VIMS Specular Reflection and Kraken, spectacular T104 image Options

[Jason W Barnes]

Since tooting my own horn is apparently my primary role here, I call attention to a new VIMS composite image from T104 that we just released. Here's a version of the image:



This is awesome because we can see the entirety of Kraken in a single shot. The specular reflection is coming from just north of the islands west of the Throat of the Kraken that Ralph Lorenz discussed in his recent paper. You can also see in the noodle to the north the liquid channel connecting Kraken and Ligeia. The Romulan-Warbird-shaped orange thing to the right of the Kraken-Ligeia connection is a cloud over the northeast portion of Ligeia Mare.

[ngunn]

We're already discussing it! But I think a dedicated topic is definitely warranted so maybe the admins can move those posts out of the 'polarisers' thread and into this one?

Nick here. I put a link in your last post over there to move additional discussion about this image here.

[ngunn]

From the other thread: Spectacular, wonderful, so beautiful in the chosen colour scheme - and definitely shiny!! Words could never do it justice. What a journey we have been on in the few short years since Kraken Mare itself was first glimpsed.

EDIT: From the image caption -This particular sunglint was so bright as to saturate the detector of Cassini's Visual and Infrared Mapping Spectrometer (VIMS) instrument, which captures the view. . . . . Because it was so bright, this glint was visible through the haze at much lower wavelengths than before, down to 1.3 microns.

Reading this makes me wonder if the specular reflection of the sun is so bright that it allows Cassini VIMS to 'see' beyond the normal limits of the methane windows for Titan. A less restricted infrared spectrum could potentially yield a wealth of new information about the atmosphere and maybe the surface too, at least the wet bits.

[nprev]

Jason, congratulations to you & your team on this image. I'd call it iconic!

Question: You guys seem to be getting better & better at penetrating Titan's haze over time. Is anyone working on developing a surface imager optimized for Titan for possible application on a future mission? If so, what in your opinion might be the best achievable resolution from a reasonable altitude, say 1000 km above the surface?

[tanjent]

It's a beautiful image.
I have tried to orient it to the map found here:
http://www.bbc.com/news/science-environment-26622586
If I am wrong please correct me.

Actual clouds seem to be white if they do not catch the sun, or orange in the case of the War Bird feature.
The darker features all seem to be lakes, although initially I mistook some of them for clouds.

[ngunn]

Reading this makes me wonder if the specular reflection of the sun is so bright that it allows Cassini VIMS to 'see' beyond the normal limits of the methane windows for Titan.

Apologiies for posting that as a question. The answer is of course here: http://www.barnesos.net/publications/paper...ransmission.pdf

So it's a big 'Yes' and the only question is how much further the latest observation will extend the data below the 1.969 micron wavelength listed in that paper.

[Jason W Barnes]

The darker features all seem to be lakes, although initially I mistook some of them for clouds.

Here's my own annotated version that I guess JPL decided not to release with it. I post it here for your enjoyment It's pretty amazing that every little dim pixel that you see is basically a lake.

[ngunn]

Thanks for that, Jason. While you're here I was wondering if there's any chance of seeing by itself the single tile within the big mosaic that contains the specular reflection? The 'glint' is rather abruptly truncated by the high resolution strip in the published version. Also of interest would be to see the exact specular point located on the SAR map. If the surface is really smooth my rough calculations arrive at a solar reflection only 1km across. Is that about right?

One more question - The mosaic has a hard circular outline but VIMS must have captured the atmosphere around the limb as well. Why is that not shown?

[Jason W Barnes]

Thanks for that, Jason. While you're here I was wondering if there's any chance of seeing by itself the single tile within the big mosaic that contains the specular reflection? The 'glint' is rather abruptly truncated by the high resolution strip in the published version. Also of interest would be to see the exact specular point located on the SAR map. If the surface is really smooth my rough calculations arrive at a solar reflection only 1km across. Is that about right?

Sure; once the data are public. The specuar relfection is coming from north of the islands west of the Throat of the Kraken. Previous specular reflections had solar footprints maybe ~1km in size, so I would expect similar for this one.

One more question - The mosaic has a hard circular outline but VIMS must have captured the atmosphere around the limb as well. Why is that not shown?

Right. Well, each of these VIMS cubes was acquired from a different spacecraft position. In fact, due to the way that VIMS works -- it actually has just one pixel that it shifts around to build up an image -- each PIXEL gets acquired with different geometry. Hence while I call it a 'mosaic', what it really is is each individual cube, mapped onto a cylindrical map, and then that map mosaic gets projected orthographically to get the final result. Hence there's no way to properly map atmosphere, so it the resulting image has that hard edge.

- VIMS-J

We're already discussing it! But I think a dedicated topic is definitely warranted so maybe the admins can move those posts out of the 'polarisers' thread and into this one?

Whoops -- sorry about jumping the existing thread. I had looked at that one, but I must not have gone down to the bottom of page 2. My bad. . .