Rev 69 Looking ahead is up!

http://ciclops.org/view/4889/Rev_69

The T44 Flyby highlights include:

1. ISS of Hotei Arcus
2. SAR RADAR Swath over Xanadu (Tui Regio) and N Central Shangri La (this is gonna be good!) and S Dilmun
3. More radiometry and scatterometry (over W Belet?)

-Mike

Ciclops doesnt speak for all of Cassini. They write their own stuff, based on earlier project
discussion. In this case they may be wrong - I think the scat and rad had to be deleted because
of the DSN being taken by Phoenix. Better to refer to the project flyby summary

I know that Ralph. I mention that in the summary.

T44 Mission description is now up!

http://saturn.jpl.nasa.gov/multimedia/prod...description.pdf

TITAN-44 SCIENCE HIGHLIGHTS

• RADAR : T44 altimetry will be close to Hotei, over an area that was SAR imaged by T43. The SAR swath sweeps northwest across Xanadu, over the Shangri-La dunefields and onto Dilmun. The SAR will image the southern edge of Xanadu, which shows a sharp boundary in microwave emissivity that is not presently understood. The SAR data is hoped to yield information on Xanadu's large-scale topography, as well as the influence of Xanadu on regional wind patterns as revealed in the dunes, and a partial overlap with T13 SAR may give stereo information and refine estimates of Titan's rotation state.
• INMS uses the RADAR orientation, and because of the higher altitude of this flyby the spacecraft is above most of ionosphere and INMS will obtain exospheric observations. The team will use these observations to identify what chemical compounds are escaping from Titan’s atmosphere, looking at both altitude and the difference between the northern and southern hemispheres.
• CIRS continues to extend spatial and temporal coverage of Titan, from low-spectral resolution disk maps to high spectral resolution nadir and limb integrations. Getting good time resolution is very important because we are looking for seasonal changes in the stratosphere, especially the expected break-up of the northern polar vortex in northern spring. In a rare occurrence, during the T44 targeted Titan flyby, CIRS will be observing the rings of Saturn. Usually, the Titan observations are considered more compelling during the flybys since the geometries and opportunities are so spectacular, so this Rings observations is quite unique. CIRS will determine the mean thermal gradient across Saturn's many-particle-thick rings by executing radial scans of Saturn's main rings (A, B, C) over multiple illumination geometries (including phase, S/C inclination, and solar elevation) on the lit and unlit sides of the rings. This is one of those observation sets.
• VIMS observations concentrate on determining time scales for cloud formation and dissipation.
• ISS: The T44 flyby geometry shows a half-illuminated Titan as Cassini approaches and recedes. On approach ISS will carry out night-side imaging for photometry and searching for lightning and aurora. ISS will also acquire a regional-scale map of Hotei Arcus, its highest-resolution observation of this region to date. Outbound, ISS will see portions of Belet and Adiri and territory to the north, capturing global and full-disk mosaics. As the geometries of the T41 through T44 flybys are very similar, ISS has opportunities to detect clouds in this region every few weeks.
• RPWS: As Titan is out “in front” of Saturn, the T41 through T44 flybys put the spacecraft in an ideal location to have another opportunity to see Titan outside of Saturn’s magnetosphere, in shocked solar wind ahead of the magnetosheath as happened on T32. We are interested in duplicating the flyby geometry to look for shorter time-scale phenomena in Titan’s plasma environment, so this series of four flybys, especially T41 through T43, will offer that opportunity.

I wonder if it would be possible to include the expected SAR RADAR Swath track in the mission description?

I'm really curious to know if this swath will view Kerguelen Facula (which I bet will look like Sotra Facula) or image any parts of the Sliced Carrot feature of NW Shangri-La.

-Mike

No, the swath cuts a little further north than Kerguelen.

The SAR swaths are not as straightforwardly pipelined a product as the image views are.

Nothing is impossible. Everything takes work.

Who do you think writes the captions for these image releases? It's part of the job, but not
a part that gets you fame and fortune. (Arguably writing papers for Science doesnt get you
those either, but at least journal publications are a metric by which planetary scientists'
careers are partly judged.)

I've spent many an evening browsing through the Planetary Photojournal. I've found the captions easily understandable and very well written. The legends usually capture the essence of a key concept in planetary science. Each image provides yet another vignette of a beautifully complex system slowly being revealed.

I see it as a part of the continuum of research and education. The scientific papers have the full research, but are accessible and understandable to a limited few (and don't even get me started about journal access). In contrast, the Planetary Photojournal images and CHARM presentations are freely available and are for a much wider audience. Even in the UMSF domain of amateur enthusiasts, most of the Planetary Photojournal images are picked up and discussed immediately, while a lesser fraction of the scientific papers are presented.

I'd be interested in knowing how many hits an image in the Planetary Photojournal gets compared to an article in a scientific journal.

Even more important, who is reading it? I can imagine an interested high school student surfing the Planetary Photojournal, but not easily browsing the latest issue of Icarus. (Most high school libraries don't carry Icarus).

-Mike

Very good points, Mike. I guess you're guilting us into being more diligent about these!

FYI, what happens is the team decides on image segments to release (e.g. that do not compromise
upcoming publications and perhaps adjust/improve their appearance, since first SAR processing run
with predicted attitude and ephemeris can be ratty) and then writes a draft caption. Captions then get
edited and approved by JPL and HQ, which typically takes several days - this process usually entails the
introduction of english units and the removal of terms that are too arcanely geological (i.e. specific and
accurate). So it can be pretty thankless.

Based on comments a friends of mine made about the athletic shoe industry, I've always seen space science aficionado-dom similarly. There is a tiny group of hardcore practitioners doing active research at the top, then a larger but still small group of heavy fans, then a much larger group of people who give the topic their attention from time to time, and the larger still, perhaps, group of people who don't care at all.

The career rewards that Ralph allude to key very highly off the responses of the tippy-top alone, factoring in appeal to the next segments down almost not at all. Unless, like Carl Sagan, you create a PR tour de force like "Cosmos". Of course, that's not all Sagan did...

It's true in other disciplines as well. You've got some jazz musicians out there who are respected largely by other jazz musicians and hardly sell any records at all. As to which deserve more accolades is a matter of philosophy -- and funding.

Sounds like a perfect job for some UMSF volunteers.

Janus - 189,602 kilometers away
Enceladus - 515,115 kilometers away

I just noticed the subheading....last flyby of the primary mission already, I can remember when she was launched

Has it really been 44 titan flybys? Truly amazing, it feels like the first mapping began yesterday

well, really it's been 45, unless you count T0, in which case it is 46

remember Cassini counting, 0, A, B, C, 3, 4, 5,......44

Raw images are up! An interesting one is shown below (1). Looks like a cloud band in N00111091 taken on May 28, 2008 from approximately 43,517 kilometers away using the CL1 and CB3 filters. Not sure of the location, probably in the southern hemisphere (see mission description image (2) below) at the -40 degree latitude where cloud bands are commonly seen (as shown in the Keck image from 2004 (3).

1) Click to view attachment 2)Click to view attachment 3)Click to view attachment

I wouldn't assume that. Most of the more recent clouds have been either at 60N or closer to the north pole. Given where we had image plans and what we've seen lately, I presume this image is from our GLOBMAP observation and shows these high northern clouds (haven't gotten into work yet so I have checked the image geometry).

EDIT: No, that's our Hotei stuff. But still the clouds are at a more northern latitude from the looks of it.

The photo with the cloud seems to show the unilluminated side of Titan to the right. The T44 description and the solar system simulator shows this configuration to be before closest approach. As Cassini travels at approx. 21,600 km/h the photo (taken at 43,162 km from Titan) would have taken about 2 hrs before closest approch putting more of the southern hemisphere in view (the 2 hr before closest approach diagram shows an imaging center of -20 to -30 latitude). To me this suggests the clouds are more likely in the southern hemisphere. Agree it may not be at -40 however, possibly -25 to -30 ( approx. window of the NAC at time). The cloud may therefore be just east of Hotei Arcus. The inbound VIMS cloud map imaging should help decide.

Image from June 13th distant peek:

N00112025.jpg

Someone please tell me this isn't what it looks like.

-Mike

It isn't what it looks like.

Cool.

What causes this effect?

-Mike

A cosm[et]ic ray hit. Looks like this one was a whopper, though. Oblique particle entry angles can cause streaks like this.

Ouch. Hope nothing got permanently hurt.

Hits like this occur all the time, but since the camera is not taking pictures most of the time, you don't notice them. The CCDs were clobbered this way for 11 years now. Most hits don't do real damage, but some can produce hot pixels or otherwise affect/degrade the sensitivity of the chip. Space is harsh.

Yes, I remember that noise hit... I curse what ever produced that cosmic ray. I spent a half hour removing that thing by hand (time increased though by listening to a Phoenix telecon at the same time).

Nice view of the north polar hood from T44 flyby.
Click to view attachment

PIA10956: Xanadu's Channels
http://photojournal.jpl.nasa.gov/catalog/PIA10956

Very interesting. Looking through our Ta and Tb data to see what ISS has to say about this region. Though, I should point out that the edge of Xanadu is not seen here. Just the edge of the mountainous region in Xanadu.

Does any part of that image overlap with the T13 Swath, or does it just miss?

I think I've almost got it located but I'm not sure...

-Mike

(Any chance the rest of the swath will be released? It's been a while since we've seen a full one)

So is that dark object in the PIA10956 a dome or a lake with a crusty zone?

Click to view attachmentClick to view attachment

RADAR look angle seems to be coming from the NW, as inferred from the reflection pattern of the carved channel (left image).
(steep faces reflect back radar signal and appear bright, or reflect away RADAR signal and appear dark, depending on angle towards or away from RADAR look direction.)

Based on the RADAR look angle and the RADAR brightening on the near margin of the the dark circular feature (right image above), it could be a raised Ganesa-style pancake dome, but on a much smaller scale, or it could be a circular lakebed that dried and has a surrounding slightly RADAR brighter "crusty zone". (With the SW side of the "crusty zone" not visible for some reason)

-Mike

'Does any part of that image overlap with the T13 Swath, or does it just miss?

I think I've almost got it located but I'm not sure...'

Seems its very near the overlap of the lower border of T13 and upper border of T44. (see grid map below). Location of PIA10956 is given as -15 (S) and 121 (W) so I've placed the center of the image over that grid point. Clearly within Xanadu as volcanopele pointed out.

Click to view attachment

'So is that dark object in the PIA10956 a dome or a lake with a crusty zone?'

That radar dark area reminds me of a degraded crater (or dried up lake) with a delta wash through deposit. There appears to be a channel (black arrows) flowing from (do I dare say) from East to West (white arrow). Can't quite make out the outlet breach for the shizzle but I wonder if it eventually joins the larger delta to the west.

Click to view attachment

It must be located somewhere between and slightly north of Eir Macula and Tui Regio:

I think there's some seriously complicated stuff going on in this image:

Click to view attachment

I suspect that there is a long channel (tectonic fault? ancient riverbed?) running from NW to SE (red arrows in image; red dotted line in diagram).
This may have been an old river channel.

This runs parallel to the bright dark boundary and seems to run parallel to some of the mountain chains (and also to the RADAR seam - so the line up of the mountain chain could be a look angle effect).

The violent bend (indicated by blue arrow in image) in the western wide RADAR-bright channel (channel A, dark blue in the diagram) happens right where it intersects this long channel. Could it be that it captured part of the ancient stream channel?

Going upstream a tad from the first 90 degree bend, the channel turns away from the long NW to SE channel and cuts through the mountains. It appears that it's direction is altered due to a roughly W-E tectonic ridge (black dashed line in figure) that breaks the NW-SE channel.

It is VERY interesting how the Stream channel A cuts straight line through the NW-SE mountains. ("Like butter").
To me, that implies that either the stream existed first, and the mountains rose up slowly as the stream cut through (example: New River in the Appalachians) or that the river was cutting a straight course in a sl. sloping soft landscape and erosion slowly revealed the mountain range as the covering landscape eroded away (example: Green River through the Uinta Mountians).

On the other side of the EW tectonic ridge, near the circular feature there is a RADAR-brighter wispy feature ("B", light blue, I'm not comfortable calling it a channel near the circular feature) that runs roughly parallel to the tectonic ridge until it turns into the NW-SE long channel.

The current drainage pattern seems to be constrained by the EW tectonic ridges, but use (capture) segments of the (older?) NW-SE long channel.

-Mike

This "dome or crusty lake thing" is really bugging me. There appears to be a RADAR darker outer margin as well.

It is a RADAR dark circular feature with a RADAR-brighter margin facing the look angle, as well as an outer RADAR-dark outer margin in the direction of the look angle.
This would be consistent with a RADAR dark feature with a semicircular trench/channel/valley at the edge.

The dark outer margin of the Xanadu feature is puzzling: the Ganesa Macula dome doesn't look like this, the lakes (even the crusty ones) don't look like this. The RADAR-bright margin of these Ganesa and the crusty zone lakes blends into the background.

The only thing I've seen similar is another dark circle in the NW Xanadu tectonic ridge image (PIA10654). It also has the same aspect with regard to look angle. (It is also situated next to an EW tectonic ridge as well).

Here is an graphic showing these two features in comparison. (I'm no longer real comfortable calling the NW Xanadu feature a degraded crater.)

Click to view attachment

-Mike

The analogue I keep thinking of is water flowing on top of a glacier, creating total chaos:


And the channels starting out from both on top of and beneath the glacier forming channels on the plain...


So what are the chances that you get the solid phase being eroded by the liquid phase of the same compound in those radar bright areas? With ice/water on earth on polythermal glaciers, you also get the occasional supraglacial lake:


I guess it's required to have temperatures both above and below the freezing point at various times in the year...

Not necessarily. (Those are really pretty pictures, BTW)

You could have some sort of organic solid being extruded out onto the Titanian surface. It could be plastic enough when it comes out to make a pancake shape when it hits a flat surface (like pancake batter). But some of the materials may be easily dissolved, or could be liquid themselves. (Hypothetical example, a mixture of acetonitrile and ethane bubblin' up from the ground, as the acetonitrile sets up, the ethane separates out and flows away, like liquid water in the glacier examples above.)

That would leave you with a dome of an organic solid (acetonitrile in the example above) with flow features around the margins.

Altough the dome shape might be similar, the mechanism would be different from a cryovolcanic pancake dome like Ganesa Macula. Ganesa is presumably cryolava (molten ice + organics). The "chemical glacier" described above is more like a mud volcano or seep of a different material than the crustal stuff and at lower temperature. It is interesting that the two examples in Xanadu both seem to be up against a mountainous area (tectonic ridge) on their backsides.

-Mike

The Ganesa-like feature you point out Mike looks like a modified crater to me. There is a hint of a shadow along the margin that would suggest that it is a depression. The bright edge could just be rougher terrain along the edge of the depression (larger rocks washed down from the surrounding mountains perhaps).

I'll buy that.

The dark outer margin is the depression inside the rim. The RADAR-bright inner margin is rockfall from the rim, and the overall dark stuff in the center is the typical fine mud deposits.

That explanation also kinda hints as to why the surrounding streams are so bright - Xanadu rocks like to break into big RADAR-bright chunks.

(But I'm still at a loss for why the backside of these features aren't also RADAR bright. I woulda thought rockfall around the rim would be pretty uniform.)

-Mike

Yup! There are four frames in the flyby set with clouds. Three of them make a sharp line at -19 S.
(That particular frame N0011091 is the one I can't figure out, but I think it's somewhere on Xanadu very close to Hotei Arcus.)

Three of the frames connect nicely across the "Pinecone" feature of Hotei Arcus, and the clouds overlap on the images.

So if we are seeing equatorial clouds, does this mean rain is coming soon?

(And are these methane clouds, or something upwind volatiles up?)

Nice. I've just checked the diagram with all the observed cloud locations on P14 of the recent Turtle, Perry et. al. lakes and weather paper. It does seem that -19 is one of the favoured latitudes, though rather less so than the others at -70, -40 and +56.

EDIT - The 'nice' image is of course in the Xanadu thread here http://www.unmannedspaceflight.com/index.p...st&id=16801

I think the T44 images are part of the data that was presented in the figure of the Turtle, Perry et al paper.

I'm pretty sure they correspond to the red rectangles (2008 data) in the figure. Which means that the fourth image NO111091 should be on a line with and to the W of the westmost image in the mosaic.

Which...I...just...couldn't...make....fit...

[I'll need to use the T47 Xanadu mosaic to make a T46 mosaic; then use the T46 mosaic to line up the last T44 image. The T46 set seems a little more accessible, is nice and high-res, and doesn't have as much apparent vignetting.]

One thing I noticed, is that even after lining up the surface features between two images, the clouds themselves seemed to move between images. There was a slight shift from one frame to the next. This might be a parallax effect, or it could be from me not being able to line up the images well. I think the clouds might be waaay the heck up there.

Might be fun with someone with more math skills to try to estimate cloud height based on the slight shift due to spacecraft motion. (Unfortunately, only one cloud frame was obtained over "The Pinecone", that would have made image lineup and distance estimation easier).

-Mike

I'm pretty sure they correspond to the red rectangles (2008 data) in the figure. Which means that the fourth image NO111091 should be on a line with and to the W of the westmost image in the mosaic.

Which...I...just...couldn't...make....fit...

Mike. The photos were taken at different distances from Titan by NAC. According to the raw images N0111091 was taken by the NAC about 2hrs before closest approach (at 43,517 km out). The frame of the NAC from mission description (and presumably any photos taken ) would cover latitudes 25-30 deg South, a bit different from the latitude of your cloud band. (see post # 16 and # 18). Photos N00111076 to N00111079 were taken a bit farther out from 57,911 to 54,583 km so a slightly different latitude may have been centered in the NAC. Also about 30 minutes would have elapsed between N00111079 and N0111091 and some cloud movement and configuration change may have occurred.

T44 - Equatorial Anti-Saturnian hemisphere (Southern/Southwestern Xanadu, Eir Macula, Eastern Tui Regio, North-central Shangri-la, Southern Dilmun)
Click to view attachment

T44 SAR Swath released as PIA12989