IPB

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
[Enceladus] What am I looking at?, Weird distortion here!
EDG
post Nov 28 2010, 05:45 AM
Post #1


Junior Member
**

Group: Members
Posts: 74
Joined: 9-October 10
From: Victoria, BC
Member No.: 5483



http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=216998



What's going on here? The limb of Enceladus looks like it's all melted like wax! smile.gif

I'm going to hazard a guess at some kind of really strange image saturation from an over-bright Saturn maybe? If so, I've not seen that look so 'curvy' before.

The next image in the sequence is also strange: http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=216997
Go to the top of the page
 
+Quote Post
tasp
post Nov 28 2010, 05:56 AM
Post #2


Member
***

Group: Members
Posts: 903
Joined: 30-January 05
Member No.: 162



I wonder if spacecraft motion combined with image sensor saturation might be a fuller explanation.

We get through the holiday weekend, I'm sure we'll get the real explanation when the appropriate folks check back in here.

Go to the top of the page
 
+Quote Post
volcanopele
post Nov 28 2010, 07:34 AM
Post #3


Senior Member
****

Group: Moderator
Posts: 3225
Joined: 11-February 04
From: Tucson, AZ
Member No.: 23



Two possible explanations: Either "That's no moon..."™ or it is as you said, over exposure from Saturn.


--------------------
&@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io
Go to the top of the page
 
+Quote Post
ZLD
post Nov 28 2010, 07:36 AM
Post #4


Member
***

Group: Members
Posts: 555
Joined: 27-September 10
Member No.: 5458



This looks like image bleed to me. The description tells us that both color wheels are set to clear so this is a straight black and white, with all recordable colors contributing. The affected regions in both photos appears to be roughly the same region along the edge of Saturn and is likely the most intense region in both photos, causing bleeding into the edges of Enceladus. Dropping the gamma and trying a few other tricks turns up little around the edges. Seems to be a case of overexposure.

After looking at some of the other photos taken on that date, it seems like the camera was possibly in need of a calibration as well.


--------------------
Go to the top of the page
 
+Quote Post
ugordan
post Nov 28 2010, 12:21 PM
Post #5


Senior Member
****

Group: Members
Posts: 3648
Joined: 1-October 05
From: Croatia
Member No.: 523



It wasn't in need of calibration. The exposure was deliberately set for Enceladus high phase imaging.


--------------------
Go to the top of the page
 
+Quote Post
dilo
post Nov 28 2010, 02:32 PM
Post #6


Senior Member
****

Group: Members
Posts: 2492
Joined: 15-January 05
From: center Italy
Member No.: 150



Very simple explaination, indeed: CCD images suffer of smear in the direction of charge transfer when pixels are close to saturation. In this case, charge shift is vertical and saturation occurs on the brightest part of the Saturn limb...



--------------------
I always think before posting! - Marco -
Go to the top of the page
 
+Quote Post
EDG
post Nov 28 2010, 06:51 PM
Post #7


Junior Member
**

Group: Members
Posts: 74
Joined: 9-October 10
From: Victoria, BC
Member No.: 5483



OK, I suspected as much. I just thought it looked very odd!

What about this one?
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=228082 (If you do a search for Enceladus on the Raw Images page, this is on page 3)

You can barely see Enceladus in the middle of the image, but the rest has all these splotches on it - I'm just wondering if those are just normal dust blotches, or if Cassini had flown through a plume or something shortly before the image was taken?
Go to the top of the page
 
+Quote Post
volcanopele
post Nov 28 2010, 07:10 PM
Post #8


Senior Member
****

Group: Moderator
Posts: 3225
Joined: 11-February 04
From: Tucson, AZ
Member No.: 23



Yep, those are the WAC equivalent of dust donuts. We can remove those via flatfielding when we calibrate this data.


--------------------
&@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io
Go to the top of the page
 
+Quote Post
dilo
post Nov 28 2010, 07:11 PM
Post #9


Senior Member
****

Group: Members
Posts: 2492
Joined: 15-January 05
From: center Italy
Member No.: 150



You're right, EDG... you see diffraction images from dust grains on the optics, revealed from diffuse light of sun entering in the optical system... you can barely see also Enceladus jets and contribution from diffuse E-ring light (the night side of Enceladus appear slightly darker than background). Hard to say if dust amount increased from first images, however I see another feature (lens reflection near the center) which I never noticed before! ph34r.gif


--------------------
I always think before posting! - Marco -
Go to the top of the page
 
+Quote Post
ugordan
post Nov 28 2010, 09:19 PM
Post #10


Senior Member
****

Group: Members
Posts: 3648
Joined: 1-October 05
From: Croatia
Member No.: 523



QUOTE (volcanopele @ Nov 28 2010, 08:10 PM) *
Yep, those are the WAC equivalent of dust donuts. We can remove those via flatfielding when we calibrate this data.

Flatfield or subtract out? These are apparently due to scattered light in the optics so they represent additional unwanted light hitting the detector. Doesn't look like something you can just divide out like your normal dustring flatfield variations.


--------------------
Go to the top of the page
 
+Quote Post
EDG
post Nov 28 2010, 09:45 PM
Post #11


Junior Member
**

Group: Members
Posts: 74
Joined: 9-October 10
From: Victoria, BC
Member No.: 5483



I'm just surprised at how much dust is on the lens (and how good the pictures are that are taken through it despite that!)!
Go to the top of the page
 
+Quote Post
nprev
post Nov 28 2010, 10:16 PM
Post #12


Merciless Robot
****

Group: Admin
Posts: 8783
Joined: 8-December 05
From: Los Angeles
Member No.: 602



That poses an interesting question, actually. VP, have you guys noticed any changes in the lens contaminants over time (locations, sizes, quantities, etc.?) Doubt that anyone's tracking that, of course, and such changes undoubtedly have occurred for a variety of reasons...but it's a fascinating thought that there just might be a particle or two of Enceladian material on there. wink.gif


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
TheAnt
post Jul 29 2014, 02:34 PM
Post #13


Member
***

Group: Members
Posts: 495
Joined: 12-February 12
Member No.: 6336



More on the tiger stripe geysers.
Go to the top of the page
 
+Quote Post

Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 19th March 2024 - 06:52 AM
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 funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.