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Posted by: peter59 Oct 6 2007, 07:17 PM

T13 - Targeted Distant Look (Huygens Landing site)

Posted by: Juramike Oct 6 2007, 07:20 PM

I took Ugordan's enhanced image of the T36 ISS mosaic he created and attempted to line it up with the easternmost part of the T8 Swath.

A few distinguishing features (pretty colored shapeds) were identified in both images and these were used to line up the two images. Next pretty purple orientation lines were added that can be used to help correlate features seen in both images:

Enjoy!

-Mike

Posted by: Juramike Oct 6 2007, 07:50 PM

Wow, talk about exciting!

Thanks, peter59! I lined this up with the T36 ISS mosaic made by Ugordan and the T8 RADAR Swath:

-Mike

Posted by: Juramike Oct 7 2007, 06:09 AM

With the availability of the T39 ISS mosaics and the T13 distant flyby strips, I attempted to correlate all these with the T8 Swath and the DISR image from Huygens.

I used the sightline from the two distinctive bright islands to the north as well as the eroded crater wall E of the Huygens landing site, then put everything to about the same scale. (These are indicated by the yellow arrows). The purple lines help correlate features across the images.







The DISR image should be the equivalent of the red box/orange circle in each of the images.

(It still seems that the T8 Swath gives about the best resolution of idetifiable features, but the T13 distant flyby really nails the location of the dune field and channel to the north of "Huygens island".)

-Mike

Posted by: ngunn Oct 7 2007, 07:02 PM

Thank goodness someone's at last had a go at this. Did you do anything to the ISS raws (like stacking) to improve the detail? The bright island familiar from the Huygens DISR images does finally seem recognisable. Very nice work Mike, thanks for sharing it.

Posted by: Juramike Oct 8 2007, 05:02 AM

I matched up the Huygens landing site DISR mosaic PIA06438 with the T8 RADAR Swath zoomed to the same scale. In the second graphic I've indicated the "spooky dude" formation in light blue. These pixels are almost resolvable in the RADAR as slightly lighter pixels compared to immediate neighbors. The darker portion of the channel seen in the DISR mosaic is also apparent in the T8 RADAR swath zoom area. (The "spooky dude" formation is just south of a RADAR stitch zone).

I've created a colorized terrain map of the Huygens landing site based primarily on the DISR mosaic, but also including the T8 RADAR data, as well building on the information presented in Soderblom's recent article (Soderblom et al. Planetary and Space Science (2007), doi:10.1016/j.pss.2007.04.015 "Topography and geomorphology of the Huygens landing site on Titan.")


In the tectonic ridge (bright island) terrain, yellow is for the upper ridge portion identified by both DISR topology model and RADAR bright ridgetops in the T8 Swath and T13 distant view. The eroded ridge terrain mantle deposits (RADAR bright gray) are left uncolored (thus gray) in the graphic..

For the channel terrain, lighter shades of blue are for the brightest (DISR) upper channel deposits (such as the spooky dude formation) while darker shades of blue and purple are for the DISR dark and RADAR dark smooth ice muds. There is a much larger range of DISR shading than represented by these five colors. This would be a really fun place to try contrast enhancement to bring out all the subtleties.

The lightest blue terrain could correspond to low density nanoporous clathrate cobbles (cryopumice) that has been floated into drifts during flood events. These could be the identity of the cobbles that we saw in the final Huygens images on the surface.

Another possibility is that the light blue terrains could be the extension of the tectonic ridge across the channel, and that this portion of the ridge has been breached, carved, and heavily eroded during flooding and tidal events through the channel. (An argument against these being original ridge sections is that these have been breached crossways at a later point during weaker flows – that indicates these are easily carved materials. These are seen in closeup images of the spooky dude formation close to the touchdown area)

On the southeastern shore of the channel, there is another little island-section of bright tectonic ridge (the island to the SE of the Huygens landing site), as evidenced by RADAR bright terrain in the T8 Swath.

The mantle of the SE Island that extends into the channel (indicated in the diagram by orange semi-transparent shading) looks similar by RADAR to that of the NW island, but by DISR the terrain looks very different. By DISR, the mantle doesn't have any obvious channels - it looks like a confusing mess of visible bright and visible dark terrain. Although these images are not well-resolved, there appear to be a series of pits among the bright dark patterns. Is it possible that this is some of the "rotted terrain" like was described in post http://www.unmannedspaceflight.com/index.php?s=&showtopic=4177&view=findpost&p=100295, Equatorial Sand Seas thread?


Overall, I think this is a pretty cool example of the information and possible interpretations you can extract by combining low-altitude visual (DISR) and orbital RADAR information. And it allows a good characterization of "channel" terrain on Titan.

-Mike

Posted by: ngunn Oct 8 2007, 10:56 AM

I think there's a case for a new thread where all the various imagery of the Huygens area can be collated and discussed together - DISR, RADAR, ISS and VIMS. Recent posts by yourself and others from various threads would make more sense together. It's a bit late to start afresh from now, but if the admins agree maybe one of them would be kind enough to do some retroactive weaving.

Posted by: Stefan Oct 8 2007, 12:11 PM

I had a go at it too, but cannot show that here. We at the MPS have prepared a paper about the Huygens landing site, to appear in P&SS in the (distant?) near future. It is certainly interesting to read Mike's thoughts and interpretations, thanks for that.

Stefan.

Posted by: ngunn Oct 8 2007, 12:21 PM

Excellent! I'm sure there are quite a few of us here who are dying to read that paper. Hope it doesn't cost $30.

Posted by: rlorenz Oct 8 2007, 03:20 PM

There is a paper still in the works at Icarus (peer review is sooooooo slooooww..) by Lunine et al
making the DISR / T8 landing site comparison; doesnt include the T13/T8 comparison, though.

I showed T8/T13 at DPS a year ago IIRC - not much to say, the place overall looks the same
apart from maybe one little patch. Of course, the lower spatial resolution for T13 makes a bit
of a difference, as does the number of looks. Surprisingly, despite the different ranges of the
observations, the incidence angles were almost the same.

I'd support the suggestion of a separate thread

Ralph

Posted by: djellison Oct 8 2007, 03:58 PM

Stuff

Posted by: ngunn Oct 8 2007, 09:02 PM

Ah, there we are now, thanks Doug.

A project for Mike or someone - somewhere out there is the map-projected version of the Huygens high altitude mosaic, the one that extends out to the two dark dunes to the north of the landing site. I would love to see that accurately overlain on the latest ISS from T36 (a blink comparison perhaps?) I wonder how many features could be clearly identified in both?

Posted by: Juramike Oct 9 2007, 02:44 AM

Here is the Huygens altitude mosaic (overlain on the T8 RADAR Swath - PIA06437) in same-size oriented comparison with the T36 mosaic from Ugordan, the T36 enhanced mosaic from Alexton, the T8 Swath zoom (the backgrouond for PIA06437), and the T13 distant targeted look.

Separately:






And all together for a side-by-side comparison (the "spooky dude formation" is indicated in blue for comparison):




It is really, really hard to pick out any fine details from the ISS mosaics shown, although Huygens Island's brightest pixel pattern in the ISS images looks very similar to that of the T8 RADAR brightest pixels.

-Mike

Posted by: ngunn Oct 9 2007, 08:35 AM

SUPERB, Mike. Having you around makes me very lazy.

Posted by: ngunn Oct 16 2007, 02:48 PM

Crop from the new Titan map. On enlargement the Huygens Island shows up nicely (but annoyingly close to the corner of an overlapped image).

Posted by: ngunn Oct 20 2007, 02:14 PM

Here are the papers specific to the landing site:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6T-4NKJ0HT-3&_user=10&_coverDate=11%2F30%2F2007&_rdoc=14&_fmt=full&_orig=browse&_srch=doc-info(%23toc%235823%232007%23999449986%23671066%23FLA%23display%23Volume)&_cdi=5823&_sort=d&_docanchor=&_ct=14&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=efc7ff22aab789a5aa3aff944ee73b7a#


http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6T-4NKJ0HT-6&_user=10&_coverDate=11%2F30%2F2007&_rdoc=13&_fmt=full&_orig=browse&_srch=doc-info(%23toc%235823%232007%23999449986%23671066%23FLA%23display%23Volume)&_cdi=5823&_sort=d&_docanchor=&_ct=14&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=42afc0039ccf363175d3be7f58169f33

Thanks for the posting the links to the full publications Bjorn, and a BIG thanks to the publishers for making these issues freely available.

Posted by: scalbers Oct 20 2007, 04:01 PM

This looks like a good thread to reiterate that the PSS Soderblom et al paper (pages 2025-2036) discusses how the correlation of bright and dark areas between the VIMS and SAR views varies near the Huygens landing site. Markings are much better correlated just east of the landing site compared with the western portion of the region.

Posted by: ngunn Oct 22 2007, 09:35 AM

Very roughly the picture seems to be:
Dunes - dark in both.
Highlands (or rather 'roughlands', not always high as Emily has pointed out) light in both.
Duneless plains give poor correlation - mainly dark in RADAR, but either light or dark in VIMS.

Does anybody know why this study specifically excludes the ISS imagery?

Some parts of the interpretation, for example the idea that the highlands are only VIMS bright because of a thin mantling of bright organics, strike me as informed guesses rather than definitive fact. I have difficulty picturing mantled hills dissected by cleaned valley floors rather than the reverse.

Posted by: Juramike Oct 22 2007, 02:09 PM

ISS and RADAR are giving two seperate pieces of information:

ISS dark = low reflectance materials through methane windows
ISS bright = high reflectance materials through methane windows

RADAR dark = smooth surfaces
RADAR bright = rough surfaces (or porous at RADAR scale)


So one possible interpretation could be:

ISS:
- Light for highlands (in Equatorial Sand Seas) and highlands and plains (in farther temperate and polar regions)
- Dark for Equatorial Sand Sea basins (and putative cryovolcanic airfall zones)

RADAR:
- Darkest for smooth areas [Lakes and Seas]
- Dark for Equatorial Sand Sea basins and dune areas (and putative cryovolcanic airfall zones)
- Darkish for smoother muddy areas
- Gray for plains or eroded mantles
- Bright for rough ridges or porous materials [ridgelines, bright eroding streambeds, "rotten terrain"]

The Equatorial Sand Seas have the highest ISS contrast possibly because this area is not subjected to as much organic material depostion from rainout. To really provide evidence that ISS dark = below last flood level and ISS bright = above last flood level in the Equatorial Sand Seas will require a detailed correlation of ISS vs. RADAR altimetry for an area over a Sand Sea basin. I believe this was done for Adiri during one of this summers passes (although the results have not been published).

-Mike

Posted by: ngunn Nov 7 2007, 10:31 AM

More high res imaging of the landing site area to come on the next flyby (according to the REV 52 'Looking Ahead' now up on Ciclops).

Posted by: jekbradbury Jun 1 2008, 08:53 PM

I took Mike's side-by-side comparison of the four images and overlayed the three complete ones as RGB. Cool, but I don't think it has a practical use.