Reprocessing Historical Images, Looking for REALLY big challenges? |
Reprocessing Historical Images, Looking for REALLY big challenges? |
Jan 19 2007, 10:41 AM
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#501
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
Viking orbiter color filters were violet, blue, green, orange <called "red"> minus blue <=yellow> and clear. The vidicon tubes' long wave response went to zero in the middle of what the human eyeball calls "red", resulting in an effective "orange" filter response, with a very large overlap with the passband of the green filter. Violet and green had near zero overlap. Usually, color sequences included orange, green and violet frames (or I think orange, green, clear, and violet). When working with Voyager and Galileo images I have found that to make the color more realistic I need to use B images instead of V. If they are not available I make synthetic B from G and V images (or even O and V). Galileo didn't carry a B filter so in that case I always need to make synthetic B. Voyager had a B filter but sometimes only V images are available. The color improvement by using B instead of V is somewhat target-dependent. For example you get a big improvement for Io, a significant one for Saturn but not a very big one for Jupiter. See my experimental renderings page for details (scroll down to "Io's color" and "Jupiter's color"). I haven't attempted Viking Orbiter color processing so I don't know how the Viking dataset compares to Voyager and Galileo and how Mars compares to Jupiter, Saturn and Io but I wouldn't be surprised if something similar applied there as well. |
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Jan 19 2007, 11:06 AM
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#502
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
Bjorn: off-topic, but regarding Io's color; I believe that upper left Galileo-based image might actually be very close to "true" color. The only thing that might be slightly off are some areas that are too bluish (essentially the color variation should be smaller). A while ago I did a crude try to use VIMS spectra to get the color for some of the galileans. Its accuracy is questionable given the sheer distance the spectra were taken and also the noise problems of the spectrometer, but the result is distinctively yellow for Io. Europa and Ganymede turned out much less colorful. Here's what I got. Now, this is not to imply Europa and Galileo are whitish, the data quality drowned out their intrinsic color, but Io's yellowness still stands out and that's noteworthy.
Edit: There's also this Cassini-Galileo release that shows Cassini's view also as very yellowish, though I don't recall seeing any Cassini RGB sets for Io in the PDS so it might have been simply adjusting to the Galileo colors. -------------------- |
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Jan 19 2007, 11:34 AM
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#503
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
I saw your VIMS images some time ago but had forgotten about them. Here's what I get when I blur and resample my Io images:
Interestingly, the images in row 2 are more similar to your image than the images in the top row. The implication is that Io's color should be roughly intermediate between the 'Galileo color' and my 'best color' although this is almost certainly an overinterpretation of the very limited existing data. I'm not very familiar with New Horizon's instruments but cannot but wonder if any 'VIMS-like' color observations are possible... |
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Jan 19 2007, 04:44 PM
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#504
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
They said in the press conference yesterday that their plans included spectroscopy with the "highest spectral resolution ever" on the Galilean satellites, and that they'd also manage to get some imaging coverage at higher resolutions than Galileo in some spots that Galileo missed. I don't know whether that's just infrared spectroscopy or also visible. The Ralph instrument does both, though if I read it correctly there is less spectral resolution in the visible than the infrared wavelengths.
--Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Jan 20 2007, 07:29 PM
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#505
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
I have redone the global view taken while the dust storm was still in progress. I think the newer version is much cleaner.
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Jan 20 2007, 07:49 PM
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#506
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Solar System Cartographer Group: Members Posts: 10190 Joined: 5-April 05 From: Canada Member No.: 227 |
Going back to an older post on this thread, about nomenclature.
The names of albedo markings are still official for telescopic use, but it's rare (and would be confusing) to combine the albedo feature names with the topographic names on a single map. However, virtually all of the non-crater features take their names from the old albedo feature names. Acidalia Planitia roughly coincides with Mare Acidalium, for instance. Even where this is not so obvious, careful comparison with old maps will often turn up the corresponding albedo feature. A very good guide to this is Jurgen Blunck's "Mars and its Satellites" (Exposition Press, 1982, second edition). The historical lists of old maps in it are also very useful. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Jan 20 2007, 09:31 PM
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#507
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Perhaps actual topographic features and gross albedo markings ought not be on the same maps. But I definitely think that some form of albedo-marking map ought to be officially recognized. As long as amateur skygazers on Earth look at Mars through their 'scopes, they ought to have the pleasure of saying that they saw Syrtis Major, or Sinus Meridiani, when they glanced through the eyepiece. Or, at the very least, have the pleasure of saying that they saw *something* they can name, as opposed to "you know, that big dark triangular feature" or "the big dark thing that looks like a claw-ended arm, right along the equator."
For me, the great reaching claw of Sinus Meridiani has always been the "face" of Mars, the look that defined the planet in pre-space age telescopic images. The fact that one of our plucky little rovers is sitting at the tip of the Meridiani claw is just cool beyond words, to me... -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Jan 20 2007, 10:44 PM
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#508
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Solar System Cartographer Group: Members Posts: 10190 Joined: 5-April 05 From: Canada Member No.: 227 |
Well, just to clarify, I mean the two sets of names are not usually combined on one map, but IAU does have official nomenclature for both albedo and topographic features. Many maps combine albedo and topo features, but they are usually only shown with the topo names. USGS has global maps of topography with and without albedo. And of course ALPO and others routinely map Mars albedo features at every opposition, since they change with time.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Jan 22 2007, 01:47 PM
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#509
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
I have added a Phobos-2 Thermoscan pan to my site. It is a false color view, combining an "RGB" creation using thermal infrared as red, near infrared/red as blue, and a synthetic green with some VSK color data to give it a "Marsy" look. I also did a lot to correct for the variations in the Thermoscan data caused by the fact that the morning side was much darker than the evening side. I am still tweaking it, but it is nearly a finished product. I removed the shadow of Phobos, which appeared as a streak through the center of both images (because Phobos-2 was in a similar orbit to Phobos at the time), because due to the fact that the intensity of the streak varied based on the amount of time an area had been in eclipse in thermal infrared, while in visible/near infrared it was simply a matter of illumination, the color results were garish. I have posted a small version below, and hyperlinked it to a full-size view.
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Jan 22 2007, 03:23 PM
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#510
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Senior Member Group: Members Posts: 2488 Joined: 17-April 05 From: Glasgow, Scotland, UK Member No.: 239 |
Ted:
Delicious! Do you make a point of letting the Russian chaps see this sort of image, or does it just leak out once on the WWW? Bob Shaw -------------------- Remember: Time Flies like the wind - but Fruit Flies like bananas!
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Jan 22 2007, 04:11 PM
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#511
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
I have in the past, although I haven't had much contact along those lines recently.
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Jan 22 2007, 11:40 PM
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#512
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Member Group: Members Posts: 378 Joined: 21-April 05 From: Portugal Member No.: 347 |
Ted, your new page is coming along very nice! I like your new processings, very consistent!
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www.astrosurf.com/nunes |
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Jan 24 2007, 07:09 PM
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#513
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
Thanks!
I have added some new stuff. It can be accessed via this link, which is my moon page (there is also an Asteroid page, but the Stardust page is the only entry, and it is already linked to from the moon page. Ted -------------------- |
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Apr 13 2007, 03:56 AM
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#514
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
I have updated my site with a new Mariner 7 page, although it is still very much a work in progress.
http://www.strykfoto.org/mariner69/mariner7.htm -------------------- |
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Apr 13 2007, 04:57 AM
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#515
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
Wow! I don't know if I have ever seen any of those. Thank you, Ted.
Why do they look so...impressionistic? --Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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