Is Europa really the "highest priority" of the community?, Cleave said it was at LPSC? Options

[Guest_BruceMoomaw_*]

It's arguably your fault if you state it as absolute truth without going to any effort to verify it, though.

Hokay. Call me naive, but -- even given the number of times central NASA HQ has routinely lied to us -- the thought that JPL's (multiple) spokesmen might be deliberately lying through their teeth, not only to me but to all the scientists at that meeting, never occurred to me. (It never occurred to the scientists there, either. If Mike Caplinger can confirm that tidbit, they won't be very amused to learn about it.)

[Guest_BruceMoomaw_*]

I'm not too sure of this. The Level 1 science objectives in the Decadal Survey for the Flagship-class "Europa Geophysical Explorer" are very distinct from the New Frontiers-class "Jupiter Polar Orbiter with Probe(s)" aka Juno. While the latter may contribute second tier science for the former, and politicians might seize on this continue delaying a Europa mission, the EGE Level 1s remain. So as long as the scientists have any input in the process, I don't see Juno doing any real harm to a Europa mission.

Yeah. The thing about New Frontiers (and Discovery) is that they are on entirely separate funding tracks from the money provided for the unique Flagship missions, and the specific selection of missions to various Solar System targets for both those competitive programs is supposed to be wholly separate from the actual total amount of money provided to both programs. So -- unless an NF mission specifically takes a bite out of the science goals for Europa itself -- there should be no connection at all between the particular set of missions selected by the review board for the NF program, and the amount of funding that Europa Orbiter gets. Juno is entirely a nonbiological mission aimed at Jupiter itself -- not only will it not make any astrobiologcal studies, but the current plans are for it not to make any observations whatsoever of any of Jupiter's moons (and its orbit won't even let it come close to Europa, although theoretically they could set up close flybys of Ganymede or Callisto).

Concerning the distribution of money between big Flagship missions and smaller space-science missions as a whole, however, the OPAG site has just reprinted some useful new documents -- confirming that, if push comes to shove, space scientists prefer funding smaller missions (and providing general research & technology money) to funding bigger ones:
http://www.lpi.usra.edu/opag/science_cuts.pdf
http://www.lpi.usra.edu/opag/07_budget_bagenal.pdf
http://www.house.gov/science/hearings/full...h%202/index.htm

I haven't looked at the last of those documents yet, but the heads of NASA's four current space science subdivisions all agree with the philosophy already noted by Emily: usually, the bigger individual projects are, the LESS scientifically cost-effective they are. They prefer -- in order of priority -- research, then technology development, then small missions, then medium-sized ones, then flagship ones.

But the main flagship projects for the Universe and Sun-Earth divisions -- the Webb Telescope and the Solar Dynamics Observatory -- are already well underway, and cutting their funding now would just prolong the total length of the projects and thus increase their total cost. And the Earth Science division's flagship, the GPMM mission, has already been repeatedly delayed, so the director of that branch says he'd prefer instead to delay the somewhat cheaper Landsat replacement. By contrast, the Solar System (non-Mars) division's main flagship mission, Europa Orbiter, hasn't been started yet, and so delaying it is much more practical. (We could also consider delaying MSL -- since it's just getting started -- but Mars missions remain one of NASA's Holy of Holies.) One should also consider Fran Bagenal's comment: "I feel on thin ice asking for additional funds -- new money -- when a second glance at the NASA budget reveals the current rhino in the room to be the fact that we have lost control of mission cost growth."

So perhaps what we should be focusing on right now is: are there any ingenious new ways to explore the moons of the outer satellites with New Frontiers-class missions? The traditional line has been that there aren't, but then this has been based on a confidence that Flagship-class missions WILL be flown to them. The loss of those makes a careful reexamination of ideas for NF-class missions to the outer-System moons -- ANY of them -- worthwhile again.

[JRehling]

So perhaps what we should be focusing on right now is: are there any ingenious new ways to explore the moons of the outer satellites with New Frontiers-class missions? The traditional line has been that there aren't, but then this has been based on a confidence that Flagship-class missions WILL be flown to them. The loss of those makes a careful reexamination of ideas for NF-class missions to the outer-System moons -- ANY of them -- worthwhile again.

Tight as money is, I'm not convinced that mission funding is not in that nonlinear zone that government specializes in, where it's not necessarily twice as hard to get money for something twice as expensive. So maybe the flagship/NF distinction is misleading.

But I would certainly think that a free/cheap-return flyby sampler of Enceladus's plumes could be done in the NF budget. Would it be possible to do this with solar panels plus batteries and extensive use of "sleep" mode? Sampling Titan's upper atmosphere would seem to be possible, but less obviously desirable. Seems to me that any Enceladus-sniffing mission has to cross Titan's orbit twice anyway, so in principle, it's doable. In fact, given that you could have this craft lose velocity and still back to Earth, an aero-braking pass through Titan's atmosphere might even be the thing to make it work! This all seems possible, but screaming of super-tight engineering constraints. A double sample return on a budget would be a stunning success, and any remote sensing that rode along would be bonus. Note that this craft would also cross the orbit of most of Saturn's other satellites twice -- including Iapetus. Barring constraints with Iapetus's inclination and obvious geometric constraints, and the fact that Cassini might just finish the Iapetus saga...

Imagine a one-shot mission that flies on the cheap, wakes up just to image Iapetus's most intriguing terrain that Cassini doesn't get around to (this could also happen on the out-leg), samples Titan's upper atmosphere, images the Tiger Stripes up-close while sampling Enceladus's plumes, and returning the two samples to Earth. The proponents of whatever mission this was competing with would have to get a little sweat on their foreheads.

[Guest_JamesFox_*]

What I was thinking of myself, is pretty much a New-Frontiers class moden mini-version of Galileo: a smallish Jovian orbiter with one RTG or solar panels, designed to study the Galilean moons via sucessive flybys. With the faliure of Galileo's HGA, even a little orbiter with modern instruments could easily outstrip Galileo in the volume and quality of the data returned. It might lack charisma, but it might be the logical replacement for a Europa Orbiter that cannot be afforded.

[nprev]

What I was thinking of myself, is pretty much a New-Frontiers class moden mini-version of Galileo: a smallish Jovian orbiter with one RTG or solar panels, designed to study the Galilean moons via sucessive flybys. With the faliure of Galileo's HGA, even a little orbiter with modern instruments could easily outstrip Galileo in the volume and quality of the data returned. It might lack charisma, but it might be the logical replacement for a Europa Orbiter that cannot be afforded.

The only thing that would concern me here is that the bean-counters would use such a mission proposal as ammo against future Flagships and resurrect 'do more with less'...and we all remember the ugliness that followed from that.

Unpalatable as it sounds, the community needs to blend in some marketing pizzazz along with its proper focus on science objectives; this means that new missions probably have to accomplish at least one unmistakably new thing, ideally with a high coolness factor. How about adding the "bowling ball" Europa lander to JamesFox's proposal? The idea would be to do a Cassini/Huygens-style drop-and-listen flyby, and get a couple of hours of invaluable ground-truth data along with some nice pics...

[Guest_BruceMoomaw_*]

It would take a LOT bigger retrorocket.

By the way, I've just gotten a new E-mail from Paul Lucey in response to my account to him of how the Europa penetrator idea was greeted at the Europa meeting. Despite my own rapidly growing doubts about the idea, HE still thinks it's workable, but expresses his pleasure that a piggyback lander of ANY sort is being considered. (Assuming, of course, that Europa Orbiter ever flies at all.)

[JRehling]

It would take a LOT bigger retrorocket.

A nice resource for this board, and something that ought to be derivable in a one-time shot, would be a list of delta-vs, like the mileage chart in the road atlas. Earth would usually be the From (!), but there are many parameters for the To (given a world, there is flyby, elliptical orbit, circular low orbit, soft lander...).

Now, who will generate that table?

[Guest_BruceMoomaw_*]

Imagine a one-shot mission that flies on the cheap, wakes up just to image Iapetus's most intriguing terrain that Cassini doesn't get around to (this could also happen on the out-leg), samples Titan's upper atmosphere, images the Tiger Stripes up-close while sampling Enceladus's plumes, and returning the two samples to Earth. The proponents of whatever mission this was competing with would have to get a little sweat on their foreheads.

Don't overdo it, as Hubie told Bertie. That would require incredibly fancy piloting plus a hell of a lot of luck -- even if you cut out Iapetus and just stick with adding Titan. It would be much more practical -- especially for an NF-cost mission -- just to sample Enceladus and (maybe) the ring particles of Saturn. (It might also be possible -- as James Oberg suggests -- for the craft, during its Jupiter flyby, to set up a sampling flyby of the particles in Io's plumes, or maybe of the dust in the outer part of the Jovian ring. If you can't time it just right to fly by Io after all, you still have a major mission.) As for Iapetus: much more cost-effective to just set up one or two more Iapetus flybys during Cassini's extended mission.

By the way, Freeman Dyson was pushing just the same idea (in "The Atlantic", of all places) about 7 years ago for Europa: why land there when we can just collect the material thrown up into Jovian orbit by its geysers and check that for freeze-dried biological evidence? But he failed to consider the fact that Jupiter's radiation would almost instantly scramble biological organic compounds beyond recognition -- and now we also know that Europa's geysers, if any, have apparently shut down during this particular geological era of its life.

[mcaplinger]

the thought that JPL's (multiple) spokesmen might be deliberately lying through their teeth...

Of course they weren't lying through their teeth, Bruce, the world is not so black and white as you seem to think. But they were, I suspect, being overly optimistic about what the technology development groups were telling them. The same thing happened in the last EO project: the AO claimed that there was all this wonderful "X2000" radhard technology available, and as the proposal process went on, all of it proved to be vaporware. After that experience, I'd need more than a JPL scientist's claim that it was really ready for flight. As just one example, what non-volatile memory technology are they claiming is megarad-hard? Current flash memory cannot survive more than a few tens of Krads, and MRAM is neither dense enough or flight-proven that I know of.

[Guest_BruceMoomaw_*]

Regarding other ideas: two of the second-tier NF missions proposed by the Decadal Survey were an Io Observer (a Jupiter orbiter to make repeated Io flybys), and a Ganymede Observer (ditto for that world). It doesn't take much imagination to envision using one copy of the same type of craft -- with few design changes -- for all four Galileans, for a lower-cost and higher-data replay of Galileo. The main problem might be that you very much want an Io Observer to have a polar rather than equatorial orbit to minimize its radiation dose, which minimizes your ability to do a gravity-assist tour of the other moons.

As for Titan: the cheaper version of the Titan Organics Explorer -- the wind-blown hot-air balloon that would make repeated landings to sample the surface -- was projected at the COMPLEX meeting to cost about a billion dollars (although this would probably turn out to be about as accurate as NASA's other cost estimates). It would have kept itself within that cost limit largely by simply skipping any accompanying Titan orbiter, and communicating directly with Earth instead. If so, then -- IF Cassini can locate a spot on Titan that seems likely to have water volcanism, and thus water-processed organics -- it might be possible, within the NF budget, to drop off a stationary lander onto that one spot, do the same analyses planned for TOE, and have it radio its data directly to Earth.

Alternatively, it might be possible within the NF budget to drop off, by itself, a wind-blown balloon that would never land, but would just blow around Titan mapping its surface in far more detail than any orbiter can do. (While the spectral windows for sunlight piercing Titan's atmosphere would seriously limit the ability of such a low-altitude permanent balloon to map the surface composition of Titan itself with near-IR, could it use a cluster of small lasers at different frequencies to illuminate the surface and allow such a near-IR spectrometer on the balloon to look for especially interesting spectral lines?)

All this, to put it mildly, is uncertain within the NF budget; but then we ARE just trolling for possibilities right now. And NASA has already announced that it will include as many as 6-10 overall Solar System mission concepts within its next New Frontiers AO in 2008.

[Bjorn Jonsson]

What I was thinking of myself, is pretty much a New-Frontiers class moden mini-version of Galileo: a smallish Jovian orbiter with one RTG or solar panels, designed to study the Galilean moons via sucessive flybys. With the faliure of Galileo's HGA, even a little orbiter with modern instruments could easily outstrip Galileo in the volume and quality of the data returned. It might lack charisma, but it might be the logical replacement for a Europa Orbiter that cannot be afforded.

The only thing that would concern me here is that the bean-counters would use such a mission proposal as ammo against future Flagships and resurrect 'do more with less'...and we all remember the ugliness that followed from that.

This all depends on how likely outer planets flagship mission are to get approved in the not-too-distant future. Having started following solar system exploration in the 1980s I'm getting worried that no such flagship mission is likely to get approved as a 'new start' before 2020 (if ever).

[JRehling]

As for Iapetus: much more cost-effective to just set up one or two more Iapetus flybys during Cassini's extended mission.

If you can view longitudes that aren't the same ones we've seen over and over.

The problem is the orbit has a node, and the node stays the same, and it keeps visiting Iapetus at one of two orbital positions. To get the new science, you need not only to have the orbit pop back out to Iapetus distance, you also need to alter the node. This is compounded in difficulty because Iapetus has an inclined orbit, so if you want to avoid passing way above/below Iapetus, you need to find an orbit that is inclined enough to visit Iapetus and still get back to Titan (ie, be back in the orbital plane when Cassini is at Titan orbital radius). This isn't trivial.

[tedstryk]

I'll admit that I am a big fan of the Galileo-2 style NF idea. What would really be cool is to do it with two craft, one that primarily deals with the outer three moons in an equatorial orbit, and one that primarily deals with Io in a polar orbit. But this will happen when devils ice skate.

Part of the bias is that, frankly, while I find Europa interesting, I don't find it any more interesting than Io and Ganymede. I think selling Europa by assuming that the idea of life in its ocean will attract interest is a dangerous game, because it rests on a long shot. If NASA continues to sell that line, and we eventually get down to that ocean to find it as dead as a door nail, NASA will have egg in its face that it may never be able to clean off.

[Guest_BruceMoomaw_*]

One can conceive a craft in polar Jupiter orbit, with an extremely low periapsis that "threads the needle" of the doughnut-shaped zone of highest-intensity Jovian radiation (like Juno), and which initially has an apoapsis allowing it to make repeated flybys of Callisto before it fires its engine again to lower its apoapsis again for repeated flybys of Ganymede, and so on for flybys of Europa and finally of Io. This would not, after all, require any more fuel total than a craft that initially brakes itself into such an orbit for Io intercepts. The question -- which I can't even guess at -- is how much freedom this would give us for flying by different portions of the moons' surfaces, as compared to an equatorial-plane Jupiter orbiter.

I've been thinking more about the question: could such a Jupiter orbiter that makes repeated Europa flybys serve, after all, as an adequate substitute for Europa Orbiter?

Maybe.

One of the main organizers of the Europa Focus Group meeting asked the sum total of assembled scientists in the room (and there were a lot) whether anyone thought this kind of intensive study of Europa would be justified if the place didn't have biological significance. Dead silence followed. Europa Orbiter is intended strictly as necessary advance preparation for the next mission, the big Europa Astrobiology Lander that would touch down and analyze the upper layers of the ice (perhaps down as deep as 100 meters or so, if it does its sampling with a short-range cryobot) for evidence of life.

Now, EO officially has two main purposes. One is to nail down once and for all absolute proof that Europa DOES have an ocean. A Jupiter orbiter cannot use a laser altimeter to make adequately sensitive measurements of the degree of tidal flexing of Europa's crust to answer that question -- but the induced magnetic field measurements of Galileo have almost totally nailed it down already. In fact, William McKinnon reported that the latest analyses of Galileo's data have flatly ruled out the slightest possibility that the field it detected was produced by any conductive material that wasn't in a layer very close to the surface. Indeed, the thickness of the layer indicated by the latest analysis of it is so thin -- maybe only 20 km thick -- that even seawater isn't conductive enough to generate the field unless a large amount of sulfates are dissolved in the water (which, of course, is precisely what the near-IR spectra of Europa's ice also indicate). A flyby craft with a magnetometer, making far more flybys of Europa targeted for this purpose than Galileo did, would surely get enough more induced-field measurements to nail this down even more solidly. We'd need repeated simultaneous data from two magnetometers in different places to be able to use it to gauge the thicknesses of the ice layer and the ocean itself, but that data is not in itself necessary to plan the Astrobiology Lander (which I will hereafter call EAL).

The other main purpose of EO is to find good landing sites for EAL. It would obviously be of huge assistance in that -- but if we're really strapped for money, we need to ask whether EO is absolutely necessary to pick out a good first landing site for EAL. Torrance Johnson, at the last astrobiology conference at Ames Research Center, said flatly that he thinks we can pick out a satisfactory first one just from the limited data we've already gotten from Galileo. That seems highly doubtful to me -- but a follow-up Jupiter orbiter with a properly working high-speed data link could do a lot of additional reconnaissance for such sites during its flybys of Europa, quite possibly enough for us to find a pretty satisfactory place even without full-scale coverage of Europa from an EO. It would unquestionably carry a high-resolution camera, a thermal mapper to look for any recent sites of vented water, and a near-IR spectrometer to map the makeup and concentration of materials that had oozed up to the upper ice from the ocean underneath -- and the likely spot for EAL will be one where that concentration is high, and where the lack of surface cratering and regolith suggests that the surface material has been exposed to Jupiter's radiation for only a relatively short time. It could map a lot of Europa just with those instruments.

There seems to be serious question as to whether or not such a flyby craft could get meaningful data from ice-penetrating radar -- even for just a few short strips of Europa's surface. But, again, while IPR is obviously extremely important for general studies of Europa, we have to ask whether it is absolutely necessary to pick out the best landing site for EAL, given the data we'll get from those other instruments. The main relevance of IPR for that particular purpose would be to try to locate pockets or fissures of liquid water very close to the surface -- within just 100 or 200 meters. But it might be possible to at least detect -- and map the horizontal extent of -- pockets of liquid water that close to the surface in a lot of places with a relatively insensitive, shallow ice-penetrating radar of the sort that a flyby craft MIGHT be able to use, even if it didn't measure the actual depth below the surface of such pockets beyond telling us that they were near-surface. And such a less ambitious and sensitive radar instrument used from a flyby craft might also be able to measure both fine-scale surface roughness -- very important data in picking out the EAL landing site -- and also the content of other material (rock dust and salts) in the ice, which could be very important in designing any sampling cryobot carried on EAL.

So, if we're as seriously strapped for cash as we now seem to be, it might -- repeat, might -- be feasible to replace EO with such a cheaper and simpler "Galileo 2" Jupiter orbiter that could survey not only Europa but also Ganymede, Callisto and maybe Io, as all the advance preparation we'd need to then jump straight to the Astrobiology Lander as the next Europa mission.

[Guest_BruceMoomaw_*]

Come to think of it, the kind of radar instrument I'm talking about for a repeated Europa flyby is actually very similar to the SAR on Cassini -- its purpose would be not mapping depth, but mapping the horizontal extent of features such as near-surface water pockets. In that respect, it would resemble the SAR that Tom Campbell proposed for a Mars Scout orbiter (and will now propose again, under the name "Eagle"), which would work at a wavelength allowing it to punch through just the upper surface soil layer of Mars to make SAR maps of the bedrock features underneath. It would also resemble the "Mini-SAR" that Bruce Murray will put on both the upcoming US and Indian lunar orbiters: a relatively lightweight instrument to map the horizontal extent of lunar polar ice deposits. It would presumably work on 2 or 3 frequencies, one to map Europa's actual surface roughness and radar reflectivity, and another to probe some distance beneath the surface for near-surface water pockets. But, viewed this way, we could certainly design one that would work from a flyby craft, and might be able to cover quite large areas.