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Unmanned Spaceflight.com > Outer Solar System > Saturn > Cassini Huygens > Cassini general discussion and science resultsJanus/epimetheus Orbital "swap", Planned observations? |
 Dec 24 2005, 01:56 AM
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Member  Group: Members Posts: 204 Joined: 20-November 05 From: Mare Desiderii Member No.: 563  |
A while back I gave myself the impression (by playing with JPL Horizons) that the next instance of the famous orbital "swap" was going to take place around Jan/Feb 2006. Is that right?
I'm not familiar with the precise orbital dynamics[*], but I got the impression that the moons would become close, but not spectacularly so. (But I don't have the data in front of me now.) Does anyone know what sort of Cassini observations are planned (indeed, what if any interesting observations can be made, other than ultra-precise trajectory determination)? Any eye candy?  [*] I had a quick Google, but couldn't find any good animation to help visualise what really happens, with a rotating frame or something - just this, which I'm not convinced by. Anyone know of anything better?) |
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| Guest_BruceMoomaw_* |
Dec 27 2005, 08:46 AM
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Guests |
I've never heard of any study suggesting that the Janus-Epimetheus pair isn't stable over the very long run -- after all, if they weren't, they wouldn't still be here!
By contrast, the trio of Prometheus, Pandora and the F Ring may NOT be stable over periods of more than a few tens of millions of years -- it's quite possible that one or both of those moons were created comparatively recently from F Ring material, and will be destroyed fairly soon, with more new moons later being created out of F Ring material to replace them. |
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Dec 27 2005, 11:06 AM
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 Special Cookie Group: Members Posts: 2168 Joined: 6-April 05 From: Sintra | Portugal Member No.: 228 |
Can someone tell me what was going on here?...
http://saturn.jpl.nasa.gov/multimedia/imag...eiImageID=59067 -------------------- "Ride, boldly ride," The shade replied, "If you seek for Eldorado!"
Edgar Alan Poe |
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Dec 27 2005, 11:47 AM
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 Senior Member Group: Members Posts: 3652 Joined: 1-October 05 From: Croatia Member No.: 523 |
That's one of what the spacecraft team calls "mutual events". Since right now Cassini is still in the plane of the rings (though that may not be the case after T9?), it's got a nice edge-on view of the entire satellite system. Most of the satellites are practically in the same plane as the rings. Every now and then they "appear" to be passing by or even eclipsing each other.
Given the vast distance these shots were taken from combined with Cassini's narrow FOV gives the impression the moons are on top of each other, when in reality they're all normally following their mostly circular orbits. -------------------- |
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JTN Janus/epimetheus Orbital "swap" Dec 24 2005, 01:56 AM
elakdawalla QUOTE (JTN @ Dec 23 2005, 05:56 PM)[*] I had ... Dec 24 2005, 05:45 PM
JTN I had another go at Horizons. Attached are some ro... Dec 24 2005, 08:35 PM pat Current best guess is a closest approach of ~10,30... Dec 24 2005, 10:41 PM JTN QUOTE (pat @ Dec 24 2005, 10:41 PM)Current be... Dec 24 2005, 11:35 PM nprev QUOTE (JTN @ Dec 24 2005, 04:35 PM)Thanks... Dec 26 2005, 12:56 AM JTN QUOTE (nprev @ Dec 26 2005, 12:56 AM)Too bad;... Dec 26 2005, 12:33 PM nprev QUOTE (JTN @ Dec 26 2005, 05:33 AM)I don... Dec 26 2005, 06:55 PM pat QUOTE (nprev @ Dec 26 2005, 01:56 AM)Too bad;... Dec 26 2005, 06:59 PM nprev Hmm. Thanks, Pat and JTN.
So, just how often do t... Dec 24 2005, 10:59 PM BruceMoomaw Yeah, it was announced the moment they were discov... Dec 26 2005, 10:49 PM nprev Thank you very much, Bruce; that was most interest... Dec 27 2005, 12:09 AM ustrax QUOTE (ugordan @ Dec 27 2005, 11:47 AM)That... Dec 27 2005, 11:57 AM pat It occurred to me that I should probably mention t... Dec 27 2005, 08:16 PM Tman According Tilmann Denk, currently in Boulder (CO) ... Jan 20 2006, 12:09 PM elakdawalla I'm trying to write a description of this for ... Jan 20 2006, 10:16 PM pat QUOTE (elakdawalla @ Jan 20 2006, 11:16 PM)I... Jan 21 2006, 12:12 AM elakdawalla QUOTE (pat @ Jan 20 2006, 04:12 PM)You might ... Jan 21 2006, 01:47 AM gpurcell QUOTE (elakdawalla @ Jan 21 2006, 01:47 AM)Th... Jan 22 2006, 04:40 AM BrianJ Hello - my first post on UMSF !
Just wondered... Jan 22 2006, 12:53 PM scalbers Thanks to Emily's discussion I think I'm b... Jan 21 2006, 05:46 PM canis_minor Here's a nice long-term plot of the semimajor ... Feb 6 2006, 09:53 PM Tman Thanks for the plot!
Do you know who it made... Feb 8 2006, 09:58 AM |
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