Titan's clouds?

[jose21]

I don't know whether this is possible, but I'll ask anyway. Would it be possible to extract the coulds from the black-and-white map of titan that was recently released?

[Pliskin]

Hmm, you might like This topic

[jose21]

Thanks, but I agree with many others that Titan should appear from orbit as it really does, and that means no surface texture, just a thick yellow ball. I figured, however, that the clouded region in the South would be visible from space. So no, I'm not looking for a Titan surface map, I'm looking to make Titan appear as realistic as possible.

[granthutchison]

I figured, however, that the clouded region in the South would be visible from space.

The pictures I've seen that show the south polar cloud all seem to be in the infrared, so I'm not sure if or how well it would show up in visible light.

Grant

[Bob Hegwood]

Thanks, but I agree with many others that Titan should appear from orbit as it really does, and that means no surface texture, just a thick yellow ball.

Does this mean that you would also do away with the surface texture for Venus?
Don't know about you, but the radar-images are the only means we have of
exploring the surface of Venus now, and I like this capability. You wouldn't want
to do this with Titan? I vote for a surface texture *however* it has to be obtained.

Much more interesting to see the features on the surface of the planet too, isn't it?

Thanks, Bob

[Pliskin]

Thanks, but I agree with many others that Titan should appear from orbit as it really does, and that means no surface texture, just a thick yellow ball. I figured, however, that the clouded region in the South would be visible from space. So no, I'm not looking for a Titan surface map, I'm looking to make Titan appear as realistic as possible.

Try page 2 or 3 of that thread I gave you .

You can download the opaque clouds and make titan appear as a thick yellow ball of cloud( as I would put it).

[t00fri]

Thanks, but I agree with many others that Titan should appear from orbit as it really does, and that means no surface texture...

Is'nt that a quite narrow point of view or in orther words: what do you mean with Titan's real appearance?

Many people like to wear Polaroid sun glasses when they drive for long distances, in order to get rid of the unpleasant glare on the road, for example.

I get rid of the light pollution from our street lights by using a simple interference filter with my telescope. And so on...

It's all a matter of the wavelength and various filters we conveniently may chose to look at an object.

Cassini for example looks at Titan with near infrared light to penetrate the haze and uses polarizing filters to reduce the multiple scattering of light from the droplets in the haze.

What is unreal here?? It's not our fault that human eyes represent a relatively "insensitive" narrowband detector design...

So how does Venus look in your installation, once you switch off the clouds by pushing the key "I"??

Do you use the radar surface texture, too? That is not real either, of course, according to your very restricted view.


Bye Fridger

[jose21]

Please don't get angry, I'm not at all trying to insult your work, it looks great, all I'm saying is, you have had to take some artistic license. It's based on real data, but the real data is limited. What color is Titan's surface? We really don't know. So to make a texture with a color is just guesswork at this point.

The Venus comparison, in my opinion is flawed. We haven't yet landed on Titan, you're making assumptions about what the color of the surface would look like. With Venus, we know that the atmosphere makes it appear orange because we've seen photos from the Venera lander.

Plus, right now, I could be wrong, but I haven't seen any photos/info that suggests the cloud layers are nearly as transparent as your texture makes them.

When I say "real" I mean, if I were standing there, looking at Titan, I want it to appear like that. Does that mean you shouldn't use infrared data? Of course not. However, it does mean, the infrared data should be used to show visible features. Meaning, when I'm above the atmosphere, I shouldn't see surface details that can only be detected using infrared. When I go below the atmosphere, that's fine, because at the moment, infrared is the only source we have for surface details.

I could turn out to be totally wrong, when Cassini approaches Titan, it could turn out to look exactly like your texture, I'd just prefer to wait until we find out for sure before using it.

[t00fri]

Please don't get angry, I'm not at all trying to insult your work, it looks great, all I'm saying is, you have had to take some artistic license. It's based on real data, but the real data is limited. What color is Titan's surface? We really don't know. So to make a texture with a color is just guesswork at this point.

The Venus comparison, in my opinion is flawed. We haven't yet landed on Titan, you're making assumptions about what the color of the surface would look like. With Venus, we know that the atmosphere makes it appear orange because we've seen photos from the Venera lander.

Plus, right now, I could be wrong, but I haven't seen any photos/info that suggests the cloud layers are nearly as transparent as your texture makes them.

When I say "real" I mean, if I were standing there, looking at Titan, I want it to appear like that. Does that mean you shouldn't use infrared data? Of course not. However, it does mean, the infrared data should be used to show visible features. Meaning, when I'm above the atmosphere, I shouldn't see surface details that can only be detected using infrared. When I go below the atmosphere, that's fine, because at the moment, infrared is the only source we have for surface details.

I could turn out to be totally wrong, when Cassini approaches Titan, it could turn out to look exactly like your texture, I'd just prefer to wait until we find out for sure before using it.

Wait a second...

you seem to be mixing things together. In my previous post I answered to your original statements above. My answer had nothing to do with my Titan textures!

-- I was arguing only against your statement referring to Titans "real" appearance. My point was simply that this statement of yours reflected both a narrow view and also is ill-defined. You must always quote the wave-length of the light that is used, when talking about "reality"...

--You seem not to be aware of my later updates in my t00fri's Titan@Celestia thread. My final Titan-cloud textures exist (for download) in two varieties:

a) entirely opaque with colors perfectly matched to the most recent truecolor photo by Cassini.
In this form, they will be also included in the 1.3.2 Celestia version.

b) "almost opaque" in a way that would certainly be compatible with the appearance of the surface markings in the near IR window!

From the start, I have pointed out the uncertainty wrto the color of the surface. So just call my surface texture "false color" if you like. Same is definitely true in case of Venus. My colors were in fact optimized to display fine surface details. That was the main criterion for their choice as I discussed also.

Clearly your personal constraints can be most easily satisfied, if you personally just ignore my Titan texture...

When I say "real" I mean, if I were standing there, looking at Titan, I want it to appear like that. Does that mean you shouldn't use infrared data? Of course not. However, it does mean, the infrared data should be used to show visible features. Meaning, when I'm above the atmosphere, I shouldn't see surface details that can only be detected using infrared. When I go below the atmosphere, that's fine, because at the moment, infrared is the only source we have for surface details.

This view I cannot share at all...There does not seem to be any logical basis for that interpretation and it was also impossible for anyone to infer such an "exotic" view from your original post...

Bye Fridger

[jose21]

This view I cannot share at all...There does not seem to be any logical basis for that interpretation and it was also impossible for anyone to infer such an "exotic" view from your original post...

Perhaps I'm being "narrow minded" again, but how exactly is the view from the human eye considered "exotic"? Seeing as how exotic means unusual or strange, I ask, how is the view from the human eyes strange? With the exception of those people with vision diseases, it is the least exotic view that mankind is familiar with!

Also, I've yet to see any maps of Titan from Cassini other than the infrared surface maps. So wouldn't your "yellow cloud" map be somewhat artistic as well?

But anyway, this has gotten off topic. Maybe my point of view is "restricted," or "narrowminded," but I was not trying to convince anyone to agree with me, so I see no need for an argument. You might disagree with me, which is fine, but I don't see why I should be deemed "narrowminded" simply because you don't agree with the manner in which I'd like my Celestia to look.

[t00fri]

This view I cannot share at all...There does not seem to be any logical basis for that interpretation and it was also impossible for anyone to infer such an "exotic" view from your original post...

Perhaps I'm being "narrow minded" again, but how exactly is the view from the human eye considered "exotic"? Seeing as how exotic means unusual or strange, I ask, how is the view from the human eyes strange? With the exception of those people with vision diseases, it is the least exotic view that mankind is familiar with!

...

But anyway, this has gotten off topic. Maybe my point of view is "restricted," or "narrowminded," but I was not trying to convince anyone to agree with me, so I see no need for an argument. You might disagree with me, which is fine, but I don't see why I should be deemed "narrowminded" simply because you don't agree with the manner in which I'd like my Celestia to look.

I notice a certain tendency that you do not read my posts well...

I have nowhere called you "narrow minded"!

Arguing that someone has a "narrow point of view" or a "narrow view" about something is quite different from calling someone "narrow minded"!

I find your point of view also "exotic", since you advocate to "ban" the use of infrared light and polarizers beyond a certain distance from Titan, but admit it below that distance! Same with Venus, apparently.

The only consequent attitude along your line of thinking can then be to only admit a gray structurless LOK texture for the surface of Titan and Venus together with a totally opaque cloud texture.

Astronomers (and space flight missions) tend to employ less and less visible light to observe the universe, recently...And this has good reasons!

Also, I've yet to see any maps of Titan from Cassini other than the infrared surface maps. So wouldn't your "yellow cloud" map be somewhat artistic as well?

Finally, it would be very useful for such discussions, if you read either my t00fri's Titan@Celestia thread more carefully and/or the official NASA resources!

I recall for you the recent truecolor photo from Cassini about Titan's haze appearance in visual light:


My final clouds-texture that I made available for download, perfectly matches this image...

Bye Fridger

[jose21]

I find your point of view also "exotic", since you advocate to "ban" the use of infrared light and polarizers beyond a certain distance from Titan, but admit it below that distance! Same with Venus, apparently.

I don't understand how this is so strange to you. Consider this, you are standing outside my house. I ask you to draw a picture of the house. What would you draw? Would you draw a box with a roof, windows, and doors? Or would you break out the infrared scanner and begin to survey the objects inside? From the outside, you cannot see the interior, and therefore a drawing that presents the interior from outside is *inaccurate*. Now, if I also asked you to draw the objects inside (without going in), then you'd be correct to use infrared. However, you'd construct two images. One of the exterior, and one of the interior. Using infrared is not inaccurate, however, presenting infrared light in such a way that it alters the perception of visible light (superimposing the interior on the exterior) is inaccurate. Same with Titan. Having a surface texture in infrared is fine. However, making it so the surface is visible (even 1% visible) through the clouds is inaccurate.

That's all I ever said. I never said don't show the surface in infrared, I simply said don't make things visible through the clouds which really aren't.

I recall for you the recent truecolor photo from Cassini about Titan's haze appearance in visual light:

Yeah, and as I said, that's not a map. Maybe Titan has blue clouds that float around in the atmosphere, and at that time, the clouds happened to all be on the other side. Perhaps the atmosphere is not uniformly thick and on the otherside it is possible to see some surface details, etc. It's unlikely, but we don't know. And until we do know, I'd rather not pretend like we do. I'm not trying to argue with you, all I'm saying is I'd rather use scientific data rather than artistic embellishments.


Anyway though, I'm through with this thread, I've already received the answer to my original question.

[folks]

Glowing Titan: Atmospheric Glow
http://saturn.jpl.nasa.gov/cgi-bin/gs2.cgi?path=../multimedia/images/titan/images/PIA06419.jpg&type=image

While it is possible to render auroras on Jupiter and Earth as night lights,
it is not a great solution because the night lights appear to be mapped onto the surface texture.

On Titan, according to the link above, green light is the fluorescent emission of methane on the night side the moon glows red out for over 200 kilometers (125 miles) altitude, indicating carbon-monoxide emission. ( Granted enhanced vision may be required )

For Titan night lights don't work since there is glow on day and night sides.

For Io it is difficult to show the hot spots and atmospheric glow which
also varies between the day and night sides of the moon.

Is there a good way to implement atmospheric glow and planetary hot spots in Celestia?

-- Scott

[selden]

Celeestia v1.3.2 (I think starting with prerelease 10) has had the "occlusion" bug mostly fixed. SSC objects now can entirely contain one another and get properly drawn. There are still some remaining problems, but I think most of them can be worked around. Multiple planets at the same position, each with its own CloudMap, don't seem to get drawn quite right, for example.

This means that you now can design a translucent shell which carries the image of the glow and have it surround Titan. Below I've provided one possible SSC definition for such an object, but I'll leave it to one of you artists to actually implement the spherical model and its associated surface texture image.

Don't forget that the glow seen by Cassini is in the infrared, not in visible light.

Code: Select all

"TitanGlow" "Sol/Saturn" {
    Mesh "titanglow.3ds"
    Radius 2650
    CustomOrbit "titan"
}

[folks]

Thanks selden

Interesting approach. If I understand it correctly we could make the texture that defines the translucent shell Emissive to make it glow?
Be a good way to map hots spots and plumes on Io also.

I was thinking about the discussion in this tread concerning visible vs infrared, etc.

Perhaps in the same way that we specify coordinates, coordinate systems, time, orientation and the lens we are looking through we should specify the range of spectrum which we can view.

It would mean that a ssc definition would, optionally, be able to specify the spectra range at which the objects were imaged.

Of course it is not just for Titan and the Io but things like the Milky Way Billboard in IR and many other images.

-- Scott
Mac OS X 10.3.4 :: Nvdia GForce4 MX 32 MB :: Celestia 1.3.1
Hope that we get 1.3.2 on Mac soon so I can try this technique.

[Guest]

Greetings,

One thing I can point out is that reprocessed Voyager orange filter images actually
do show some very faint surface detail on Titan, so perhaps having some surface detaill
barely visible might be sort of realistic.

For both Venus and Titan, I wonder if increasing surface detail (even if radar based)
can be shown as one approaches the object and descends under the cloud layers.
At least in the case of Venus, I think there is a fairly large clear gap between cloud base
and the surface.

It would be possible to use surface topography data to help augment the
radar brightness though any "bump map" shading might be unrealistic if the
sunlight is diffused by the clouds.


Steve Albers

[granthutchison]

One thing I can point out is that reprocessed Voyager orange filter images actually
do show some very faint surface detail on Titan, so perhaps having some surface detaill
barely visible might be sort of realistic.

Trouble comes from the other well-scattered wavelengths, which dilute the contrast visible in the relatively transparent waveband. The authors of the Icarus article that reported this (Icarus 170 (2004) 113-124) thought about this topic and concluded:

Even by isolating only this wavelength range by means of red 'sun-glasses,' the surface contrasts are only of the order of 5%. Human vision has a radiometric resolution of only 50-200 gray levels ... so Titan's surface features would therefore be at the limit of, but perhaps just within, human capabilities.

That seems optimistic to me, since it requires Titan's haze to be transparent over >10% of the visible spectrum and for areas of maximally different albedo to occur next to each other along a sharp boundary. (Maybe we should experiment in Celestia with ~1% transparent clouds and see if we can see any of Fridger's surface texture through them?)
But it certainly has implications for seeing the Sun from the surface of Titan - a sharp-edged red disc embedded in a blue-green patch of scattered short wavelengths?

Grant

[t00fri]

One thing I can point out is that reprocessed Voyager orange filter images actually
do show some very faint surface detail on Titan, so perhaps having some surface detaill
barely visible might be sort of realistic.

...
But it certainly has implications for seeing the Sun from the surface of Titan - a sharp-edged red disc embedded in a blue-green patch of scattered short wavelengths?

Grant

My saying all along...I was always pointing out that according to my estimates on should be able to make out the diffuse location of the sun from Titan's surface.

We'll eventually know for sure...

Bye Fridger

[granthutchison]

;-) My saying all along...I was always pointing out that according to my estimates on should be able to make out the diffuse location of the sun from Titan's surface.

If only you'd felt able at the time to tell us what evidence your estimates were based on we could have moved along so much more quickly ...

Grant

[t00fri]

;-) My saying all along...I was always pointing out that according to my estimates on should be able to make out the diffuse location of the sun from Titan's surface.

If only you'd felt able at the time to tell us what evidence your estimates were based on we could have moved along so much more quickly ...

Grant

Well, to some extent I think I did. I also wrote to you from Switzerland that I had done extensive calculations (again;-)) based on Mie theory. Unfortunately since this summer my available time for posting is shrinking more and more, so my statements were admittedly not as detailed as I had wished...

Other "busy" people in this forum tend to even write less, recently;-)

Bye Fridger