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The First Europa Lander, What can be done first, cheapest & best?
Guest_Myran_*
post Jun 29 2006, 03:36 PM
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Yes I agree with djellison and others.
To give the Europa lander plan the chance to get trough the budgetary squeeze it will have to be the lightest and in some ways simplest kind of lander imaginable. So the actual landing might not even be a 'soft' one but actually take advantage of getting buried to ensure that the lander doesnt die from radiation prematurely.

Then again about radiation, would there be any advantage of landing on Europas trailing side?

A buried or semi-buried lander might also include a simple sampling system.

Imagine adding a radiactive heating element of a similar kind to those the MER are using, such would melt a bit of ice which would pour inside to any choice of sensors the designers could fit into such an instrument package. This one could answer some basic questions such as:

Have the ice on the landing spot ever been circulated in the interior or Europa? Does it contain any gasses? If so which ones?

Have the contents of the sample been changed in any way by radiation?

Lastly: Does it contain anything else but lighter elements? If not, which ones and what are their origin?
Yes I think of possible volcanic matrial from Io of course, if we're very lucky we might get one small peek at an Io sample for free.
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JRehling
post Jun 29 2006, 05:51 PM
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I don't think we can bet that a Europa rover wouldn't land in a hopelessly craggy "warzone" of infinite overlapping crevasses that make roving impossible. A bouncing lander would have an increased chance of settling into such a cranny. Remember that in the case of Mars, smooth at low resolution has tended to mean rough at high resolution and vice versa. On Earth, that's not quite true. So we can't bet on landing on what seems to be a smooth frozen pond and getting a slick, smooth surface: it could be bad news at rover-wheel scales.

I did a quick web-search to see if there are any results from terrestrial radar on the roughness of Europa, but it's clear that terrestrial radar is not well disposed to answer the question: a 2001-published study using 70cm wavelengths didn't even *find* Europa. The icy Galileans are very bright at shorter wavelengths. We know from the best Galileo images that some of Europa looks very rough at 6m/pixel. That is already an important answer for a rover that would want to travel more than 12 m!

Simply put, we can't bet the bank there there exists any Europan terrain that a wheeled vehicle can traverse, so we're not going to invest billions on one and hope for the best.

Furthermore, we don't know if anyplace on Europa is interestingly diverse at rover scales. If we did land on a big smooth homogeneous ice sheet, why rove at all?
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JRehling
post Jun 29 2006, 05:55 PM
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QUOTE (Myran @ Jun 29 2006, 08:36 AM) *
Then again about radiation, would there be any advantage of landing on Europas trailing side?


DISadvantage! Jupiter rotates much faster (~7x) than Europa orbits, so it's precisely the trailing side that gets the most radiation. This generates obvious effects on Callisto, at least, where the pattern of CO2 deposition shows lead/trail effects.

To make good on your idea, landing smack in the middle of the leading side would block some radiation. I imagine a bouncing lander that ended up in a "hollow" would get some additional help. The radiation exposure of a well-placed lander might be a factor of a few less than something orbiting Jupiter as a Europa trojan.
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RNeuhaus
post Jun 29 2006, 08:14 PM
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Now I understand that it is very expensive to send a spacecraft around Jupiter due to the high radiation exposition. That is the factor that leads to build a more expensive spacecraft in having a good radiation hardened on many eletronic parts (camera, pancam, navcam, telescope, sensors and others electrical parts) and also shielding on these components externally. At the end, that will add much weight to the spacecraft and also increase even further the weight for propulsion landing combustible.

In spit of the fact of high radiation on Europe, there will be any kind of camera shoothing on the surface?

Rodolfo
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djellison
post Jun 29 2006, 09:07 PM
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QUOTE (RNeuhaus @ Jun 29 2006, 09:14 PM) *
will be any kind of camera shoothing on the surface?


We have no actual mission in place - so we don't know smile.gif

Doug
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nprev
post Jun 30 2006, 12:50 PM
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Harkening back to the origin of this thread, I completely agree that the first Europa lander should be as simple, inexpensive, and rugged as possible in order to mitigate risks and maximize science return, particularly since it would almost certainly be a piggyback on EO or some other Flagship-class mission.

With that in mind, I just don't see a feasible way to get a camera on the surface given the implicit constraints imposed by likely landing methods unless some variation of the Pathfinder/MER balloon system is employed...and even then, would this instrument provide truly critical science data in comparison to other possible instruments?

Don't get me wrong--I'm a pic junkie like everyone else! smile.gif --but investigating as many of the geophysical questions about Europa as possible during the first surface mission has to be priority #1 in order to justify the expenditure. If it ever comes to a choice between a cam or a seismometer, conductivity sensor or a GCMS, I have to go with any of the latter three.


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A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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algorimancer
post Jun 30 2006, 01:13 PM
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My rationale behind sending a rover initially is that, unlike with Mars, missions to the outer solar system are rare and expensive, and you may as well invest a little extra in versatility. Choosing to use an existing rover design which just happens to be good enough to be appropriate to the destination means minimal required investment in R&D (a big part of the price of MSL and other missions), so all you need to do is build a copy from the existing plans and launch it. Heck, build an assembly line and just get in the habit of sending a stanardardized rover out every year or two with incremental inprovements; we could in short order have rovers on every body of interest in the solar system (Ceres, Vesta, the other Galilean satellites, Titan, Triton, Mercury, and some of the other icy satellites). Note that I'm recommending the MSL design, not MER, so no airbags and bouncing would be involved. Sure it might get there and immediately get stuck in a crevice... but it might not, it might be able to rove for hundreds of kilometers and see amazing things. As to the radiation on Europa... I don't know enough about it to determine whether it's a show stopper. And yes, realistically I know that with the current diversion of resources to the manned program [a rant I won't go into here...], this isn't going to happen any time soon. Just wishful thinking. More generally, I think that we need to start developing some standard plug-in compatible components for orbiters and rovers so that putting a mission together is more like building a PC... pick the parts you want, put 'em together, and send them somewhere, with no need for a big engineering project that reinvents the wheel for every mission. Okay, rant over... wink.gif
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Bob Shaw
post Jun 30 2006, 01:50 PM
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QUOTE (algorimancer @ Jun 30 2006, 02:13 PM) *
More generally, I think that we need to start developing some standard plug-in compatible components for orbiters and rovers so that putting a mission together is more like building a PC... pick the parts you want, put 'em together, and send them somewhere, with no need for a big engineering project that reinvents the wheel for every mission. Okay, rant over... wink.gif


Ah, the good old Soviet method, eh? The US always built a few Cadillacs, while the USSR built Ladas by the thousand...

Bob Shaw


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JRehling
post Jun 30 2006, 05:52 PM
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QUOTE (RNeuhaus @ Jun 29 2006, 01:14 PM) *
In spit of the fact of high radiation on Europe, there will be any kind of camera shoothing on the surface?

Rodolfo


I would guess that a panoramic camera of some kind would be landed. Other than shifting conditions of lighting as Europa rotates, there would not be any expectation of any change in the scenery, so a single panorama taken as soon as possible after landing would be just about as good as extended coverage over a longer lifetime. If nothing changes, why keep photographing it? That does a lot to blunt concerns about radiation, because it's fine then if the camera dies a few hours after landing. If it survived to take a second panorama as daylight shifted, that would be nice, but not crucial.
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Bob Shaw
post Jun 30 2006, 07:26 PM
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QUOTE (JRehling @ Jun 30 2006, 06:52 PM) *
I would guess that a panoramic camera of some kind would be landed. Other than shifting conditions of lighting as Europa rotates, there would not be any expectation of any change in the scenery, so a single panorama taken as soon as possible after landing would be just about as good as extended coverage over a longer lifetime. If nothing changes, why keep photographing it? That does a lot to blunt concerns about radiation, because it's fine then if the camera dies a few hours after landing. If it survived to take a second panorama as daylight shifted, that would be nice, but not crucial.


There may be tradeoffs between camera longevity, power sources and data transmission rates - all of these will have to be just right.

Bob Shaw


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djellison
post Jun 30 2006, 07:35 PM
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Perhaps the cunning technique that would have been used with Beagle 2 for the first couple of sols.....a parabolic mirror with a single camera under it.

Make it a 2k x 2k CCD, and a good sharp mirror - and you'd have the equiv of something like a 1000 x 500 pixel 360 degree panorama. You also could seperate the camera electronics from the actual field of few - tuck it down in the body of the spacecraft, shielded, looking up through some think optics to the mirror at the top.

Doug
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DDAVIS
post Jul 1 2006, 01:16 AM
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QUOTE (djellison @ Jun 30 2006, 07:35 PM) *
Perhaps the cunning technique that would have been used with Beagle 2 for the first couple of sols.....a parabolic mirror with a single camera under it.

Make it a 2k x 2k CCD, and a good sharp mirror - and you'd have the equiv of something like a 1000 x 500 pixel 360 degree panorama. You also could seperate the camera electronics from the actual field of few - tuck it down in the body of the spacecraft, shielded, looking up through some think optics to the mirror at the top.


I like this kind of thinking, on how to get a camera on landers as part of the challenge. Each place we send a spacecraft to which has anything to see should be looked at.
Video is the next frontier of visual documentation of at least selected targets. If there is expectation of dynamic visual events, such as in landing near an active volcano on Io, basing a rover design on the MSL landers would presumably include their video capability which would greatly enhance the public sense of 'being there'. Just as launch cams are becoming a standerd practice in major launches, landing videos will be seen as an opportunity not to be missed once the first Mars landing video is seen. Bandwidth issues are part of the hurdle to overcome and recieve due attention over time.


Don
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RNeuhaus
post Jul 1 2006, 02:45 AM
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QUOTE (Bob Shaw @ Jun 30 2006, 02:26 PM) *
There may be tradeoffs between camera longevity, power sources and data transmission rates - all of these will have to be just right.

Bob Shaw

The visual science might means more than any other sensor science. With a good picture, we can interpret many applied sciences such as geology, minerology, biology, astronomy, glacialogy, vulcanology, and much more what you can count!, pa!

Rodolfo
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Guest_Richard Trigaux_*
post Jul 1 2006, 06:01 AM
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There are three ways to protect electronics from radiations:

-shielding. An overal shield is out of question, due to its weight. But some crucial parts could be shielded with some very local shields, like power transistors in a DC-CD converter (which can break from a single event, and are critical). A CCD camera chip can also be shielded, classical shield behind, and lead glass optics in front

-short working time. As JRehling and Bob Shaw say, there is no need of a camera working for months, at least not on a static lander.

-hardened electronics. This is about a variety of techniques used to make electronic parts, especially semiconductors, less sensitive to radiations. But this is difficult, and not much can be gained, say one or two orders of magnitude, and that is not enough on Europa. So I suggest to use completelly different methods, such as triodes or electrostatic microrelays, as I already explained on the Venus lander thread.


An alternative to a simple lander would be a very low orbiter. Its orbit could be set to decay little by little, so that it would graze the ground, allowing to send quantities of very high resolution images, showing things like pebbles on large regions. Of course, it would impact the ground sooner or later, with too much speed o survive. But by letting a rope hang to the ground, we could obtain some free braking, before using a rocket to end braking.



Europa ground looks smooth from altitude, but it is likely a kind of ice regolite, with large blocks, pebbles, and much sand. Worse, it seems that there are many equilibrium slopes, so that climbing them would result in avalanches. A rover nightmare!

So, rather than wheels, it would require a kind of large spider, working with some hydraulic system, like scorpio legs. This could make very long legs with a reasonable weight.

But I think that, fortunately, the most interesting regions are the reddish chaotic regions, which formed with breaking and melting of the ice crust. As there was liquid water on the surface, it frozen hard, not in blocks. So, between the small hills if the chaotic regions, there must be flat hard regions, the most interesting place to find chemmicals or biological particules into the ice. The best place to search, and the best place to land...

Three techniques:
-the homing missile, using a high resolution picture to land on a selected place. Variant 1, with a rocket to land at small speed
-same, but variant 2, lands at high speed and buries itself in ice.
-the airbags, which we can expect they will bounce toward a bottom, precisely where we want to go.

Eventually a cluster of small landers with only such crude guidance, have much chances to land, at least one, in the right place. It would be short lived landers, but with analysis tools, microscope, etc. A small chemical heater could melt some ice.


A lander with a long lived seismometre could land in the same way into the same place, where it would find solid ice to operate properly. The variant with a high speed landing is prefered, because it would provide a shielding against radiations.
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edstrick
post Jul 1 2006, 08:50 AM
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In the outer solar system, we have tended to find that higher albedo objects have more active, self-cleaning (due to activity) surfaces. These surfaces tend to be the roughest on a meter scale, while the cratered-to-hell-and-gone iceballs like Rhea or Callisto have relatively block and rubble free undulating but smooth meter-scale surfaces. They've been hit so much you just make the rubble bounce and pound it finer.

I'm overstating this, but it's a clear trend.
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