IPB

Welcome Guest ( Log In | Register )

5 Pages V  < 1 2 3 4 5 >  
Reply to this topicStart new topic
Mimas Flyby, August 2, 2005
tedstryk
post Aug 3 2005, 03:40 PM
Post #31


Interplanetary Dumpster Diver
****

Group: Moderator
Posts: 4383
Joined: 17-February 04
From: Powell, TN
Member No.: 33



I think a major factor too is that when it comes to the saturnian satellites, we are used to looking at underexposed, tiny views that have been greatly stretched and enlarged. The enlargement, plus attempts to reduce noise, made the worlds look smoother than they really are.

This brings to mind a memory. When I was growing up, I enjoyed following the Voyager Neptune encounter. Also, our local library had NASA's Voyages to Saturn and Voyages to Jupiter. Both in the case of the Neptune images, as well as the Jupiter and Saturn images, approach sequences were shown using images enlarged to be the same size...so as the spacecraft approached, the image got sharper rather than larger. I am embarrassed to recall the hours I spent trying to figure out why these worlds looked blurry from far away rather than smaller. I have done similar processing to my Enceladus approach sequence to demonstrate. The above row is a sequence of color images taken as Voyager-2 approached (unfortunately, since various color combinations had to be used, it isn't very even). The lower row shows the same sequence, but resampled to be about the same size. It creates a strange appearance of snapping in to focus. While it is useful for comparison - you can really see Enceladus rotating better than when the different sizes are shown, it looks artifically smooth in the early images.



Also, previews are up!
Mimas Previews


--------------------
Go to the top of the page
 
+Quote Post
gndonald
post Aug 3 2005, 04:32 PM
Post #32


Member
***

Group: Members
Posts: 212
Joined: 19-July 05
Member No.: 442



QUOTE (volcanopele @ Aug 3 2005, 11:05 PM)
the sharp craters could be expected given this a fairly low gravity world, though some craters do show some signs of degradation.  I'm pretty sure, given the ancient age of the surface, that there isn't present day activity.  At least I would be VERY shocked to see any.  Maybe a landslide or two, but not cryovolcanism.
*


I'd agree on the cryovulcanism, but the images have bought up some interesting detail on Herschel (see here), firstly, the 'right' rim of the crater appears to be higher than the left rim and there is also what looks like a landslide in the same region.

The central peak is elongated 'north-south' (where north is the top of the picture) and appears to be flat-topped, there's also what looks like a fresh impact just above the central peak.

I have'nt looked through all the raw images yet, but Cassini does not seem to have imaged the area directly opposite Herschel where the greatest seismic effects would have been felt.
Go to the top of the page
 
+Quote Post
dilo
post Aug 3 2005, 07:38 PM
Post #33


Senior Member
****

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



QUOTE (tedstryk @ Aug 3 2005, 02:50 PM)
Some great work, dilo and malgar.  Dilo, I have a question about your Cassini color images.  How do you compensate for stretching?
*


Yes, in all images I needed to carefully compensate shift between different filters pictures and sometimes I need also to rescale (or even rotate) two of the 3 images in order to match to third one in the best way... however, sometime result still not perfect due to parallax effects (motion of spacecraft+satellite rotation) sad.gif
It's a patient work, and time is never enough to make all I would like to do! mad.gif
Bye, Marco.


--------------------
I always think before posting! - Marco -
Go to the top of the page
 
+Quote Post
Bill Harris
post Aug 3 2005, 08:34 PM
Post #34


Senior Member
****

Group: Members
Posts: 2620
Joined: 30-October 04
Member No.: 105



(Post#32)
QUOTE
I'd agree on the cryovulcanism, but the images have bought up some interesting detail on Herschel (see here),
http://tinyurl.com/a96qf


And notice that the interior of Herschel is hummocky, much like the landslide surface noted in the above post. Is it rebound phenomenon, cryovolcanism, or what? We'll know more once we get a closer view of this crater.

--Bill


--------------------
Go to the top of the page
 
+Quote Post
alan
post Aug 3 2005, 09:36 PM
Post #35


Senior Member
****

Group: Members
Posts: 1829
Joined: 20-November 04
From: Iowa
Member No.: 110



new batch is up smile.gif
http://saturn.jpl.nasa.gov/multimedia/imag...3/N00037712.jpg
Go to the top of the page
 
+Quote Post
tedstryk
post Aug 3 2005, 09:36 PM
Post #36


Interplanetary Dumpster Diver
****

Group: Moderator
Posts: 4383
Joined: 17-February 04
From: Powell, TN
Member No.: 33



http://saturn.jpl.nasa.gov/multimedia/imag...3/N00037665.jpg

How cool is Tethys!

http://saturn.jpl.nasa.gov/multimedia/imag...3/N00037693.jpg

Mimas near closest approach!


--------------------
Go to the top of the page
 
+Quote Post
alan
post Aug 3 2005, 09:42 PM
Post #37


Senior Member
****

Group: Members
Posts: 1829
Joined: 20-November 04
From: Iowa
Member No.: 110



Rings in the background
http://saturn.jpl.nasa.gov/multimedia/imag...3/N00037682.jpg
Go to the top of the page
 
+Quote Post
tedstryk
post Aug 3 2005, 09:59 PM
Post #38


Interplanetary Dumpster Diver
****

Group: Moderator
Posts: 4383
Joined: 17-February 04
From: Powell, TN
Member No.: 33



Beautiful! Thanks for finding that.

I have put together a global view near closest approach. There are some problems from spacecraft motion, but there is also some other distortion - I can't get it to look round. Perhaps Cassini was just too fast...this might require reprojecting. But this is the best I could do in 10 minutes. rolleyes.gif



I added another one - this one is a bit better...but there is still distortion.


--------------------
Go to the top of the page
 
+Quote Post
dilo
post Aug 3 2005, 10:18 PM
Post #39


Senior Member
****

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



QUOTE (tedstryk @ Aug 3 2005, 09:36 PM)


Cannot resist! tongue.gif


--------------------
I always think before posting! - Marco -
Go to the top of the page
 
+Quote Post
Guest_Sunspot_*
post Aug 3 2005, 10:42 PM
Post #40





Guests






QUOTE (tedstryk @ Aug 3 2005, 10:59 PM)
Beautiful!  Thanks for finding that.

I have put together a global view near closest approach.  There are some problems from spacecraft motion, but there is also some other distortion - I can't get it to look round. 


Mimas isnt round to start with, so it might not be distortion due to the motion of Cassini. great image by the way.
Go to the top of the page
 
+Quote Post
scalbers
post Aug 3 2005, 10:55 PM
Post #41


Senior Member
****

Group: Members
Posts: 1254
Joined: 5-March 05
From: Boulder, CO
Member No.: 184



Mimas is a tri-axial ellipsoid - like Enceladus but significantly more out of round. I'm still guessing a bit at the numbers, I had seen some published values of 418x392x382km. Curiously, in doing some limb fitting in the course of making my map, I seem to get a better limb fit by assuming numbers like 398x392x382km. I'll have to see if this holds up when adding in the images from the current flyby.

That's part of the mystery with regards to tidal heating. Why should Mimas have less apparent tidal heating compared with Enceladus, even though it is more out of round with a more elliptical orbit? I've seen a recent paper on-line by J. Wisdom suggesting a spin-orbit resonance in the case of Enceladus.


--------------------
Go to the top of the page
 
+Quote Post
malgar
post Aug 3 2005, 11:39 PM
Post #42


Junior Member
**

Group: Members
Posts: 61
Joined: 5-June 05
From: 46.283N 11.433E :))
Member No.: 401



Another DTM extrapolation with 3D rendering and an anaglyph of one big crater captured from lastest images of Mimas. rolleyes.gif


Attached Image



Attached Image
Go to the top of the page
 
+Quote Post
volcanopele
post Aug 3 2005, 11:45 PM
Post #43


Senior Member
****

Group: Moderator
Posts: 2963
Joined: 11-February 04
From: Tucson, AZ
Member No.: 23



QUOTE (malgar @ Aug 3 2005, 04:39 PM)
Another DTM extrapolation with 3D rendering and an anaglyph of one big crater captured from lastest images of Mimas.  rolleyes.gif


Attached Image



Attached Image

*

Are these using photoclinometry or are you creating stereo from multiple images?


--------------------
&@^^!% 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
malgar
post Aug 3 2005, 11:56 PM
Post #44


Junior Member
**

Group: Members
Posts: 61
Joined: 5-June 05
From: 46.283N 11.433E :))
Member No.: 401



QUOTE (volcanopele @ Aug 4 2005, 01:45 AM)
Are these using photoclinometry or are you creating stereo from multiple images?
*


photoclinometry! just one input image.
Anaglyph is created from DTM.
Go to the top of the page
 
+Quote Post
Bjorn Jonsson
post Aug 4 2005, 01:05 AM
Post #45


IMG to PNG GOD
****

Group: Moderator
Posts: 1881
Joined: 19-February 04
From: Near fire and ice
Member No.: 38



I'm attaching two images rendered from a quick-and-dirty DTM I did of one of Mimas' craters. They look rather ugly, a major problem is the horizontal stripes in the DTM. They are especially prominent in the second rendering where the illumination is very different from the illumination in the source image. This something which is not nearly as prominent in malgar's DTMs for some reason. Despite this I seem to be using a similar algorithm so I'm not sure why this is.
Attached thumbnail(s)
Attached Image
Attached Image
 
Go to the top of the page
 
+Quote Post

5 Pages V  < 1 2 3 4 5 >
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 26th June 2017 - 08:57 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 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.