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Posted by: Decepticon Jan 20 2005, 11:00 PM

A little early to start a topic maybe I'm just so excited about this flyby.
I do have questions about this flyby.



1. What hemisphere will be imaged on this flyby?
2. Will Radar be used this time?
3. Any Non targeted Observations? (Besides Enceladus)

Posted by: volcanopele Jan 21 2005, 12:30 AM

1. Same as last time. No massive regional scale mosaics this time, just some global scale observations and a high resolution set over the T3 RADAR altimetry swath. Don't worry, T4 and T5 on March 31 and April 16 respectively will cover new terrain. Both will cover the sub-saturnian hemisphere.
2. Yes. the swath will be over a little bit farther south than during Ta. Rest assured it will cross a known bright/dark boundary and some interesting albedo features seen by ISS including the multi-ring albedo structure seen here: http://photojournal.jpl.nasa.gov/jpegMod/PIA06154_modest.jpg.
3. There appear to be some distant high phase observations of Mimas, Rhea, Dione, and Tethys, designed, when combined with this orbit and subsquent orbits, to map out the variations in scattering properties of the surfaces of these moons.

Posted by: Decepticon Jan 21 2005, 12:54 AM

Great! Looking forward to that.

Posted by: Decepticon Feb 1 2005, 03:34 AM

2 weeks to go!

I'm already excited!

*Trys to Kick start thred*

Posted by: pioneer Feb 3 2005, 09:33 PM

Will the Huygens landing site be studied further on this flyby? I think VIMS reveals the surface of Titan better than ISS. Will VIMS be used to on this flyby too?

Posted by: volcanopele Feb 3 2005, 10:31 PM

No, neither ISS nor VIMS take a good look at the landing site. We have some 1.4 km/pixel imaging of the area, but frankly we have better images of the area on the ground already. In terms of what VIMS will be doing, they will mostly be riding along with other instruments but they will get observations.

Now, about that comment regarding what VIMS and ISS can see. VIMS can see Titan at farther infrared wavelengths than ISS can. As waavelength increases, optical depth decreases. So at the same pixel scales, VIMS can see more surface contrast than ISS can However, this only becomes at factor at the highest resolution, for VIMS, this is at around 2km/pixel. At that point they can see greater detail than even our best images. However, we can plan our images to mitigate this. First, we can use longer exposure times and more images at the same footprint to improve SNR. Second, we can look much closer to the sub-spacecraft point on the highest resolution observations to improve observed contrast by not looking through so much atmosphere. Combining these steps, we should see better than VIMS at our highest resolution. But it is true, that at the same pixel scale, VIMS can see more detail.

Posted by: Decepticon Feb 4 2005, 01:24 PM

VP will the Images be more to the east compared to the last flybys?

Posted by: BruceMoomaw Feb 5 2005, 04:48 AM

In his recent very informative NAI lecture, Don Lunine agreed that the best resolution for VIMS at Titan is indeed about equal to the best possible resolution for ISS, IF -- and it's a big if -- the latter is handled the right way. The reason, sez he, is that VIMS' CCDs aren't as sensitive as those on the ISS cameras.

Posted by: David Feb 13 2005, 05:14 PM

There are a couple of new images of Titan available from jpl:
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=31851
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=31850

Posted by: Decepticon Feb 13 2005, 08:34 PM

^ Very Nice!

Looking forward to the radar map.


I wonder whats taking so long for a Titan global map updates with the previous flybys.

Posted by: Sunspot Feb 13 2005, 08:44 PM

Those pictures arrived on Earth yeaterday, i've been clicking on "Browse latest 500 RAW images" - which doesn't see to bring up the latest images lol Using the search and WA/NA camera filters does.

Posted by: tedstryk Feb 13 2005, 09:20 PM

Looks like some interesting features. Here is my enhancement. Two circular features look interesting.

Posted by: Decepticon Feb 13 2005, 09:44 PM

Cool!

My guess : Ice Volcanos! ,<Wishful thinking.



What did you do to bring the detail out?[B]

Posted by: David Feb 13 2005, 10:12 PM

Those features are also seen in an image that Sunspot posted to the Titan Surface Features topic on 12/17/04:



I thought at first that the bright semicircle had to be a cloud, but it is seen on the image from two months ago and has not changed. The more northerly structure definitely strikes me as a large impact crater that has been modified by fluids, something like http://antwrp.gsfc.nasa.gov/apod/ap001213.html in Quebec. The other feature seems odder. A mountain range left over from an impact? Or raised by some other process, like vulcanism?

Posted by: tedstryk Feb 13 2005, 11:27 PM

I created a mask based on smoothed versions of images that only showed the atmosphere. I then partially subtracted an enhanced contast version of this from the original image. That brought out surfaced details without making the image look too terribly awkward. I would have done more, but the jpeg effects in the original image made this not useful. I think the Lake Lake Manicouagan analogy and the volcano idea are possible. Hopefully radar will cross one of these regions soon. Remember, after Mariner 7 they thought Nix Olympica was a crater. Nix Olympica ("Snows of Olympus," so-called because it is often surrounded by clouds and thus looked bright in groundbased telescopes without the resolution to reveal its true nature) turned out to be Olympus Mons. I doubt there is anything of that scale in terms of topography on Titan, but I bring this up to say you never know what a feature might be from imagery of this quality.

Ted

Posted by: volcanopele Feb 14 2005, 01:56 AM

The next version of the map is coming...soon...and no, not this week.

Posted by: alan Feb 14 2005, 09:20 PM

I havn't been able to find a picture showing the T3 SAR path so I made my own estimate
http://img142.exs.cx/my.php?loc=img142&image=t3sar2ds.jpg

Posted by: volcanopele Feb 14 2005, 09:39 PM

Nice job. BTW, that is the next version of my map...

Posted by: Decepticon Feb 14 2005, 10:01 PM

Wow, very nice.

Posted by: volcanopele Feb 15 2005, 04:07 PM

The first set of raw images are now posted.

Posted by: alan Feb 15 2005, 04:57 PM

Wow, look at the layers in the upper atmosphere.
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=31954

Posted by: volcanopele Feb 15 2005, 05:08 PM

yep, that's my new favorite atmospheric image..

Posted by: BruceMoomaw Feb 16 2005, 02:20 AM

Nice map of the T3 swath, Jason, but there is another one at http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1714.pdf (which also shows the T-a swath).

Posted by: volcanopele Feb 16 2005, 02:32 AM

I didn't put the swath on the map. I made the map.

Posted by: Decepticon Feb 16 2005, 03:00 AM

Looks like that radar swath gets close to that suspected crater to the side of the Sideways looking "H: figure.


Do we get close to it or part of it?

Posted by: BruceMoomaw Feb 16 2005, 03:01 AM

Oh. Sorry. I got you and Alan mixed up somehow.

Posted by: David Feb 16 2005, 04:06 AM

Jason, your map seems to go up only about to 35° N but I thought that parts of the Titanian northern hemisphere were visible up to about 45° N for this season? Is there a northward extension of the map -- and how long will it be before we can get illumination of the entire northern hemisphere?

Posted by: volcanopele Feb 16 2005, 04:54 AM

I croped it since the emission angles in that region are so high right now that they are not very useful. As the mission goes on, better coverage will be obtained to the north.

Posted by: Sunspot Feb 16 2005, 04:24 PM

New RAW images have been posted, this is a great view of the haze layers in the upper atmosphere:

http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS08/W00004800.jpg

Quite a few RAW images availbale here too:
http://ciclops.lpl.arizona.edu/view_event.php?id=10

Posted by: Sunspot Feb 16 2005, 04:55 PM

Here's my attempt at processing one of the Titan RAW images

The circular feature should have been observed with the radar during the flyby .

Posted by: Decepticon Feb 17 2005, 12:41 AM

RADAR!!


Giant Crater!


http://www.jpl.nasa.gov/news/news.cfm?release=2005-029

Posted by: alan Feb 17 2005, 12:50 AM

Wow! I wasn't expecting that until next week.

Posted by: Mongo Feb 17 2005, 01:03 AM

Giant cat scratches?

http://saturn1.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1371

Very interesting...

Bill

Posted by: Sunspot Feb 17 2005, 01:18 AM

Giant Crater? Are they referring to the large "bulls eye" feature visible in the image attached?

Posted by: Decepticon Feb 17 2005, 01:36 AM

JPL press release calls it a crater.

Posted by: alan Feb 17 2005, 02:00 AM

This is where I believe the radar patches are

http://s04.imagehost.org/view.php?image=/1919/radar_patches.jpg

I'm assuming the dark patches in the radar correspond to dark patches in the photos, I may be wrong.

Posted by: volcanopele Feb 17 2005, 02:03 AM

yes

Posted by: volcanopele Feb 17 2005, 02:25 AM

We had an hour long meeting over this and you found it as well. Good job. That's exactly where we think it is.

Posted by: Decepticon Feb 17 2005, 02:46 AM

Maybe Cassini should do more radar imaging and reduce on the images.

Clearly we are seeing the surface much better than imaging it.

Trust me, I thought I would never say that.

Posted by: alan Feb 17 2005, 03:23 AM

I think they are doing the maximum possible. The two patches that have been released are about 1/4 of the radar pass for this orbit. I suspect they were focusing on the atmosphere during Tb to prepare for Huygens so they had no radar pass then.

Posted by: David Feb 17 2005, 03:52 AM

The radar views of Crater "Manicouagan" show what I take to be two river systems flowing into the crater -- lower left corner.

Posted by: BruceMoomaw Feb 17 2005, 05:00 AM

So Titan DOES have some craters. Speak of the Devil (and assure everyone that he doesn't exist) and he shall appear. Obviously Titan has dramatically refaced itself, but not as dramatically as Io.

To my way of thinking, though, the most interesting thing in that image ( http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1372 ) is the economy-size drainage channel running INTO the crater on the lower left -- right across its rim, which it clearly cuts into. We badly need altimetry on this crater; it would appear that it really is a flattened-out, softened palimpsest with very little actual vertical relief (as suggested by the optical analysis of the previous fuzzy ISS images of it). And, by God, we are looking at really major-scale liquid flow across the surface of Titan -- something I never thought had a serious chance.

The second newly released SAR image ( http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1371 ) is at least as interesting. Those parallel grooves scattered across its field look to me exactly like analogies of those three weirdly super-straight and near-parallel drainage channels -- they're unlike any rivers on Earth; they look instead like irrigation ditches -- visible in Huygens' mosaic of the area that drains into its dark playa ( http://www.futura-sciences.com/communiquer/g/showphoto.php/photo/510/sort/1/size/medium/cat/525/page/1 ). I think that we are looking here at Ganymede-style tectonic parallel grooves and ridges, not at wind-carved phenomena -- with the liquid methane draining along the centers of such parallel valleys in the Huygens image.

By the way, Jonathan Lunine recently told either Aviation Week or Science -- I can't remember which -- that Cassini's later flybys do indeed need to be modified to provide more radar than had been thought.

Posted by: centsworth_II Feb 17 2005, 02:50 PM

I'm sure that a top priority for an extended Cassini mission will be full radar mapping of Titan. The wonders will never cease for years to come!

Posted by: David Feb 17 2005, 04:31 PM

There are more channels visible in the lower right of the "cat scratch" radar image. These are, in fact, the upper reaches of the valleys which we see flowing into the crater in the lower left "Manicouagan" image -- I'm afraid someone with more skill than I have will have to patch the two together, but they do fit very nicely. This suggests to me that the "cat scratches" are actually a highland terrain, as the rivers appear to be flowing down from them.

To my eye it also seems that there are several channels flowing west to east from the western wall of the crater to a north-south "shoreline" within the crater. On the eastern wall there seem to be more channels that flow down the wall to the crater floor and then stop -- if the shoreline represents a single altitude, then perhaps the western floor of the crater is raised higher than the eastern floor.

Posted by: volcanopele Feb 17 2005, 05:27 PM

The mosaic back together just fine. Just take the full-size JPEGs and fit them together. No need for resizing, brightness adjusting, etc.

Posted by: OWW Feb 17 2005, 09:37 PM

You mean like this?

Posted by: OWW Feb 17 2005, 10:36 PM

It is very interesting to compare the ISS and RADAR images of this new terrain. EVERY dark patch in the ISS image is a grooved 'hole' in the RADAR image! The Ta-VIMS image also showed grooved terrain in the dark areas.

Maybe the entire surface of Titan is grooved, only covered with a thick 'snow'-layer in the bright areas such as Xanadu.
It is difficult to see depth in the RADAR-mosaic, but it looks like the ridged holes are lower than the bright stuff, as if the snow melted there to the bottom. In the lowerleft corner you can even see a small channel flowing into the ridged terrain.

Posted by: Mongo Feb 18 2005, 12:20 AM

I find it interesting that all the "scratches" are more-or-less parallel to the axis of the RADAR strip. If a ridge were to be perpendicular to this direction, would it be picked up in the image?

Bill

Posted by: volcanopele Feb 18 2005, 02:39 AM

yes

Posted by: David Feb 18 2005, 01:02 PM

I don't get the same impression of the images.

First, on comparison of the radar and ISS images, it appears to me that while all of the grooved terrain is dark in ISS, there are dark areas which are not grooved. Note, for instance, the area around the bright "island" above and to the left of the rightmost grooved terrain. This is dark, but not grooved.

Second, it appears to me that the lighter-hued areas of the grooved terrain are continuous with the surrounding bright terrain. It is my impression that the darker lines are cracks in the brighter surface, possibly revealing a darker layer below, but I do not think that the grooved terrain as a whole underlies a brighter covering.

Third, I do not observe a channel flowing into the grooved terrain, at least, not one resembling the eastward (or northeastward)-flowing channels that are observable as bright lines in the lower right of the "catscratch" image. I see one short channel-like line which otherwise resembles the grooves of the grooved terrain; however, it does not connect to the grooved terrain, and if it is a channel carved by liquids, its direction of flow is ambiguous.

Posted by: OWW Feb 18 2005, 02:13 PM

David, I think you're right about the bright ridges being the same material as the bright plains, and that dark line does look more like a crack to me now. However, the Huygens panorama also showed a lowlying dark basin with bright ridges in it...

I still think all of the reasonably large dark areas are ridged. Take a look again at the VIMS-Ta image. Compare it to part of the catscratch RADAR image ( same scale ). Both images are 150 km high.

Posted by: OWW Feb 18 2005, 07:15 PM

New radar images!!!
http://saturn.jpl.nasa.gov/news/events/titan3/index.cfm

Second crater in two days... Who said Titan had no craters?

Posted by: David Feb 18 2005, 10:33 PM

That is a very nice crater -- or two, if that's its little brother to the right and below.

But I still have not yet had my surfeit of channels:

http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1379

This is a beautiful image of at least three very large rivers flowing into a basin -- which, interestingly, appears bright in this image, like the rivers themselves -- and their lakes.

This patch is said to be just to the east of "Manicouagan" (which jpl insists on calling "Circus Maximus" ) but doesn't exactly fit; there seems to be a small gap between the two. Our ISS images of the area are also rather sketchy.

The big thing I'm taking away from this is that what appears dark in ISS images can be several different kinds of terrain! The "cat scratches" for one, but also this smooth radar-bright region.

ObsessedwithWorlds will happily note the presence of more grooves -- or, perhaps, ripples -- in the upper right of this image; perhaps comparable to those in the Ta VIMS image.

Posted by: volcanopele Feb 18 2005, 10:41 PM

actually the radar bright terrain seen in the channels image, is dark terrain to ISS, but rubbly, thus making it appear bright to radar. What this suggests to me is that these channels are dry river beds and the radar bright area a dry lake bed, similar to the DISR landing site.

Posted by: David Feb 18 2005, 10:46 PM

Okay, rough radar-bright region...

I was simply noticing that it doesn't seem to have a lot of variation until you get to the "ripples" in the upper right. I guess it is "evenly rubbly".

Posted by: exoplanet Feb 19 2005, 03:56 AM

These *craters* look more like calderas to me. Notice that they seem to be positioned higher in the bright terrain. Very, very eroded rims but still bubble like non eroded features internally. The calderas even seem to have flows and crevasses on thier flanks (like glaciers). Perhaps this is what made the cat scratches that we see in the latest radar images. I am curious what some of you think.

Posted by: alan Feb 19 2005, 06:21 AM

Approximate positions of SAR patches

http://s05.imagehost.org/view.php?image=/0722/Radarpatches2.jpg


A movie showing the locations is here

http://www.nasa.gov/mission_pages/cassini/multimedia/pia07369.html

Posted by: BruceMoomaw Feb 19 2005, 08:22 AM

JPL retains its annoying habit of not publicly releasing the entire "noodle" (long, thin strip) mapped by Cassini's SAR on each flyby. I didn't get a good look at the whole strip from the T-A pass until it was finally released at http://www.lpi.usra.edu/meetings/lpsc2005/pdf/2294.pdf -- and there's a lot of interesting-looking stuff in parts of it other than those which WERE publicly released early on.

And, so far, the only view we've seen of the entire noodle from the T-3 pass is the very fuzzy view of it in this QuickTime movie. Notice the several bright, circular features on the left end. Are they additional impact craters? Who knows? JPL ain't giving us what we need to form an opinion yet.

Posted by: Bubbinski Feb 19 2005, 08:50 AM

I'm wondering when Cassini will get to turn its radar toward the Huygens landing site and compare the radar image with Huygens "ground truth". And it would be nice if Cassini could end up orbiting Titan to get a full look at its surface. Lots of interesting stuff....Titan is very reluctantly giving up its secrets.

Posted by: OWW Feb 19 2005, 10:58 AM

You're right. Judging from that fuzzy strip they released only about half of it.

Posted by: Decepticon Feb 19 2005, 12:07 PM

Amen! I was waiting for someone to point that out.



I think they should focus more on Radar passes than imaging the surface.

Cleary we are not seeing much with the imaging.

Posted by: OWW Feb 19 2005, 12:41 PM

Not if you compare it to what we had before Cassini. For global imaging at least, ISS is fine.

Keck image:


Cassini ISS:

Posted by: Decepticon Feb 19 2005, 01:58 PM

DOH!

Posted by: David Feb 20 2005, 07:47 AM

On second thought, I'm wondering how we know that the bright basin in the "Channels" image is a rubbly lake-bed rather than liquid. The radar does show that the surface is rough, but that could be due to choppy waves on a liquid surface. At a guess (I don't know of any experimental work on the subject), wave crests could be higher in lower gravity, which would yield an even rougher surface.

What really puzzles me is the radar-brightness of the areas where the channels appear to widen. Assuming that the channels are or were carved by the flow of fluids at some time, I would expect such regions to be smooth and radar-dark regardless of current conditions -- while the steep banks of a stream may be radar-bright, both the smooth surface of a wide river and the smooth bottom of an widening in a dry river (presumably, an old or intermittent lake) ought to be radar-dark.

Posted by: BruceMoomaw Feb 20 2005, 08:53 PM

There's been quite a lot of work on the likely height of waves on Titan -- and, yep, they would be several times higher (I'd have to do a little digging to get the exact estimates; Ralph Lorenz has done some work on it). The plan for determining whether a rough surface is waves or solid features is simply to re-observe it at different times and look for any changes in surface roughness that might be caused by changes in wind speed -- although, of course, this means that we can only check those small patches of Titan that will be SAR-mapped more than once, and it assumes that Titan's surface wind speeds change dramatically with time. (If I may bitch once again about the selection of instruments for Huygens: why didn't they put an anemometer on it as one of the Surface Science sensors?)

Posted by: djellison Feb 20 2005, 09:31 PM

Could surface winds be determined from Doppler at the instant before touchdown?

Given the 3 minutes design surface life - an anemometer wouldnt have been much use.

Doug

Posted by: BruceMoomaw Feb 21 2005, 10:04 AM

Yes, they can use Doppler to detect the speed at which Huygens was moving all the way down to the last moment before landing, and no doubt have done so.

As for the usefulness of an anemometer: they had no idea how long Hugyens would last on the surface. That three-minute figure was the period listed as defining officially complete mission success -- although they would hardly have been heartbroken if it hadn't survived landing at all; that part was always optional. If it DID survive landing, they thought it likely that it would continue to operate until the batteries wore out -- which meant at least 30 minutes. That period of time really would have made an anemometer (and a precipitation sensor) useful on the surface.

Once again, I don't understand why they instead put so many SSP sensors on Huygens that would be useful only if it landed in liquid -- and even then would only provide indirect compositional data that could be better provided by incorporating a heated core tube into the penetrometer shaft, with a feed to the GCMS.

Posted by: Decepticon Feb 21 2005, 02:53 PM

I'm wondering why JPL didn't put there own probe on cassinni?

Posted by: djellison Feb 21 2005, 03:06 PM

$$$

Posted by: BruceMoomaw Feb 22 2005, 12:33 AM

Yes indeedy. I've been following Cassini's history since 1978, when it was a mere twinkle in the eye of NASA itself -- and would have been an all-US project called "Cronus" (aka "Saturn Orbiter with Twin Probes") and including an entry probe of Saturn as well.

Indeed, I have a several-hundred page NASA document called "The Saturn System" which records the proceedings of a 1979 U. of Chicago conference to discuss its possible design -- and it's fascinating to see how much things have changed. After all, this was held even before Voyager revealed the utter weirdness of Jupiter's Galilean moons -- let alone the astonishing complexity of Saturn's rings (which at the time of the conference were still thought to be very simple in structure), or the strangeness of Enceladus. (The Committee agreed that the orbiter's official requirements should include flybys only of Iapetus and "one of the icy inner moons", since the latter were supposed to be very similar -- although it would be "desirable to add one small outer satellite to this list", presumably either Hyperion or Phoebe.)

In those days, they were talking about minimizing costs by basing both the main spacecraft and both entry probes on the Galileo designs as much as possible, just fiddling around with the experiment set a little. They were also thinking about launching it before the late 1990s Jupiter gravity-assist opportunity, which would have required fastening it to a solar-powered ion drive module that would have fired until partway through the Asteroid belt before being separated -- an idea they still very much have in mind for a lot of future outer Solar System missions.

Of course, the Shuttle was still in the process of sucking all the blood out of the US space science program at that point -- it hadn't quite completed the job yet. By 1982 that crisis had evolved further, and so the National Academy of Sciences study that recommended both Mariner Mark II and the Planetary Observer program (both of which soon died, to be reborn in new forms) suggested that the four most urgent Solar System missions after Galileo -- also including what later became Magellan, Mars Observer and the cancelled CRAF -- would be a simplified mission involving a Titan probe dropped off by a simplified spin-stabilized Saturn flyby craft (which would also make brief SAR and visible/near-IR observations of Titan). Had the ESA not decided to team up with NASA, the US might very well have flown this stripped-down Titan mission -- but Cassini allowed every part of the original ambitious SOTP scheme to be flown after all, except of course for the Saturn entry probe. (One study concluded that it would have been cost-effective to add that to Cassini -- but there just wasn't the money for it, especially since it would have required a larger version of the Titan 4's solid boosters.)

Posted by: Decepticon Feb 22 2005, 01:20 AM

Interesting read. Thanks!

Posted by: OWW Mar 2 2005, 10:12 PM

Complete radar swaths: http://volcanopele.blogspot.com/
T3 swath is full size. Wow.
And again: "cat scratches" in the dark areas!
These scratches have been described as windblown ripples, but I still think they look like cracks. The dunes on Mars look so different...

Posted by: volcanopele Mar 2 2005, 10:24 PM

I'm starting to buy into the dune idea given their behavior near the "islands" in the far left hand side of the T3 swath. Not something I would expect from tectonic landforms.

Posted by: OWW Mar 2 2005, 10:49 PM

Linear dunes on Earth. Lake Eyre in Australia. Similar?

Posted by: volcanopele Mar 2 2005, 11:03 PM

That would be one example, yes. And in the case of Lake Eyre, the analogy may fit very well. Imagine a dry lake bed (or sea bed). The finer particles would get blown downwind, leaving coarser particles behind. As the sand reaches a topographic boundary, it forms longitudinal dunes parallel with the prvailing wind direction.

Posted by: volcanopele Mar 22 2005, 09:56 PM

Post removed...