Enceladus E03 Flyby Options

[edstrick]

Regarding the image<s> of Enceladus with a possible plume in the south polar region. There is a series of short exposure images of the crescent on the JPL RAW pictures pages and a longer exposure (posted on the CICLOPS web page as "862-1905-3", cleaned up and without JPG artifacts). An even longer exposure on the JPL RAW pages is N00028218. The images show Enceladus as a thin crescent, illuminated by sunlight from about a 4:30 clock angle and as a fatter crescent, illuminated by Saturn from the 9:00 clock angle.
The unilluminated side of the moon between the crescents is visible in silhouette against a lighter background. This background is *NOT* the ring-lit nightside of saturn, 1.) since the dayside of saturn is to the left and out of the image, and 2.) because all images show stars or nearly horizontal star-trails, all parallel, tilted slightly down to the right, and varying in length in proportion to the exposure. I have to conclude that we are probably seeing the diffuse E-Ring in forward scattering, with Enceladus between the spacecraft and the bulk of the E-Ring.
I'm attaching a composite image with the two images named above, and two spatial-bandpass-filtered enhancements of 862-1905-3. These have been processed to enhance fine detail in the plumelike feature close to the moon's limb, and details further away from the limb. None of the images, including the long exposure N00028218, show any trace of the feature against the darkside of the moon above the sunlit crescent, and structures in the plumelike feature converge on the bright limb just like cometary jets seen at comets Halley and Borelly and Wild. There seem to be maybe 3 "sources" for the main plume-like feature and a fainter single-source plume-like feature to the right.
Except for a faint diagonal line "behind" Enceladus, visible in the last picture, which I suspect is a camera artifact or something, all features in this image seem consistent with the plume-like feature being real, not light scattered by contamination in the camera (which is a problem with the NA camera) or a lens-flare. I would have to see the images of other moons with simlar faux-plume features referred to a couple days ago by a team member (earlier in this thread) and apply contrast stretching and enhancement to them (using clean versions, not RAW's from the JPL website) to convince me this feature is not real and is not active plumes from Enceladus.

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[Guest_BruceMoomaw_*]

Personally, I'm waiting to find out whether Cassini detected any signs of outgassing with its multiple instruments suitable for that purpose (UV, mass and plasma spectrometers; dust analyzer).

I do note that two of the new LPSC abstracts reveal that (to the surprise of their experimenters) the UV and plasma spectrometers have not detected any sign of a nitrogen torus in Titan's orbit, indicating that at this time it is losing little nitrogen -- but there is a strong nitrogen torus centered on the E Ring, suggesting that something in that area is emitting ammonia. Enceladus would seem to be the obvious suspect. It HAS already been announced that its VIMS surprised evryone during the close flyby by not detecting any signs of frozen NH3 or CO2 on Enceladus' surface, which seems to be almost pure water ice. Is it possible that the water/ammonia mixture expelled from Encealdus' vents is warm enough that all the ammonia and CO2 vaporize and escape from the moon completely, leving just pure water ice behind?

[Bjorn Jonsson]

I have now updated my Cassini page by adding a new simple cylindrical map of Enceladus based on three T3 images. It can be seen here:

http://www.mmedia.is/bjj/misc/css_stuff/index.html

[volcanopele]

I have now updated my Cassini page by adding a new simple cylindrical map of Enceladus based on three T3 images. It can be seen here:

http://www.mmedia.is/bjj/misc/css_stuff/index.html

Very nicely done, Bjorn!!

[cIclops]

has there been an official statement from the Cassini folks about the cause of the pointing error during the T3 Enceladus close encounter?

[alan]

They expected pointing problems:



"A mission plan has not been made available for the Enceladus encounter, because it is a "nontargeted" flyby. Nontargeted flybys are targets of opportunity that occur because of a fortuitous alignment of the moons with Cassini's orbital path, while targeted flybys are set up with careful application of Cassini's thrusters to ensure that both the moon and the orbiter are in the same place at the same time. Cassini mission planner and Ultraviolet Imaging Spectrograph team member Amanda Hendrix explained that "because we are just two days after Titan-3, and it's not a targeted flyby" involving a thruster maneuver to trim the orbital path, "the orbital uncertainties will be high." This is especially true after a relatively close flyby of Titan, when Cassini will actually feel some drag from the outermost reaches of Titan's atmosphere."



"At the closest approach point, the cameras would be capable of images with resolutions as high as 9 meters per pixel, but it's not certain that these pictures will be captured. "At closest approach, we can't track Enceladus, since we're going by so close and are on [reaction] wheels," Hendrix explains. Cassini's reaction wheels are a more efficient way of pointing the spacecraft, but they cannot slew the spacecraft's pointing as quickly as the thrusters can, and Cassini will be moving very quickly past the closest approach with Enceladus. So while the cameras will be taking pictures at the closest approach point, mission planners can't be certain that Enceladus will be exactly at the spot where the pictures are being taken. "

From Planetay Society article for Feb 10
http://www.planetary.org/news/2005/cassini..._plan_0211.html

No Titan encouter before the next Enceladus flyby so this problem shouldn't reoccur.

[scalbers]

Greetings,

I had noticed that apparent plume also, glad to see it being discussed. I wanted to pass along that I have been working on a cylindrical Enceladus map the past few weeks. It's now in reasonably good shape to get ready for the next encounter this coming week. You can see this at my web site URL:

http://laps.fsl.noaa.gov/albers/sos/sos.html


Later,

Steve Albers

[Decepticon]

^ I love your Site!!!! Keep the excellent the work UP!

[teck]

Have a look at this image: is this a geiser at the bottom left end of the long fissure?

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[teck]

After some investigation, I did a small movie around the "geiser" image. It look like something is going on in this area. Unfortunately, we cannot see further down the image. For this movie I used those images: N00030070.jpg N00030071.jpg N00030072.jpg

If you look straight up the images, you see a wide valley with semi-cicular features which could be coming from this outpouring of "stuff" from a sort of moving "hot spot" under the crust or a moving crust. Does this make sense?

Thanks

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[Decepticon]

Neat, But I'm not sure where to look?

Is there any way to stable the image better?

[ilbasso]

There's definitely something there that is blurrier than the rest of the image - that puff or whatever stays blurry even as the rest of the image sharpens. Unless it's a reflection in the lens, it has to be a cloud of some sort.

[Bjorn Jonsson]

Simply looks like a smooth crater to me.

[Gsnorgathon]

Not everything that looks blurry is a cloud. I've seen quite a few MOC images where you'd swear the image was out of focus, but then you notice some feature, maybe a small, fresh impact crater, and realize that the image is in fact quite crisply focused and the landscape itself is blurry.

The 14 March 2005 MOC image of the day provides a reasonably good example. The dunes themselves are fuzzy, but if you look closely at the space between the dunes, you'll notice there's quite a lot of fine detail.

[alan]

Here is a better view of the blurred area, near the center of the image
http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=34966
The crater is on top of the fissure, therefore younger, the blurred area is its ejecta blanket.