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Europa Orbiter, Speculation, updates and discussion
Decepticon
post Sep 16 2005, 12:47 PM
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I was thinking more in the lines of a Melt its way threw type probe.


Or how about this! biggrin.gif
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Marcel
post Sep 16 2005, 12:55 PM
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QUOTE (Decepticon @ Sep 16 2005, 12:47 PM)
I was thinking more in the lines of a Melt its way threw type probe.
Or how about this! biggrin.gif
*

What the h... is that ? laugh.gif laugh.gif laugh.gif
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ljk4-1
post Sep 16 2005, 01:12 PM
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QUOTE (Marcel @ Sep 16 2005, 07:55 AM)
What the h... is that ?  laugh.gif  laugh.gif  laugh.gif
*


Ever seen the sequel to 2001: A Space Odyssey?

biggrin.gif

It actually looks both plausible and Soviet.

laugh.gif


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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Bob Shaw
post Sep 16 2005, 01:30 PM
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QUOTE (Marcel @ Sep 16 2005, 01:41 PM)
But soft landing without an atmosphere isn't possible. At least not for the allocated mass of the lander.
*


Marcel:

Let's think outside the box...

...Ranger-A plus airbags?

Bob Shaw


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Marcel
post Sep 16 2005, 01:37 PM
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QUOTE (Bob Shaw @ Sep 16 2005, 01:30 PM)
Marcel:

Let's think outside the box...

...Ranger-A plus airbags?

Bob Shaw
*


laugh.gif I suppose that IF we could make airbags that strong, it would easily thump! back into space far beyond the escape velocity of 2,2 km/sec.....it would buy us about a nanosecond on the surface laugh.gif
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Decepticon
post Sep 16 2005, 01:41 PM
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I'm 30 now, I hope that before I kick the bucket that I'll know for sure if there is a Subsurface ocean or not. blink.gif

Life or No life.

Just the fact that a ocean other than our own is out is very cool.

A subsurface/orbiter probe should be Top Priority. *Ducks at Tomato's* smile.gif
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antoniseb
post Sep 16 2005, 04:15 PM
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QUOTE (Marcel @ Sep 16 2005, 08:37 AM)
laugh.gif I suppose that IF we could make airbags that strong, it would easily thump! back into space far beyond the escape velocity of 2,2 km/sec.....it would buy us about a nanosecond on the surface  laugh.gif
*


If the orbiter released a craft from low orbit and the craft had a small rocket to de-orbit and layers airbags intended to pop on impact you might sufficiently decelerate a fairly hard set of instruments (perhaps 60 to 100 g's).

I'll have to do a few quick calculations to see if this is reasonable. The big doubt item is whether anything useful can be put in a small enough lander.
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ljk4-1
post Sep 16 2005, 04:17 PM
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QUOTE (antoniseb @ Sep 16 2005, 11:15 AM)
If the orbiter released a craft from low orbit and the craft had a small rocket to de-orbit and layers airbags intended to pop on impact you might sufficiently decelerate a fairly hard set of instruments (perhaps 60 to 100 g's).

I'll have to do a few quick calculations to see if this is reasonable. The big doubt item is whether anything useful can be put in a small enough lander.
*


They had airbags on Luna 9.


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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JRehling
post Sep 16 2005, 04:37 PM
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QUOTE (Redstone @ Sep 15 2005, 09:25 PM)
I think you have to balance the size and capability of the spacecraft against the permissible frequency of visits. Because of Europa's distance, and the large delta-v required to go into orbit, a sequential program like that for Mars is not going to be feasible. So there is more demand for the number of question-answer cycles to be kept to a minimum, even if that means more capable, and hence more expensive missions.
*


An alternative is to be resigned to the fact that Europa exploration is going to take a lot longer than Mars exploration. The trade-off, simply put, is: Do we want to get the most bang for our buck but have it take more time to fly all the missions we want, or do we want to get the science sooner and risk some missions/instruments that end up missing the point due to some yet-unknown characteristic(s) of Europa?

Don't kick me out of the enthusiast club, but I can't fabricate a case for urgency here. If it takes 8 billion-dollar missions to reach a certain level of understanding, vs a quartet of 3-billion-dollar missions completed in half the time, how do you explain (to the public??) that getting the answers sooner is worth the extra $4 billion? Assuming a fixed budget for exploration, this also means the rest of the solar system gets gyped out of many missions. There is opportunity cost.

QUOTE (Redstone @ Sep 15 2005, 09:25 PM)
When it comes to any form of lander, I think anything complex will send mission risk and cost too high. But penetrometers may be vulnerable to being axed once the squeeze begins for spacecraft resources and funding, even if we are looking at 7 tonnes for the mission. The Decadal Survey *did* identify a Europa orbiter and lander as separate missions, after all. If the lander is an international contribution, that would make it more secure.
*


I think a smash-and-grab mission that uses an impactor to blast some ice up to a collector that is on a free-return trajectory to Earth has to be considered.

As I see it, the lander concept comes down to two main investigations: What is the composition of the non-H2O stuff? Is there a seismic/thermal/magnetic indication of the structure/activity of the crust and subcrust?

An orbiter can start to speak to the magnetic and probably thermal (by scanning the nightside and eclipsed-dayside in IR) issues. Smash-and-grab would give us a point sample of composition.

I think a very strong candidate plan for the first two missions would be an orbiter that performs detailed surfacing mapping, including scrutiny of whether or not the non-ice component is the same compositionally everywhere. This mission would screen for the best possible locations for any future surface mission, whether it be smash-and-grab, a Pathfinder-style lander, or a penetrator-lander. It is certainly risky to launch a lander of any style without having that basic reconnaisance completed.

The case for the second mission being a lander seems elusive to me. The magnetic and thermal questions will be addressed in part by the orbiter (of course, note: the conditional nature of that statement is already evidence that the second mission should be designed around the results of the first). A smash-and-grab mission would not provide the seismic data of a lander, but would provide infinitely better analysis, in earthly labs, of surface samples -- for far less delta-v.

The combo strategy I have mentioned before for the first landed mission would be to have a lander with seismic capabilities touch down (or penetrate) first, then have an impactor (with its own camera, of course) strike the surface nearby shortly thereafter, providing a known seismic event that would probe the crust fantastically. That same impactor could be the one spraying particles up to the catcher's mitt on the free return trajectory. In all, three elements involving the surface, designed according to the results of the orbiter mission, with a broad wealth of returned data: seismic, magnetic, and thermal data from the landed probe at one location, closeup imagery of a second location, precise seismic data which would give excellent data on one location in the crust, and samples for earthly labs!

Seen this way, the great upside is not to link Mission 1 and Mission 2 to the same launch, but Mission 2 and Mission 3.

QUOTE (Redstone @ Sep 15 2005, 09:25 PM)
The HiRISE style camera is interesting. Certainly the 30 day prime mission is way too short a time to return the amount of data involved in mapping at that kind of resolution. Since the mission will have a wide angle camera for the global mapping, the question would be where to aim the big mirror. One aspect of the mission that would help is the many flybys and steady final approach to Europa before orbit insertion, which would give lots of opportunities for preliminary surveys. Also, if the mission carried a lot of onboard memory, then once in orbit thumnails could be sent, and then selected detail returned. But at that point the mission team would have to make up its mind *fast* (i.e. on a daily basis) on what was to come back in high resolution.
*


I agree that sophisticated regimes for selecting imagery returns are called for. I don't see why such a mission could not have truly massive memory (cmon, that's light), and the ground crew would have the entire duration of the mission to request imagery for downlink -- imagery taken the first day should still be available for downlink on the last day. Store everything, or at least a heck of a lot. It's a nice thought that the orbiter could have a great set of high resolution imaging in its memory, and the ground crew could peruse the low resolution map, and then request detailed observations in terms of a downlink, as opposed to in terms of a new, future observation.
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ljk4-1
post Sep 16 2005, 04:54 PM
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QUOTE (JRehling @ Sep 16 2005, 11:37 AM)
I think a smash-and-grab mission that uses an impactor to blast some ice up to a collector that is on a free-return trajectory to Earth has to be considered.

*


Such a mission was developed called Europa Ice Clipper. A 50-pound ball would be slammed into Europa by a flyby probe, which would fly through the debris cloud, grab some samples of Europa, and return them to Earth.

http://www.astrobiology.com/europa/ice.clipper.html


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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Guest_BruceMoomaw_*
post Sep 17 2005, 07:53 AM
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I've been thinking for some time about a modified version of Ice Clipper, in which the spacecraft would be based not on Stardust (with a small impactor) but on Deep Impact (with a much bigger Impactor kicking up a much larger amount of debris, and kicking up almost all of it from depths far below the radiation-modified upper layer). The Impactor's camera could also get extremely high-res final photos which could provide additional valuable information on small-scale surface ruggedness for the purposes of lander design.

I've even wondered if it might be advisable to launch such a mission BEFORE the Orbiter; a high-res camera and near-IR camera on the main craft, coupled to a very high-capacity and high-speed data recorder, could get high-resolution terrain and compositional data on quite a respectable part of Europa's surface just from a flyby (like the "Firebird" Io flyby once proposed as a Discovery mission). One possible motivation for such a mission flying first has disappeared, though: Janus Eluszkiewicz's argument that Europa's upper layers might be riddled with large cavities that would seriously interfere with the depth penetration of a radar sounder -- making it advisable to test the effectiveness of Europan radar sounding from a flyby first -- has come under very serious fire on the grounds that he simply assumed that such cavities could exist when the physical evidence is against it: http://www.lpi.usra.edu/meetings/lpsc2005/pdf/2346.pdf .

And the big problem with a smash-and-grab mission remains: given the very small amount of surface material that it would collect, could even supersensitive Earth-based labs properly inspect the sample for biological evidence? (Especially since it's quite possible that the heating the samples would inevitably undergo as they plowed through the aerogel collector layer would break down organic compounds.) if so, it might be preferable to initially analyze Europa's ice using in-situ instruments, even given their greatly reduced sensitivity and flexibility, simply because they could analyze much bigger amounts of material. JPL's own design study for an initial lightweight Europa soft lander ( http://www.lpi.usra.edu/opag/jun_05_meetin...ssion_Study.pdf ; http://www.lpi.usra.edu/opag/jun_05_meetin..._Trace_OPAG.pdf ) calls for such an organic-isotopic analysis -- using a combined liquid chromatograph and mass spectrometer -- as one of the two top priority instruments for a Europa lander, the other being a seismometer for data on ice-layer total thickness. I myself would regard organic analysis as even more important.

The problem is collecting a big enough sample for such analysis on a small lander -- and collecting it from a fair depth, below the radiation-scrambled surface layer, using a lightweight sample-collection system. The JPL study (which focuses on a surface lander, just because that's the one design it was contracted to examine) expresses concern about this, but doesn't mention specific solutions. A penetrator would seem to be the logical solution. The "Polar Night" Discovery mission proposed to analyze lunar polar ices -- which could well end up as the second in the new series of US lunar exploration probes -- called for three penetrators, each weighing only 30 kg, surviving a crash into the surface at 75 meters/sec and burying themselves 1-2 meters deep ( http://www.nrl.navy.mil/techtransfer/exhib.../PolarNight.pdf ; http://www.mae.usu.edu/faculty/tmosher/Gen...edia/Mosher.pdf ). They would each carry a neutron spectrometer (not necessary for Europa) and a mass spectrometer, and impact tests in which these instruments were fired into a 2-meter layer of plywood and exposed to 1200 Gs (four times their planned load) showed them surviving just fine.

Again, though, if interesting compounds are seriously diluted in the Europan ice, the problem is acquiring enough of them to analyze -- which might require a heated probe to melt its way down through several dozen meters of ice and filter diluted compounds out of the resulting large amount of meltwater ( http://lasp.colorado.edu/icymoons/europacl...ps_EurAbode.pdf ). But such a probe would almost certainly be too big to carry as a piggyback on Europa Orbiter.

If a small penetrator COULD have a chance of analyzing enough material to be worthwhile, however, it would seem vastly preferable to a surface lander as a piggyback on Europa Orbiter in almost every way. It would easily dig below the radiation-modified surface layer (unlikely to be more than a meter or so deep); it would be much lighter than a surface lander; it could land on virtually any terrain, no matter how rugged; it would bury itself and thus provide its own shielding from Jupiter's radiation (which is otherwise a major problem for a moderately long-lived lander); and it would couple its seismometer to Europa far more rigidly than a surface lander. It would probably be unable to obtain post-landing terrain photos, but it could record descent photos during the last few seconds before impact and play them back later for almost equally good imaging data.
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Guest_BruceMoomaw_*
post Sep 17 2005, 07:57 AM
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Stop press! While poking around on the Web for the above note, I've just found that Paul G. Lucey -- the Principal Investigator for "Polar Night" -- is also working on "Thunderbolt: In-Situ Detection of Biotic Compounds on Europa" ( http://www.higp.hawaii.edu/cgi-bin/higp/di...ame=PaulG.Lucey ). This is surely a Europa penetrator, and I intend to talk to him about it immediately.
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deglr6328
post Sep 17 2005, 07:36 PM
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Not being familliar with Luna-9, I checked it out and.....did the engineers include something of an easter egg in this image? laugh.gif
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Bob Shaw
post Sep 17 2005, 09:03 PM
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QUOTE (ljk4-1 @ Sep 16 2005, 05:17 PM)
They had airbags on Luna 9.
*


I don't think so... ...there was a big insulating cover over the lander - is that what you're thinking of?


--------------------
Remember: Time Flies like the wind - but Fruit Flies like bananas!
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post Sep 18 2005, 12:34 AM
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QUOTE (BruceMoomaw @ Sep 17 2005, 12:53 AM)
If a small penetrator COULD have a chance of analyzing enough material to be worthwhile, however, it would seem vastly preferable to a surface lander as a piggyback on Europa Orbiter in almost every way.  It would easily dig below the radiation-modified surface layer (unlikely to be more than a meter or so deep); it would be much lighter than a surface lander; it could land on virtually any terrain, no matter how rugged; it would bury itself and thus provide its own shielding from Jupiter's radiation (which is otherwise a major problem for a moderately long-lived lander); and it would couple its seismometer to Europa far more rigidly than a surface lander.  It would probably be unable to obtain post-landing terrain photos, but it could record descent photos during the last few seconds before impact and play them back later for almost equally good imaging data.
*



Penetrators have been proposed for many missions, but they always suffer from the same problems: very limited room for sophisticated instruments (big difference between a spectrometer that can detect water and one that can unambiguously classify organic molecules) and the need for entry into the surface to be near vertical. At the same time, there are some nice features to penetrators for Europa: they did beneath the surface ice (good for sampling) and have a meter or two of ice shielding them from the radiation (good for a longer life). A potential issue: if the Europeans do the lander, I don't think they have much experience with penetrators, but could be quite wrong on this.
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