Kraken Mare through polarisers, Cassini looks for lake shine Options

[ngunn]

The latest 'looking ahead' gives a nice description of the pi-transfer, introducing the curious concept of a 'rev' that is only half a revolution. It also contains this sentence:

"With Kraken Mare near the field of view, scientists can also use this effort to see how using polarization filters affects the appearance of large bodies of liquid methane on Titan."

Titan followers here may remember why I'm excited about that.
http://www.unmannedspaceflight.com/uploads...78901_thumb.jpg

[ngunn]

Any news on this?

[ngunn]

Is it finally time for a third post in this thread?

If I'm not mistaken this image is one of a pair taken with polarisers at 0 and 90 degrees:

http://saturn.jpl.nasa.gov/multimedia/imag...3/W00059373.jpg

I suspect that Kraken Mare is marginally visible between 4 and 5 o'clock in this view. Now the question is: how are the filters oriented with respect to the picture frame? If they're horizontal and vertical that would put the lake at about 45 degrees to both.

If I'm way off with all this somebody please tell me quick!

[djellison]

If our duck-pond revelation in another thread is true - then a specular reflection is going to be TINY and thus probably unresolvable.

[ngunn]

I agree, probably, but we won't know for sure without giving it a proper try. I'm not saying either that this was that attempt. Kraken Mare (if seen at all) is way too close to the limb there. BTW Doug, can you answer the question about Cassini's polariser orientations w.r.t. picture frame?

It's just the first time I've noticed a pair of images taken with 90 degree polarisers that may include some wet stuff. Forgive me for getting a little excited.

[djellison]

Not a clue There will be a PDF somewhere - and it'll be huge, and on page 1874 - it'll tell you.

Whilst waiting for something else to render, I spat this out just to test the concept myself.

Attached thumbnail(s)

 

[remcook]

Page 3 here might be of use for the IRP90 and IRP0 filters (which are the ones that are used http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=200189 ):
http://pds-rings.seti.org/cassini/iss/COIS....8.2_wac_fm.pdf

edit: so I guess horizontal and vertical indeed.

[ngunn]

Now there's an interesting thing. The latest distant Titan shots include a set of three with polarisers at 0, 60 and120 degrees. This was probably atmospheric study (is that a cloud streak near the centre?) but Kraken Mare was in view just a couple of days ago, so I'm wondering - well you know what I'm wondering.

http://saturn.jpl.nasa.gov/multimedia/imag...0/N00155223.jpg

[ngunn]

The thread from the dead returns! Three more today: 0, 60 and 120, and I think that's Kraken Mare at lower left. I can't see any obvious differences (but a three way rotating blink would be nice if any image hand fancies the job).
http://saturn.jpl.nasa.gov/multimedia/imag...5/N00165578.jpg

[volcanopele]

Well, keep in mind that Kraken Mare is in the muck in these views, and that might limit any differences due to the use of different polarizers.

Good though to see the public image site get the real time stream, I wish we did too... I hope too that this isn't all we got from the Titan observation.

[titanicrivers]

Looks like some CL1 CB3 filtered images have arrived. Surface features are a bit clearer.

[ngunn]

Well, here we go again, and this time I think there may be a detectable effect. The images in question are N00172716 (P0 and CB2), N00172717 (P60 and CB2) and N001728 (P120 and CB2). It's my impression that the lake looks slightly darker, and hence more visible, in the P0 image than in the other two. Of course I have no idea whether the polarisation, if present, is happening at the lake suface or higher in the atmosphere.

Anyhow, I have a request which I hope will interest somebody with the necessary image processing skills. I would like to see ratio images with N00172716 and either, or each, of the other two.

[ngunn]

Another set of three using polarisers with the lake in frame today. Again differences are not immediately obvious but somebody might like to take a closer look and maybe make a blink comparison.

http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=256691
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=256690
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=256689