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Updated Titan Map
Decepticon
post Dec 30 2006, 02:40 AM
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^^Maybe next Holiday Season! wink.gif
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Olvegg
post Dec 30 2006, 11:31 AM
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Well, there are some changes on Titan surface! blink.gif Mezzoramia looks very pale compared to previous map and two or three white spots appear near 15 and 20 degrees WL. Yet another one white dot encircled in dark near 50 WL 65 SL disappear. What can it be? Really changes, artefacts of processing or just clouds?
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nprev
post Dec 30 2006, 06:34 PM
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Good eye, Olvegg. I'd have to bet on convective clouds, especially for high-latitude features like these; seems like the polar regions are where most of the action's at for Titan's weather.


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volcanopele
post Dec 30 2006, 06:52 PM
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Yeah, really bright spots at high latitudes are more than likely clouds. It seems that when ever we look at the south polar region at decent enough emission angles that the images can be used in maps, there are clouds down there, so it is hard to remove ALL the clouds from the map.

In terms of contrast difference, I chalk that up to differences in the my sharpening filter in the last 2 years.


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JTN
post Dec 30 2006, 11:16 PM
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I've always been surprised that there aren't more amateur Titan ORS mosaics here. (I realise it's a bit of a challenge, but that doesn't usually stop you lot...)
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ugordan
post Dec 31 2006, 12:06 AM
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Surprisingly, there aren't a whole lot of people playing around any Cassini images that I can see. Titan would make a pretty hard target to work with, given no easy way to reduce atmospheric haze. You really need excellent flatfields and either you can brew your own ones (hard to do manually) or work with the not so good ones on the calibration volumes. There's a lot to be desired there, especially for the wide-angle camera flatfields which would make simple mosaics easier than taking a shot at high-res NAC footprints. Geometric reprojection would also be handy since the exposures are long and the flybys pretty fast. SPICE kernels in other words...


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nprev
post Dec 31 2006, 02:31 AM
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Just had an odd thought...Is Titan a cold "desert" planet?

Specifically, it almost seems as if the polar regions are the only areas where precipitation seems to occur with any degree of regularity. If Titan was a terrestrial planet with a similar pattern, the expectation would be that the lower latitudes were too hot to sustain an Earth-style hydrological cycle, and only the poles were temperate enough for habitation...like some of the pre-UMSF ideas about Venus, in some ways.

Again, just a thought. No matter how good our maps get, I think that interpreting them within an understandable framework will be a challenge for a LONG time.


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JRehling
post Dec 31 2006, 03:49 AM
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QUOTE (ugordan @ Dec 30 2006, 04:06 PM) *
Surprisingly, there aren't a whole lot of people playing around any Cassini images that I can see. Titan would make a pretty hard target to work with, given no easy way to reduce atmospheric haze. You really need excellent flatfields and either you can brew your own ones (hard to do manually) or work with the not so good ones on the calibration volumes.


Yeah. When the first flybys happened in 2004, I tried my hand at it, with some success, but it was a lot of work to lead to a modest product not that far in advance of the "pro" releases. I attached my work from the first 24 hours of the first flyby in July 2004. I didn't try this again.

I used a Hapke map I'd produced for some other world to adjust for phase effects, but I forget which world I had developed the model for. Mercury, I think. Then I just twiddled in Photoshop with no principles but what seemed to look OK. Composite of three ISS frames.
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Decepticon
post Dec 31 2006, 04:01 AM
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Is there any online reference as to how the titan images are produced??

Tricks and Tips! biggrin.gif
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Gsnorgathon
post Dec 31 2006, 07:45 AM
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QUOTE (nprev @ Dec 31 2006, 02:31 AM) *
Just had an odd thought...Is Titan a cold "desert" planet?

...

Why is that an odd thought? It sure seems a good fit to the available evidence. I wouldn't want to make any firm generalizations about poles vs equatorial regions until we've seen what happens as the equinox approaches, though. I'm hoping Cassini lasts long enough.
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Bob Shaw
post Dec 31 2006, 08:08 AM
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QUOTE (nprev @ Dec 31 2006, 02:31 AM) *
Just had an odd thought...Is Titan a cold "desert" planet?


Hmm... ...that'd mean camels, wouldn't it? Camels might indicate *life*. If there's life there must be awl (it's a dessert, see?). If there's awl, we better invade!

Hey, things are looking up for the unmanned spaceflight budgie!

Still, if it's a dessert the proof will always be in the pudding.


Bob Shaw


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scalbers
post Dec 31 2006, 03:51 PM
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QUOTE (Decepticon @ Dec 31 2006, 04:01 AM) *
Is there any online reference as to how the titan images are produced??

Tricks and Tips! biggrin.gif


I think there was a CICLOPS release illustrating some of the processing steps. VP may also have mentioned some details. One of the more unique steps involved subtracting an image in a neighboring wavelength (from the 900nm passband) thus acting as a flat field. I suppose having a simple atmospheric model can provide similar flat-fielding information.

There were some sharpening steps as well to compensate for the haze diffusion.


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volcanopele
post Dec 31 2006, 07:28 PM
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QUOTE (Decepticon @ Dec 30 2006, 09:01 PM) *
Is there any online reference as to how the titan images are produced??

Tricks and Tips! biggrin.gif

Check out my LPSC abstract on the subject from a couple of years ago:

http://www.lpi.usra.edu/meetings/lpsc2005/pdf/2312.pdf


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nprev
post Dec 31 2006, 08:40 PM
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QUOTE (Bob Shaw @ Dec 31 2006, 12:08 AM) *
Hmm... ...that'd mean camels, wouldn't it? Camels might indicate *life*. If there's life there must be awl (it's a dessert, see?). If there's awl, we better invade!

Hey, things are looking up for the unmanned spaceflight budgie!

Still, if it's a dessert the proof will always be in the pudding.
Bob Shaw


Well, at least we know the ice cream won't melt...EVER! rolleyes.gif

BTW, does anyone know what the current thinking is as far as 'methane monsoons'? Presumably they occur (if in fact they do) twice per Saturn year as the polar illumination gradually switches, and they probably wouldn't happen precisely at the time of the equinox due to thermal inertia. Any evidence of convective clouds creeping north from the southern hemisphere yet, or even happening further south due to the aformentioned inertia?

Some of the features in the equatorial regions remind me more and more of arroyos in the US Southwest. You have to wonder whether the atmosphere becomes supersaturated with methane and then one day just busts loose all over the equator... blink.gif


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JRehling
post Dec 31 2006, 10:17 PM
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QUOTE (nprev @ Dec 31 2006, 12:40 PM) *
Well, at least we know the ice cream won't melt...EVER! rolleyes.gif

BTW, does anyone know what the current thinking is as far as 'methane monsoons'? Presumably they occur (if in fact they do) twice per Saturn year as the polar illumination gradually switches, and they probably wouldn't happen precisely at the time of the equinox due to thermal inertia. Any evidence of convective clouds creeping north from the southern hemisphere yet, or even happening further south due to the aformentioned inertia?

Some of the features in the equatorial regions remind me more and more of arroyos in the US Southwest. You have to wonder whether the atmosphere becomes supersaturated with methane and then one day just busts loose all over the equator... blink.gif


I happened to drive across Arizona on I40 on a snowy day shortly after the second (?) Cassini flyby of Titan and I couldn't help but notice how much it seemed to fit what we knew about Titan.

What we know from Voyager and Cassini seems to indicate that the summer pole gets a ring of convection around 80 N/S that creates a lot of rain there. What happens at the equinox or in the dark of the winter pole we don't know yet, but notice that there appear to be lakes in the winter pole now and perhaps at the summer pole as well. I imagine Ralph Lorenz has ventured some opinions. I would guess that the (near) poles get more rain than any other location, enough to fill up lakes that are still full through a decades-long drought.

One of the most important things about Cassini's extended mission will be to see what seasonal changes take place on Titan. Bigger cloud structures can be seen from Earth, though, and presumably from the Webb Space Telescope.
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