Rev166: May 11th - May 28th 2012, Tethys, Methone, Titan Options

[jasedm]

Latest looking ahead article is available.

I've been looking forward to this one for a while as we get our first decent look at Methone Closest ISS activity is from 4,500km, which should yield images comparable to the best views we have so far of Atlas.

There are also images planned of Tethys' trailing hemisphere from mid-ranges, and of course a close (955km) Titan flyby with specular-reflection searches, and radar swaths at C/A. This is the flyby whereby Titan bends Cassini's orbit 'down' and out of the ring plane for the next couple of years.

I know we can't have it all, but I was hoping for another decent look at Telesto on this rev (Cassini buzzes past at around 11,000km) which would have given us images at high phases and from almost the same range as the flyby in 2005. Never mind, there's another similar-range pass to Telesto in 2015.

Lots to look forward to.

Jase

[Holder of the Tw...]

... we get our first decent look at Methone ...

At last.

[jasedm]

Re: Methone, Emily's wish came true....(from 6 years ago on this forum):

"Although I wouldn't call this a "main focus," I would like to see the trajectory studied hard for the opportunity to do a pretty close flyby (say around 2,000 km) of one of the itty bitty moons, and to give the flyby a resonably dense set of observations. The closest Cassini will get to any of those things during the primary mission is 10,000 km from Telesto, which happened on October 11. Hyperion looked so bizarre up close, I'd like to see what one or two of the itty bitty ones -- Methone, Pallene, Calypso, Polydeuces, or Helene looks like from that kind of perspective."

--Emily

[machi]

Does anyone know why is imaging from 4,500 km and not from ~2,000 km (closest distance to Methone)?

[nprev]

I'm guessing that the relative motion at closest approach might be too high for a target with such a small angular diameter.

[Phil Stooke]

Or maybe the closest view direction would be very high phase angle? (mostly shadow)

Phil

[machi]

According to great PS site http://www.planetary.org/explore/space-top...sinis-tour.html ,
Methone flyby is at modest speed 5.1 km/s, but relatively high phase angle 126°, so I think, that Phil can be right.
But on other side, even high phase angle images are very useful, not only because Methone will be much closer in this case (1861 km), but because of photometric investigations of Methone's surface (regolit roughness etc).

[jasedm]

My guess is that there is perhaps still sufficient uncertainty about perturbations to Methone's orbit, that the further distance ensures Methone falls within frame. (remember the Helene flyby where some the closest NAC frames missed Helene altogether)

Jase

[ugordan]

Titan's south polar haze layer is certainly starting to look interesting. Judging by these CB2 and BL1 images, it would appear larger particles (judging by the prominent visibility in the infrared CB2 filter as well) are piling on top of the detched haze layer (!?).

[titanicrivers]

Interesting indeed. A bright portion is visible even in the CL1 CB3 images. Using the filters' depth penetration one can build a nice visual analysis of the S Polar haze from Cassini's most recent Rev 166 images.

[belleraphon1]

Methone and Tethys images are here:

Methone - wow!? Smmooth....
http://saturn.jpl.nasa.gov/multimedia/imag...3/N00189072.jpg

Tethys
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=261595

Craig

[Bjorn Jonsson]

Wow. At this resolution Methone seems completely free of craters. Coated with a thick layer of dust or could this small body simply be a 'clump' of dust?

[belleraphon1]

Probably getting coated by a lot of ice particles from Enceladian plumes? Cool little worldlet.

[Phil Stooke]

Spectacular! Here's a cleaned-up and contract-enhanced image of Methone. There are real albedo variations across it.

Phil

[machi]

Wow! This must be the biggest egg in the Universe!