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: 8783 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, 06:21 PM
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
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. Hmm. That's a very persuasive point, Ted; we haven't really completed a Cassini-quality survey of the Jovian system yet. Might change my mind here, gotta think about it. -------------------- 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, 06:44 PM
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
Two things that I would really like to see are long term monitoring of Jupiter by remote sensing instruments, with high resolution movies of clouds and lightning (on both the day and night side), which was the science goal most damaged by Galileo's antenna problems, as well as high resolution multispectral mapping of the moons. Galileo's color coverage was awful (except for Io, but this was low resolution). Most color images that were returned are low resolution color images overlayed on a high resolution image, which can be deceiving. Often the images were made by taking a full pixel resolution green image (often with lossy compression) and then taking the other colors with more compression plus 2x2 binning. The 2x2-binned color data would be overlayed on the green image. Not only does that make the color boundaries seem less distinct, but it means that the grayscale is based on only one filter, which wrecks havoc on colorful worlds. Ganymede is full of tectonic features, but also appears to have many largescale color variations. It may prove quite interesting to map these with more filters and at high resolution. We may discover something completely unexpected.
Building on this, I fear that a mission like JSO may never fly if EE flies first. And again, I disagree with the Europa fettish (at least at this point). The sequence reminds me of Rhea-Tethys-Dione-Enceladus (and several others, such as Mimas and Iapetus may or may not fit in there somewhere). They are worlds that formed out of the same stuff that have had very different amounts of activity. Trying to understand one of the moons with only spotty coverage of the others would be a mistake (Granted, for the Enceladus mission, this wouldn't be a factor, since Cassini is providing excellent coverage). -------------------- |
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