OPAG Reports, Formal proposals/evaluations of future outer SS missions |
OPAG Reports, Formal proposals/evaluations of future outer SS missions |
Nov 9 2007, 08:28 PM
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
http://www.lpi.usra.edu/opag/announcements.html
That's one little URL with a lifetime's worth of reading material. Three detailed studies are available in PDF format. The missing body is Titan, which will be the subject of a forthcoming report. The three focus missions are: Europa Explorer: Fairly detailed description of a mission that is pretty much what Europa Orbiter would have been. Jupiter System Observer: Basically, Galileo 2 (without the antenna mishap!). The craft would start with a 3-year tour of all the Galileans, then spend 1 year in an elliptical Ganymede orbit, then the rest of the mission in a tight, polar Ganymede orbit (like MGS at Mars). That would map the heck out of Ganymede, but also be close enough to the rest of the system to make long-range observations for years. Note that Ganymede would thereby provide a lot of radiation shielding. Enceladus: where three profiles are examined in depth: Enceladus Orbiter only; Enceladus Orbiter with soft lander; Saturn orbiter with Enceladus soft lander. There's more to chew on here than I have had (or may ever have) time for, but I'll throw in my two cents' worth: Seems like a Europa-only mission would only benefit from coming after a JSO. EE would explore Europa much better than JSO would; why even have JSO observations at Europa if EE came first? In many ways, these two missions are competitive. EE would have the big payoff, but JSO seems like basic recon that would prime EE, especially giving specs on radar performance. But if we waited til JSO was 4 years into its mission before completing design of EE, then put EE sometime mid-century. If an Enceladus mission included a Saturn orbiter, then maybe the same orbiter could provide data relay for separate Titan elements. However, a lot of the Enceladus science goals would require an Enceladus orbiter, so I don't think a Saturn orbiter for Enceladus/Titan will win out. Note that Enceladus orbital velocity is low enough that the craft could manage to take lots of hits from ice pellets and survive. Put a bulletproof vest on the craft and let it soar through the plumes endlessly. |
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Nov 19 2007, 01:48 PM
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Merciless Robot Group: Admin Posts: 8784 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Although I'm not really a Europaphile myself, I'd have to vote for EE as the pick of this litter. Not only would we get nice new coverage for the other Galilean moons (and remote monitoring of Io), but remember that Europa's been declared a high-priority objective in close alignment with one of NASA's top-level science goals. Therefore, EE would probably be easier to sell to senior management then the other missions.
(My emphasis here is on getting an outer-planet mission in the pipeline ASAP; we're looking at quite a gap already after Cassini & NH). Nigel, you're right; I don't envy the task of whomever has to choose amongst these proposals, I want to fly them all. Is this Alan's new job? -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Nov 19 2007, 06:05 PM
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
Although I'm not really a Europaphile myself, I'd have to vote for EE as the pick of this litter. Not only would we get nice new coverage for the other Galilean moons (and remote monitoring of Io), but remember that Europa's been declared a high-priority objective in close alignment with one of NASA's top-level science goals. Therefore, EE would probably be easier to sell to senior management then the other missions. Depends. Both would do Europa science. However, it is my understanding that JSO is significantly cheaper because of not having to stay as far inside the Jovian magnetosphere for an extended period of time. It also would, for the same reasons, not require as much new technology. And frankly, I think it would help us better select instruments and priorities for future missions. Galileo's coverage was so spotty that you can't convince me that there aren't new major areas of interest we are missing. I mean, look at all we have found on Mars with imagers since the Mariners and Vikings? Galileo and Voyager coverage of the Galileans doesn't even begin to compare. For instance, JSO might discover plumes eminating from Europa a la Enceladus (which would be much smaller because of Europa's greater gravitational pull). If so, it would be desireable to have appropriate instruments for in situ studies (sort of a below-the-ice freebie, although it wouldn't exactly be pristine material after being propelled into space). Galileo did a plume search, but it was never likely to suceed, given the extremely limited number of images it was able to take. JSO could even continue such a search from Ganymede if it was deemed desireable. My point is that Europa could still be used as a selling point. -------------------- |
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Nov 19 2007, 06:45 PM
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
Galileo's coverage was so spotty that you can't convince me that there aren't new major areas of interest we are missing. True. However, even if there's some important area of interest waiting for us there, there's one that was clearly already identified - Europa. Should we dismiss it some more just so we can go chasing other (possibly) interesting stuff in the Jovian system or concentrate on scrutinizing Europa right now? I'm in favor of the second option. The other areas will pop up eventually anyway. Studying Europa potentially has much bigger implications biologically and even philosophically than, say, mapping locations of Ionian volcanoes (I probably alienated quite a few folks now). JSO (from what I understand) would provide us with a very rounded-up investigation of the Jovian system, but it probably wouldn't amount to a "quantum leap" in knowledge about any particular object. Winding up in Ganymede's orbit, it would give us awesome coverage of the moon. That's great, but is Ganymede really that worthy of a target? Compare this to EE which wouldn't give as a nice round-up like that, but it sure would provide for that "quantum leap" and for an object that is identified as a high priority, likely solving questions that were raised since Voyagers flew through the system. I get a feeling (maybe unrightfully so) that JSO would be a sort of Galileo on steroids. Voyager flybys gave us that "wow, the Jovian system is very interesting, we should go into orbit there". Then came Galileo and we basically went "wow, Europa is really intriguing, we should go into orbit there". That's why EE, not JSO seems like the next logical step to me. I'm a sucker for cool imagery as much as the next guy and would like to see great coverage of all the moons out there, but there's more to it than mapping surfaces. As much as I like images of colorful Io, Ganymede and Callisto, I want to find out what's beneath that frigid ice crust of Europa even more. If there is anything except more ice. Even if that means having to look at more greyish-bland imagery than at other Galileans. I wouldn't call it a fetish or some trendy thing to want to understand Europa, the moon's under the microscope for a good reason IMO. -------------------- |
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Nov 19 2007, 10:28 PM
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
but is Ganymede really that worthy of a target? Wow, this debate has really taken off! Without denigrating EE I would just like to address the question above. My answer is yes. If we make the pessimistic assumtion that the Europan ocean is not full of jellyfish then a geophysical study of Ganymede and the dynamical history of the whole Jovian system become the main research targets. Topography old AND new, the whole history is there. Magnetic dynamo - how does it work and what protection does it provide? Long term vantage point: perfect. |
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Nov 19 2007, 10:43 PM
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
If we make the pessimistic assumtion that the Europan ocean is not full of jellyfish then a geophysical study of Ganymede and the dynamical history of the whole Jovian system become the main research targets. With all due respect, should we really be making such assumptions? With foreknowledge, 20/20 hindsight and whatever, then yes, a Ganymede orbiter would make more sense. We just don't know what's out there, that's why we want to send missions there in the first place. Isn't that kind of like saying "if we assume Titan and its surface is not that worthy of closer scrutiny (i.e. dull and dead, despite evidence to contrary), we can concentrate on investigating other wonderful moons in the Saturnian system"? -------------------- |
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