Rev 141 - Nov 20-Dec 10, 2010 - Hyperion and Enceladus E12 Options

[jasedm]

The latest article has been up a few days, and goodies include a doppler-tracking pass over Enceladus' northern hemisphere, a search for Rhea co-orbitals, and the first reasonable-range imaging of Hyperion for five years.
The article doesn't state whether a different hemisphere will be on view than that imaged during the targeted flyby in '05, but I suppose it would be very unlucky if this was the case.

Images from the Hyperion encounter should be comparable to this:

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[Holder of the Tw...]

The rotation of Hyperion is chaotic, so it may not be possible to predict how it will be oriented very far in advance.

[Hungry4info]

Hyperion images are down.

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[nprev]

Thank you, Hungry. Always good to see new views of our favorite celestial sponge!

Speaking of new views, has Hyperion's spin state been decisively resolved yet? I remember some buzz a few years back that it may be chaotic, but have heard nothing further for quite some time now.

[Hungry4info]

Any time .
Hyperion's rotation axis was found to be chaotic from ground-based photometry after the Voyager encounters. Something to do with Titan being nearby?

[nprev]

Yeah, it does get pretty close to The Big Guy, and that'd do it!

So, Cassini planners aren't completely sure what they're going to see during each of these encounters. Interesting. I wonder if there's any attempt to see if the spin-axis precession might be "stochastic" instead of straight-up chaotic (if you know what I mean) given that we can now resolve & record the relative positions of small-scale surface features during these encounters.

[Hungry4info]

I was wondering the same thing and did some digging earlier and came across this paper, which seemed to rule that out.

The chaotic rotation of Hyperion

As tidal dissipation drives Hyperion's spin toward a nearly synchronous value, Hyperion necessarily enters the large chaotic zone. At this point Hyperion becomes attitude unstable and begins to tumble. Capture from the chaotic state into the synchronous or ½ state is impossible since they are also attitude unstable. The 3/2 state does not exist. Capture into the stable 2 state is possible, but improbable. It is expected that Hyperion will be found tumbling chaotically.

[Phil Stooke]

Hyperion's rotation has also been modelled as a slow long axis rotation with large precession, like the nucleus of Halley's comet and asteroid Toutatis:

Hyperion: Rotation, Shape, and Geology from Voyager Images
Icarus, Volume 117, Issue 1, September 1995, Pages 128-148
P. C. Thomas, G. J. Black and P. D. Nicholson


This would be complex but predictable, not chaotic.

Phil

[tedstryk]

Glad to see Cassini back at work. These images of Hyperion are phenomenal!

[Ian R]

Here's an early morning crack at a GRN/IR/UV colour composite:

[JohnVV]

it is looking like i am going to need to add some new images to my map of Hyperion

[john_s]

...This would be complex but predictable, not chaotic.

The latest analysis of Hyperion's rotation was presented at the 2010 DPS meeting in October. The precession of the spin axis is not behaving as expected, perhaps due to internal inhomogeneities. So we still don't have a good rotational model for Hyperion. And to nit-pick, there isn't a clear distinction between "predictable" and "chaotic" - "chaotic" behavior is always predictable in theory, given perfect knowledge of initial conditions- it's just that tiny changes in initial conditions translate to large variations in future behavior.

[edit] I should add that it's my understanding that for Hyperion the rate at which its rotation would diverge from predictions (if we had a good enough understanding of its current behavior to make predictions) is fairly slow (many months?), so while it's truly chaotic it's less chaotic than many other systems, such as the Earth's weather.

John

[Phil Stooke]

Thanks - I hadn't seen that abstract.

Phil

[ugordan]

Looks like the remaining Hyperion images have been dumped onto the raw pages.

[ZLD]

Did a little bit of processing on some of the new data and came up with this:


This is a false color image using the IR1, GRN and UV3 filters.


Also, it looks like a few images of Titan were actually snapped. A good range of filters were used including Red, GRN, BL1. After a little processing it produced this:



I'm sure someone can do better than this with the data. These were done in a really short time (less than 20m). It looks like a great flyby movie could be done of Hyperion as well.

[brellis]

Re: john's post about the distinction between predictability and chaos:

I'm reminded of one reason I'm so fascinated with astronomy and the science of not-yet-fully-understood objects like the Saturnian moons. As a music student, I found the concept of ''constrained random fields'' in orchestral instructions very interesting and it became a tool I continue to use in my compositions. A piece of music can progress along a ''predictable'' course, then have moments of chaos.

An educated ear might be able to ascertain the method employed in a chaotic passage of music, and thus find it ''predictable''.

Similarly, thanks to Cassini and their wonderful team, we might ascertain the chaotic aspects of Hyperion's orbit.

However, I doubt we'll ever be able to predict Earth's weather.

[Ian R]

Here's a 'tweened' flyby movie of this encounter:

http://www.youtube.com/watch?v=il1igwWjPds&fmt=22

[Hungry4info]

I keep getting an error.
This link works, however.

[ZLD]

Its a little rough but I like it just as well . Thanks for animating this. I was really curious how it would look.

[EDG]

These Hyperion pics are awesome! The movie's very cool too.

[DFinfrock]

I was really curious how it would look.

What I am really curious about is what a lander on Hyperion would see. With that complicated, tumbling, chaotic rotation, the view from the Hyperian surface, of both Saturn and Titan rising and setting at different angles and varying times of "day" must be a most unusual experience.

David

[peter59]

A surprisingly strong and well defined jets. Especially this stream to the right.
http://saturn.jpl.nasa.gov/multimedia/imag...5/N00165288.jpg

[machi]

Quick false color image (filters IR2, GRN, UV3) of Enceladus jets from yesterday's flyby.

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[ngunn]

Superb! It's amazing how adding the colour dimension, even if it's not real as-you-would-see-it colour, still adds 'reality' to the picture. (I think you've also cleverly smoothed out the greyscale steps a bit, but I'm not sure, and I don't need to know anyway.)

EDIT: Oh, and the dark limb of Enceladus is clearly visible all the way round to the bottom left of your version. Well picked out.

[EDG]

Aesthetically speaking at least, this is a particularly gorgeous image IMO:

http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=230048



There's about 25 of those plume images on the latest raw images index, I wonder if they'd be animatable so we can see changes in the plumes?

[EDG]

Also, were the Hyperion images the result of a targeted flyby of that moon, or was this a non-targeted flyby in which Cassini opportunistically imaged it because the geometry happened to be good at the time? (I'm suspecting it was targeted, since there's rather a lot of Hyperion images on the site!).

[djellison]

Also, were the Hyperion images the result of a targeted flyby of that moon

http://www.planetary.org/explore/topics/ca.../tour.html#2010

Sun, Nov 28, 2010
2010-332T03:29Nontargeted flyby of Hyperion (141H)
Inbound 71756.3 km flyby, speed = 4.9 km/s, phase = 73°


Thanks Emily

[EDG]

Ah! That's a stupendously handy reference - thanks!

(BTW, what's up with the UV1 filter on wheel 2? The images of Hyperion taken through that have lots of white speckles on them)

[djellison]

Could be that it's a very 'dark' filter (i.e. it's bandpass is either narrow, or well outside the best efficiency of the ccd, or both) and thus requires long exposure times and thus the raw unprocessed imagery is prone to noise.

[EDG]

Here's a 'tweened' flyby movie of this encounter:

http://www.youtube.com/watch?v=il1igwWjPds&fmt=22

Did you put that together? I'd like to mention/link to it on my blog if I could.

[EDG]

I've put together a sequence of images of Hyperion (false colour, from the IR/Green/UV images) from the November 2010 sequence that you guys might appreciate .

I've also written an article about the images and Hyperion on my Science blog!

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[Ian R]

Did you put that together? I'd like to mention/link to it on my blog if I could.

Yes, that's mine: you're more than welcome to use it on your blog. As it happens, I've just produced a slightly better colorized version too:

http://www.youtube.com/watch?v=U5VfYDYL3rA

[Ian R]

The Enceladan horizon from 51 kilometres above the surface:




http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=230082

[EDG]

Yes, that's mine: you're more than welcome to use it on your blog. As it happens, I've just produced a slightly better colorized version too:

http://www.youtube.com/watch?v=U5VfYDYL3rA

Great, thanks! I've updated the link on my blog to it as well.

The Enceladan horizon from 51 kilometres above the surface:




http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=230082

Blimey, that's cutting it close!

[EDG]

Nice new one of Enceladus over the rings (or maybe the shadow of the rings on Saturn?):

http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=230086

I think something weird going on here (taken with CL1 and CL2):

http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=230114

Compare that with this (same filters):

http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=230116

It looks to me like the first image has more specular reflection (and contrast) in it? Is that just down to different exposure lengths, or is something else going on? Or is it just an illusion?

[volcanopele]

It is just a different stretch used by the JPL raw images page. The first image has fewer pixels on Enceladus' night side so the black level is set at a higher I/F than in the second image.

[Phil Stooke]

Very serious case of deja vu with this image:

http://saturn.jpl.nasa.gov/multimedia/imag...5/N00165320.jpg

Doesn't the terminator region look like the well-known corona on Miranda? I think so.

Phil

[Ian R]

Here's a IR/UV/GRN combo, with the saturation increased, and the gamma decreased:



The small orange splotch that appears half way up, on the far left of the image, appears to be a real feature; it's very prominent in the UV image, and faintly visible in the GRN filter too.

[ugordan]

The small orange splotch that appears half way up, on the far left of the image, appears to be a real feature

Sorry, that's a flatfield effect. Another dust ring effect or similar.

[Ian R]

Gordan,

I stand corrected! It was the differing visibility of this feature in the individual filters that threw me: a quick check of several different UV-filtered images confirm that it is indeed an artefact.

In the meantime, here's a four-frame clear filter mosaic:

[ugordan]

Nice!

[tedstryk]

Very serious case of deja vu with this image:

http://saturn.jpl.nasa.gov/multimedia/imag...5/N00165320.jpg

Doesn't the terminator region look like the well-known corona on Miranda? I think so.

Phil

It is uncanny...

[elakdawalla]

In the meantime, here's a four-frame clear filter mosaic:

Great stuff, Ian. I tried to put that one together but couldn't figure out how to deal with Saturn's shifting position. Your cheat is quite elegant!

[brellis]

Ian, that's a great composite! thanks for posting it

[stevesliva]

Doesn't the terminator region look like the well-known corona on Miranda? I think so.

Hey, look at that, Miranda is hypothesized to have once been in a 3:1 resonance with Umbriel and had more tidal heating.

Good captioned version of the photo here:
http://nssdc.gsfc.nasa.gov/imgcat/html/obj...g2_2684620.html

[EDG]

In the meantime, here's a four-frame clear filter mosaic:

Wow, that is an absolutely gorgeous image! I love the ring in the background too!

(EDIT: Oh, now I see the "cheat" that you used that Emily mentioned - the background was changing as the images were being taken so you've smoothed that out)

[Bjorn Jonsson]

(BTW, what's up with the UV1 filter on wheel 2? The images of Hyperion taken through that have lots of white speckles on them)

Could be that it's a very 'dark' filter (i.e. it's bandpass is either narrow, or well outside the best efficiency of the ccd, or both) and thus requires long exposure times and thus the raw unprocessed imagery is prone to noise.

Yes, that's it - the UV1 images are always long exposure images and thus noisy. All (or possibly most - I'm too lazy to check it) of the UV1 images are like this.

BTW lovely mosaics and color composites by Ian.

[JohnVV]

just some fun
a few shots from the rev 141
I have been fixing my spice kernels - things got a bit messed up .


oops i need to move the post

[charborob]

There is a long series of images of a Tethys-Dione mutual event on the Cassini raw images pages. These images are just begging for an animation. (No, sorry, I can't do it myself now, I've got work to do .)

[Hungry4info]

http://www.youtube.com/watch?v=Hm955AJ_yJ4

I made no effort to re-centre Dione (seemed a lot of effort for so many images).

[Ian R]

Here's my version, making full use of the R/G/B filtered images:

http://www.youtube.com/watch?v=gN62-at3Xm4

[Ian R]

I've re-compiled the video linked in my previous post based on a very good suggestion from Emily.

[eoincampbell]

So gracious, love watching that, thanks