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Posted by: angel1801 May 16 2006, 01:50 PM

I've been using the solar system simulator of late and I can say that this orbit will be far better for icy moon imaging that the last one.

Dione: C/A at about 564,000km. Excellent view of entire Saturn facing hemisphere with a much improved view of high northern latitudes.

Rhea: C/A at about 470,000km.

Tethys: C/A at 551,000km.

Mimas: C/A at about 315,000km.

Posted by: volcanopele May 16 2006, 06:19 PM

Looks like a quiet orbit to me. Some high phase Rhea and Tethys, and view of Polydeuces at ~380 m/pixel.

Posted by: TritonAntares May 16 2006, 07:08 PM

Fine, this one hasn't been imaged close so far.
Actually when and in which distance will CASSINI pass this 13 km small co-orbital moon of Dione?

Bye.

Posted by: tallbear May 17 2006, 04:49 AM

The closest Polydeuces pass in the Prime Mission is on

2006-142T14:53:09.0 64057 km

the Rings folk ferreted out the close Rock Flybys of the PM and the ISS folk
have been going after opportunities like this as they come up...

the closest approach to Polydeuces after that will come

2007-241T19:40:42.0 127897 km

and there are a few others at around 130,000 km or so in the PM

Posted by: volcanopele May 17 2006, 04:21 PM

Actually, the closest Polydeuces pass was on Feb. 17, 2005 at a distance of ~6200 km. Unfortunately, that opporunity was not identified until it was too late to change the plan to the Rev03 Enceladus pass plan (which at the time of Polydeuces C/A included a RADAR observation and an RSS mass deterimination of Enceladus). The pass coming up next week is the closest for which observations of Polydeuces will be taken.

Posted by: JRehling May 17 2006, 05:37 PM

Just to kibbitz, I would have thought that there would be a program that was run simulating the whole primary mission in very small time units, calculating the comprehensive set of distances between Cassini and each moon, and raising a flag when any close approaches took place. Perhaps Polydeuces's ephemeris was too poorly determined for it to get that treatment, or was that seemingly-easy analysis never carried out for the big moons, either? Hard to imagine.

Posted by: volcanopele May 17 2006, 05:55 PM

No, Polydeuces was only discovered in October 2004. It wasn't until December 2004 that enough images of that new satellite had been examined, including a few pre-discovery images, that a decent enough orbital elements were determined. By then, it was too late to make any changes to the plans (or, probably more accurately, it was determined that the science gained by observing Polydecues at better than 40 meters/pixel was not as imporant as the science that would be lost if Polydeuces imaging was added). And quite frankly, I agree. The RSS mass determination of Enceladus was a key measurement in investigating the internal structure of that world.

Posted by: tasp May 17 2006, 06:32 PM

One of my weirder ideas (if this turns out to be original with me, if anyone else is working on it, Yea!):

Any chance that Polydeuces (any pronunciation guide for that? I assume 'paul-e-due-cess', but does anyone really know?) and some of the other co-orbitals are tidally lofted co-accreted satellites of their Trojan hosts? (I include Hyperion here too)

Posted by: pat May 18 2006, 09:44 AM

Polly-dew-seas is the academically accepted pronunciation of the Classical Greek.

Posted by: tty May 18 2006, 10:01 AM

It may be the academically accepted pronunciation in anglo-saxon countries, but the actual pronounciation in Classical Greek "as she was spoke" was more like Polly-dev-kess, since the latinized "c" is actually a greek kappa (hard "k").

tty

Posted by: Bob Shaw May 18 2006, 10:57 AM

Or just refer to him as 'Castor's bruv!'...

Bob Shaw

Posted by: David May 18 2006, 01:44 PM

That's the modern Greek pronunciation. Ancient Greek would have been approximately poh-loo-deh-oo-kass, with a complex intonation contour rising on the second "oo", that's easier to pronounce than to describe.

Posted by: pat May 19 2006, 10:28 AM

Yep, a modern Greek would pronounce it POLI-THEF-KIS
Homer ~3000 years ago probably something more like POLOO-DEOO-KAYS
And a modern Cambridge don POLLY-DEW-SEAS

As with the names of other astronomical objects its down to whatever the professional community decide to use ----- the story is that Charon is pronounced the way it is because Jim Christy's wife's name was Sharon and of course he couldn't name it after her but the name of Hades' ferryman was highly appropriate. The fact that people could be pursuaded to pronounce Charon almost exaclty like Sharon.........well I leave it to your imagination.


Personally I'm going to pronounce Polydeuces as POLLY-DEW-SEAS (which is the way the satellite's discoverer actually pronounces it)

Posted by: volcanopele May 19 2006, 06:38 PM

hmm, interesting discussion. I've always pronounced it "Pah-lee-doo-chehz".

Posted by: AlexBlackwell May 19 2006, 06:53 PM

This reminds me of the pronunciation of the smaller of Mars' moons, Deimos. I'm not sure which is considered canonical but among the Mars specialists, you'll hear four distinct variations: DEE-moz, DEE-mos, DIE-moz, and DIE-mos. In the past, I've heard Tom Duxbury and Peter Thomas pronounce it differently at different times.

Since Phil Stooke (and perhaps Mike Caplinger) is/are our resident specialist(s), I wonder how they pronounce it?

Posted by: Phil Stooke May 19 2006, 08:03 PM

I shouldn't be considered a specialist in this subject. I pronounce it DEE-MOSS or DAY-MOSS for no good reason.

Oh - and POLLY-DEW-SEEZ for the same (lack of) good reason.

Phil

Posted by: climber May 19 2006, 08:46 PM

Kate MOSS and SHARON Stone would have been much easier

Posted by: Bob Shaw May 19 2006, 08:49 PM

Pollux.

(Ask Phil)

Bob Shaw

Posted by: ugordan May 23 2006, 09:38 AM

Wow, check http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=76363 out: Enceladus and one of the irregulars and apparently the F ring.
Also, there's a nice Rhea high phase set on the ground, including some subtle saturnshine.

Posted by: pat May 23 2006, 10:20 AM

Its Janus and yes its the F ring.

Posted by: tedstryk May 23 2006, 10:55 AM

http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS20/N00061686.jpg

Nice Mimas shot.

Posted by: ugordan May 23 2006, 10:58 AM

That's Tethys. Notice Ithaca Chasma stretching across the disk.

Posted by: tedstryk May 23 2006, 06:27 PM

That's what I get for posting money before 6 AM my time

Posted by: ugordan May 23 2006, 07:02 PM

Rhea IR1-GRN-UV3 mosaic, using a clear filter frame as luminance to better show the saturnshine portion - JPEG artifacting kills it in the simple color composite.

This view shows some pretty obvious color dichotomy present between the south pole and mid-latitudes. If I didn't know this was Rhea, I might have been tempted to yell Iapetus!

Posted by: Bob Shaw May 23 2006, 08:24 PM

Gordan:

That's a keeper - it looks, bar the lack of stars, like the sort of science-fiction worldlet that generally causes us all such pain, what with the gently illuminated night side and so on... ...very pretty seeing it in reality!

Bob Shaw