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Enceladus-3 (March 12, 2008)
Guest_AlexBlackwell_*
post Feb 24 2006, 09:12 PM
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Excerpt from Cassini Significant Events for 02/16/06 - 02/22/06:

"As mentioned in previous weeks, the project has been working on adopting a new reference trajectory in order to raise the minimum Titan flyby altitude for various encounters. Today the project reached a decision to proceed with the 'optocc2' trajectory. Additional work is still to be performed before delivery of the final files. This will include minor tweaks that have been analyzed in other trajectories, adjusting orbit 68 timing, and capture of an Enceladus plume occultation on orbit 28."

For the record, the new reference trajectory will result in an even more spectacular Enceladus-3 flyby [61EN (t) E3] on March 12, 2008.
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Guest_BruceMoomaw_*
post Mar 9 2006, 09:36 PM
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TWENTY-FIVE KM?!! You guys are really taking this place seriously, aren't you? I hope the navigation is better than that on MCO...

In that connection, one catastrophe that has yet to strike the US space program is the failure of an long, expensive outer Solar System mission just before its arrival. What will the public and Congressional reaction be when that finally happens? It looked as though it might happen with Galileo, but JPL succeeded (to their unquestionable credit) in pulling enough chestnuts out of the fire to remove that impression in that case.

At the risk of setting off the dog (aka Alex) again: I mentioned this point to Spilker's subgroup on Europa lander design at the Europa Focus Group Workshop, and got an enthusiastic response from JPL's Karla Clark -- we do NOT want something as expensive and long-term as a Europa Astrobiology Lander to fail at the very moment it's trying to land on Europa, and for that reason the best role for a little piggyback lander attached to Europa Orbiter may well be to check out the engineering characteristics of Europa's surface rather than carrying out any specifically scientific studies.
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Guest_AlexBlackwell_*
post Mar 9 2006, 09:47 PM
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QUOTE (BruceMoomaw @ Mar 9 2006, 09:36 PM) *
...JPL's Karla Clark -- we do NOT want something as expensive and long-term as a Europa Astrobiology Lander to fail at the very moment it's trying to land on Europa...

Now that's a visionary statement.

QUOTE (ugordan @ Mar 9 2006, 09:42 PM) *
I'm wondering about this figure as well, I noticed volcanopele edited it out of his post. Does that figure really hold in the new updated trajectory?

"Officially," the new reference trajectory is still in review at the Project/Program level; a decision should be forthcoming very shortly. I won't speak for Jason, but unofficially, the 25 km figure is the new Enceladus-3 flyby C/A altitude under all options that were being considered.

QUOTE (ugordan @ Mar 9 2006, 09:42 PM) *
What exactly is the scientific justification of such a dangerously close pass?

More on that later; however, sooner than 2008 tongue.gif
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volcanopele
post Mar 9 2006, 10:12 PM
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Technically, that number is official (well, it isn't going to change). As the Sig. events report suggest, a few additional tweaks are planned, but nothing that will effect Enceladus-3.


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EccentricAnomaly
post Mar 10 2006, 04:43 AM
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QUOTE (volcanopele @ Mar 9 2006, 02:12 PM) *
Technically, that number is official (well, it isn't going to change). As the Sig. events report suggest, a few additional tweaks are planned, but nothing that will effect Enceladus-3.


what I heard is that the altitude is not set in stone, but could change with another new trajectory... I'm guessing is that there will be more studies made to make sure it is safe. At that low altitude, I just hope they model Enceladus as an ellipsoid rather than as a sphere... the radius differs at the pole and the equator by something like 10 km, right? ...actually, I wonder how well they really know the radius anyway.
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Guest_AlexBlackwell_*
post Mar 10 2006, 04:26 PM
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QUOTE (EccentricAnomaly @ Mar 10 2006, 04:43 AM) *
what I heard is that the altitude is not set in stone, but could change with another new trajectory...

That's a good point: any trajectory is subject to change, and I wouldn't be surprised if 61EN (t) C/A ends up being tweaked upwards slightly. Still, unless the new reference trajectory resulting from optocc2 (or even those that would have resulted from 28EN_occ3, 28EN_opt3b, or Option 3b) changes dramatically, Enceladus-3 is going to a barnstorming flyby, regardless.

And there is an important non-targeted encounter coming up later this year, September 9, 21EN (nt), which will allow for occultation data on Enceladus' plumes.

P.S. The significant events report I started out with in this thread referred to "optocc2." Is this different from optocc3? I've seen the latter referred to extensively by MP during this latest trajectory re-design but not the former. I assume both are in the same "class" but have different tweaks.
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JRehling
post Mar 10 2006, 05:32 PM
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Various notes:

However we might wring our hands over missing out on 30cm/pixel images, note that we did obtain only slightly blurred 4m/pixel images which are certainly sharp when desampled to 8m/pix. The question is how many such images Cassini could snap in E3, and if an imaging strategy could guarantee a supercloseup of a Tiger Stripe near or at a vent.

Dangerwise, I start to imagine the possible endgame of the mission, setting a trajectory that points straight ahead and gets some low-blur images of the vents without the use of a shield on a flyby where we no longer care if Cassini is destroyed. This would have to be combined with a free trajectory into its destruction somewhere besides Enceladus or Titan, and my top candidate would be the B ring. Maybe a low-inclination orbit that slices into the B ring could return some "downlooking" shots of the rings at incredible resolution before sure death when the orbit hits the ringplane. (If light doesn't go through them, neither will Cassini.) Thus, two high-value images could be obtained on the final death orbit, whenever that would be.

Astrobiologically speaking, I wonder if one of the problems for the Enceladan reservoirs might be if the water is too pure. Undoubtedly, there's no way to get life out of 100% H2O if there were no other compounds there. Nature seems to abhor purity in most cases, so hopefully that will be the case with Enceladan H2O as well.

Explorationwise, I fear we might have a reservoir under pressure with no way to get into it. Imagine trying to stick your digital camera into an open fire hydrant. There's a reason why those jets are spraying so far up, even in that super-light gravity. Even if we drill our own hole, that might just uncap a new vent.

Sarcasmwise, Alex, Bruce isn't going to get your putdowns unless you do the rhetorical equivalent of hitting him on the head with an anvil that says "2000 LBS" on the side. He's too hyped up to come down.
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Guest_AlexBlackwell_*
post Mar 10 2006, 06:07 PM
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QUOTE (JRehling @ Mar 10 2006, 05:32 PM) *
Sarcasmwise, Alex, Bruce isn't going to get your putdowns unless you do the rhetorical equivalent of hitting him on the head with an anvil that says "2000 LBS" on the side. He's too hyped up to come down.

Some veterans of my planetary_sciences Yahoo! Group may recall this exchange on July 21, 2005, which occurred at the tail end of a typical Moomaw anti-Shuttle fusilade. Of course, no one will be surprised that this message was preceded by several warnings/requests/pleas to Bruce to respect the topic of the discussion group biggrin.gif

===================

--- In planetary_sciences@yahoogroups.com, <rmoomaw@s...> wrote:

> OK. You want me to drop this particular topic completely, I'll
> drop it.

Bruce, whatever gave you that idea? ;-)

You know, this is starting to remind me of the classic SNL sketch of
the movie mogul (John Lovitz) and the washed up movie star (Phil
Hartman) - paraphrasing, since I don't remember the exact dialog:

Lovitz: You're through, you hear me! You're all washed up!

Hartman: Don't sugar coat it, tell it to me straight.

Lovitz: Everyone hates your movies!

Hartman: What's the word on the street?
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Posts in this topic
- AlexBlackwell   Enceladus-3 (March 12, 2008)   Feb 24 2006, 09:12 PM
- - BruceMoomaw   It was casually confirmed in one of the new EGU ab...   Feb 25 2006, 04:03 AM
- - volcanopele   Even though the encounter distance is closer, don...   Feb 25 2006, 04:12 AM
|- - AlexBlackwell   QUOTE (volcanopele @ Feb 25 2006, 04:12 A...   Feb 27 2006, 04:13 PM
|- - Holder of the Two Leashes   QUOTE (volcanopele @ Feb 24 2006, 10:12 P...   Feb 27 2006, 04:40 PM
|- - ljk4-1   Check this out: http://drudgereport.com/flash8na....   Mar 9 2006, 06:42 PM
|- - volcanopele   QUOTE (ljk4-1 @ Mar 9 2006, 11:42 AM...   Mar 9 2006, 07:37 PM
|- - AlexBlackwell   QUOTE (volcanopele @ Mar 9 2006, 07:37 PM...   Mar 9 2006, 07:43 PM
- - BruceMoomaw   TWENTY-FIVE KM?!! You guys are really taki...   Mar 9 2006, 09:36 PM
|- - ugordan   QUOTE (BruceMoomaw @ Mar 9 2006, 10:36 PM...   Mar 9 2006, 09:42 PM
|- - AlexBlackwell   QUOTE (BruceMoomaw @ Mar 9 2006, 09:36 PM...   Mar 9 2006, 09:47 PM
||- - volcanopele   Technically, that number is official (well, it isn...   Mar 9 2006, 10:12 PM
|||- - AlexBlackwell   QUOTE (volcanopele @ Mar 9 2006, 10:12 PM...   Mar 9 2006, 10:17 PM
|||- - EccentricAnomaly   QUOTE (volcanopele @ Mar 9 2006, 02:12 PM...   Mar 10 2006, 04:43 AM
|||- - AlexBlackwell   QUOTE (EccentricAnomaly @ Mar 10 2006, 04...   Mar 10 2006, 04:26 PM
|||- - JRehling   Various notes: However we might wring our hands o...   Mar 10 2006, 05:32 PM
|||- - AlexBlackwell   QUOTE (JRehling @ Mar 10 2006, 05:32 PM) ...   Mar 10 2006, 06:07 PM
|||- - RGClark   QUOTE (JRehling @ Mar 10 2006, 05:32 PM) ...   Mar 10 2006, 06:26 PM
||- - AlexBlackwell   QUOTE (AlexBlackwell @ Mar 9 2006, 09:47 ...   Mar 15 2006, 08:38 PM
|- - The Messenger   QUOTE (BruceMoomaw @ Mar 9 2006, 02:36 PM...   Mar 9 2006, 10:23 PM
|- - ugordan   QUOTE (The Messenger @ Mar 9 2006, 11:23 ...   Mar 9 2006, 10:34 PM
|- - The Messenger   QUOTE (ugordan @ Mar 9 2006, 03:34 PM) Yo...   Mar 10 2006, 06:37 AM
- - Richard Trigaux   Passing at 25 kms of Enceladus would be very inter...   Mar 9 2006, 11:05 PM
|- - DDAVIS   To take images? Wow fantastic images from such an ...   Mar 9 2006, 11:38 PM
- - Sunspot   I think this is the highest resolution image taken...   Mar 9 2006, 11:49 PM
|- - JRehling   QUOTE (Sunspot @ Mar 9 2006, 03:49 PM) I ...   Mar 10 2006, 12:04 AM
- - BruceMoomaw   Unfortunately, as Jason noted back on his own (sor...   Mar 10 2006, 05:01 AM
|- - Richard Trigaux   QUOTE (BruceMoomaw @ Mar 10 2006, 06:01 A...   Mar 10 2006, 08:44 AM
|- - AlexBlackwell   QUOTE (BruceMoomaw @ Mar 10 2006, 05:01 A...   Mar 10 2006, 03:52 PM
|- - EccentricAnomaly   QUOTE (BruceMoomaw @ Mar 9 2006, 09:01 PM...   Mar 10 2006, 05:57 PM
- - gpurcell   If the E-Ring is caused by the venting, why not tr...   Mar 10 2006, 07:13 PM
- - tty   Isnít landing on Enceladus an unnecessarily compli...   Mar 10 2006, 07:24 PM
|- - Richard Trigaux   QUOTE (tty @ Mar 10 2006, 08:24 PM) Isnít...   Mar 10 2006, 07:41 PM
- - BruceMoomaw   QUOTE (AlexBlackwell @ Mar 10 2006, 03:52...   Mar 10 2006, 07:24 PM
|- - AlexBlackwell   QUOTE (BruceMoomaw @ Mar 10 2006, 07:24 P...   Mar 10 2006, 07:44 PM
|- - JRehling   QUOTE (AlexBlackwell @ Mar 10 2006, 11:44...   Mar 10 2006, 08:12 PM
- - volcanopele   a few notes: E3 Imaging: Don't expect super h...   Mar 10 2006, 07:36 PM
|- - AlexBlackwell   QUOTE (volcanopele @ Mar 10 2006, 07:36 P...   Mar 10 2006, 09:34 PM
|- - RGClark   QUOTE (volcanopele @ Mar 10 2006, 07:36 P...   Mar 10 2006, 10:48 PM
|- - RGClark   QUOTE (volcanopele @ Mar 10 2006, 07:36 P...   Mar 11 2006, 03:33 PM
|- - JRehling   One Enceladus mission I could see flying would be ...   Mar 11 2006, 06:58 PM
- - BruceMoomaw   OK. All I can report is what I saw: before Ms. Cl...   Mar 10 2006, 09:16 PM
|- - AlexBlackwell   QUOTE (BruceMoomaw @ Mar 10 2006, 09:16 P...   Mar 10 2006, 10:15 PM
- - BruceMoomaw   QUOTE (AlexBlackwell @ Mar 10 2006, 10:15...   Mar 10 2006, 11:20 PM
|- - AlexBlackwell   QUOTE (BruceMoomaw @ Mar 10 2006, 11:20 P...   Mar 10 2006, 11:51 PM
|- - helvick   QUOTE (AlexBlackwell @ Mar 10 2006, 11:51...   Mar 11 2006, 01:54 AM
|- - AlexBlackwell   QUOTE (helvick @ Mar 11 2006, 01:54 AM) I...   Mar 11 2006, 02:00 AM
- - BruceMoomaw   Fine -- especially since the whole damn thing was ...   Mar 11 2006, 02:50 AM
- - BruceMoomaw   I found Jason's blog entry from almost a year ...   Mar 11 2006, 11:19 AM
|- - EccentricAnomaly   QUOTE (BruceMoomaw @ Mar 11 2006, 03:19 A...   Mar 11 2006, 06:01 PM
- - BruceMoomaw   The NEP idea -- which would orbit Saturn and fly t...   Mar 11 2006, 10:53 PM
- - BruceMoomaw   QUOTE (EccentricAnomaly @ Mar 11 2006, 06...   Mar 12 2006, 11:30 PM
|- - volcanopele   QUOTE (BruceMoomaw @ Mar 12 2006, 04:30 P...   Mar 13 2006, 02:46 AM
|- - ugordan   QUOTE (BruceMoomaw @ Mar 13 2006, 12:30 A...   Mar 13 2006, 08:38 AM
- - volcanopele   The planetary society Cassini tour page now has th...   Mar 15 2006, 10:06 PM
|- - AlexBlackwell   QUOTE (volcanopele @ Mar 15 2006, 10:06 P...   Mar 15 2006, 10:19 PM
- - AlexBlackwell   I just read the materials in the 060323 Reference ...   Mar 28 2006, 09:26 PM
- - BruceMoomaw   Can you tell us anything more about just what they...   Mar 29 2006, 01:11 AM
- - AlexBlackwell   QUOTE (BruceMoomaw @ Mar 29 2006, 01:11 A...   Mar 29 2006, 06:10 PM


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