[X] My Assistant

[jmknapp]

Interesting science plan item today (Jan. 17):

CIRS_020EN_FP3MAP001_PRIME

If I read it right, Enceladus, specifically the south polar region, occulted Tethys at 3:23UTC this morning:

BEGIN_TIME: 190729625.184386 (2006 JAN 17 00:26:00 UTC)
END_TIME: 190742465.184390 (2006 JAN 17 04:00:00 UTC)

FP3 disk map of Enceladus. One SI at 01:47 into observation. Length extended to accommodate all ORS instruments. Duration 03:34. Enceladus is above the lighted disk of Saturn for the first 15 or 20 minutes. S/C just below ring plane, EN above, and ring shadow above that. EN passes edge of ring ansa ca. 02:30. Splendid opportunity for wonderful WAC PR image. For CIRS, this will be an excellent opportunity to determine scattered radiation from CIRS primary - i.e., with a semi-infinite IR source surrounding the small (~3 mrad) cold disk of EN as a sharp occulting disk. AD=3.0-3.4, phase=19-24, (-1, 192)-(0, 230); EN south polar region occults TE (AD=1.9) northern hemisphere at 03:24-03:28; perhaps should center FP3 on center of TE from 03:23-03:29 and blink to cover occultation and EN S polar region........

Low-phase though so maybe any plumes would be invisible against Tethys' disk.

[ugordan]

I was bored waiting for the perpetual delays on New Horizons launch to end and made 2 Enceladus shots, a R/G/B true color one:

Oops, that one was oriented wrong, sorry about that, fixed now...

Obviously a Kodak-moment shot, R/G/B backdrop of Enceladus against Saturn's disk. Suffers from major compression artifacts, but it's a preview to the official release that's bound to come sometime:

[jmknapp]

Hey, fits their description of the PR shot exactly--very nice. Now for the Enceladus occultation... but I wonder if the trajectory was changed so that didn't happen. This appears to have been taken in that time interval around 3:20UTC:



http://saturn.jpl.nasa.gov/multimedia/imag...7/N00048268.jpg

Missed it by that much....

[ugordan]

Missed it by that much....

Actually, it most likely didn't miss it at all. The image needs to be rotated 90 degrees clockwise for the north poles to point up. The moon motion is then sideways. It's obvious Enceladus DID occult Tethys at some point, but clearly the camera missed the exact time it happened.
The times for the occultation duration are given as 03:23-03:29. Are those minutes:seconds or hours:minutes? If the former is the case, I'm not at all surprised ISS missed it.

[jmknapp]

Actually, it most likely didn't miss it at all. The image needs to be rotated 90 degrees clockwise for the north poles to point up. The moon motion is then sideways. It's obvious Enceladus DID occult Tethys at some point, but clearly the camera missed the exact time it happened.
The times for the occultation duration are given as 03:23-03:29. Are those minutes:seconds or hours:minutes? If the former is the case, I'm not at all surprised ISS missed it.

It's hh:mm so there seems to have been plenty of time--6 minutes. The intent stated above was to "blink" the camera which I guess means to operate it as fast as possible?

[ugordan]

It's hh:mm so there seems to have been plenty of time--6 minutes. The intent stated above was to "blink" the camera which I guess means to operate it as fast as possible?

I get the impression the "blink" refers to the CIRS instrument while ISS just rides along. And yes, 6 minutes is long enough for at least 6 ISS frames to be taken. I have no idea why they chose not to grasp at the imaging opportunity.
I'm actually surprised the occultation lasted that long, most other mutual events last perhaps less than a minute and here the S/C was near periapse so the perspective should have changed even faster. I guess Enceladus was catching up on Cassini's viewpoint pretty well...

[jmknapp]

I get the impression the "blink" refers to the CIRS instrument while ISS just rides along.

Aha, so maybe they got good data from the CIRS--long wait time on that though.

[um3k]

Here is a super-res color image:


And here is the same image with the color saturation greatly increased:


EDIT: Images rotated so north is at the top. Thanks, volcanopele!

[volcanopele]

Nice work, um3k and ugordan. North is to the left in the originals so rotating the images 90 deg. CW should put it in them in the right orientation.

[dilo]

Here is a super-res color image:
[attachment=3474:attachment]

And here is the same image with the color saturation greatly increased:
[attachment=3475:attachment]

Cannot download.. (images not available!)

[um3k]

Cannot download.. (images not available!)

Try again.

[jmknapp]

Looks like an extravaganza of high-phase imaging of icy satellites is scheduled today (Jan. 18)--Enceladus, Tethys, Rhea, Mimas, and Dione.

One planned obseration of Enceladus will be like so:



17:20-17:50 ISS_020EN_094W151PH001_PRIME Enceladus spectrophotometry/ phase coverage: Turn -Y to Enceladus; Do 1x1 mosaic 3 clear + 4 NAC color + 9 NAC polarizer + 4 WAC polarizer filters; turn to WP

Looks like pretty good plume-observation geometry, except the disk is small.

[dilo]

Try again.

Thanks, now I see them.
I like color enhancement, however images appear quite defocused... is this due to rescaling? If it is a super-res, how many images did you used?

[um3k]

Thanks, now I see them.
I like color enhancement, however images appear quite defocused... is this due to rescaling? If it is a super-res, how many images did you used?

I think I used 5 images. Using any more would have made it even blurrier due to misalignment. I intentionally blurred the color image before combining it with the super-res image in order to reduce JPEG artifacts. The color, by the way, is IR3-GRN-UV3.

[dilo]

Wow, look at this new plume image guys!
http://saturn.jpl.nasa.gov/multimedia/imag...7/N00048586.jpg
Not only plume: Satutrn + rings in shadow+ superexposed rings related!
Cool!

[Decepticon]

Enceladus reminds me of a firecracker when you ignite it.

[Bob Shaw]

Wow, look at this new plume image guys!
http://saturn.jpl.nasa.gov/multimedia/imag...7/N00048586.jpg
Not only plume: Satutrn + rings in shadow+ superexposed rings related!
Cool!

Wowowowowowow!

What a picture!

Bob Shaw

[scalbers]

Interpreting this spectacular Enceladus plume and Saturn image is a bit of a head scratcher for me. I attempted to reproduce this in Celestia and I could get the general idea, yet I either had the Enceladus crescent pointing the wrong way, or it was on the wrong side of the rings. Are we looking at the daylight side of Saturn here? We may be looking at the dark side of the rings. Perhaps if I rotate my display this would make sense assuming we are viewing the night side of Saturn (aligning more logically with the Enceladus crescent). I did note that in this case Enceladus was passing behind Saturn.

[ugordan]

Are we looking at the daylight side of Saturn here? We may be looking at the dark side of the rings.

Yes, we seem to be looking at the (overexposed!) night side of Saturn, lit by light reflected off the rings. Whether Cassini is above or below the ring plane is beyond me, but I get the feeling the former is the case.

[jmknapp]

Yes, we seem to be looking at the (overexposed!) night side of Saturn, lit by light reflected off the rings. Whether Cassini is above or below the ring plane is beyond me, but I get the feeling the former is the case.

I get a sub-Cassini latitude of 0.2 degrees N, longitude 101W. The subsolar point is 63E, 15S. So the sun would be almost on the opposite side. Time: 18JAN2006 23:42UTC.