IPB

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
T82 Flyby (February 19, 2012 / Rev 161), CIRS checks if springtime is in the air
Juramike
post Feb 15 2012, 04:50 PM
Post #1


Senior Member
****

Group: Moderator
Posts: 2711
Joined: 10-November 06
From: Pasadena, CA
Member No.: 1345



T82 Flyby page: http://saturn.jpl.nasa.gov/files/20120219_...y_quicklook.pdf

CICLOPS Rev 161 Looking ahead article: http://www.ciclops.org/view/7080/Rev161?js=1


--------------------
Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
Go to the top of the page
 
+Quote Post
Juramike
post Feb 15 2012, 05:02 PM
Post #2


Senior Member
****

Group: Moderator
Posts: 2711
Joined: 10-November 06
From: Pasadena, CA
Member No.: 1345



Why is CIRS data so interesting?

It can be used to determine upper atmospheric temperatures. Once you have the temperature profile, it can be used as the background and the teeny specific IR absorptions of the different molecule components can be teased out. Then you can see where the atmospheric components are located, their relative concentrations, and how they change with time.

Here is a cool summary of some earlier CIRS data and how it was used to infer atmospheric circulation (or barrier to circulation): http://solarsystem.nasa.gov/scitech/displa...amp;FIELDNAMES=

Note how cyanoacetylene (NC-CC-H) concentration spans over 2 orders of magnitude at the same altitude. (Figure 3 middle plot on right).

Titan is sophisticated.



--------------------
Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
Go to the top of the page
 
+Quote Post
remcook
post Feb 16 2012, 08:25 AM
Post #3


Rover Driver
****

Group: Members
Posts: 1001
Joined: 4-March 04
Member No.: 47



Actually, the different lines of the different gases are not so teeny: they form the entire signal! smile.gif I tried to find a non-pay picture of a CIRS spectrum and on this page there is a simulation of a 'limb' obervation:
http://www.markelowitz.com/titan.htm
CIRS measures the thermal radiation coming off Titan as a function of wavelength. The molecular signals are caused by the fact that different molecules absorb and emit only at very specific wavelengths. The difference in thermal flux for different wavelengths is basically a result of the difference in altitude (and corresponding temperature at those altitudes) at which the thermal radiation originates. At wavelengths of high absorption, the radiation comes from higher in the atmosphere (for non-limb observations). For optically thin limb observations (you can look straight through the atmosphere at space at the horizon) higher absorption by the gases means more radiation is emitted.
In both cases you first need to know the temperature of the atmosphere as a function of altitude before you can derive the amounts of gases present, because the thermal emission is dependent both on the temperature and the amount of absorption by the gases.
Here's an example of looking for seasonal variations: http://adsabs.harvard.edu/abs/2011epsc.conf...20T
Go to the top of the page
 
+Quote Post
Juramike
post Feb 17 2012, 01:56 PM
Post #4


Senior Member
****

Group: Moderator
Posts: 2711
Joined: 10-November 06
From: Pasadena, CA
Member No.: 1345



RGB composite of Titan created from Cassini raw images (Feb 16, 2012):

Attached Image


--------------------
Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
Go to the top of the page
 
+Quote Post
titanicrivers
post Feb 19 2012, 06:08 PM
Post #5


Member
***

Group: Members
Posts: 554
Joined: 1-April 08
From: Minnesota !
Member No.: 4081



QUOTE (Juramike @ Feb 17 2012, 07:56 AM) *
RGB composite of Titan created from Cassini raw images (Feb 16, 2012):

Very nice Mike! A question: are your RGB channels each at 100% when they are combined for the final picture. I am using Emily's scheme for photoshop elements http://www.planetary.org/explore/topics/im...al_rgb_pse.html and coming up with a white-ish final color for Titan (not the detached haze though) unless I decrease the BL1 (blue) filter image contribution to 75-80% or so and that seems too arbitrary. Any suggestions?
Go to the top of the page
 
+Quote Post
ugordan
post Feb 19 2012, 07:17 PM
Post #6


Senior Member
****

Group: Members
Posts: 3562
Joined: 1-October 05
From: Croatia
Member No.: 523



QUOTE (titanicrivers @ Feb 19 2012, 07:08 PM) *
that seems too arbitrary.

The automatic contrast stretch on the raw jpegs posted on the web scales the brightest feature in each filter to maximum brightness. That means anything you do won't be any more "arbitrary" than trying to guess the original (non-stretched) relative filter brightnesses. It's a matter of using known, calibrated images as a color reference for the raw images, there's not a single recipe for raw images. For Titan (when it's alone in the frame) that means you have to significantly darken the blue filter as well as the green filter to a lesser extent.


--------------------
Go to the top of the page
 
+Quote Post
Juramike
post Feb 19 2012, 08:13 PM
Post #7


Senior Member
****

Group: Moderator
Posts: 2711
Joined: 10-November 06
From: Pasadena, CA
Member No.: 1345



As a starting point, I use Photoshop curves and allow the maximum point of the red channel to be at 100% (230).
I drop the maximum point of green to be about 210, and blue to be about 180.
(Actually, I think it was Gordan who gave me these suggested values a few years ago...)

Then I drop the midpoint of the curve for each channel: usually blue is the most, green a little, and red just a touch, then basically just fiddle with things until it "looks" about right.
It's pretty subjective.


--------------------
Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
Go to the top of the page
 
+Quote Post
ugordan
post Feb 20 2012, 10:46 PM
Post #8


Senior Member
****

Group: Members
Posts: 3562
Joined: 1-October 05
From: Croatia
Member No.: 523



Outbound WAC RGB shot:

Attached Image


--------------------
Go to the top of the page
 
+Quote Post
ngunn
post Feb 20 2012, 11:05 PM
Post #9


Senior Member
****

Group: Members
Posts: 3113
Joined: 4-November 05
From: North Wales
Member No.: 542



Great stuff Gordan (the rings one too). Keep posting. smile.gif

Here's a raw image for the benefit of atmosphere fans who don't routinely check the Cassini site http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=252519
Go to the top of the page
 
+Quote Post
Adam Hurcewicz
post Feb 21 2012, 10:57 AM
Post #10


Junior Member
**

Group: Members
Posts: 61
Joined: 29-January 10
From: Poland
Member No.: 5205



Hi, my version of Titan (19 Feb. 2012)

Attached Image


--------------------
Adam Hurcewicz from Poland
Go to the top of the page
 
+Quote Post
titanicrivers
post Feb 22 2012, 09:10 AM
Post #11


Member
***

Group: Members
Posts: 554
Joined: 1-April 08
From: Minnesota !
Member No.: 4081



Nice rendering Adam! (color looks a little off, see Mike and Ugordon's comments above)
Here's a view of Yalaing Terra from the wide angle camera taken Feb 19th from 44K km. Yalaing is highlighted (basically more contrasted using the levels adjustment in Photoshop) in the left panel. On the right are narrow angle camera images from about 1M km with a bit lower resolution. Upper right is pre arrow storm and lower right is the Dec 20 2010 PDS version post arrow storm. Current appearance still differs from those older images especially in area indicated (white arrow).
Attached Image
Go to the top of the page
 
+Quote Post
titanicrivers
post Mar 4 2012, 10:53 PM
Post #12


Member
***

Group: Members
Posts: 554
Joined: 1-April 08
From: Minnesota !
Member No.: 4081



Menrva and Fensal are visible in this CL1 CB3 image from 2/29/2012 during Rev 161. The background color image is from the Solar System Simulator. http://space.jpl.nasa.gov/
Attached Image
Go to the top of the page
 
+Quote Post

Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 1st September 2014 - 06:39 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is a project of the Planetary Society and is funded by donations from visitors and members. Help keep this forum up and running by contributing here.