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 12 2007, 08:19 PM
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#2
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Member Group: Members Posts: 220 Joined: 13-October 05 Member No.: 528 |
Drats. Everytime I try to download the Europa report I only seem to get four pages. I wonder if my Adobe Reader needs to be upgraded. The other reports come down fine.
As I recall the whole idea for a JSO / Ganymede orbiter mission came along a couple years back. The proposal was made to fly a very high resolution imaging package and eventually park it in orbit around Ganymede. The idea was to keep it alive a lot longer by keeping it out of the heavier radiation it would encounter in Europa orbit. My impression was that it was beleived that it would be cheaper to develope the JSO because it wouldn't need all the radiation hardening you would have on a Europa orbiter. I scanned through the JSO report, and saw budgetary numbers in the 3 billion range. If NASA headquarters was hoping that these studies would provide them with a cheaper alternative then one of two possibilities comes to mind. Either (a) those hopes were in vain and you just can't save that much by this route, or ( someone didn't get the memo and the JSO engineers decided to go whole hog with a full fledged (and radiation hardened) Flagship study and go for the gold. Gold in this case being 'plated'. A third more cynical possibility would be that people really want the Europa orbiter and so purposely made the JSO come out just as expensive and therefore no more appealing from a budget standpoint. Please note that I'm NOT advocating that third option... just saving someone else from suggesting it. I'm leaning more towards option (a) as an explanation. |
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Nov 12 2007, 08:57 PM
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#3
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Member Group: Members Posts: 706 Joined: 22-April 05 Member No.: 351 |
Drats. Everytime I try to download the Europa report I only seem to get four pages. ... My impression was that it was beleived that it would be cheaper to develope the JSO because it wouldn't need all the radiation hardening you would have on a Europa orbiter. I scanned through the JSO report, and saw budgetary numbers in the 3 billion range. It's not your Acrobat reader -- I get just four pages, too. As for JSO, I spent some time going through the budget figures. There's really two missions described. One uses up all the potential flagship budget (~$3B) and the other reduces the amount of Ganymede science through some instrument descope and an elliptical rather than circular orbit. The descoped mission appears to be about 2/3 the cost of the proposed mission (there are more expensive versions, for example with an atmospheric probe). See figure 3-4 on page 3-5. The report also says that no attempt was made to define a minimal acceptable mission, although some descope options are presented that suggest ideas. My take is that once you get to this class of mission, you are in $2-3B range, and the choice of moons doesn't matter that much. It is a shame the Europa report isn't up. I'd like to compare the science packages. From the JSO report, it appears that two instruments weighing about 100 kg are needed to enable long distance observations (a combined camera/NIR spectrometer and and an IR spectrometer). I think it would be criminal to return to Jupiter with a 3-axis stabilized craft and not include these instruments plus along with flybys of Io and a long orbital tour to observe satellites not to be orbited plus Jupiter. -------------------- |
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