[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...