[X] My Assistant

[Guest_AlexBlackwell_*]

Since Emily posted in her LPSC notes:

"So, so much for Titan. All in all, there wasn't a lot that was new, either new data or new insight. I wish now that I'd skipped the latter part of the Titan session and gone to the rovers, but it was too late for that. The radar story will get more interesting, because after a long hiatus in the acquisition of radar data they are going to be getting a lot more radar passes beginning with the T13 flyby on April 30, so there is much to look forward to there."

I guess I'll go ahead and post the science highlights for the T13 flyby:

T13 - Science Highlights

Imaging Science Subsystem (ISS) – will observe particle properties, vertical distributions (~6 km/px. 0.6 Mbit/frame with 2x2 summing). ISS will also examine wind/cloud motions; (3-12 km/px, 3 images/timestep in CB1 filter to increase SNR), and search for and monitor lightning/aurora. (high-resolution imaging, 50-200 m/px, special targets, emission angles < 45 prefer IR-polarizer (phase 45-110)).

Cassini Plasma Spectrometer (CAPS) – will investigate large-scale and distant aspects of the Titan interaction by observing during entire period around an encounter from 10 to 25 RS.

Composite Infrared Spectrometer (CIRS) –will obtain information on trace constituents in Titan's stratosphere. Integrate on limb at two positions POINTING: Obtain information on CO, HCN, CH4. Integrate on disk at air mass 1.5-2.0. POINTING: -y to Titan, x away from sun.

Ultraviolet Imaging Spectrometer (UVIS) – will observe star Beta Ori as it becomes occulted by Titan’s atmosphere.

Visible and Infrared Mapping Spectrometer (VIMS) – will obtain new high resolution images that will help understand Titan's geology and the fate of CH4.

Magnetometer (MAG) – will investigate large-scale and distant aspects of the Titan interaction by observing during entire period around an encounter from 10 to 25 RS. (23TI (T13)) T13 is an equatorial wake flyby under plasma conditions near Saturnian local midnight with 1852 km altitude at CA. Thus it is very similar to T11 even according to local time.

Magnetospheric Imaging Instrument (MIMI) – will investigate micro-scale and near aspects of the Titan interaction by observing during about one hour period around an encounter. With -Y pointed toward Titan, when within 30 minutes of the targeted flyby, optimize secondary axis for co-rotation flow as close to the S/C -X, +/- Z plane as works with the other constraints on pointing. Also, measure Titan exosphere/magnetosphere interaction by imaging in ENA with INCA (when sun is not in INCA FOV).

Ion and Neutral Mass Spectrometer (INMS) – will obtain data regarding Titan’s atmospheric and ionospheric composition and thermal structure. INMS will also observe the magnetospheric/ionospheric interaction.

Radio and Plasma Wave Spectrometer (RPWS) – will perform observations in the immediate vicinity of Titan, including thermal plasma density and temperature measurements with the Langmuir probe, search for lightning and other radio emissions, characterization of plasma wave spectrum, search for evidence of pickup ions. Langmuir probe within 90 degrees of spacecraft ram at closest approach, co-rotational ram outside of +/- 15 minutes.

RADAR – will perform low and high resolution SAR (Synthetic Aperture RADAR) imagine of Titan’s surface. Additionally, RADAR will collect Altimetry, Radiometry, and Scatterometry Data.

[ljk4-1]

It was a pleasure, ljk4-1, but the credit actually belongs to Mr. Pesek, (1919 - 1999), a great space artist - especially his works on Mars. Still, it should help us while away the time until the RADAR team releases the first portions of the SAR swath.

Yes, Ludek Pesek was one of the great "reality" space artists. I fondly recall his
work in the National Geographic magazines of the early 1970s. I always end up
comparing other's similar work to his.

It that the same NGM issue which depicts a Venera lander on the Venusian surface?

[Guest_BruceMoomaw_*]

Marvelous new SAR images. Regarding the ambiguity as to whether the circular features we're seeing are craters or calderas, there was yet another LPSC abstract at http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1659.pdf . It's beginning, however, to look more and more ominously possible that Cassini's coverage of more and more of Titan's surface area may not enable us to understand much more about just what it is we're actually looking at -- for that we'll need higher resolution, which Cassini cannot provide.

(A pity that features on Titan aren't named after famous monsters of myth. In that case we could have "Dracula Facula".)

[Thorsten]

Absolutely great pictures! Amazing, but the channels appear to be more easily discernable in the ISS pictures than in the RADAR release (especially the “Thames” at the bottom of Shikoku/”Great Britain”. Also, could that be a second, partially degraded, impact crater (middle left at the height of “Wales”)? The image to the left is taken from Porco et al., 2005.

Attached thumbnail(s)

 

[The Messenger]

[url=http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1659.pdf]

From Bruce's reference:

This T7 feature would be interpreted without doubt as an impact crater if it were imaged by radar on
Venus or the Moon. The reason for certainty there, but hesitation on Titan, is that those other worlds
exhibit a continuum of crater sizes....

Ink Dots: Another class of dark floored rings is abundant in the western end of the T8 swath. These
are generally clustered together and are much smaller, typically only 1-2 km wide. Ink Dots appear
less likely to be impact craters because of their clustering – they are not secondary craters because
there is no apparent primary crater. Ink Dots may be the small end tail of the distribution of DFF.

Wouldn't a cluster likely occur when a comet-like object from the Kuiper belt broke up before impact? Are not comets a likely source of impact fodder after Titan's resurfacing?

[remcook]

you can't see the crater(?) at all in the visible images! submerged?

[ugordan]

Communication from the spacecraft was temporarily interrupted for nearly five hours during the data playback following the flyby. The most important science data from the flyby were protected by a contingency plan put in place in advance of the flyby. The flight team believes the outage was likely due to a galactic cosmic-ray hit on a power switch in the spacecraft communications subsystem. The anomaly resulted in the loss of some science data. However, the spacecraft is now performing normally.

Ahhh... lucky number 13 strikes again... Even though we all know it was actually flyby number 14

Does anyone know more about what science data was lost? I was somewhat surprised to see so few high-res ISS footprints in the raws. Also, it's nice they came out and told us openly about the problem -- unlike T7.

[volcanopele]

Absolutely great pictures! Amazing, but the channels appear to be more easily discernable in the ISS pictures than in the RADAR release (especially the “Thames” at the bottom of Shikoku/”Great Britain”. Also, could that be a second, partially degraded, impact crater (middle left at the height of “Wales”)? The image to the left is taken from Porco et al., 2005.

I think that the resolution of the SAR data at Shikoku, which if you look at the ISS-RADAR comparison movie you can see that it is very close to the end of the swath (the right edge was just a temporary cutoff until the rest of the data was processed after that movie was made), is only a little bit better than the best ISS data at Shikoku. For example, look at the dark circular spot in NE Shikoku. If you look about one spot diameter south of it, you see a very bright spot (also visible in the ISS image). Below that is a dark channel that runs to the east. If you trace that channel west, it splits in two. Okay, that channel is visible, just barely, in ISS data from T10 I think. so in this area, the sar is low enough in resolution to be comparable with the ISS data. as you go farther east, like with the Guabonito section, the resolution obviously improves. BTW, I don't see that second crater you mention.

you can't see the crater(?) at all in the visible images! submerged?

Well, it simply means that you have the same type of material (water ice, acetylene, plutonium... ) that shows up as bright in ISS and "blue" in 1.3-2-5 micron VIMS data but can be either smooth or rough. Some how, this smooth area has avoided being filed with dark material.

Does anyone know more about what science data was lost? I was somewhat surprised to see so few high-res ISS footprints in the raws. Also, it's nice they came out and told us openly about the problem -- unlike T7.

We lost a lot of our more distant images of titan on this encounter. We also lost half of our high-res mosaic. I head that some of our high phase satellite observations post-T13 may have been lost due to the contingency recovery of part of the Titan C/A data (UVIS occultation, SAR), but some of that is now on the JPL raw images page, so who knows...

[ugordan]

I head that some of our high phase satellite observations post-T13 may have been lost due to the contingency recovery of part of the Titan C/A data (UVIS occultation, SAR), but some of that is now on the JPL raw images page, so who knows...

Am I correct in assuming the losses were solely due to data being overwritten by subsequent (non-Titan) observations? Those lost high phase observations that you mention would then be lost simply because the s/c team quickly repartitioned the recorder usage so as not to overwrite other, more important data? Or did they simply cancel those observations?

[volcanopele]

Am I correct in assuming the losses were solely due to data being overwritten by subsequent (non-Titan) observations? Those lost high phase observations that you mention would then be lost simply because the s/c team quickly repartitioned the recorder usage so as not to overwrite other, more important data? Or did they simply cancel those observations?

The data that would have been played back Tuesday, will not be played back, instead the SAR and other Titan C/A data was.

[scalbers]

Nice to see the new radar data so quickly. I played around with a smoother on the Shikoku Facula image to see whether it makes details easier or more difficult to see. I'll let the forum be the judge though I like some aspects of it.

http://laps.noaa.gov/albers/sos/saturn/tit...08426_sm3x7.jpg

It's also interesting to see the CICLOPS release comparing the ISS and radar. Perhaps a still image highlighting more a merged image of ISS & radar would look interesting? Also, some fancier Fourier type filtering might be applicable to combining the ISS & radar while passing in spatial frequencies in such a way to suppress some of the radar noise. Easy for me to say as I haven't actually tried this.

[volcanopele]

hmm, interesting.

one mode of comparison I like is to outline the bright and dark boundaries in an area on the ISS image then past those outlines on a co-aligned RADAR view to see how these boundaries line up, for example how they compare to the distribution of longitudinal dunes.

[mchan]

(A pity that features on Titan aren't named after famous monsters of myth. In that case we could have "Dracula Facula".)

Or take a page from Mel Brooks if the area has high methane concentration, ergo, Flatula Facula.

[Guest_BruceMoomaw_*]

You know, we may have a new parlor game here.

[ngunn]

Regarding the ambiguity as to whether the circular features we're seeing are craters or calderas, there was yet another LPSC abstract at [url=http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1659.pdf] .

Regarding the circular features: Impact craters and volcanic calderas are mentioned here, but are these the only possibilities? What sort of appearance would we expect from the remains of an ice/clathrate diapir that slowly made it all the way to the surface, rather like a terrestrial salt dome? (A kraken rather than a vampire?)

[Thorsten]

[quote name='volcanopele' date='May 4 2006, 06:04 PM' post='52766']
I think that the resolution of the SAR data at Shikoku, which if you look at the ISS-RADAR comparison movie you can see that it is very close to the end of the swath (the right edge was just a temporary cutoff until the rest of the data was processed after that movie was made), is only a little bit better than the best ISS data at Shikoku.

Thanks a lot, volcanopele. That was very informative!

The abundance of channels at Shikoku Facula is quite impressive, when compared to similar RADAR- and IR-bright regions at the same equatorial latitude (such as Adiri from the T8 SAR swath, where there is only one indication of fluid flow (at the NW of PIA03568 – Diverse Geology)).
Could this abundance of channels be somehow related to the topography of Shikoku – but why should that be so much different from Adiri, which also contains mountain ridges/ hills/ elevated terrain?
Or are the channels derived from underground methane released after the formation of the impact crater in NE Shikoku. However they appear to run parallel to the crater rather than starting from it. Furthermore, they seem to be more branched than the rather primitive looking channel features E of Menvra (in the T3 SAR picture PIA07366 - Huygens Landing Site Similarities). So could they possibly be the result of rainfall? Interesting!

However, for people who are fond of channels – like me - I could imagine that the T16 SAR swath at July 22 (which should cover regions close to the – presumably much wetter – north pole) will probably be a dream come true.