IPB

Welcome Guest ( Log In | Register )

40 Pages V  « < 31 32 33 34 35 > »   
Reply to this topicStart new topic
Mercury Flyby 1
ugordan
post Jan 30 2008, 08:06 PM
Post #481


Senior Member
****

Group: Members
Posts: 3631
Joined: 1-October 05
From: Croatia
Member No.: 523



QUOTE (mps @ Jan 30 2008, 08:41 PM) *
I'd like to see the REAL true colors of Mercury.

I've made a two-segment linear approximation (with a knee at blue-green wavelength) of the released Mercury spectra, ran it through some CIE XYZ code and this is the (non-gamma-corrected) resulting color:



I took the "green" channel from that color release which approximates red in real color and "blue" which approximates blue (contrast-wise, the channels were equalized in brightness in the official release), created a synthetic green and adjusted the levels by the above result. This is what it ought to appear to human eyes:



This is not gamma-correct, rather a simple lowering of saturation to mimic the 2.2 gamma saturation, while at the same time preserving contrast of features. Gamma-correct look (assuming the team did no contrast manipulations already) can be found here. Very soft colors, reminiscent of some Moon shots, but with a touch more saturation to it. An interesting comparison of the display-correct version to an image of the Moon from Apollo 10: http://www.hq.nasa.gov/office/pao/History/...0-35-5249HR.jpg
If you think the albedo features in the gamma-correct version are too bland, consider the Moon. Take away the maria and you're left with very subtle contrasts as well.

"Natural" color indeed can look less than impressive, but we should be aware how the planets look nevertheless. I get nauseous when I see an orange-red Venus painted with Magellan data. That's pretty much every time it's depicted anywhere, be it a poster, a textbook, a certain JPL site...


--------------------
Go to the top of the page
 
+Quote Post
MarcF
post Jan 30 2008, 08:21 PM
Post #482


Member
***

Group: Members
Posts: 221
Joined: 16-May 06
From: Geneva, Switzerland
Member No.: 773



The "spider" in the center of Caloris reminds me the one found in the center of Mannann'an crater on Europa:
http://photojournal.jpl.nasa.gov/jpegMod/PIA01406_modest.jpg

Was also considered as something never seen before.

Of course, the scale is not the same, the surface material is quite different, but who knows, may be the formation processes are similar.

Marc.
Go to the top of the page
 
+Quote Post
mps
post Jan 30 2008, 09:34 PM
Post #483


Member
***

Group: Members
Posts: 118
Joined: 18-November 07
Member No.: 3964



Thanks, ugordan.

I know that true colors images are often less spectacular than false color images, but I always prefer natural colors.
Just like to know, how would it look like trough my own eyes smile.gif
Go to the top of the page
 
+Quote Post
ngunn
post Jan 30 2008, 09:47 PM
Post #484


Senior Member
****

Group: Members
Posts: 3492
Joined: 4-November 05
From: North Wales
Member No.: 542



QUOTE (mps @ Jan 30 2008, 09:34 PM) *
Thanks, ugordan.


I'd like to echo that, much appreciated - especially since I can't access any of the NASA stuff from home. Until I get to work tomorrow I'm dependent on the ripples produced here by the data release.
Go to the top of the page
 
+Quote Post
Bill Harris
post Jan 30 2008, 11:12 PM
Post #485


Senior Member
****

Group: Members
Posts: 2621
Joined: 30-October 04
Member No.: 105



Either there is a stitching artifact running across the middle of Prockter06.jpg or we've got some sort of strike-slip fault...

--Bill


--------------------
Go to the top of the page
 
+Quote Post
DrShank
post Jan 31 2008, 02:44 AM
Post #486


Member
***

Group: Members
Posts: 207
Joined: 6-March 07
From: houston, texas
Member No.: 1828



looks very much like a standard image offset, not a strike-slip. Im sure people will be looking for them.

here is an stretched version of the color mosaic. all sorts of different colors pop out. looks like 3 to 4 basic units,
including caloris fill, volcanic and impact plains and young crater units. should make interesting mapping . . .

paul

Attached thumbnail(s)
Attached Image
 


--------------------
Go to the top of the page
 
+Quote Post
edstrick
post Jan 31 2008, 06:54 AM
Post #487


Senior Member
****

Group: Members
Posts: 1870
Joined: 20-February 05
Member No.: 174



Attached Image
I ran ratio enhancements of the Proctor7 image and then applied the colors back onto two versions of the bandpass enhanced average of the 3 bands. Here are the results. Caution and warning: There appear to be discrete boundaries in the cratered plains, for example southwest of caloris near the image center. I think these are digitization levels in the color channels of the JPG and not real geologic features.

The "enh-3" image shows the most color and terrain/albedo detail in a balanced fashion.
The "enh-bw-2" image shows the enhanced average of the 3 bands
The "enh-2" image has stronger colors overlaid on the "enh-bw-2" version.

Note various craters and other non-crater features, some in Caloris, some elswhere, that show a distinctive orange-yellow color: south Caloris rim vicinity, a crater N of Caloris, the center only of a crater south of the image center, scraps of terrain WSW of Tolstoj. Some dark albedo features near frame center and crater rims in the south mid latitudes are dark and blue <all colors relative>. The double-ring basin halfway beteween Caloris and the terminator have distinctive light-blue colors in the ring of peaks, as does the large crater to it's SSW with a sharply defined ring of central peaks. There seem to be a LOT of craters with central peaks totally different in color from the rest of the crater: floor, walls, ejecta and surroundings.

Plains filling craters and basins and inter-crater-plains tend to be somewhat higher albedo than adjacent non-plains and somewhat redder: yellowish, tanish, compared with surroundings. It's clear that we're dealing with volcanic fills, rather than impact melt sheets -- the Caloris ejecta is remarkably non-distinctive -- but none or essentially none of them appear to be dark like lunar basalts.


Attached thumbnail(s)
Attached Image
Attached Image
 
Go to the top of the page
 
+Quote Post
JRehling
post Jan 31 2008, 08:01 AM
Post #488


Senior Member
****

Group: Members
Posts: 2224
Joined: 20-April 05
Member No.: 321



[...]
Go to the top of the page
 
+Quote Post
ugordan
post Jan 31 2008, 08:27 AM
Post #489


Senior Member
****

Group: Members
Posts: 3631
Joined: 1-October 05
From: Croatia
Member No.: 523



QUOTE (JRehling @ Jan 31 2008, 09:01 AM) *
Something in the normalization of the raw data could also be at work.

Residual bias in the CCDs can easily be the culprit, such as incomplete removal of dark current (say due to different camera parameters or different lookup tables used). Another reason might be flatfield effects near the left side of the detector.

The levels of excessive saturation applied seen here will bring out even the tiniest filter-to-filter differences.


--------------------
Go to the top of the page
 
+Quote Post
Bill Harris
post Jan 31 2008, 09:11 AM
Post #490


Senior Member
****

Group: Members
Posts: 2621
Joined: 30-October 04
Member No.: 105



Good work, edstrick. This does highlight important compositional differences in the surface (and subsurface, counting the excavations).

A good reference to the nearest "terrestrial analog" (our Moon) is at Steve Alber's website. Warning: it seems that the data file is corrupted at the site, I can only get some 3mB of te 4.8 mB file and can't view the southern 1/3 of the image.

http://laps.noaa.gov/albers/sos/moon/moon_...olor_brim16.jpg

--Bill


--------------------
Go to the top of the page
 
+Quote Post
Gladstoner
post Jan 31 2008, 09:16 AM
Post #491


Member
***

Group: Members
Posts: 687
Joined: 3-January 08
Member No.: 3995



.
Go to the top of the page
 
+Quote Post
edstrick
post Jan 31 2008, 09:27 AM
Post #492


Senior Member
****

Group: Members
Posts: 1870
Joined: 20-February 05
Member No.: 174



They're relatively blue as are the central peaks of the peak-ring, the DARK splotches outside of them are intensely blue. <wavelength-relative> as is the dark area between the peaks. The rest of the crater floor and walls and surroundings are utterly nondescript other than a yellowish tinge to the walls, rim and close-in ejecta.

There are scattered things like this in the Mariner data.... oddities, more seen at high sun than at low sun so relief is uncertain, generally not well seen...
It's been hard to do more with them than scratch dandruff at them.

The dark and blue might be high-titania...... but.. ?basalt?.. nothing dark like basalt seems to be widespread.

Note: These images had to be degraded to get them online here. More jpg artifacts than in the original enhancements.
Attached thumbnail(s)
Attached Image

 
Go to the top of the page
 
+Quote Post
Bill Harris
post Jan 31 2008, 09:27 AM
Post #493


Senior Member
****

Group: Members
Posts: 2621
Joined: 30-October 04
Member No.: 105



>The white splotches

The almost look like alluvial fans. I wonder if the uplifted rock unit of the central peak is not of a composition that weathers to a light-toned deposit?

--Bill


--------------------
Go to the top of the page
 
+Quote Post
edstrick
post Jan 31 2008, 09:36 AM
Post #494


Senior Member
****

Group: Members
Posts: 1870
Joined: 20-February 05
Member No.: 174



I'm going to add two more enhancements, both black and white: the enhanced red and the enhanced blue component of the "enh-2" color version.
The "Super-Red" image largely suppresses low contrast ejecta splatters and turns the brightest, bluest of them black, vastly reducing ejecta interference with underlying terrain differences. the "Super-Blue" image, conversely, nearly eliminates widespread, reginonal albedo and color variations between units, rendering any lighter and bluer ejects with Tycho-Ejecta like-new effect.
Attached thumbnail(s)
Attached Image
Attached Image
 
Go to the top of the page
 
+Quote Post
edstrick
post Jan 31 2008, 09:42 AM
Post #495


Senior Member
****

Group: Members
Posts: 1870
Joined: 20-February 05
Member No.: 174



"I wonder if the Hapke function varies for different wavelengths. The amounts of excess green near the terminator and yellow near the limb seem suspicious. Something in the normalization of the raw data could also be at work"

Yes, and the distinct UV to IR upward slope in the spectrum is the sort of thing that brings out weak photometric color effects, but I doubt that's significant here. As commented above, tiny errors in image calibration can wreck havoc with really strong enhancements like these. 1/2 DN <digital number> can wash your color differences with a color cast near the terminator. I had a horrible red cast near the terminator in the approach image color enhancement I posted a few days ago. There turned out to be 3 DN of scattered light near the terminator on the dark side in the "red" channel, less than 1 in the "blue" channel. Subtracting appropriate zero-level offsets vastly improved the result though it was not perfect.

For quick-and-dirty calibration, i'm NOT complaining. This promises high quality results from carefully calibrated and non-jpg degraded 11 channel data to come.
Go to the top of the page
 
+Quote Post

40 Pages V  « < 31 32 33 34 35 > » 
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 31st March 2020 - 02:02 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.