The beauty of an RTG is that it creates a LOT of "waste" heat that can be put to use here for "free".
Also the electricity generation efficiency can be increased if there is an effective cold sink.

So an RTG probe is Perfect - as long as you don't hit a buried rock/meteorite.

Nick

If they do add a small lander to the first Europa orbiter -- and that is a very big "if" -- I've been a fan for some time of making it a penetrator rather than a surface lander, for a whole swarm of reasons:

(1) Such a penetrator can punch down a meter or two into the ice just by impact, giving it a good chance of getting below the radation-modified upper layer. (As far as I'm concerned, no lander that doesn't drill down that far is worth sending.)

(2) It could couple a seismometer -- the second most important instrument for a Europa lander, according to the science working group -- to the crust far more firmly than a surace lander.

(3) It would bury itself in the ice deeply enough to be shielded from Jupiter's radiation -- a very serious problem for an exposed surface lander.

(4) It could land on virtually any kind of terrain, no matter how rugged.

As far as I can tell, its ONLY disadvantage is that it would have more trouble getting post-landing surface photos -- but it could carry a descent camera and memory buffer to record and later play back the last few images before impact to get imaging data almost as good.

Sure enough, Paul G. Lucey -- the Univ. of Hawaii scientist who has proposed the "Polar Night" Discovery-class penetrators to look for lunar ice (they would weigh only 65 kg, penetrate 1-2 meters into the surface, and carry mass spectrometers which have already survived impact tests at four times the planned landing speed) -- is now proposing "Thunderbolt", a mission to look for Europan surface organics. He hasn't yet described it -- and I'm still waiting to hear any details from him -- but it is surely another penetrator mission.

However, there's another problem, as Chris Chyba pointed out in "Europa As An Abode of Life": the probe may have to process one hell of a lot of meltwater to filter out enough organics for study -- quite possibly 100 times more than any pentrator or small surface lander could possibly collect. We may have instead to fall back on a larger and later surface lander with an attached heated melt probe capable of melting down at least 100-200 meters, and filtering all the large amount of meltwater which it produces in the process. And while the waste heat from an RTG would do just fine to generate the melting heat -- that's been the plan from the start -- if Europa's ice is as highly saline as many think, a salt crust would build up ahead of any simple melt probe. It may need both a melting head AND a rotating drill head to chew through the accumulated salt. In any case, I don't see any way to put either of these on a penetrator.

Here's a use for an Europa Ocean Probe - as a neutrino detector!


Paper: astro-ph/0511243

Date: Wed, 9 Nov 2005 17:14:51 GMT (304kb)

Title: Development of Acoustic Sensors for the ANTARES Experiment

Authors: Christopher Lindsay Naumann, Gisela Anton, Kay Graf, Juergen Hoessl,
Alexander Kappes, Timo Karg, Uli Katz, Robert Lahmann and Karsten Salomon

Comments: 5 pages, 3 figures. Proceedings of the ARENA 2005 Workshop
\\
In order to study the possibility of acoustic detection of ultra-high energy
neutrinos in water, our group is planning to deploy and operate an array of
acoustic sensors using the ANTARES Neutrino telescope in the Mediterranean Sea.
Therefore, acoustic sensor hardware has to be developed which is both capable
of operation under the hostile conditions of the deep sea and at the same time
provides the high sensitivity necessary to detect the weak pressure signals
resulting from the neutrino's interaction in water. In this paper, two
different approaches to building such sensors, as well as performance studies
in the laboratory and in situ, are presented.

\\ ( http://arXiv.org/abs/astro-ph/0511243 , 304kb)

Anyone know if clay minerals exist on Europa, or could exist?

http://www.spaceref.com/news/viewpr.html?pid=18272

I know this has come up before but is it possible to do a Europa fly-by within a Discovery cost-cap?

Given that the Europa Orbiter is going to be 2012 at the earliest, surely there is scope for someone to propose something for Europa at the next Discovery AO.

I don't know that much about the design of orbiters, and this may
demonstrate (and probably does) some fundamental misconceptions, but I was
curious about a return to fly-by missions instead of orbiters like Galileo,
Cassini, EO etc. From what I have gathered, for many missions, the largest
problem is the energy required to brake into science orbit, particularly
where there is no potential for aerobraking, meaning a huge percentage of
the mass budget must be spent on a powerful engine and the requisite
propellant. I was under the impression that these problems were vastly
reduced in fly-by trajectories (?) With VEEGA trajectory perhaps this would be possible on a very economical LV (though it seems everything going forward is flying on Delta IV and Atlas now, not Delta II?) Okay so not a Taurus but there must be something in between Taurus and Delta/Atlas EELVs.

So instead of spending mass on an large engine with enough fuel to get into
a science orbit, couldn't the spacecraft instead focus on acquiring a huge
amount of data over a very short period of time in a low-altitude fly-by?
It would then sample a small area of the target at high-resolution.

It could carry (and I'm only guessing, the exposure/integration
times/pointing accuracy might make it truly impossible) stereo cameras and a
high
resolution imaging spectrometer on a motion compensation
scan-platform. All would operate
simultaneously, with power from advanced Solar arrays (Rosetta heritage?) lithium-ion batteries,
which would be charged during the cruise phase by the array to make up for any
power deficit during the very short and high-demand encounter phase. They could even be augmented with lithium primary batteries if required. The
spacecraft would be equipped with extremely wide and fast data busses,
caching the acquired data to memory and writing it out to solid-state disks
for later playback. No-RPS, easier admin. burden, compatibility with Discovery AO.

It would record this to high-capacity solid-state data recorders (multi-100s
GB), and then replay it once it had left its target, potentially over a
period of months or even years, depending on how much power was available,
local limits on the downlink and so on. This eases DSN management perhaps? Offline compression would be helpful, especially given that there might be issues with heavy compression in the Jovian environment (I'm suprised ICT did so amazingly well).

As an added bonus some of the
radiation hardening requirements would be reduced, as the spacecraft would
not be remaining in the most dangerous areas for a prolonged period,
repartitioning mass away from shielding and to the science payload. Lithium polymer batteries might be decent for providing some incidental shielding in any case.

I suspect I am heavily overestimating the ability of the scan platform to
provide adequate motion compensation, and the amount of time needed for the
instruments to acquire data - but I was curious about the idea because it
leverages some of the things that have become much better and cheaper over
time, like bus bandwidth, memory, disk write performance, processing power,
detector resolution/sensitivity - to replace things that have not, like
putting large amounts of propellant and engine mass into orbit.

I read a bit about Firebird recently, which seemed to utilize a similar approach. Perhaps there is geometry which would make possible a "Fire and Ice bird" (like the old JPL 'Fire and Ice' theme) ?

I've wondered out loud about this on other forums but no-one ever seems to have any ideas (other than Orbiters are better, which of course they are...)

Roly

It's not just that orbiters are better (though that rather goes without saying, in many ways).

First, there is the issue of time-and-change-dependent observations. If one of your goals at Europa is finding places where the ice crust is thin enough to provide some form of access to the ocean below, you need to observe Europa over a matter of weeks and months and track the movements of the crust.

Second, there is the issue of coverage. No matter how you design your approach trajectory, you're going to be able to observe only a tiny fraction of the surface during a fast fly-by. And there will only be one side sunlit during that snapshot. So no matter how capable a fly-by probe might be, its choice of what it can view is severely limited.

Lastly, there is the politics of funding. We are *barely* to a point where we can think about getting Congress to fund a Europa Orbiter mission -- a mission that we really need, in order to answer fundamental questions and set up a possible landing mission (and, more ambitiously, a mission to explore the subsurface ocean). Because of the points I raised above, a fly-by mission is far less likely to provide those answers, no matter how much data it returns about a very small portion of Europa. And now, *in addition* to funding an orbiter for a billion or more dollars, we're going to ask them to fund an interim fly-by mission for another half a billion dollars? If we were to do that, we'd end up with either the less-useful fly-by and NO orbiter, or (more likely) just getting laughed off the Hill for trying to get them to fund *two* different missions to the same chunk of ice millions and millions of miles away -- a chunk of ice most of them think is worthless in the first place.

Is that a little better answer than a simple "orbiters are better" statement?

-the other Doug

Something that the continued Cassini imaging of Saturn's many moons has made me aware of is the value of terminator observations, which are even more severely limited than observations intended merely to map albedo. A single flyby will show a world in 50% illumination, but only a small fraction of the surface in the low sun angles near the terminator. When Cassini's mission is done, we will be able to generate low-resolution DEMs for all of Saturn's inner icy moons, which would be very hard to achieve by performing direct measurements of altimetry for so many worlds (JIMO comes to mind).

Amateur astronomers know how dull an object the full Moon is, and Mariner maps of Mercury show how much more detail is seen at the terminator than mid-disk. An orbiter (even a Jupiter-orbiting craft) would provide not just twice the imaging of Europa -- in terms of terminator observations, it would provide perhaps 100 times as much imaging.

Any flyby of Europa better be a sample return.

At rough guess, it is possible, if there are basaltic rocks at the bottom of the ocean. clay is the usual result of slow chemical attack of such rocks by water. But perhaps the chemistry of Europa water is very different of Earth rainwater, so the result may be different. And if Europa has a carbon layer around its rocky core, clay becomes unlikely.

That this clay may arrive at the surface is another question. Europa shows strong evidences of the ice layer being broken is small icebergs and turned upside down, from some catastrophic events. So things in the ocean can reach the surface. That some clay from the bottom of the ocean could reach the surface needs a double transfer, first into the ocean, second into the ice layer. Maybe the catastrophic events can achieve both in the same time.

So a lander could search for such particles in the molten ice. From them it could give clues about the core of Europa

Would not an economic trajectory achieved with a ship in orbit around Jupiter, using the moons as a gravitational assistance, until getting a nearby circular orbit at the level of Europa, which provides the most economic way to brake and land?

The only inconvenience of this is that it would require some months, and also staying into radiation belts for a long time. So what is gained in fuel may be lost in hardening the electronics.

That is exactly the plan that has ALWAYS been written for Europa Orbiter -- it will make, first, about 6 flybys of Ganymede and about 3 of Callisto, and then (in the so-called "Tour Endgame") as many as a dozen close flybys of Europa itself to almost match orbits with that moon before orbital insertion. (For a drawing of a typical such tour, see page 10 of http://www.lpi.usra.edu/opag/jun_05_meetin...ssion_Study.pdf .) The whole process will take roughly 18 months, during which EO will soak up about 900 kilorads of radiation -- equal to the dose it will get during its 1 month in orbit around Europa itself.

As for aerocapture for EO, it's been considered, but -- besides the fact that aerocapture technology won't even nearly be ready for an EO launch by 2014 -- I was told at the COMPLEX meeting that studies indicate that aerocapture doesn't provide much of an advantage for this particular mission. (The plan, by the way, is also to use a flyby of Ganymede to help brake the craft into orbit around Jupiter initially, as Galileo used a flyby of Io for that purpose.) But -- even with all this gravity-assist -- half of EO's weight must be propellant. This is simply a difficult mission.

Another description of the "Tour and Endgame" can be found on pg. 23-26 of the most detailed description of the original Europa Orbiter concept at http://outerplanets.larc.nasa.gov/outerpla.../Europa_MPD.pdf . (One nice recent development: calculations now indicate that the total radiation dose that EO will get during this mission is less than half of the originally estimated 4 megarads. This by itself lops 200 kg off the needed shielding weight, and thus about 400 kg off the total spacecraft weight.)

Also, you'll notice that the Endgame involves only about half a dozen Europa flybys, rather than a dozen as I stated above.

Perhaps this will require a separate topic, but what will it take to put a lander on Io? Just imagine what surface images will look like from there!

That will be a while coming -- the radiation level at Io is 30 times that at Europa!

Thanks for the replies about the orbiters - the constitute the most compelling explanation yet of why you don't bother with fly-by missions unless the target is exceptionally hard. I can see the political point is also important when there is a [F]lagship class mission looking for money (that's a capital 'F' for the large clas flagship that EO will doubtless end up being).

Counting the days until EO arrives. I wish Juno could do some science on the Galilean moons, but I guess that's totally not the point, given the orbit. New Horizons Jupiter encounter should be great.

Roly

Yeah, it's been made clear to me by Scott Bolton that they don't WANT to fly Juno close to any of the Galilean moons, even if they get the chance. (Although I would presume that its camera could make some observations of Io's continuing activity.)

In fact, he's now made one interesting point that I had never thought of: Juno is definitely NOT going to have a long prolonged mission. It will have taken a considerable radiation dose by the end of its one-year primary mission, and they want to make sure it doesn't break down before they have a chance to deliberately crash it into Jupiter to make sure it doesn't eventually hit Europa. He's talking about an extended mission of -- at most -- one month, and they will in fact be monitoring its behavior carefully on the chance that they may have to end its mission a little ahead of schedule. (A landslide majority of its useful science will have been done by the first 6 months.)

This one is scientifically aimed at Jupiter -- period -- and (like Mars Climate Orbiter had it succeeded) it's going to do very little that will be of interest to the general public.

By the way, its launch has definitely been bumped now into July 2010 or August 2011.

Is the Europa Orbiter Still on? on was it replaced by Juno?

Just saw a program on Science Channel that mentioned it

You know this is very confusing lately. I was gonna suggest a area on this board with a listings of approved missions and future mission as well as canceled/on ice missions.

No, Juno AND the Europa orbiter (under its new name, "Europa Geophysical Explorer") are both planned, although EGE won't get its official program start until 2007.

However, one thing that is on hold for now is the previous plan for a Deep Jupiter Multiprobe mission, for which they won't give any go-ahead until they examine the Juno results -- that is, not for quite a while (since Juno won't arrive till 2016). There has recently been a very dramatic, but apparently firm, change in the science community's attitude toward the giant-planet entry probe program, which is yet another item in my "Astronomy" article that I must leave dangling for now.

"Astronomy" needs to pay you a sales commission, Bruce

Any news on what issue your article will appear in?

Or deduct from what they've paid him since he's dropping so many hints

Seriously, though, it's a good thing he didn't submit the article to Science or Nature because his comments here, as helpful and useful as they are to the forum, might constitute "prior publication," which both journals use as grounds for rejection or refusal to publish.

My article will be appearing in either the February or March issue. Unfortunately, I ended up with enough material to write a 9.5 page article (AFTER extensive trimming), and so the editors will be hacking it down to 4 pages -- and I'm not sure what complete sections they're going to cut out to do so. I will, at any rate, try to get "SpaceDaily" to publish whatever info "Astronomy" doesn't; and anything relevant that gets cut out there will get put into this blog at some point, rest assured.

Too bad about the extensive cuts. did you learn that after it was already written?

Bruce:

Perhaps it was a slip of the keyboard, but the word 'blog' caught my attention. Do you produce one? Do you have *time* to produce one?

I'm sure we'd all be fascinated, were you to do so - even when we (quietly) disagree with you, your comments on the unmanned spaceflight scene are without peer!

Bob Shaw

Nope, no blog -- I've never quite had the time and/or the nerve. (One recent "New Yorker" cartoon shows one dog telling another: "I considered starting a blog, but I finally just decided to go in for pointless barking instead.")

As for the article, they told me from the start that 4 pages was the length. The trouble is that whenever I attend one of these damn conferences, I get enough interesting material for SEVERAL articles, and then go through the torments of hell trying desperately to hack a 12 to 15-page article down to a few pages while the article bleeds and screams piteously. As with my 2004 article on the MER-A landing for "Astronomy", I finally just had to throw myself on the mercy of the editors by submitting an oversized article and letting them do the dirty work. (A far cry from those bright college days when I was straining desperately to inflate puny term papers.)

And I've always wondered why the articles are so fricken short.

Bruce, what month in 2004 was that?

Also, hard to say if you used the best approach with the editors. Did you consider 2 versions? one short, one long.

In your opinion did they retain the best stuff? or would you have preferred alternate surgery?

I/we can sympathisize with your pain and torment.

Editors are evil. They should be outlawed.

I guess that, if they weren't short, there'd be no room for the pretty pictures. That was something that _did_ bother me about Astronomy when I was a kid. But I guess that full page images of Saturn are probably a big selling point to the general public.

Bruce:

I dunno what the copyright issues are (hopefully, you'd be paid *twice*), but perhaps the editors of Astronomy could be persuaded to do a web-only version of your articles, perhaps a month or two after the print version, and which would be somewhat longer? It'd be the sort of thing which might drive us guys to their website, thus giving them a double-whammy on the advertising...

There are publishing imperatives in print media which don't always suit in-depth articles, but there's no reason these days not to claim back the high ground on the WWW!

Bob Shaw

Reminds me of an old Isaac Asimov short story in which a writer had been cursed by Satan such that he was incapable of writing anything except pact-with-the-devil stories. The upshot is that, after the writer died and went to Hell, the only thing he could end up submitting to the publishers in the Underworld were........


.....wait for it.....


.....pact with the Editor stories!

:::ducking:::

-the other Doug

Heh. I dare say almost everything is a pact-with-the-editor story.. and I dare also say that almost everything is dulled down and bland-ized so that it won't 'confuse anyone'. Yeah, why make people think when they can just read pap that reinforces their already long-held beliefs.. WHERE'S MY PAYCHECK SO I CAN WATCH MORE 'FRIENDS'

But I digress...

My MER story -- along with a 1-page piece on Stardust's comet flyby, during which I expressed my belief in a theory of the craters which I gather is still not proven, but still seems to me probable -- is in the April 2004 issue.

Both then and this time, from the very first they warned me that the final article wouldn't be allowed to go over about 2000 words. I never dreamed I'd have such trouble deciding what to cut out. I was somewhat disappointed that the finished product for MER-A simply didn't include any news you couldn't have gotten from other articles on the subject, but with that short length you just couldn't do much else. The only thing that made me really grind my teeth was that the editor took it on himself to insert a passage in which he listed a bunch of elements and described them as "minerals", thus leaving me holding the bag for looking like a scientific illiterate.

On the bright side, while I hung around JPL for the first 11 post-landing days, I finished the article just before Spirit's computer crisis, which would probably have led me to include a gloomy passage on how the mission was Certainly Doomed.

Here
Russia Plans "Long-Lived" Venus Probe
was dicussed the idea of using unconventionnal electronics to sustain the high temperatures (460°C) at the surface of Venus.

There was mainly three methods proposed:
-unconventionnal semiconductors
-micro-sized vacuum tubes implemented witht he techniques of integrated circuits
-micro-sized electrostatic relays

I note that the two latest proposals are also suited to resist to high radioactivity levels, so that they will be a good solution for a Europa orbiter (and even a Io orbiter) by increasing reliability and removing the weigh of shielding.

Developing such techniques will need only a series of small scale test, and then after a relatively short period of large scale development, in a total duration which is not uncompatible with the launching of the mission.

It's seemed to me that if we found a way to transform the radiation from charged particles into energy, we'd solve two problems at once for Jupiter missions. Surely if the particles were segregated, this would be possible. I imagine the problem is that the net charge of any stream would be neutral and trying to segregate them would require more energy than you would get out of them... although I'm not *sure* that is so. If you could "split the beam" and get a net negative hitting a cathode and a net positive hitting an anode, you could run a current strong enough to power the beam splitter... in principle. Then you'd have a mission that would would *want* to fly, eg, near Io/Europa orbit. (And a generator that wouldn't much work anywhere else.)

Uh-uh. Back when I was posting to the Europa Icepick website, I once did the actual calculations on the energy flux from Jupiter's radiation belts -- which turned out to be pathetically small: about five orders of magnitude less than you need to power a spacecraft! The belts are splendid at poisoning solid-state electronics (or biochemistry), but as a power source they stink.

However, running a long conductive tether from a spacecraft and letting it plow through Jupiter's intense magnetic field is a very different matter -- for an orbiter of Jupiter or one of the moons, that will work beautifully, if you're willing to put up with the tether.

There was such an attempt by the NASA to fly a tethered satellite around Earth using this system, and it worked very well, providing a good power, except that the mechanical forces acting on the cable were stronger than expected, breaking the cable. Around Jupiter it would work well, and perhaps too around other giant planets. That will be safer than using a RTG, and potentially it could yeld more power. (RTGs too are good at poisoning electronics, although around Europa their action is smaller than the indigenous radiations)

"except that the mechanical forces acting on the cable were stronger than expected, breaking the cable"

Actually, they had undetected flaws in the insulation on the conductive tether, possibly some grit in the insulation or between it and the wire (not sure working from memory). It electrally shorted through to one of the pulleys or guides on the deployment mechanism, and the considerably higher ELECTRIC CURRENT than expected burned through and severed the tether. That part of the experiment worked too well... oops!

Yep. In fact, when I finally read about that incident in detail, I was startled to learn that it was due to a completely unexpected phenomenon that they still can't explain: they had an electrical arc run from the cable to the end of the deployment boom that -- amazingly -- continued to flow for several seconds after it had melted through the cable, while the end of the cable was drifting away from the boom. Apparently some kind of gas leaked out of the Shuttle to allow the arc, but they have never solved the mystery. This makes me a bit more inclined to forgive the Italians for having us fly that Shuttle mission twice and have it fail both times.

This is really odd, and cannot explained by the static charge of the shuttle: it had to receive current from somewhere else, to form a circuit with the cable. And the arc had to be pretty long, to be still sustained seconds after breaking.

There may have be some halo of gaz around the shuttle. Weren't emptying their toilets at that time? Letting some ice block stuck at the shuttle sending high flow of steam all around? This could be the origin of many "unexplained" phenomenon, water steam being especially conductive.

With my opinion this experiment should be made again, using two technological satellites, not the shuttle.

Some bad news about the prospects for a Europa Orbiter have just been posted by Lou Friedman of The Planetary Society

see this link:

http://www.planetary.org/programs/projects...e_12142005.html

first 3 paragraphs:

By Louis Friedman
December 14, 2005

In the recently passed NASA Appropriations bill, the US Congress directed NASA to begin work on a Europa orbiter and to make a request for a new start for a Europa mission project in fiscal year 2007. This was welcome news to NASA, who lost their focus on Europa when the nuclear propelled Jupiter Icy Moon Orbiter mission was cancelled last spring.

But now word has it that there will be no Europa proposal in the 2007 budget proposal that will be made to Congress early next year. The Washington Aerospace Briefing, a respected newsletter publication of Space News, is reporting that the Administration’s Office of Management and Budget is denying the Europa request on budget grounds.

The Planetary Society will fight for a Europa mission. Whether or not is in the budget request, we will lobby in Congress for its inclusion in the NASA program. Our Explore Europa Campaign is already in full swing. Having Congress insert funds in the ’06 budget was a good start, but we need to ensure support in 2007 and beyond.

NASA's science budget is a mess -- too many missions, several with large overruns. It would be irresponsible to add a $1B+ mission into the pie until everything else gets straightened out. What might be useful, though, is some early development money next year to get things moving again.

The plan was to just insert about $10 million this year for initial design studies -- including making absolutely sure that they DO want to fly Europa Orbiter before any of the other possible Flagship-class missions. Once again, we have a case of the idiotic manned program eating the rest of NASA alive.

I could have not said that better!

Not that I don't think that NASA's manned space program is becoming a larger and larger money pit, but I'd like to see hard evidence that money not spent by NASA there would be transferred over to space science. A great many legislators appropriate funds for Shuttle/ISS because the money is spent in their districts for that specific purpose. It's amazing how many people believe that eliminating billions of dollars from the NASA EMSD would automatically result in an increase for NASA SMD.

The very fact that Congressmen fund NASA as pork to their home districts indicates that if the manned-program budget was cut, SOME of the money thus saved would get transferred to the unmanned program.

I dont see how you can make that connection. Your suggestion may or may not be true

Hopefully this truly worthy mission does get funded somehow, despite the gloomy outlook.

It has always seemed to me that the problem with the manned program is not that allocated funds are coming at the expense of the unmanned programs. The problem is that *cost overruns* in the manned program are carved out of the hide of the unmanned program. This nails you every year even after a mission is scoped and funded. Heck it even nails you during ops.

Still, this argument has been going on since forever. The reality is that the unmanned program has to live within the boundries defined by the, admittedly excessive, needs of the manned program. I don't like it but I don't see a way to change it. It is inlikely that money cut from the manned program will end up in the unmanned program. However, a reined-in manned program would be less of a yearly threat to the unmanned program and cause fewer 're-engineerings', 'budget exercies', 'descopes', 'stand-downs', 'development deferrals' ... pick your favorite euphemism for feeding the beast that is the manned program.

My personal feeling on a Europa mission is that it needs to focus on two questions: "is there (still) liquid water (for sure)?" and "where are the thinnest parts of the ice?". One has to hope the answers will be such that the justification for follow-on missions will lead to penetrators and landers, etc. The tendency towards a Galileo style tour must be avoided at all cost. It should be a Europa only tour. Otherwise the flight ops budget alone would kill the mission when you start adding all the systemic requirements for mission planning and resource allocation. I know we don't go out there very often and Jupiter ain't Mars, but I don't see any Galileo/Cassini style missions coming along anytime soon (or long term to be honest).

Perhaps a Europa mission should become a near term component of the Origins Program (would that be a good thing or more likely to kill it?)

Actually, the Europa Orbiter is a good deal more complex as a mission than a replay of Galileo would be, given the technology and experience we now have. Indeed, a Jupiter orbiter that makes dozens of Io flybys is one of the second-rank candidates for a New Frontiers mission -- which means, given NASA's likely change to the NF proposal rules, that they'll accept ideas for it in the next round of NF selections in 2008. Such a craft would make Ganymede and Callisto flybys anyway to keep modifying its orbit to fly over different parts of Io's surface and at different phase angles, so it could easily be turned into a mission to study all three of the remaining Galilean moons. Indeed, it could be a virtual duplicate of the Europa Orbiter but with much less onboard fuel -- the radiation shielding for EO would allow such a craft to make at least 25 close Io flybys (maybe 50; I've got to recheck my records).

In fact, since EO itself will have to make a total of about a dozen Ganymede and Callisto flybys to get into position for Europa orbit insertion, it is virtually certain to make major observations of those moons -- and Jupiter itself -- during the 18 months or so before it goes into orbit around Europa itself.

I guess this is one of the tendencies I think probably dooms a Europa Orbiter. I really do understand the forces which would drive the desire for such observations (particularly given the loss of atmospheric dynamics data from Galileo) but such observations do not come for free. Building this into a reference mission plan will lead to instrumentation choices driven partially by such observations. It is expensive to develop such observation plans. Would there now be a scan platform? That costs in many ways (hardware design, assembly and test; ops planning software; constraint checking; etc.). No scan platform? Then you have the attendant fights over spacecraft orientation. An S/C designed to be an orbiter can be purely a nadir look design with perhaps a side look radar.

Allowing for 'cruise science' grows the flight team during what could be quiescent time. Getting into orbit aroudn Europa *is* complex. It just seems to me that a mission design that avoids any additional complexity or design drivers would have a greater chance of approval. By allowng cruise science you now require an S/C that is part fly-by and part orbiter. Throw in serviing as a delivery bus for a lander and you are starting to talk real money. As more is added, there is a non-linear increase in integration costs.