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

[Guest_JamesFox_*]

But would such a mission tell us anything significantly more about Europa that would allow NASA to drop the need for a dedicated Europa orbiter and go straight to the lander-cum-borer-cum-diver mission? If there still needs to be an EO first somewhere down the track wouldn't that make another Galileo-type-tour, for all the useful science it might acquire, merely a stopgap mission?

If a stopgap mission is all that can be afforded, then better a stopgap mission than nothing. Also, Europa is far from the only Moon in the Jovian system that needs follow-up missions. Admittedly, the lack of RTG's on a low-cost mission would probably make close-up observations of Io or Europa more difficult, which would probably reduce the appeal of a low cost mission...

[mcaplinger]

First, the outer System is just unavoidably bloody hard and expensive to explore...

Just because, e.g., Galileo was expensive (and I don't know what the total runout cost was but $4B wouldn't surprise me) doesn't mean that a properly-designed reduced-scope mission would have to be. I'm not talking about orders of magnitude less cost, but 2-3x doesn't seem impossible, if there was in fact much real motivation to save money.

Second, the things we have been trying to observe -- unlike those in the inner System -- usually comprise miniature solar systems in their own right, and they include a hell of a lot of different types of physical phenomena that are going on simultaneously and interacting with each other, so that you need simultaneous observations of them with a large number of different instruments to properly understand them.

That's the party line, but I'd be prepared to argue that Cassini could lose half of its instrument complement without losing half its science. If instruments alone were a huge cost fraction of a mission (they're usually less than 25%, maybe more like 10%), that might be important.

[djellison]

I wonder what might be feasable using the Juno platform, but augmented with a larger capacity for Delta V - perhaps under an New Frontiers budget.


Doug

[Mariner9]

Is one Europa orbiter more cost effective than 3 lower cost missions? Yes it is, I'll admit it.

In fact, there are some things (like laser altimetry measuring the tidal flex of the moon) that are just not going to happen unless you go into orbit. So It wouldn't be 3 lower cost missions, more like 1-2 lower cost missions and you end up eventually coughing up the dough for the Europa Orbiter anyway.

And the argument "the missions are so few and far between we have to have the largest ship we can manage in each mission" .... remember my point about MSR in the late 70s early 80s? Well, the "get the most out of each mission" argument was bandied about a lot in those days. The result was (with the growing Shuttle budget helping) no launches for over 10 years.

With CEV swallowing everything in sight, we could push for Europa for years, and end up always just teetering on the brink of a new start, then loosing it in the next budget crunch.


So in my mind, another JUNO in the hand is worth 2 Flagships in the bush.

[Bjorn Jonsson]

Regarding EO vs. Galileo vs. a 'Galileo 2' vs. Juno vs. a New Frontiers class Jupiter orbiter let's not forget that a Galileo satellite flyby and a satellite flyby by a 'modern' orbiter are two completely different things. An orbiter equipped with carefully selected instruments and a large solid-state recorder can acquire a lot more data (both in terms of quantity and quality) during a single flyby of e.g. Europa than Galileo did over its entire mission (with the obvious exception that you see only one lit hemisphere at most during a single flyby). This is true even if the modern orbiter is smaller and less expensive than Galileo. For example a datarate on the order of a few kbps (compared to Galileo's originally inteneded 100+ kbps) would be sufficient to accomplish a very respectable mission although more is always better.

Collaboration with ESA has sometimes been mentioned as a possible way to reduce (or rather to distribute) costs. Does anyone know if this is even practical today (as opposed to when Cassini-Huygens was being designed and constructed) because of ITAR ?

[Mariner9]

One last point.


Viking was scaled down from original plans to use Saturn 1B or even a Saturn V for a multi launch of a much larger probe.

Voyager was the scaled down compromise when TOPS was canceled in the early 70s.

NEAR was the 150 million dollar scaled down compromise when the endlessly studied 500 million dollar JPL asteroid mission couldn't get a new start.







OK, I lied. Just two more points.


I agree with the "modern orbiter" argument. Can you imagine what multiple flybys of Europa could accomplish with a HIRISE ????????

I admit we're talking a bit over the New Fronteirs budget. But we are not talking flagship costs.

Imagine such a vehicle making multiple passes of Io. .... live volcanos, direct sampling of the plumes ..... congressmen love pretty pictures, and the public may not care the least about gravity field mapping, but they understand massive volcanoes.

[Guest_AlexBlackwell_*]

It was an excellent piece of work...

I'll second that motion. And I'll go even further: Emily's LPSC coverage this year has been the best I've ever seen for that event, even ahead of Kerr's typically good LPSC pieces in Science.

[Guest_BruceMoomaw_*]

This is turning into an awfully interesting debate, and I need to put in some more thought on it. So for now I'll just mention that consideration is apparently being given to adding one more instrument to Juno's payload: a combination near-IR spectrometer and camera.
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1564.pdf

Looking at it again: during Juno's (brief) extended mission, this gadget might -- repeat, MIGHT -- provide justification for having the craft make one close flyby of Io, to get the detailed mineralogical data that Galileo couldn't get because of the last-second partial failure of its own NIMS, and to map hotspots on Io better. This is a longshot, though -- their primary concern is making sure that the craft is destroyed before it has any chance to hit Europa.

[Guest_AlexBlackwell_*]

This is turning into an awfully interesting debate, and I need to put in some more thought on it.

Yes, it's a good thread with several good thoughts scattered throughout the posts.

[Guest_AlexBlackwell_*]

Yes, it's a good thread with several good thoughts scattered throughout the posts.

Torrence Johnson et al. have an interesting abstract for COSPAR 2006.

[JRehling]

This has been insightful.

Europa currently has large advantages in what I would call "programatic" factors: The science has been digested, and the priorities have largely been evaluated. Enceladus and Titan won't catch up for a while. As it stands now, Europa should clearly get the next mission.

However, if CEV and other factors keep us from flying a Europa mission for long enough, some of those advantages will evaporate. If we find ourselves in the unfortunate circumstance of being 10 years past Cassini's death and nothing has flown yet, Enceladus or Titan could catch up in terms of Cassini science having been assimilated, and either of them might prove to be easier missions that Europa. Then Europa's only advantages might be that it has been a subject for exploration longer and that the other Galileans would benefit from the tour leading to Europa orbit.

[Stephen]

This is turning into an awfully interesting debate, and I need to put in some more thought on it. So for now I'll just mention that consideration is apparently being given to adding one more instrument to Juno's payload: a combination near-IR spectrometer and camera.
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1564.pdf

Looking at it again: during Juno's (brief) extended mission, this gadget might -- repeat, MIGHT -- provide justification for having the craft make one close flyby of Io, to get the detailed mineralogical data that Galileo couldn't get because of the last-second partial failure of its own NIMS, and to map hotspots on Io better. This is a longshot, though -- their primary concern is making sure that the craft is destroyed before it has any chance to hit Europa.

What are the chances of it achieving the latter by doing a Ranger-style kamikazi swan dive straight into Io, snapping pics etc all the way down to the surface?

======
Stephen

[Guest_AlexBlackwell_*]

What are the chances of it achieving the latter by doing a Range-style kamikazi swan dive straight into Io, snapping pics et all all the way down

That would be cool, and reminiscent of one of the original (ca. 1979) end-of-mission scenarios for Galileo.

[Guest_BruceMoomaw_*]

I very much doubt it could transmit them fast enough; its bit rate is far lower than Galileo's would have been had it worked right. (After all, most of Juno's data is non-imaging, and it's supposed to transmit back its relatively small amount of imaging data at its leisure.) I'll recheck its bit rate, but I believe it's no more than about 8000 bps. For that matter, I'm not even sure that they can set up a close flyby of Io during its operating lifetime; I'll have to take another look at the chart of its orbital tilt at different times during its mission. Nor do I even know -- yet -- that it's even likely they'll put this instrument on it at all, although I intend to E-mail Scott Bolton tonight on the subject.

Since, however, one "Science" retrospective on Galileo did say that its biggest disappointment at Io was its failure to get any high-resolution mineral composition measurements, it would certainly be nice if they could pull this off.

[Guest_BruceMoomaw_*]

This thing is apparently also quite a wide-angle camera, which means that -- even if it could send back photos live during a crash into Io -- the last ones it sent back would almost certainly be no better than Galileo's sharpest ones, and probably a good deal worse. (But the spectral resolution of the accompanying near-IR point spectrometer is twice as good as NIMS, over the 2 to 5 micron range, improving its mineralogical powers. And any near-IR thermal photos taken by the accompanying near-IR camera would surely be sharper than any thermal maps of Io made by either the NIMS or the PPR on Galileo.)

In any case, since it seems likely that it will be a long time before we get any kind of closeup look at Io again (Europa Orbiter wouldn't come near it, although it's now a long-shot possibility that the next New Frontiers mission selected may be a Jupiter-orbiting Io mapper), it seems worthwhile looking into any possibility.