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Posted by: MahFL Mar 5 2014, 12:53 AM

http://news.yahoo.com/nasa-plots-daring-flight-jupiters-watery-moon-215733641.html?bcmt=comments-postbox

Posted by: vexgizmo Mar 8 2014, 04:35 PM

But would that mission do any science? And would it steal the New Frontiers budget?

http://www.planetary.org/blogs/casey-dreier/2014/0305-nasa-wants-europa-on-the-cheap.html

Posted by: 0101Morpheus Mar 9 2014, 11:20 PM

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.

Posted by: Roly Mar 11 2014, 10:56 AM

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

Posted by: vjkane Mar 12 2014, 08:06 AM

I looked at various options that may be considered for a $1B mission: http://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.

Posted by: Roly Mar 12 2014, 11:27 AM

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

Posted by: Vultur Mar 15 2014, 08:49 PM

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?

Posted by: 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.

Posted by: Vultur Mar 16 2014, 06:26 AM

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?

Posted by: dvandorn Mar 16 2014, 12:40 PM

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

Posted by: JRehling Mar 16 2014, 02:26 PM

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.

Posted by: Explorer1 Mar 16 2014, 08:14 PM

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.

Posted by: dvandorn Mar 16 2014, 08:56 PM

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

Posted by: Explorer1 Mar 16 2014, 10:29 PM

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)!

Posted by: algorimancer Mar 17 2014, 08:28 PM

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.

Posted by: djellison Mar 17 2014, 09:31 PM

Navigation isn't a 'matter of software'. It's a matter of the huge, powerful and complex infrastructure of the DSN combined with comms onboard a spacecraft used as two way and indeed three-way links and regular Delta-DOR for accurate navigation. Your proposal would require quite extraordinarily accurate gravity assist for the return flight to Earth ( if the E-J-E free return trajectory is doable without significant propulsive maneuvers ) - that level of accuracy can't be coded away - it requires ground-in-the-loop hardware, comms etc.

Moreover - name a spacecraft - any spacecraft - that flew as far as Jupiter and Back - without requiring human intervention due to safe modes, TCM's, etc etc.

It's a non starter.

Posted by: ngunn Mar 17 2014, 10:04 PM

First, a big round of applause for DSN Now. Everybody go look. I've just a small comment on getting low mass spacecraft back to Earth accurately from distant destinations. I think light sailing could play an important role here.

Posted by: djellison Mar 17 2014, 10:22 PM

Doesn't matter if you get your delta-V from mono prop, bi prop, ion, solar sail...the navigation challenge still remains.

Posted by: Explorer1 Mar 17 2014, 11:17 PM

But saving all that mass by not carrying a gigantic HGA has to count for something, right? Galileo navigated just fine with low-gain only.
The main issues in that case would be limiting data corruption on the trip to Earth. And of course, waiting years instead of hours to find out if an experiment had a payoff will play havoc with blood pressure back home!

Posted by: mcaplinger Mar 18 2014, 02:22 AM

A lot of the mass in a telecom system is in the modulation and RF circuits. The "Small Deep Space Transponder" http://en.wikipedia.org/wiki/Small_Deep_Space_Transponder weighs 3 kg and doesn't include the output power amplifier.

Define a detailed mass breakdown with components you can actually buy and I'll believe it. Until then you're just writing science fiction.

Posted by: Explorer1 Mar 18 2014, 02:49 AM

Oh, I know it's all SF (per Doug's reply to algorimancer). The accuracy needed for some sort of 'free return' from Jupiter/Europa is implausible.
And honestly the best way to show that it can't work is the fact that no one's tried it yet in 50+ years (even from as close as the Moon!)

Posted by: dvandorn Mar 18 2014, 03:18 AM

Actually, the concept of a self-navigating Earth-return planetary probe goes back to the late 1950s, when Charles "Doc" Draper (of the MIT Instrumentation Lab) was approached to design an auto-navigation system for a Mars flyby-and-return probe. The concept was a probe that would autonomously navigate itself to a Mars flyby, expose several rolls of film using automated cameras, and come back for an Earth return.

The probe never made it out of an early study stage, but Draper's early work on it evolved into numerous applications of inertial guidance systems.

-the other Doug

Posted by: monitorlizard Mar 18 2014, 04:43 AM

As far as maximizing science return for minimum cost, I've always liked the idea of a Europa flyby craft with high data rate sensors (e.g., high resolution) and a data recorder
of 10 terabytes or more. Do as many flybys as the recorder (and other mission constraints) allow, then boost the spacecraft to a high orbit, away from the intense
radiation. You could then take your time returning the data to Earth without the need for a return capsule or a large spacecraft antenna. Of course, laser communications
would make the whole idea moot.

Posted by: mcaplinger Mar 18 2014, 05:18 AM

Using what as a storage medium? Flash is quite radiation-soft and MRAM, while promising, is not dense enough yet.

Posted by: monitorlizard Mar 18 2014, 05:48 AM

I am not an expert in such things, but I was thinking along the lines of the Honeywell Aerospace Satellite Data Server.

See http://www.honeywell.com/sites/aero/Data-Processing3_C81A0CEAA-6658-FAB9-52DC-CAA2E754579D_HD6F9E0E8-4434-2DE8-41BA-BA6EC2FAE1F6.htm

It's radiation-hardened, but of course that's for the Earth orbit environment. Perhaps a combination of this design and spot shielding would enable Jovian operations.
The Honeywell product is 16 Tbits. I believe there are larger recorders, but they may be classified.

Posted by: mcaplinger Mar 18 2014, 11:58 AM

The lack of specs makes this hard to evaluate, but the box looks like it weighs multiple kilos and it doesn't say what memory technology it uses.

A typical box designed for the GEO environment will have a hard time at Jupiter without a lot of extra shielding. A lot.

Posted by: vjkane Mar 18 2014, 03:47 PM

My understanding is that the core spacecraft electronics are less of a problem than the sensor electronics. The former can be put inside a radiation shielded vault (think aluminum plates and surrounding fuel tanks). The sensor heads, on the other hand, must be exposed to the environment (although they can be shielded on sides other than their viewing outlet).

NASA is using a lot of the preformulation money to fund radiation hardening of the instruments.

Posted by: mcaplinger Mar 18 2014, 04:48 PM

Less of a problem, though getting non-volatile memory to survive is still a significant issue.

At any rate, we were discussing this in the context of a very small spacecraft. IMHO, this is simply infeasible with current technology for a whole host of reasons.

As for sensors, there's nothing I can say without getting into competition-sensitive areas. From an engineering perspective, I don't see a lot of rational and realistic system trades having been made as far as Europa missions are concerned.

Posted by: Roly Mar 19 2014, 02:22 AM

Many thanks Mcaplinger, this was very interesting to read. That issue of storage seems to always be "very soon now", I seem to remember chalcogenide / phase change and FRAM being promised in the JIMO-era studies. On the trades, does the option of spending much of the time "standing off" at Ganymede with a suitably massive and impressive mirror make any sense? I only ever saw it proposed in those MIDAS slides, and they were build around what seemed to be special optics.

Posted by: mcaplinger Mar 19 2014, 03:32 AM

Not to me. Shielding is easier to make than big optics and may well weigh less.

If people want to get some insight into some of the engineering that goes into these sorts of missions, the JUICE proposal information is a good read http://sci.esa.int/juice/ JUICE is actually a fairly good start for a Europa mission, too bad they didn't pick our camera

Posted by: Roly Mar 19 2014, 04:56 AM

My thanks for your appraisal Mcaplinger, that makes sense, especially if there is no striking advantage in mass (even more so if it is potentially less favourable for mirror c.f. shielding). I do look forward to reading the JUICE materials - and imagine that the camera you proposed for that was extremely interesting, given the quality of the track record.

Posted by: TheAnt Mar 19 2014, 12:08 PM

What's in a name, the acronym for the JANUS camera is in Latin: "Jovis, Amorum ac Natorum Undique Scrutator."
Jovis mean Jupiter, Scrutator is nearly the same as the English 'Scrutinise' but after that I had to give up to the meaning.
Italian instrument so the name figures to some degree at least. =)

Related link, as for the selection of instruments http://www.pro-physik.de/details/news/4397251/JUICE_Auch_DLR_ist_mit_an_Bord.html as well. German page.

Posted by: JRehling Mar 19 2014, 04:30 PM

Although it pains me to see Europa exploration further delayed, the situation persists that we're still in search of the right mission architecture for the realities of Europa. Some post-Galileo discoveries, mainly based on analysis of Galileo data, have upended what we might have previously thought would make a good next step.

IMO, given the ability to detect plumes, but an incomplete knowledge of their temporal patterns of occurrence makes planning the next mission an absolute non-starter. If the plumes occur at every apojove, that's one reality to plan for. If they occur at 10% of apojoves, with no apparent pattern, that's another reality to plan for. If in a decade we see them only a few times, that's yet another reality. There is no wise mission design for Europa that precedes this sort of knowledge.

JUICE is planned to wrap up its main mission around 2033. If the idea of waiting for that mission to end before planning the next one doesn't make you wince, you're very young and very patient. Maybe recon from Earth-based/orbiting telescopes can allow us to plan pre-JUICE, but that still calls for at least a couple of years of observations and analysis before we can plan the next step.

Maybe the best bet is to time a free-return plume-sampling mission to arrive when JUICE is active and use JUICE's observations to adjust the outbound trajectory to time a fly-through more favorably. I'm not sure, though, if such an option even makes sense in terms of engineering and orbital mechanics.

The analogy I would use is that if exploring Europa is chess, the plumes are the king. We can make plans for mapping and radar, etc., and focus on the rooks and queen, etc., but getting a sample of the plumes back to Earth is checkmate. If we can play for checkmate, we should.

Posted by: vjkane Mar 19 2014, 11:14 PM

I rarely disagree with John, but this is one time I will. We don't yet know that the plumes are real. The plume signal was at the edge of detectablity -- much like the measurements of ozone at Mars. Going straight to a sample return mission is premature in my opinion. We don't even have a good idea of particle size or density. If they plumes exist, it does not mean that they are connected to a deep subsurface source -- look at the explanations for the Enceladus plumes that do not require as subsurface ocean. Also, do the plumes occur every orbit or once a decade?

There are excellent reasons for flying a dedicated multi-flyby mission whether or not the plumes exist. The strategy that makes sense to me is a synergistic mission with JUICE. JUICE can do the global studies stand offstudies of the plumes with its UV spectrometer. However, it will be limited to a small number of flybys within a narrow range of Jovian longitudes. A Clipper-like mission can make many flybys and adjust its Jovian encounter longitude to match the peak plume output (assuming it exists).

I don't think that the discovery of plumes requires that the only mission that now makes sense for NASA is a sample return. In my opinion, do global surface studies as already highly prioritized, map the subsurface of the possible plume region to understand the source, include the mass spectrometer that is already a high priority for in situ measurements, and perhaps also include a dust counter and/or dust spectrometer to give us particle size. Once we understand the nature of the plumes and can place their source in context, we can plan an optimal sample return mission.

Ideally, we'd fly the survey mission this decade and if appropriate the sample return mission the next decade. But I don't agree on NASA doing no dedicated Europa mission until JUICE confirms the nature and sources of the plumes.

Posted by: TheAnt Mar 20 2014, 12:10 AM

Even if they turn out to exist, there could indeed be other explanations, a magnetic field at Europa could for example focus charged particles from the extremely powerful radiation belts around Jupiter at the poles.

Some models that have been presented do take into account possible reservoirs of water encapsulated in the ice sheet on Europa.
A water plume might originate in one such reservoir and so be of less interest, especially in providing any answers for the eventual habitability of Europa.

And indeed Enceladus is a good example for more reasons than that, we should remember how long it took before the final proof arrived in that first blurry backlit image in 2005.
Even though the report on possible water plumes is very interesting, it is quite too early to spin doctor / build a mission to sample any possible plumes from the meagre data we have.

I am all in favour of a mission to Europa, JUICE will take its time to get built and sent there. And we can only hope it will provide the answers to this question as to so many others we have.

Posted by: stevesliva Mar 21 2014, 03:03 AM

Especially because you get situations like Titan. Now that we know a lot more about the surface, we seem no more likely to take another more informed look. And the nature of things is not that you can cache goodwill for forgoing a mission opportunity. You take it.

Posted by: JRehling Mar 21 2014, 07:11 PM

It's not that we should plan a sample return, but we should extend at least the techniques used to detect the plumes into a broader survey before a plan.

If further observations find limited or no recurrence of the plume, then a sample return would be either a bad prospect, a risky one, or a complicated one. Still, such observations are of low cost compared to the cost of a mis-designed mission.

Jupiter is passing one season of opposition now. I'm not sure the quality of observations made this year. Hopefully this and/or the next opposition will yield some good follow-up to help pin down the question. So far, we have only two seasons of observations with any data reported, and whatever the cost (and potential ambiguity) of more observations, it's worth observing first, planning second.

Posted by: mcaplinger Mar 21 2014, 07:48 PM

http://solarsystem.nasa.gov/europa/sdt2013.cfm has a bunch of reports and other information from the Europa SDT, and is useful background reading if you're interested in Europa mission architectures.

Posted by: CryptoEngineer Feb 3 2015, 04:49 AM

The Planetary Society is reporting today that a (non-landing) Europa mission will be funded:

http://www.planetary.org/blogs/casey-dreier/2015/0202-its-official-we-are-on-the-way-to-europa-fy2016.html

ce

Posted by: gpurcell May 9 2015, 02:11 PM

Looks like a lander of some sort is still a possibility:
http://blog.chron.com/sciguy/2015/05/a-europa-lander-is-possible-jpl-scientists-say-and-congress-appears-likely-to-support-it/

Posted by: dvandorn May 9 2015, 03:33 PM

Yep -- that's Adam Steltzner, of MSL landing fame, up there energetically (as always) describing JPL's ideas on building a Europa lander, complete with a melting mole to try and access open water or at least deep ice. Interesting to look at the notes on the board, the flip chart, and the PowerPoint page hung on the board at the far right of the picture.

-the other Doug

Posted by: Habukaz May 9 2015, 05:27 PM

That in itself not new, though. NASA http://spaceflightnow.com/2015/04/10/nasa-invites-esa-to-build-europa-piggyback-probe/ to provide a lander to the Europa Clipper.


Edit: changed month

Posted by: DEChengst May 26 2015, 03:34 PM

News Conference coming up later today on NASA TV. Time is in EST:

2 p.m., Tuesday, May 26 - NASA News Conference on the Selection of Science Instruments for the Europa Mission (all channels)

Posted by: Explorer1 May 26 2015, 05:51 PM

Another stream starting here too: https://www.youtube.com/watch?v=ivHHFoKn2pU

Posted by: scalbers May 26 2015, 06:52 PM

Interesting news conference overall on the instruments. Just a passing reference in response to a question about studying a lander. Studies on that are in progress and should be finished later this year.

Posted by: Mariner9 May 27 2015, 03:26 AM

I just read the blog posting on the instrumenta over on the Planetary Society website. Nine instruments on this mission. Wow. I know it is considered a Flagship mission, but with all the talk of trying to keep mission costs down I expected a bit smaller payload.

Not that I am complaining.

The item that really caught my eye was the EIS (Europa Imaging System).
- Near global coverage at 50 meters per pixel, and selected areas up to 100 times higher. -

My back of the envelope math comes out to highest resolution images being a half meter per pixel. Very nice.

Posted by: dvandorn May 27 2015, 04:59 AM

Well, think about it. If you're prospecting for the best places to melt through the ice down into the Great Ocean, you need to characterize the surface on a global scale. You can't run your ice-penetrating radar and sounding radar globally, so you have to have good enough photo coverage to match visual characterizations to the deep-structure information you get slices of from those lower-resolution, more limited coverage instruments. Then you can apply those matches to figure out all of the good potential ocean entry points, where the ice crust is the thinnest.

I would be really surprised if there aren't good visual cues in the high-resolution images of the surface that correlate to the thickness of the crust beneath. It might take some analysis, and the cues might be subtle. Bit I bet we'll find them.

Now, this all makes sense if you're using the next mission to plan your assault on the Great Ocean with a melting probe. If you're planning on bringing your melting probe with you on this next flight, well -- good luck finding a good, thin-crust spot to land it on within your mission timing constraints.

-the other Doug

Posted by: monitorlizard May 27 2015, 05:09 AM

I'm surprised that there is no laser altimeter in the Europa spacecraft payload. There's no indication of an altimetry mode in the radar instrument, so the mystery deepens. I was under the impression that determining the exact shape of Europa was important for modeling the tidal heating from Jupiter. It's possible to get some topographic information from stereo imaging, but it's hard to imagine getting the large area coverage with high resolution I think is necessary for detailed shape modeling.

Posted by: nprev May 27 2015, 05:25 AM

I would think that altimetry information would be at least indirectly acquired by the radar instrument in any case, though. Perhaps it's just a matter of mining the data properly.

Posted by: djellison May 27 2015, 02:58 PM

You can do a lot lot better with stereo imaging that you could ever do with 40 flybys with a laser altimeter.

Posted by: JRehling May 27 2015, 11:15 PM

Keep in mind that there are at least two different kinds of sub-surface water hypothesized:

1) The global ocean.
2) Lakes which are melt-lenses and may never have had direct contact with the global ocean.

The ferocious debate over the thickness of the crust may be due to the apparent contradictions created by these two distinct phenomena. Just as, once upon a time, people about the nature of nebulae, before finding out that there are several very different kinds of nebulae, the surface phenomena indicating subsurface liquid may have gotten scientists arguing because some phenomena were produced by (1) and some were produced by (2).

If so, we can virtually forget about direct probing of (1) anytime soon, but the depth down to (2) may be arbitrarily small at any given time. And then the possible pathways for future surface exploration become quite complex, presenting, for example, trade-offs between the surface units that were most recently in contact with liquid water, the surface units closest to subsurface water at present, and/or the surface units that most assuredly had contact with "dirty" ocean water at some point (however ancient) in the past.

As painful as it is to say, we're still at a quite primitive phase in understanding Europa. Mars missions are still surprising us after ≥ half dozen landers and orbiters each. Europa is at the Mariner 9 stage in its exploration, and we're only now planning the second mission after Voyager 2, which can't arrive for another 15 years or so!

The next mission there will be, roughly speaking, the Viking Orbiter of Europa (pending any pleasant surprises regarding a lander). This is a deep chess game we're playing with Europa and it's going very slowly.

Posted by: vjkane May 28 2015, 04:12 AM

Laser altimetry would be useful only if the measurements are made over the same location at different points in Europa's orbit.

Posted by: TheAnt May 28 2015, 10:24 AM

@monitorlizard: A laser altimeter would be great on one spacecraft that orbit Europe. Yet this spacecraft will orbit Jupiter and only do flyby's of Europa.

@JRehling: Yes that Europa might have water closer to the surface would fit some observations of surface features such as the chaos terrain, at the same time having a thick ice over the ocean closer to the core.
Dual layers of ice have been noted in the arctic ocean as well as in sweet water lakes in the arctic and sub-arctic region. On lakes here on Earth the energy source generally comes from above, the sun that melts snow on the surface to freeze to create the second ice sheet. On Europa the energy would come from below.
On a few rare cases I seen double ice formed from a spring of water at the bottom of the lake in lime rich areas, the icesheet formed at the inversion layer in deeper water of the lake. At least to me that provided a model of how a double ice layer might form. Blankenship Schmidt and Schenk provided a very nice model for those melt lenses, but the intermediate layer of water might be more widespread.

Posted by: Habukaz Jun 17 2015, 10:18 PM

The Europa mission has entered http://www.nasa.gov/press-release/all-systems-go-for-nasas-mission-to-jupiter-moon-europa (and has gotten itself a https://twitter.com/NASAEuropa as well):

Posted by: pioneer Jun 18 2015, 12:27 PM

I'm not complaining, but I'm wondering what this mission will accomplish that the Galileo mission didn't. Both spacecraft have a magnetometer, dust detector, cameras and UV instruments. The Europa mission will also conduct flybys rather than orbit Europa just like Galileo. With the exception of the radar and more advanced versions of the instruments Galileo had, what do scientists hope to get that they couldn't get from Galileo?

Posted by: MahFL Jun 18 2015, 01:07 PM

More detail. The camera for instance will have up to 100 times more resolution. Also GALILEO only flew by Europa two times, I believe, 45 flyby's are planned for the new mission.

Posted by: Phil Stooke Jun 18 2015, 02:18 PM

Pioneer - Galileo was useful for what it gave us, but it was absolutely - uh - challenged by its high gain antenna failure. Sometimes we only got a few dozen images (or the equivalent in highly compressed or windowed images) from an entire orbit. Cassini routinely takes thousands of images per orbit, and this new mission will do the same or better. Look at maps of Europa - only a few limited areas are high resolution. Now we will get the whole moon in superb resolution. Plus, don't forget that Galileo was roughly 1980 vintage despite its launch being delayed until 1989. Instruments designed in 2015/6/7 will be orders of magnitude better than early 1980s instruments - especially in terms of composition data.

MahFL - Galileo made a lot more than 2 close flybys of Europa, at least 11 by my count, not including more distant flybys. The first (arrival) orbit (not counted in the 11) produced about as much data on Europa as both Voyagers combined.

Phil

Posted by: Y Bar Ranch Jun 18 2015, 02:44 PM

Here's my thinking.

If you consider Europa as a constantly evolving system, then this is like the extension of Galileo. We can see what possibly changed in the years between the two, which is possible because they have the same instruments. Can you imagine the excitement when they go back to the same site and see significant changes in the surface coupled with changed measurements? Fingers = crossed.

But ultimately it is all about the bandwidth. Mooorrrrreee data. Fire hose instead of a dripping faucet.

Posted by: djellison Jun 18 2015, 03:26 PM

Data..


Galileo - 120bps.

Europa Mission - probably three orders of magnitude more.

Globe maps of Europa at significantly higher resolution that currently available

Instruments 30 years more modern than those on Galileo.

And - there may be a lander along for the ride.

What will we get from this mission that we didn't get from Galileo?

EVERYTHING.

Posted by: tedstryk Jun 18 2015, 11:51 PM

Everything except on-chip mosaics

Posted by: vjkane Jun 19 2015, 12:29 AM

You might want to read the following links that address your questions. The last talks about why, given Jupiter's radiation fields, a multifly by mission is better an orbiter:

http://futureplanets.blogspot.com/2015/06/nasa-goes-first-class-for-europa.html

http://futureplanets.blogspot.com/2013/05/europa-clipper-update.html

http://futureplanets.blogspot.com/2014/08/europa-how-less-can-be-more.html

Posted by: Decepticon Jun 21 2015, 05:54 PM

I was looking around for some information on Europa mission and noticed the design of the clipper mission has changed.

Looks more compact. http://www.nasa.gov/europa


Sadly I don't see a scan platform. I hope all the science instruments face in same direction.

Posted by: nprev Jun 21 2015, 06:15 PM

Cassini doesn't have a scan platform; has not been a problem. After Voyager 2's jammed I think that there's been a shift away from them in order to minimize mechanical complexity and thus reduce the chances of mission-limiting malfunctions.

Cassini also doesn't have a furlable HGA, partially for the same reason & after Galileo. I know that some of the early designs considered one.

Posted by: Paolo Jun 21 2015, 07:24 PM

IIRC, Cassini's design had a scan platform up to about 1992, but lost it as a cost reduction move

Posted by: Decepticon Jun 21 2015, 07:31 PM

Its all ok with me as long as they have backups for each reaction wheel. Lots of failures as of late.

Posted by: nprev Jun 21 2015, 08:12 PM

It's true that Cassini's scan platform was eliminated due to cost constraints, but by now I think it's safe to say that was a serendipitous good move.

There's an old thread that discusses this & other spacecraft moving parts issues http://www.unmannedspaceflight.com/index.php?showtopic=4819.

Posted by: JRehling Jun 21 2015, 09:58 PM

One of the quirks of Europa's geography is that the crust preserves a record of tidal stresses on a global scale. The pattern of faults and grooves is like a fingerprint showing the history of fault creation as Europa's crust slowly rotates, decoupled from the sub ocean surface. In this regard, seeing a quarter, half, or even three quarters of the surface leaves our understanding significantly incomplete.

On a world where, say, impact cratering was the only major contribution to surface morphology, that wouldn't be much of a problem. You could assume that the 3/4 you didn't see was about the same as the 1/4 you did see. But Europa's not that kind of place.

Galileo offered a certain level of resolution for very tiny, select regions on Europa, which sampled Europa's terrain types to some degree, but did virtually nothing at global scale. The figures and tables here give you an idea of the coverage.

http://lasp.colorado.edu/JUPITER/CH15/Ch15.html

Where you see tiny rectangles on these maps, for example,
http://lasp.colorado.edu/JUPITER/CH15/EuropaFootprintMap.jpg

…you see how little of the surface was imaged at maximal or near-maximal resolution. In many areas, Europa has not been imaged at better than 5 km/pixel resolution.

In summary, Galileo had the ability to take close-up images of any particular place on Europa, but because of the data limitations, couldn't provide a global survey. Re-flying a Galileo clone with the same instruments but unimpaired data transmission would have been an enormous boost to our understanding. Now, 20 years later, we're only planning the design of the mission that will finally begin to fill those gaps. But, as others have made clear, will be superior to a mere Galileo clone.

Posted by: pioneer Jun 21 2015, 10:35 PM

Thanks everyone for all your replies

Posted by: vjkane Jun 22 2015, 01:58 AM

Actually, the lack of a scan platform or independently steerable antenna on Cassini has been considered a continuing nuisance, and one that future missions will want to avoid.

However, that's not so much of a problem for Europa Clipper. Cassini makes observations throughout its orbit, and so scheduling time when remote sensing can be done versus data returned to Earth has been a problem. The Clipper will make observations only in the day or two around each encounter. Almost all of the rest of the orbit will be spent returning the data to Earth. (Presumably there will be some time spent observing Europa from a distance for plumes.) So there isn't the degree of scheduling problem.

Where the lack of scan platform/steerable antenna is a problem is for precise tracking for gravity measurements during closest encounter. The last plans I saw had two small antenna that would point to Earth during the encounters.

Posted by: Decepticon Jun 22 2015, 03:15 AM

Found a High Res image. http://www.jpl.nasa.gov/images/jupiter/europa/20150617/europa20150617-16.jpg


Reminds me of the old soviet Mars probes.

Posted by: tedstryk Jun 22 2015, 11:34 AM

It has been a mixed bag. The design for Cassini that had one could have done imaging and radar at the same time, which would have been nice. But it wouldn't have been able to do the ultra-stable long exposures that Cassini is known for without smearing them.

Posted by: ngunn Oct 27 2015, 07:36 PM

Great article on Europa from Mike Brown with a landing site recommendation, plus link to the new paper with free access:
http://www.mikebrownsplanets.com/2015/10/i-know-i-know.html

EDIT: Coincidentally Van Kane has just posted a couple of Europa entries, also discussing a possible lander, on his futureplanets blog.
http://futureplanets.blogspot.co.uk/2015/10/a-european-spacecraft-to-accompany.html

Posted by: JRehling Oct 28 2015, 04:45 PM

The Europa science and plans are exciting, as Europa news always is.

I'm trying to connect this discussion of Europa to the melt-lens theory of melt-through, in which the water that causes chaos is not arising directly from the ocean, but in lens-shaped zones of liquid water that sometimes contact the surface, but are not in contact with the ocean when they do.

It seems like the dynamics of ocean-surface contact are still way outside our understanding, and of course, the Europa mission would be the step to inform that (further? totally?).

As exciting as a lander would be, it sounds like the risk is very high. Maybe radar could be used to find a flat landing site, but the close-ups from Galileo make it look like Europa may not have a lot of flat landing sites.

Posted by: vjkane Nov 2 2015, 10:23 PM

John - the purpose of the hi-res imager on the spacecraft is specifically to find the smooth(er) spots in the interesting areas,which all seem to be fractured surfaces.

The ice penetrating radar (they have a surface topography mode as I recall) probably don't have a small enough footprint to safely target a landing site. They should determine whether or not there are lake lenses within the ice.

Posted by: JRehling Nov 3 2015, 01:16 AM

If there's a reflective mode, radar can determine smoothness/roughness at the scale of the wavelength, which is much smaller than the scale of the footprint. But that's ambiguously confounded with other properties of the surface, and I don't know if the data will be useful for that purpose.

Posted by: vjkane Nov 6 2015, 05:13 AM

Surface roughness within the beam footprint can be determined. I believe the footprint is pretty relative to safe landing areas in the interesting areas.

Posted by: Explorer1 Jan 7 2016, 12:02 AM

ESA wants to jump in now too, with an unspecified addition of some kind:
http://spaceflightnow.com/2016/01/05/esa-wants-to-be-a-part-of-nasas-mission-to-europa/

Posted by: scalbers Jan 7 2016, 06:18 PM

Without getting too political, it's interesting that Congress has mandated a lander be included, so ESA collaboration (hinted at last year) may be a great way to accomplish this. And indeed the Europeans want to be involved in a mission to their namesake moon.

Posted by: antipode Jan 7 2016, 10:38 PM

This could be the moment where high speed penetrators (maybe 2 in that mass budget?) finally get their much delayed moment in the (dim) sun.

P

Posted by: nprev Jan 8 2016, 01:59 AM

As I recall, penetrators have been proposed in the past but the unknown level of roughness at small scales (i.e., angular surfaces) combined with the hardness of ice at Europa's temperature introduce a LOT of risk...and this is not a mission that can be reflown easily or soon.

My (completely amateur) dream design would be a tiny analog of MPF with a retro assist; let it bounce around & open up the petals. Small panoramic camera, a little arm to stab the surface & measure regolith (cryolith?) conductivity & maybe other things, a UHF uplink to the orbiter, and as big a battery as they could fit onto it.

Posted by: Explorer1 Jan 8 2016, 03:31 AM

How plausible are solar panels for such a mission? Juno has it easy being an orbiter, with plenty of wingspan, but how large would efficiency advances in the next half decade have to be to make them worth it for extending a surface mission's duration?

Posted by: katodomo Jan 8 2016, 01:36 PM

Beginning-of-life efficiency on current production GaAs triple-junction solar panels is close to 30% (InSight's panels are 26% iirc). Fraunhofer ISE designed some solar cells with up to 45% efficiency in 2013, which I think is still the record.

At Jupiter's distance with minimal absorption by Europa's atmosphere 45% would yield 22.5 Watt per square meter. Given time-to-travel, after three years that'd probably be around 80-85% of that, and after one year near Jupiter around 65-70%. Hence about 14.5 W/m² assured yield with theoretical high-efficiency solar panels, up to about 8.5 W/m² with what's currently employed (for comparison: Juno's panels are expected to yield around 6.0 W/m² at life end, about 3.5% more than what's needed for operations).

Pretty much not feasible on solar alone. Possibly feasible with relatively large panels (3+ m²) combined with RHUs, provided rather minimal operations after a battery-powered first science phase and bouncing communications via a nearby space unit (i.e. flyby Clipper or orbiter). For ease of comparison, a single MMRTG at Jupiter distance would be pretty much equivalent to around 7.5 m² solar panels at the above high efficiency, or about 13.0-13.5 m² at current off-the-shelf efficiency.

Posted by: Explorer1 Jan 8 2016, 08:42 PM

Thanks for the info; looks the weight constraints are such that anything but batteries is still a no-go? I suppose it's now a question of how long a battery would last, like Huygens....

Posted by: katodomo Jan 8 2016, 11:45 PM

There's a JPL analysis on that here:
http://www.lpi.usra.edu/opag/meetings/aug2015/presentations/day-2/11_beauchamp.pdf

Covers pretty much all that, including weight constraints, batteries etc.

Posted by: Jaro_in_Montreal Dec 27 2016, 03:29 PM

Lander rocket exhaust effects on Europa regolith nitrogen assays
Ralph D. Lorenz,
Johns Hopkins University Applied Physics Laboratory

http://www.sciencedirect.com/science/article/pii/S0032063316300484

• Europa soft-landing is particularly susceptible to ammonia exhaust deposition on cold surface.
• Europa may be starved of nitrogen so its compounds are of particular interest as limiting nutrients.
• Abundance, nature and isotopic compositions may be affected by exhaust deposits.
• Lunar, Mars landings suggest a region ~9 m around a 200 kg lander will be affected.

Posted by: Steve5304 Dec 28 2016, 09:17 PM

Surprised they would even consider a crane style landing and not a higher up retro rocket and bubble landing like a Soviet Mars 3 in 71... I know its not a rover mission, but I would hate to waste all the time and money just to get a sterilized sample of the surface showing jetfuel. It certainly could be done.

https://www.youtube.com/watch?v=Twgb41iAF2A

I'm very excited about this mission because of the lander. Even if it doesn't have camera's (And its possible it wont)

Posted by: Explorer1 Feb 9 2017, 07:49 AM

Science definition report completed (with lander concept art!) https://www.nasa.gov/feature/nasa-receives-science-report-on-europa-lander-concept

Posted by: Habukaz Feb 9 2017, 10:17 AM

My life-detection strategy: look for whale bones.

ADMIN: Good one, but please review rule 1.3. Letting this post stay up for now because we're discussing possible policy revisions, but we do ask that everyone please refrain from biological discussions. Thanks!

Posted by: bobik Feb 9 2017, 07:12 PM

A brief description of the http://www.hou.usra.edu/meetings/lpsc2017/pdf/2654.pdf proposal submitted to the https://www.cosmos.esa.int/web/call-for-m5-missions call of ESA.

Posted by: Roby72 Mar 16 2017, 11:50 PM

https://spaceflightnow.com/2017/03/16/trump-budget-blueprint-focuses-on-deep-space-exploration-commercial-partnerships/

Europa multiple flyby mission is supported in these budget blueprint but an expensive lander mission is cancelled

Robert

Posted by: nprev Mar 17 2017, 01:35 AM

ADMIN NOTE: As a reminder to esp. our newer members, please remember rule 1.2 at all times before posting. No politics, everybody. Thanks!

Posted by: Explorer1 Mar 17 2017, 04:57 AM

There's not much news here in terms of the lander component anyway, since there's always negotiation before any proposed budget actually passes. The Planetary Society has a http://www.planetary.org/blogs/jason-davis/2017/20170306-trumps-first-nasa-budget.html In the meantime, we can discuss other details...

Posted by: JRehling Mar 18 2017, 04:06 PM

Agreed. The last launch for a Jupiter+Europa mission, Galileo, was in 1989 so I'm not too concerned about a shakeup in plans for the mission after the next one. One might say that planning now for a Europa mission could even be premature when we don't know what EMM will find. We've seen portions of Europa's surface at respectably high resolution, but it's not out of the question that a thorough reconnaissance will identify landing sites that require different engineering and science specs than anything we know of now.

Moreover, the tentative identification of time-varying geyser activity really broadens the possibilities for what the next step at Europa might be. In accessing aqueous materials that have recently been in contact with the ocean and/or lens melt lakes, there are potentially several very different targets:

1) A surface location where liquid water from below has recently risen and frozen.
2) A surface location where geyser outflow is falling in the current time frame.
3) A geyser fly-through and sample return.

Moreover, there's some potential synergy here with Enceladus exploration.

It's a bit sad that the delays between missions are significant fractions of a human lifetime, but it's important that the second mission is planned better rather than sooner.

Posted by: Decepticon Mar 18 2017, 10:01 PM

Im confused is the Europa Clipper mission still happening?

I thought it was Cancelled?

Posted by: nprev Mar 18 2017, 10:21 PM

Europa Clipper is on. The putative Europa Lander is currently not funded.

Posted by: mcaplinger Mar 19 2017, 12:23 AM

To be clear, Clipper recently passed its Key Decision Point-B review but it doesn't move forward into implementation until KDP-C. I don't personally consider a mission to be "on" until after KDP-C.

The lander never was funded for real so it couldn't be "cancelled" -- there are still technology development programs that are funded and have some applicability for the lander; e.g., https://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=554244/solicitationId=%7B5C43865B-0C93-6ECA-BCD2-A3783CB1AAC8%7D/viewSolicitationDocument=1/CLDTCH16%20Abstracts%20.pdf

Posted by: JRehling Mar 19 2017, 10:40 PM

Perhaps a source of confusion: There was a mission concept called Europa Ice Clipper that involved an impactor and a sample return. That concept was never funded and is not currently active.

The mission concept that is currently active was tentatively called Europa Multiple-Flyby Mission. That has formally been named, very recently, Europa Clipper.

Other than the name and the world that's being targeted, there's little relationship between the two missions.

Posted by: mcaplinger Mar 20 2017, 12:11 AM

FWIW, not by anybody I ever heard talking about it. I think Europa Clipper was a semi-official name used for the latest concept of a lower-cost multiple-flyby mission that took over when the Europa orbiter was decided to be too expensive. One could do some history on OPAG minutes and such like if one really cared.

At any rate, it's now officially Europa Clipper and I guess we'll see if it ever happens.

Posted by: djellison Mar 20 2017, 05:14 AM

Yeah...what's now called Clipper was known as Clipper really from the outset....we even called it that when I added it to Eyes on the Solar System. Then from on high it was decided it just be called 'The Europa Mission' and we all tried to remember NOT to call it Clipper, Now....it's Clipper again.

Posted by: JRehling Mar 20 2017, 05:32 PM

Thanks for further clarification on the naming issue. I was pointing out just one source of confusion – there's been quite a mishmash of mission concepts and names.

The Europa Ice Clipper proposal was not for a lander + sample return – the combination of delta-v and radiation shielding would be very problematic. The Europa Ice Clipper idea was for an impactor to hit the surface and throw up a cloud of material that would allow mid-flight collection of a sample by a craft that would never enter Europa nor even Jupiter orbit and would return to Earth on a direct-return solar orbit. This is sort of a mashup of Deep Impact and Stardust, avoiding the problem of the delta-v associated with landing and return. A similar concept was earlier proposed for Mercury and a fly-through sample return from Enceladus' plumes has also been discussed.

Posted by: nprev Mar 21 2017, 04:58 AM

Four posts that were wandering OT removed. Topic title edited for clarity.

Posted by: scalbers Feb 25 2018, 09:29 PM

Some presentations on Europa mission instrumentation were shown at the https://www.lpi.usra.edu/opag/meetings/feb2018/posters/, including a Micro-Raman spectrometer for a possible lander. Also an update on mission planning status in this https://twitter.com/elakdawalla/status/966323529485508611. The Critical Design Review mentioned there is in late 2019.

Posted by: JRehling Apr 4 2018, 02:58 PM

According to various sources, the recent NASA budget requests include increased funding for planetary exploration, including funding for a Europa Lander to follow Europa Clipper (or for the two missions to run concurrently).

Meanwhile, on the planning side, there has been some iteration on the design of such a lander.


http://spacenews.com/europa-lander-concept-redesigned-to-lower-cost-and-complexity/

I have only barely dared to believe that a Europa Lander might occur in the next ~15 years, but there are some encouraging signs now pointing that way.

Posted by: antipode May 12 2018, 05:07 AM

https://www.nasa.gov/press-release/nasa-hosts-live-discussion-about-europa-findings-potential-for-life/

Hmmmmm, plumes anyone?

P

Posted by: nprev May 12 2018, 06:06 AM

Doesn't look like a press release, just a general Q&A. Might be some nuggets about Europa Clipper and maybe something about the status of lander studies, but wouldn't expect anything momentous.

Posted by: Habukaz May 12 2018, 08:24 AM

I don't know what rules or norms this forum has for embargoes, but we likely do know what they will be discussing on Monday (new science).

Posted by: Explorer1 May 12 2018, 02:01 PM

It was mentioned in congressional testimony, (an odd way of 'leaking'!)

https://arxiv.org/abs/1711.03628, based on looking at old Galileo flyby data as well as the more recent Hubble observations.

Posted by: ynyralmaen May 21 2018, 02:46 PM

The paper discussed was actually https://www.nature.com/articles/s41550-018-0450-z - evidence of a plume signature recorded in in-situ Galileo magnetometer and radio wave instrument data.