impact basin on Mercury, is visible as a circular brightish region along the eastern portion of the mosaic. Another large (and relatively young) impact basin, Raditladi, can be seen to the west of Caloris basin. Both basin are unique because they are host to Mercury's only known extensional tectonic features, represented by concentric and radial grabens (troughs). One such extensional feature, Pantheon Fossae, is a prominent feature in the central part of Caloris basin and consists of a radial pattern of cracks.

[volcanopele]

High Resolution Equatorial Mosaic



http://pirlwww.lpl.arizona.edu/~perry/Hire...rged_levels.jpg - JPEG, 15402x3664, 7.26 MB

This regional mosaic showcasing Mercury's equatorial region consists of 68 MDIS Narrow-angle Camera images acquired during the MESSENGER spacecraft's January 14, 2008 flyby of Mercury. These images were acquired when MESSENGER was between 4,110 and 6,322 km from Mercury or between 16 and 22.5 minutes after closest approach. This mosaic has a resolution of 125 m/pixel. This mosaic uses uncalibrated MDIS images and the brightness was adjusted to improve the visibility of surface features. This is MESSENGER's highest resolution mosaic acquired during the January 2008 flyby. This mosaic is centered on 4.5 South Latitude, 128 East Longitude.

Reason for edit: Mosaic uses uncalibrated images

[volcanopele]

Inbound Crescent Mosaic



http://pirlwww.lpl.arizona.edu/~perry/1st_...ound_mosaic.png - PNG, 4122x7563, 9.22 MB

This global mosaic of Mercury's crescent consists of 29 MDIS Narrow-angle Camera images acquired during the MESSENGER spacecraft's January 14, 2008 flyby of Mercury. These images were acquired when MESSENGER was between 19,189 and 17,853 km from Mercury or between 58 and 54 minutes before closest approach. This mosaic has a resolution of 513 m/pixel. This mosaic uses uncalibrated MDIS images and the brightness was adjusted to improve the visibility of surface features. This is MESSENGER's highest resolution mosaic acquired during the January 2008 flyby. The features seen in this mosaic were observed by Mariner 10 in the 1970s, but the high-phase angle allows scientists better study the topographic structures in this region.

Reason for edit: mosaic uses uncalibrated images

[volcanopele]

Regional Mosaics
-------

Raditladi impact basin and ejecta blanket



http://pirlwww.lpl.arizona.edu/~perry/Raditladi_Hires.png - PNG, 3306x3341, 5.36 MB

Eminescu and Xiao Zhao impact craters



http://pirlwww.lpl.arizona.edu/~perry/Emin...osaic_hires.png - PNG, 4872x2936, 7.36 MB

Central Portion of Caloris basin



http://pirlwww.lpl.arizona.edu/~perry/Calo...Basin_Hires.png - PNG, 3912x2744, 4.89 MB

These mosaics consist of portions of the Northern Hemisphere mosaic and spotlight several of the interesting features in that region, including Raditladi (a relatively young, double-ring impact crater), Eminescu, Xiao Zhao, and the central portion of Caloris impact basin.

[ugordan]

The raw data from MESSENGER's January 14, 2008 flyby of the planet Mercury are now online on NASA Planetary Data Service's website:

http://pds-imaging.jpl.nasa.gov/data/messe...grmds_1001_new/

Ahh, so that's where you got the data from. Looks like the new release includes all the old data as well, too. Plus, it looks as the flatfields have finally been corrected, judging by their file sizes, although I'll have to check this.

What software did you use for calibration?

I can't wait to be back on my primary computer and have a hack at the color data and see how far off I was with previous fudged "natural" color attempts.

[volcanopele]

I used ISIS3 for calibration.

I'm going to try the color global mosaic next, not sure how that will look. But people can feel free to post their own products based on the MESSENGER raw images here. There are plenty of anaglyph opportunities certainly.

[ugordan]

Yay, the flatfields finally work correctly:

No dust rings to be seen even after substantial enhancement.


A couple of familiar Mercury shots now in approx. natural color using calibrated E,D,C filters:



Compare the outbound frame with my fudged version of the official false color mosaic here. It helps to know the planet has a pretty flat spectral curve, doesn't it? I believe both versions use the same set of frames, but different filters. For some reason they magnified their image 2x.
There's WAC color data for a higher resolution mosaic than that, but it will probably require map reprojection to work out.

[remcook]

Great work!

[jasedm]

You two should have your own show.
Outstanding.

[ugordan]

There are several wide angle color frames of a similar region taken from varying vantage points and distances. I assembled them into an animated gif showing a sort of a fly-over from the nearest frame (shown above in the middle, but non-magnified this time) to the final global outbound color frame (at right above) for context. The amount of overlap is small so the region is pretty small, furthermore the first several frames are binned additionally lowering resolution.

The feature I centered the frames on is slightly to the left of center in the first couple of frames. It's a bit hard to track it in the more distant frames as the scale changes rapidly but you can catch it after a couple of repeats. North is to the left.

Click image to play gif (1.2 meg):


The final global image is deliberately slightly overexposed at the top to make the region of interest brighter.

[elakdawalla]

Yay, the flatfields finally work correctly:

Hi Gordan, just to make sure I understand correctly: the flatfields are stored in a separate directory from the images, right? They are not applied to the raw image data? So you apply the flat fields as part of a calibration step before you compose your color images?

Nice work, I can't wait to see more

--Emily

[ugordan]

Emily: Correct, the flatfields are in the calibration dir: http://pds-imaging.jpl.nasa.gov/data/messe..._1001_new/CALIB and are ordinary FITS files. The above was just an example Venus image through the violet filter to show no mottling/dust rings are visible.

The data is completely raw, like the Cassini EDR IMG files are. I apply the calibration procedure outlined in CALINFO.TXT in the same directory. One thing I noticed is some Mercury images have residual dark current after calibration. I'm not sure if it's actual dark current or maybe stray light or whether it's an error in my code. It shows up in volcanopele's crescent mosaic as well; as variation in background color near the limb so maybe it's a systemic issue. If it's stray light, it looks filter dependant. Could be the instrument isn't completely characterized yet.

[volcanopele]

could be because the crescent mosaic uses uncalibrated images... forgot to change the caption.

[ugordan]

Approach wide-angle movie:



54 binned RGB sets total, from 2008-01-14 00:05:01 UTC (400 000 km range) to 2008-01-14 17:43:52 UTC (29 500 km range).

[ugordan]

Sigh.

(no, this ain't yet another one of my postage-stamp sized composites)

Just when I was finally able to do all calibration steps, a calibrated data volume (!) appears at the PDS, containing both the radiometrically calibrated and I/F calibrated data. The old directory VP posted in the first post was renamed to http://pds-imaging.jpl.nasa.gov/data/messe...s_1001_new_old/. There's also one more dir: http://pds-imaging.jpl.nasa.gov/data/messenger/msgrmds_1001/, which I suspect is the same as the former one.

Calibrated data, people. Dig in!

[volcanopele]

meh, ISIS3 worked just fine for me. Though I guess it helps that Mercury isn't as bland as Venus, so some of calibration issues you mentioned don't show up in the MESSENGER images.

[elakdawalla]

Calibrated data, people. Dig in!

Yummy. Now I'm glad I didn't find the time to play with this data set before! I'm updating my Cassini pages first, then I'll get back to this...

--Emily

[ugordan]

meh, ISIS3 worked just fine for me. Though I guess it helps that Mercury isn't as bland as Venus, so some of calibration issues you mentioned don't show up in the MESSENGER images.

I meant to ask this earlier: if you have access to ISIS, how come you didn't geometrically reproject the mosaics? I'd die (not literally, though) for a piece of software that can do that, I don't have the knowledge or will to be reinventing the wheel and writing my own reprojection software.

BTW, those were actually Mercury wide-angle departure frames, not Venus where I noticed calibration 'issues'. I'll be sure to check the calibrated products to see if the same thing's present there.

[volcanopele]

Mainly because I'm lazy Seriously, it takes a lot longer to geometrically correct these images than it is to let a program do all the transforms automatically. With Cassini, I get paid to spend the time to geometrically correct the images, so I'm a lot more willing to spend that extra time...

It also helps that ISIS doesn't have the info on the Mercury flyby geometry and I am not as familiar with ISIS3 to know how to fix that. I could do that with ISIS2 if that version supported MESSENGER.

[volcanopele]

I might be persuaded to give the WAC color mosaic a try, but I can't promise anything.

[Bjorn Jonsson]

Sigh.

(no, this ain't yet another one of my postage-stamp sized composites)

Just when I was finally able to do all calibration steps, a calibrated data volume (!) appears at the PDS, containing both the radiometrically calibrated and I/F calibrated data. The old directory VP posted in the first post was renamed to http://pds-imaging.jpl.nasa.gov/data/messe...s_1001_new_old/. There's also one more dir: http://pds-imaging.jpl.nasa.gov/data/messenger/msgrmds_1001/, which I suspect is the same as the former one.

Calibrated data, people. Dig in!

Looks like I really should check out UMSF more often than I do . Having spent some time figuring out that http://pds-imaging.jpl.nasa.gov/data/messenger/msgrmds_2001/ is the volume I want (reason: it's calibrated data) I see I could have saved some time by reading this thread earlier .

Back to downloading.

Now if only there was such a thing as calibrated Cassini volumes...

I meant to ask this earlier: if you have access to ISIS, how come you didn't geometrically reproject the mosaics? I'd die (not literally, though) for a piece of software that can do that, I don't have the knowledge or will to be reinventing the wheel and writing my own reprojection software.

My software can do this and in retrospect this was a fairly easy feature to add - in general, considerably easier than e.g. the the Galileo and Cassini calibration stuff (but very different of course). Maybe I should clean it up a bit and release it...

[elakdawalla]

Hi Bjorn, if you're looking for encouragement, I'll speak up to say "Yes, please!"

--Emily

[volcanopele]

The only problem is, I don't trust built-in geometry one iota. I guess if the images are high res enough, it doesn't matter, but with global to regional scale mosaics, it can be a problem.

[ugordan]

Bjorn, sign me up as an interested party as well! As far as I'm concerned, it doesn't even have to be 'cleaned-up', I'm used to rudimentary interfaces when dealing with my own software anyway.

[djellison]

Some words on img2png and the MDIS imagery would be good- - which tags we should be using for calibrated results.

D

[ugordan]

A 5000x5000 color mosaic made from the NAC departure mosaic #4 (30-odd frames) and colorized using the WAC global color view. Non-gamma corrected so the contrast and colors are enhanced.


Click image for full resolution view (9 megabytes).

[nprev]

....good grief, that's just stunning. I could spend hours looking at this. Thanks for the gift, G, sincerely.

[ilbasso]

Wow, that's almost as big as the planet itself! Incredible detail. You can even see the rim in profile of a crater on the limb at 4:00. The detail at the terminator is mesmerizing.

[tedstryk]

I LOVE this version! Not to mention the fact that for Mercury, the dynamic range issues that crop up with gamma correction are huge, given the intense solar illumination.

[ugordan]

Thanks, all. It'd be even better if it was properly geometrically reprojected. Oh well...

Ted, gamma correction has nothing to do with the amount of illumination - you simply darken the image/change the exposure. It has to do with the amount of contrast and how the physical brightness is mapped to the nonlinear video device. A corect gamma actually ensures proper DN - brightness mapping, it's not black magic of some kind. The problem is the sRGB colorspace nowadays assumes 2.2 gamma function, which digital cameras, video cameras etc. will automatically output. Spacecraft data, when calibrated, is linear so a difference arises if you simply shove the calibrated intensities into RGB values.

I'm sure you're perfectly aware of this, but for others - take a look at the following image (click):


The image on the left is a digital camera image of the Moon, which approximates what human eye sees. The image on the right is a calibrated Cassini WAC image, no gamma correction - the same as Mercury here. The middle image is the Cassini image with 2.2 gamma. Note gamma doesn't overexpose the data, I brightened the middle image to match the left one better. Both the left and middle images nicely show the Moon as it appears, while the image on the right does not.

The advantage you're probably thinking here of no gamma correction is that Mercury has lower albedo variations than the Moon does, so it would wash out details. Then again, that's how the planet actually looks like. Something like this, for better or worse.

[tedstryk]

I understand the concept. The problem is that the range from the darkest black to the brightest white is huge, especially when compared to places such as the Saturnian system. A computer monitor can't come anywhere close to portraying such a range. In fact, it is only at the Uranian system that one could truly show the full range on a monitor. The problem is that even on the best monitor, the darkest dark is nowhere near true black, and the brightest white is relatively dark compared to daylight outdoors. As a result, A lot of the detail that the eye could discern were it viewing the real planet is lost. I find the whole issue to be a lot like trying to make a flat map of a round world. No method is truly "accurate" - each have their advantages and disadvantages.

The problem in that example is that in both gamma-corrected images, the whites are murdered, especially in the Cassini one. Looking through a telescope, that wouldn't happen.

[stevesliva]

Interesting. I had been thinking that high dynamic range composites were mostly to make up for low dynamic range cameras, but a little more googling around makes it clear that it's also a compromise to the low dynamic range of computer monitors. Sounds like and HDR algorithm could take the corrected and uncorrected images and composite them into something approximating what you say you could see through a telescope. (Or is it better to try "tone mapping" the original data into an image suitable for display on a monitor?) I don't necessarily follow all of the details and terms, but the discussion here does remind me of the reasons HDR got popular (fadish?).

[ugordan]

The point of a gamma function is not to convey the entire dynamic range of what is probably a huge starting dynamic range in the first place. Your analogy with the Uranian system makes it seem that gamma correction doesn't have any place here on Earth, as you say a monitor can't cope with the huge dynamic range of our world down here. Yet it doesn't prevent anyone from watching TV here or using digital cameras on Earth and having reasonably good colors and contrast, albeit not as bright as the real thing.

Even if gamma destroys whites (and it's not exactly true, it's those white levels being close in brightness in the first place, also the Cassini image was overexposed by me accidentally), I can come up with a counterargumet that no gamma correction destroys darks - check out the terminator region in the rightmost image, it's gone. Either way - you lose detail somewhere, the question is which one is preferred.

Shoving linear data onto a computer screen has many advantages and don't get me wrong, I actually use very little to no gamma manipulation in my composites of most Saturnian system moons because they're bland as hell, but every once and again I like seeing the amount of contrast and color saturation an object would actually have in real life. Yes, the eye can make out a surprising amount of detail even in such cases especially on closer scrutiny, but having an accurate display on a screen is one step closer to what reality looks (at first glance at least, before your eye adapts to lower contrast of the real thing) than an inaccurate display.

Of all the solar system bodies, Mercury, Earth, the Moon and Mars are the places where I'd want to see gamma corrected imagery in addition to the usual processings just so I can visualize what they'd look like through a scope or simply naked eye. In case of Mercury, up until now all I saw were Mariner composites with very saturated brown colors yet observers said it just has a touch of a soft coppery hue.

[tedstryk]

The problem effects images of things on earth as well. That is why it is hard to show shadows without wiping out bright areas or vice versa. The best way around it is a nonlinear curve that is selectively set up to show details in both areas.

My point with this whole issue is to say that gamma correction isn't necissarily the same thing as showing what the eye would see, if that is one's goal (personally, I love looking at images with color shifting from infrared, which tends to bring out a lot of interesting things).

[elakdawalla]

A bunch of posts on viewing Mercury from Earth split into a topic on "Seeing Mercury."

--Emily

[Bjorn Jonsson]

Some words on img2png and the MDIS imagery would be good- - which tags we should be using for calibrated results.

I just finished a new version of IMG2PNG that can properly read the calibrated Messenger image files. However, it can't calibrate the raw images (the mdis volume) even though it reads them - I didn't see any need for this since calibrated images are available (the msgrmds_2001 volume).

The new version is available here. Further information on IMG2PNG is available here.

The only problem is, I don't trust built-in geometry one iota. I guess if the images are high res enough, it doesn't matter, but with global to regional scale mosaics, it can be a problem.

I assume you are referring to the viewing geometry information that's usually present in the IMG, LBL or index files. Yes, this is an extremely annoying problem. I'm making DEMs of all of Saturn's icy satellites and about 90% of the time the pointing information isn't accurate enough so I need to 'reverse engineer' it. In contrast, the spacecraft's location seems accurate. It's also frustrating that for any spacecraft, as far as I know updated pointing information usually isn't made available if/when it is determined. Remarkably, the pointing information for the Galileo images was usually pretty accurate though.

So my software for reprojecting images wouldn't be useful unless potential users were willing to reverse engineer the viewing geometry themselves when the results look bad (this might turn into something useful - exchanging updated pointing info...).

[volcanopele]

If, and that's a BIG if, I decide to try to mosaic these MESSENGER images using ISIS, I would have no problem sharing the pointing info I derive.

[ugordan]

If by deriving pointing info you mean limb-fitting and stuff like that, the idea I thought would be nice to implement would be to do this visually. An application would take a list of images and their corresponding spacecraft location (assuming that bit is pretty much precise) relative to the planet, project the initial geometry onto the planet spheroid and would then let you tweak the mosaic footprints by shifting and/or rotating. And allow you to do that in a graphical user interface. This would obviously be feasible for small mosaics, not likely to be useful for 80-odd footprints.

Yeah, I'll be able to implement something like that when hell freezes over...

[scalbers]

Does anyone happen to know the distance of Messenger from Mercury when these hi-res mosaics were made? What I'm getting at would be the "equivalent" distance of the projection used in making the mosaics, if this is something like the average distance of the range stated in VP's post. This would be nice to check on as I'm testing this mosaic now in my map.

Also, are we seeing all the way to the limb in this projection?

Thanks

Steve

[ugordan]

Which mosaic are you talking about, Steve? I know the global color mosaic I did uses the NAC mosaic #4, the last outbound mosaic. It was overlaid onto the last WAC global color shot and so it effectively mimics that viewpoint apart from the extreme limb to the right. There's some severely distorted terrain there which was not visible in the earlier wide-angle so it couldn't fit the global image. As a result I'd say on average something up to 100-200 pixels on the right limb can't be trusted. The south and north poles should be about right, but with a bit of distortion as well. The center portion of the disc ought to fit reasonably well.

[scalbers]

Hi Gordan. Yes I'm referring both to the one you did in post #28 and VP's in post #2. I can see this is a bit interesting and tricky if the hi-res black and white mosaic is taken from a farther distance and can see a larger portion of terrain near the limb compared with the WAC global color shot.

As an initial experiment I ran your #28 image in the map assuming it was at the same distance as the WAC shot. This appears to be close, though maybe slightly off in that I should maybe adjust the assumed distance (closer to the distance of the NAC frames) to account for some additional terrain showing up near the limb.

I also tweaked things so I used the color information over most of your image except just black & white near the terminator where the hue in the shadows may drift a bit. Overall the results even at this stage may be good enough for me to soon post.

Perhaps it might be better if I use VP's mosaic for the B&W info near the limb (if it has more coverage near the limb) and then overlay yours to show the region interior to that that has color?

Steve

[ugordan]

Perhaps it might be better if I use VP's mosaic for the B&W info near the limb (if it has more coverage near the limb) and then overlay yours to show the region interior to that that has color?

VP can chime on this, when I compared his huge mosaic to the WAC frame it showed some distortion (a kind of narrowing and "shearing" the disc) towards the bottom that might have come up if if was automatically stitched with frames taken during a prolonged period of time. MESSENGER was really hauling the mail after C/A and even a couple of minutes was enough to considerably change the viewing geometry. This was precisely the reason I used an actual WAC frame as base for NAC footprints as compromise to minimize distortions.

His mosaic is of sufficiently high resolution that maybe fitting the pieces section by section into your map might work better than attempting to fit the whole mosaic at once?

[scalbers]

I'll have to consider this a bit. Off-hand I'm basically looking for some short cuts to try and get some high-res color imagery into the map without too much distortion. Even the current attempt appears to have done that. It would take me a while to get all the 87 individual images from VPs mosaic (post #2) into the map. This would be somewhat easier though if I had the precise pointing info discussed a few posts back. The MESSENGER visualization tool has some partial info I see.

I can easily try VPs mosaic #2 in the map to see how the limb reprojects itself compared with your mosaic to get a further feel for what you have described. I could also break up VP's mosaic into larger sections if that is what you were getting at. On the other hand the NAC #4 mosaic that you used would show more terrain near the limb as it is taken from a farther distance. Given that it has "just" 25 or so images it would be easier to consider the individual frames as well.


Steve

[scalbers]

My software can do this and in retrospect this was a fairly easy feature to add - in general, considerably easier than e.g. the the Galileo and Cassini calibration stuff (but very different of course). Maybe I should clean it up a bit and release it...

Hi - I've also mentioned the IDL/GDL option in this updated thread that can theoretically work for this:

http://www.unmannedspaceflight.com/index.p...mp;#entry121476

...and as of 7/31/2008 I've posted the latest experiment with Gordan's mosaic. Perhaps this will do until I can work with the individual images or a navigated mosaic.

http://laps.noaa.gov/albers/sos/sos.html#MERCURY

Steve

[peter59]

New.
Flyby Visualization Tools.
Mercury flyby 1, Planned and Actual Images.

[scalbers]

Nice feature with the imagery that looks like an extension of the ongoing flyby animation tool.

It's good that it has things like the image center lat/lon as well as image number and range. I'd also be interested to find out some other details like the spacecraft sub-point lat/lon. A link to a full-sized version of the image would be really nice if that could be implemented. That's all I ask

[elakdawalla]

You don't ask much

I do plan to do my usual treatment on these images but I am still working on the latest Cassini release -- I'm a bit behind.

--Emily