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NASA Europa Missions, projects and proposals for the 2020s
MahFL
post Mar 5 2014, 12:53 AM
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vexgizmo
post Mar 8 2014, 04:35 PM
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But would that mission do any science? And would it steal the New Frontiers budget?

http://www.planetary.org/blogs/casey-dreie...-the-cheap.html
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0101Morpheus
post Mar 9 2014, 11:20 PM
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To add to the above, it is not known if these plumes are cyclinic (they erupt every time Europa is in aphelion like a clockwork) or they are less irregular. Not knowing the answer leaves it less then likely a mission would ever get off the ground.

Hopefully JUICE can find an answer.

And try looking at our topic on the plumes in our other Europa thread. This topic and more has been discussed there.
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Roly
post Mar 11 2014, 10:56 AM
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I appreciate that Europa missions are amongst the most thoroughly studied in the catalogue of future unmanned spaceflight, but I was wondering whether there was any discussion of the trade space for the primary mirror versus shielding mass, mass, potential orbits, pointing issues, radiation and similar. I suspect this is probably because the answers are so clear as to be self-evident, and my apologies in advance.

LORRI-class optics seemed to provide encouraging results at a reasonable stand-off range in 2007. Are there any possibilities opened up by HiRISE or supra-HiRISE (e.g. 1m, or 1.2m mirror)? More distant fly-bys for equivalent resolution to the NAC/Topographic imager, or some kind of elliptical orbit which produced very close fly-bys (Recon Imager equivalent) and then kept the spacecraft out of the most hostile area for most of the time, and perhaps forestalled the need to dispose of the spacecraft while it was still functional for planetary protection purposes. Perhaps the challenge of motion compensation with no scan platform might make it infeasible even if the mass trade was not completely ridiculous.

It probably means no prospect for a radar instrument, and perhaps the scaling of the mirror is such that it is a catastrophically poor choice compared to shielding mass.

I struggle to see how NF-class mission would work, though the older IVO proposals for Discovery (admittedly with the power supplied via GFE) seemed to suggest it was not utterly implausible.

Anyway, apologies again if these are distracting from more salient questions on the prospective Europa mission.

Edit: Search function already had some leads on the various issues with this, and OPAG discussion c. 2004 - 2006 of special optics from Ganymede - it still seemed to hold some promise at that point. Presumably the trades have not changed appreciably since then, except perhaps the new explicit science goal for plume imagery/spectra.

Roly
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vjkane
post Mar 12 2014, 08:06 AM
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I looked at various options that may be considered for a $1B mission: futureplanets.blogspot.nl/2014/01/europa-new-frontiers-mission-or-why-i.html?m=0

(Sorry, could not get the live link function to work on the antiquated phone that is my internet connection for the next while.) - Fixed (link, not your internet!) - Mod

Basically, the cheaper mission could fly fewer instruments, return less data per flyby (cheaper power amd comm systems), and/or reduce radiation harfening (which would reduce the number of flybys).

The minimum mission looked at by the Clipper team would carry just three instruments: a moderate resolution imager, an imaging IR spectrometer, and an ice-penetrating radar. All produce large amounts of data. A mass spectrometer would be the fourth instrument priority and essential for plume flybys.

For good global studies, the Clipper team analysis suggests that 20-30 flybys are needed by some study goals and up to 50 for others. By contrast, JUICE will do just two flybys and the proposed $1B Io multiflyby mission would do 6+ encounters of that moon.


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Roly
post Mar 12 2014, 11:27 AM
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Dear Van,

Many thanks for this - the post was precisely what I needed to read to get a sense of reasonable speculation as to how downscoping might work. The original radar seems very heavy c.f. modestly lower performance of the JUICE equivalent, which was interesting, as was the sharp decrement in cost (and key elements of the science) that accompanied the reduced flyby numbers of the decadal Io study and the JUICE planning. Even still, it was, in some ways, encouraging that a worthwhile mission was not utterly infeasible.

It appears that the distant special distributed optics design of the 2004 - 2006 era had that brief moment of efflorescence in the LPSC abstract and the OPAG presentations, and subsequently has not been the subject of much further pursuit (which perhaps suggests there were sound reasons to foreclose it as an option for Jovian exploration).

Thanks again for your précis here, and the Future Planets post,
Roly
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Vultur
post Mar 15 2014, 08:49 PM
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I dunno if this is the right place for this... but what is the logic behind planetary protection for Europa? I had thought that the ice crust was at minimum 1 km thick... how could a reasonably sized spacecraft at orbital speeds possibly penetrate to an 'interesting' region?
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nprev
post Mar 15 2014, 09:42 PM
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Because the ice crust may be recycled over reasonable scales of time, or a given spacecraft may hit the jackpot & impact a surface weak spot…stuff like that. Bottom line is that we really don't have a great handle on Europa's ice crust dynamics as yet, nor if there even really is an ocean underneath…too many unknowns. Therefore, the smart move is to be extremely cautious.


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Vultur
post Mar 16 2014, 06:26 AM
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QUOTE (nprev @ Mar 15 2014, 09:42 PM) *
Because the ice crust may be recycled over reasonable scales of time, or a given spacecraft may hit the jackpot & impact a surface weak spot…stuff like that. Bottom line is that we really don't have a great handle on Europa's ice crust dynamics as yet, nor if there even really is an ocean underneath…too many unknowns. Therefore, the smart move is to be extremely cautious.


Ah, OK, thanks... I just had seen stuff making it sound like it would be incredibly difficult to get through the ice intentionally (eg drilling lander) so it seemed like kind of a disconnect.

When you say recycled over reasonable scales are you talking millions of years (short compared to the age of the moon itself) or something much shorter?
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dvandorn
post Mar 16 2014, 12:40 PM
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I also believe that while Europa may recycle crust from the surface back into the interior, its surface coloration shows that material does come up to the surface from the interior. And (trying to phrase this acceptably), if a Europa probe finds anything interesting on the surface that could have come from within the putative deep ocean, you would want to be certain that it couldn't have hitched a ride on a terrestrial spacecraft.

-the other Doug


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JRehling
post Mar 16 2014, 02:26 PM
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The age of Europa's surface is approximately 60 MYa. If we naively assume that it's being recycled systematically, one bit at a time, then you'd expect an object on the surface to go subsurface after an average of 30 million years. But if you shattered a space probe into many pieces, and you happened to hit a general region that was on the "short list" for subduction in the near future, and moreover the object was dark and metallic, so hotter each day than the ice around it, it might get subsurface faster.

To be clear, I don't think we'd likely have a crashed orbiter get into the ocean very soon with any great probability, but an ocean is exactly the sort of thing you *really* won't want to risk contaminating because of potential global mobility over short time scales.
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Explorer1
post Mar 16 2014, 08:14 PM
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Anything on the surface will be fried by the radiation just as thoroughly as if in Jupiter orbit, won't it? 30 million years of 5.4 sieverts a day? Even radioadurans would have trouble with that!
But, of course, better safe than sorry.
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dvandorn
post Mar 16 2014, 08:56 PM
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Yes, materials right on the surface of Europa would be fried by radiation, but such "frying" leaves a number of remnants which can tell you a lot about the original materials. Also, ice is an excellent radiation shield, so digging down into the ice less than a meter can give you examples of materials that haven't been fried. This also goes for hitchhiking terrestrial materials on a probe that happens to crash into Europa and are buried deeply enough in the ice to provide substantial radiation shielding.

-the other Doug


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Explorer1
post Mar 16 2014, 10:29 PM
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I see your point. I figured any future landings would be soft, so nothing could escape being sterilized, but of course landing rockets can and do fail. Flybys and orbiters seem like the way to go for now (just as Clarke predicted)!
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algorimancer
post Mar 17 2014, 08:28 PM
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Some years back I was contemplating the possibilities of very small & cheap spacecraft for deep space missions; communications was always the big stumbling block. Since I like playing Devil's Advocate, this led me to wonder: what if we don't need to worry about communication? Why not carry the data physically?

Envision something like a Cubesat with a basic telescope, solar arrays, and something like a tiny ion drive for attitude control and minimal course corrections, and coupled with a small computer and hardened flash drive (capable of surviving a high-speed reentry return to Earth). Envision a mission where you launch a dozen (or more) of these things towards Jupiter/Europa, with the spacecraft completely autonomous once launched. They loop past Europa on a close flyby of a region of interest, snap a few hundred images and store them on the flash drive, use Jupiter for a gravity assist and swing back towards Earth, eventually re-entering at a pre-specified longitude & latitude, and fall to the ground, probably transmitting an electronic ping (or sending a text message over the nearest cellular network). Someone just needs to pick them up and copy the images from the flash drive (or email them over a cellular network, no need to track it down), mission accomplished.

Extending the concept, a simple conventional lander might be sent to Europa, autonomously land on the surface and collect seismic and other data, then later send burst transmissions of this data to a passing autonomous Cubesat vehicles making close flybys as above, which then deliver the data to Earth.

All of this requires rather a lot of trust in autonomous navigation, but that's just a matter of software. In principal you could launch a hundred of these things for a fraction of the cost of a regular mission, with great redundancy.
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