OPAG meeting November 2008 Options

[tty]

As for imagery...I vote IR!

How much IR would there be at that temperature?

[Juramike]

For fine IR spectral analysis, you'd need to bring your own IR source, as in this apparatus (which I refer to as "The Fickle Finger of Fate").

The diagnostic information from the IR bands that you'd get would only give you some functional group types. You'd still not be able to discern exact discrete chemisal structures ("Yup! There are some hydrocarbons in there!")
A better analytical tool would be GC analysis. Even better would be GC-MS.

For actual imaging, I'd be paranoid that a scum/crud/foam layer might extend up from the surface, and you'd be guessing how high up the mast to mount the camera to avoid looking at a bunch of suds. You might have the same problem under the surface as well.

Pure Hexanes and other hydrocarbons should be nice and clear. It is the trace polymers, emulsions, and other gookies that might crud stuff up under the surface - but the trace polymers, emulsions and gookies are exactly the things that might be the most chemically interesting.

-Mike

[rlorenz]

At the risk of sounding heretical, I would almost trade an imager for a basic underliquid sonar mapping capability...but upon further reflection, nah. We don't know enough about the liquid's composition to design such an instrument (though a depth sounder would be a must-have....

speak for yourself.....
Huygens had a depth-sounder which would have worked fine had we not dumped it in a desert.....

We know the speed of sound in liquid hydrocarbons (and the Huygens SSP
instruments were tested in the stuff). Sure, suspended gunk and dissolved goop may influence absorption/
scattering, but that's useful to measure too. I've recently looked at beam-steering sonar for Titan landers -
the difficulty is that the sound speed is high enough that for realistic frequencies the wavelength is long
enough that a beam-steering array needs to have a large physical separation between the radiating elements.

Really need to stream a sonar array behind us as we motor around doing Crazy Ivans in Kraken Mare

[nprev]

...I stand corrected, Ralph! (How about a towed transmitter with a little side-scan sonar receiver a few meters behind it for bottom mapping?)

TTY: IIRC, the best surface imagery's been observed at around 3 microns or so from VIMS? I don't think that's re-radiation from absorbed sunlight--it's probably direct solar illumination/reflection--and since it penetrates the haze & escapes to space more readily than the other bands I'm thinking that it might be the 'brightest' component of sunlight at the surface.

I bet that the liquid hydrocarbons & associated gunk absorb it pretty thoroughly, though; the mares look really, really dark.

[Juramike]

TTY: IIRC, the best surface imagery's been observed at around 3 microns or so from VIMS?

IIRC the best surface imagery is at 3 um from orbit because it has the best trade-off between useful signal and noise in an interesting region in a methane window with lower haze scattering.

Titan's atmospheric hazes really mess with the shorter wavelengths.

Shorter wavelengths (like ISS's 0.93 um and VIMS 1.28 um) have more haze-scattering (more fuzziness) but are brighter, while the longer wavelengths (like 5 um) have less haze-aerosol scattering, but are darker so there's more noise in the signal. (Graphic of Titan windows vs. water ice spectrum here)

-Mike

[vjkane]

Shorter wavelengths (like ISS's 0.93 um and VIMS 1.28 um) have more haze-scattering (more fuzziness) but are brighter, while the longer wavelengths (like 5 um) have less haze-aerosol scattering, but are darker so there's more noise in the signal. (Graphic of Titan windows vs. water ice spectrum here)

-Mike

Between the longer wavelength, atmospheric scatter, and the lack of shadows, imaging Titan is hard. Strategies such as really big cameras (think HiRise on MRO) probably won't work for increasing resolution. The proposed TSSM mission is planning on just 50 m. I work with Landsat 30 m images. This is a tool for characterizing landscapes, not for fine geology. Unfortunately, what makes Titan so interesting -- its atmosphere -- makes it harder to study. It's going to be hard to distinguish albedo features from topographic features without good shadowing.

There is one technical trick that could help. If you have a camera that looks down (nadir) and then offset to either front or back, you can generate stereo images with vertical resolution roughly the same as horizontal. Mars Express' camera does this as does the Terra ASTER camera. The data rate increases since you are taking two sets of images, but the offset image can be in a single color (the ASTER offset band is near IR, for example).

[stevesliva]

Really need to stream a sonar array behind us as we motor around doing Crazy Ivans in Kraken Mare

You expect those Titanian orcas to sneak up on you from behind?

[nprev]

Good point. Might be worth adding a hook and some bait (a nice, juicy ball of tar?) just in case!

The conditions would be ideal for trolling, anyhow; you have to move slowly to do sonar mapping or the image smears out.

[Juramike]

Gee, if we can extend the wireless range of this a few million km, we could get the Titan lake sonar results on our wristwatch.

[hendric]

The data rate increases since you are taking two sets of images, but the offset image can be in a single color (the ASTER offset band is near IR, for example).

There should be quite a bit of correlation between the two images. I think you could use a motion based compression algorithm to minimize the data transmission overhead of that extra image.

[rlorenz]

Between the longer wavelength, atmospheric scatter, and the lack of shadows, imaging Titan is hard. Strategies such as really big cameras (think HiRise on MRO) probably won't work for increasing resolution. The proposed TSSM mission is planning on just 50 m. I work with Landsat 30 m images. This is a tool for characterizing landscapes, not for fine geology. Unfortunately, what makes Titan so interesting -- its atmosphere -- makes it harder to study.

The atmosphere makes it easy to study in-situ, though, permitting the delivery to the surface of instrumentation
far easier than on an airless world. And of course permitting a balloon (or other aerial platform) which
can give you HiRise-resolution imagery...

(btw - people have said 3 microns is the best near-IR wavelength - actually it is 2 microns)

[infocat13]

The Argo PDF document is now up on the OPAG November meeting website


http://www.lpi.usra.edu/opag/nov2008Meetin...ations/argo.pdf


one trajectory option is Jupiter Saturn Neptune/Triton and then a KBO!


whats new? (from March meeting) science coverage of tritan northern hemishere

image triton unseen by voyager

[stevesliva]

Still really interesting, thanks.

On the "cost saving options" slide, it mentions making Jupiter and Saturn "missions of opportunity." Is there really enough runway to do that for Jupiter? Saturn I can believe.

Also interesting are the OPAG requests at the very end-- two of three are infrastructure! Hopefully that's an easier sell in the current economy.

[gpurcell]

Still really interesting, thanks.

On the "cost saving options" slide, it mentions making Jupiter and Saturn "missions of opportunity." Is there really enough runway to do that for Jupiter? Saturn I can believe.

I wonder if that is referring to a revenue-enhancement option rather than a cost-savings option! You've got a bare-bones NF mission under $800M and you also get $50-$100M for the MoO for Jupiter/Saturn...making the whole ball o'wax a $900M mission.