[X] My Assistant

[Guest_AlexBlackwell_*]

The T21 Mission Description document is now online (1.2 Mb PDF).

[elakdawalla]

More SAR coming up!

Emily

[ugordan]

What's with this "XXX not available for Titan-21" stuff? Seems like less and less effort is put into these flyby descriptions, as it is now only a single page or so of new information is present per flyby. The rest is pretty much copy-paste stuff.
Also, as edstrick pointed out, it would have really been nice to also include science plans for the periapsis passes, at least listing what targets and instruments will be used.

[remcook]

it would have really been nice to also include science plans for the periapsis passes, at least listing what targets and instruments will be used.

The playback list was basically that, although it didn't say where exactly it is pointing at. But the name of some of the observations gave some hints. A shame it isn't available for this flyby, since it is one of the best north polar passes we have. I find it strange as well, since these tables already exist I imagine. It would just be a matter of copying them into the press release.

[volcanopele]

This is one of the few, decent trailing hemisphere passes of the mission for RADAR. It is a short pass, but should be good enough to understand the geometry of the dunes in northern Belet so we can compared those seen on T8.

In addition to Titan, be on the look for images of Pan (from around 750,000 km) and gibbous Dione from 300,000 km centered around 30 N, 135 W.

[Guest_AlexBlackwell_*]

This is one of the few, decent trailing hemisphere passes of the mission for RADAR. It is a short pass, but should be good enough to understand the geometry of the dunes in northern Belet so we can compared those seen on T8.

A good point, Jason. And I, too, am looking forward to this particular observation.

[alan]

Titan images are down. Some clouds visible:
http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=92452

[remcook]

some more clouds:

http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=92502

they also show up very nicely in the recent VIMS/Radar release.

[volcanopele]

These aren't in the VIMS/RADAR release. these images were taken yesterday.

[remcook]

I was talking about the mid-latitude clouds in more general terms. They are more pronounced in the VIMS/Radar release.

[tasp]

( my understanding of computer image processing is rather limited, so if this is really dum, or is already being done and I didn't notice, please be gentle )

For areas of Titan where we have both high resolution NA camera images and SAR data, could a mathematical correlation of the differences between the 2 data sets be generated, and then be applied to areas of Titan where we only have the NA camera data or only the SAR data to generate the other for both areas?

I think it isn't possible, but I am clueless as to why.

[Guest_Sunspot_*]

I assume the radar didn't reveal anything news worthy this time around?

[ugordan]

Whoa, hold your horses... Not even a week has passed after the flyby + it's weekend now. No point in rushing things!

[edstrick]

"For areas of Titan where we have both high resolution NA camera images and SAR data, could a mathematical correlation of the differences between the 2 data sets be generated, and then be applied to areas of Titan where we only have the NA camera data or only the SAR data to generate the other for both areas?"

That works when the two datasets are well correlated and can work nearly perfectly if one dataset can be mapped onto another dataset by a simple one-for-one function. It doesn't have to be linear or a simple curve or anything. You just need a unique Y value for each unique X value.

In multispectal data, we've done that with rover color images with datablocks missing. If a green data chunk is AWOL, a weighted average of the red and blue channels is a good visual match, but close inspection will show the only colors in the "fudged" part of an image are varying shades and intensities of orangy red through gray through greenish blue.. No yellows or greens, where the real data would be brighter than the average, no purples, where the real data would be darker than the average.

With something like VIMS and radar data, it's essentially impossible. Though you can match up features in the two datasets, actual data values have essentially no correlation and there's no possible "reasonally good" mapping from one dataset to the other. They are truely telling you two essentially independent, different things about the same surface.

An analogy is a red and green checkerboard. a 512 channel imaging spectrometer won't tell you anything more about the red and green squares than a single well selected channel. But pick thermal infrared or millimeter waves, and you might not see the checkerboard at all, but the fiber structure of the particle-board or masonite underneath the paint formnig the red and green squares.

[tasp]

I appreciate the response, that was very helpful.

[Matt]

I assume the radar didn't reveal anything news worthy this time around?

I think they are just letting the VIMS news about the mountain range sit pretty a little while longer, before they steam in with the most fascinating new radar images so far that reveal more craters, more dunes, definite cryovolcanos as well as active geysers and Titan's version of Niagra Falls!

[volcanopele]

?? How would they know a cryovolcano was active from RADAR?

[tasp]

Interesting question, volcanopele.

How would materials in motion, like, let's say a rapidly ascending volcanic plume, interact with the radar beam and the mathematical reconstruction needed for us to see the image?

Seems like the doppler component of the signals would be distorted in a characteristic way, but does the SAR radar technique look for such characteristics in the returning signals?

[ugordan]

?? How would they know a cryovolcano was active from RADAR?

I don't know, but I do get the feeling Matt was only joking

As for Doppler measurements, I don't think RADAR has that kind of capability. It would have to be an exceptionally accurate measurement given Cassini's Titan-relative speed would be some 2-3 orders of magnitude higher than what these hypothetical plumes would churn out.

[remcook]

moving cryolava flows would be a hint
I think a waterfall (methanefall) would be a lot harder to determine

[tty]

moving cryolava flows would be a hint

That's a nifty new word for "river"

tty

[Olvegg]

Titan images are down. Some clouds visible:
http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=92452

Yes, and they are at 15 degrees south latitude! Start of monsoon season in tropics? There's also something river-like.

[Matt]

Is the sar from T21 another one of those full swaths?

[Big_Gazza]

Does anyone know when SAR results will be released? I hope the delay is due to seasonal holidays rather than any problems with the observations?

[volcanopele]

T21 was a half-swath, UVIS had prime point prior to C/A, RADAR afterward.

not sure why some of it hasn't been released yet.

[elakdawalla]

I think things just got too busy over the holidays, and now everyone's facing the LPSC abstract deadline on January 9. I'm hoping to see something after that.

--Emily

[Guest_AlexBlackwell_*]

PIA09111: Two Sides of Dunes

[peter59]

Enjoy !!!

Attached thumbnail(s)

 

[JRehling]

Enjoy !!!

Wow! I've never found the sand dunes to be pretty before, but in the middle of this image, they are.

[ugordan]

Wow, they really look like a work of art.

[Juramike]

Yeah, baby! This goes right over some of the Tiger Stripes north of the Dancing Monkey feature!

They look like broad darker gray lines bordered by subparallel sl. brighter gray lines in RADAR. I'm guessing it was a wide crack bordered by sharp ridges later buried under a bunch of atmospheric schizzle. Not big channels. (Or maybe big channels buried by schizzle)

Awesome!

-Mike

[nprev]

Wow indeed. I wonder how much we can deduce about topographic wind effects (in fact, topography itself) from this sort of data?

[David]

I'm not quite sure how to read topography out of these radar images: when you have parallel light and dark lines, does the lighter line represent the crest of the dune, and the dark line the trough, or vice versa? Or is the light line one side of the dune and the dark side the other?

[Juramike]

I'm not quite sure how to read topography out of these radar images: when you have parallel light and dark lines, does the lighter line represent the crest of the dune, and the dark line the trough, or vice versa? Or is the light line one side of the dune and the dark side the other?

Sometimes the topography in RADAR images is pretty clear. You get a strong reflection at the angle of RADAR signal, or you get a nice sharp "foldover" pattern.

For example, In T21 you can see this in some mountains (ridges) at the wide end in the overlap zone with the T8 Swath. There is a sharp bright distinct mountain chain surrounded by a brightish mantle.

But in other areas the topography is pretty muddled and is open to speculation. In general, bright = rough (or porous or other effects with dielelectric constant) and dark = smooth. So it is assumed that the brighter areas are rougher ridge tops. And it is assumed that darker broad areas are smooth muddy basins.

But there could be exceptions:
A highland swamp or marsh, although elevated, could appear RADAR-dark because it is smooth.
A rough crusty dried out lowland could appear RADAR bright, even though it is low-lying.
If the tops of the hills are smooth (covered in schizzle) they could appear smooth
If the valleys are covered in small hummocky drifts, not resolvable by RADAR, they could appear bright.

The RADAR-altimetry experiment comes in handy for determining relative altitude. [A recent presentation at DPS is discussing that contrary to initial assumptions, Xanadu is actually low lying. Xanadu is very RADAR-bright and one would assume it is thus high in altitude. ]

So divining altitude by just looking at RADAR images could get you into trouble. Go with caution...

-Mike

[Marz]

Whoa! That is one of the more enigmatic radar images I've seen so far. Those features seem way to fine and linear for wind or water... perhaps these are some form of expansion faults in the surface that became further eroded?

What do I know, since it's clear I'm not keeping up with planetary geology terms... "covered in schizzle"?!?!?
<airplane> Excuse me, but does anyone present speak Jive? </airplane>

Watch it bub, or I'll get hummocky on your euphemisms!

But there could be exceptions:
A highland swamp or marsh, although elevated, could appear RADAR-dark because it is smooth.
A rough crusty dried out lowland could appear RADAR bright, even though it is low-lying.
If the tops of the hills are smooth (covered in schizzle) they could appear smooth
If the valleys are covered in small hummocky drifts, not resolvable by RADAR, they could appear bright.

So divining altitude by just looking at RADAR images could get you into trouble. Go with caution...

-Mike

[Juramike]

OK. I'm not totally satisfied with this but...

I tried to stitch together the T30 RADAR Swath and the T21 RADAR Swath at their intersection point. I think the lines at the far end of the T30 RADAR Swath are the Tiger Stripes of Titan and I tried to match them up where they cross the T21 Tiger Stripes. (The two swaths should intersect)

I'm not super sure I got the line up exactly right, but I think I'm close. There are not a lot of obvious features in the region to help line things up ("Wecome to the Big Bland"). Maybe one of the imagemeisters in UMSF-land can take a better stab at this.



-Mike

[volcanopele]

You should be careful about calling these "tiger stripes". That nickname has become so ingrained in the community to refer to the cryovolcanic-tectonic structures in Enceladus' south polar region, that calling these features "tiger stripes" may lead people to think that these features are similar. True, these do have a superficial similarity, but quite frankly, we are not sure how these formed, though they do seem to be tectonic in origin. How about..."Zebra Stripes"?

[Juramike]

You should be careful about calling these "tiger stripes". That nickname has become so ingrained in the community to refer to the cryovolcanic-tectonic structures in Enceladus' south polar region, that calling these features "tiger stripes" may lead people to think that these features are similar. True, these do have a superficial similarity, but quite frankly, we are not sure how these formed, though they do seem to be tectonic in origin. How about..."Zebra Stripes"?

Good call. I'll start referring to them as "wavy cracks" (including the quotes as well).

Cycloids would be a pretty good term, if we get better resolution imaging and if they compare well with Europan and Enceladean features.)

(Actually, these things look kinda like the feaures on Charlie Brown's head)

-Mike