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The First Europa Lander, What can be done first, cheapest & best?
Bob Shaw
post Jul 1 2006, 01:55 PM
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QUOTE (Richard Trigaux @ Jul 1 2006, 07:01 AM) *
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.


Richard:

I quite like the idea of an ACME ™ Space Science Corporation tether being used as a brake - presumably without an anchor at the end, though...

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Guest_Myran_*
post Jul 1 2006, 02:26 PM
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Just offhand and without checking I dont think any tether would work, orbital speed are simply to high. It would merely snap when it hits any outcrop or block of ice.
Perhaps something could be made by some exotic material, but dont say carbonfiber, its very stong along the length but the force would be applied as much from the side for such a tether.

The atmosphere of Europa are also to thin for any aerobreaking, well perhaps you might get some small amount but nothing significant. Anything that takes time will be one disadvantage here.

So im still advocating the idea of one impactor, get it trough Jupiters radiaiton belt fast, perhaps not without any orbit at all at first.
If its piggyback on one Europa orbiter then it would of course have to separate early since its approach would be somewhat different than for the orbiter.
Fly it down via a swingby capture by Europa, a breaking burn and then down to the surface in very short order. That way one might buy a few days of precious science on the surface.

Addendum: I know its a pipedream, and against the suggestion of a simple Europa probe, but imagine having one instrument to detect Cherenkow flashes on one such lander/impactor.
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mchan
post Jul 3 2006, 12:20 AM
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QUOTE (Richard Trigaux @ Jun 30 2006, 11:01 PM) *
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.

Besides the ACME-ish imagery conjured up by this concept, the smear control will be a challenge. Without compensating for imager to target relative motion, the images will probably look like something out of the trip fantastique from the film 2001.
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djellison
post Jul 3 2006, 07:36 AM
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Pushbroom?

Doug
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Guest_Richard Trigaux_*
post Jul 3 2006, 09:52 AM
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QUOTE (mchan @ Jul 3 2006, 12:20 AM) *
Besides the ACME-ish imagery conjured up by this concept, the smear control will be a challenge. Without compensating for imager to target relative motion, the images will probably look like something out of the trip fantastique from the film 2001.


Of course, there is the problem of motion blur. But I am in the business of electronics. So I think it is possible to get data out of a CCD in such a way to avoid motion blur. But I won't tell it, unless some mission team hires me!

a smear-controled camera would be much lighter and smaller than a telescope, for the same resolution. But grazing Europa ground would require more fuel. So it is a trade-off, as usual. About radioactivity, it is about the same, wherever we are close or far from the ground. Perhaps a close orbit would allow to spend some time in zones which are shielded by Europa.

About a theter cable trailing on the ground, I realize it would be difficult, the part touching the ground would simply explode, transmitting little effort to the main probe. Such a cable would be heavy too, and it would not really "hang" to the ground from orbit. So it is not sure it could really work.
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Stephen
post Jul 3 2006, 11:20 AM
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QUOTE (djellison @ Jun 29 2006, 01:00 PM) *
I would wager that if you put MSL on the surface of Europa - it would be dead with a week due to radiation, MC might be able to comment, but I'd think Mastcam would just get quietly fried. 'Shield it' you might say....that would requrie so much shielding the thing would never get off the pad. (because every kg of shielding requires kg's of fuel for landing, and THAT required multiple kg's of payload capacity )

Which raises the question of the survivability of any probe sent to Europa to drill down to and release some kind of submarine probe to explore the putative Europan ocean.

Doubtless the drill bot and the sub bot will be safe enough once they have enough ice above and around them to act as a radiation shield, but until they actually start do drilling they will be as exposed to the radiation as any rover or ordinary lander. To prevent getting fried by radiation they will presumably either have to be equipped with shielding or the drilling down into the ice will need to begin almost the moment they land.

It would presumably also limit the kinds of kind of installations left on the surface to keep the lines of communication open with the Earth or with some relay probe outside the radiation zone.

Would it be enough just to leave the antenna on the surface and keep the electronics buried or would it there need to be some degree of electronics that would need to stay above the surface with the antenna? And would it even be practical to even keep the communications electronics buried? (I'm thinking here mainly of all the heat that might be generated by the electronics and what that heat might do to all the ice it's buried in...)

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Guest_Richard Trigaux_*
post Jul 3 2006, 11:44 AM
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QUOTE (Stephen @ Jul 3 2006, 11:20 AM) *
Would it be enough just to leave the antenna on the surface and keep the electronics buried or would it there need to be some degree of electronics that would need to stay above the surface with the antenna? And would it even be practical to even keep the communications electronics buried? (I'm thinking here mainly of all the heat that might be generated by the electronics and what that heat might do to all the ice it's buried in...)

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Stephen


This depends on what antenna.

At first glance, there is no inconvenience to have an antenna to the surface, and eventually 100m of cable down to the buried emitter. But things may be less simple.

-very high frequencies need less cable length, or a waveguide.

-This antenna would need to be omnidirectionnal, so with a low gain, which would require a high emitter power on Europa, and large dishes on Earth to receive. To have a large gain antenna would require some orientation mechanism, which could be more sensitive to radiation. It could work with only mechanical parts, the electronics being buried with the emitter.

About heat, it is not much a problem, I think. It would form a bubble of liquid water around the electronics, so this electronics will soon hang after the antenna cable. The problem becomes more accute if we have a RTG, because RTGs produce much heat, which has to be removed in order to ensure a correct functionning. We can fear that this heat would create a well of liquid water all the way up to the surface, so that the antenna will have to be protected against falling into this well. All this must be tested on Earth into Antarctic ice shield.
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nprev
post Jul 4 2006, 01:09 AM
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Richard, that sounds good for a long-lived stand-alone probe, but how about a basic penetrometer designed to communicate with an orbiter? You probably would still need an omni in order to compensate for the vagaries of landing/surface geometry, but it wouldn't require nearly as much power as a DTE link.


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Roly
post Sep 3 2006, 07:07 AM
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March 26 2006 Powerpoint on various Europa Lander Studies.

Much as I like the full scale soft-lander; perhaps the 65kg hard-lander would be best. Start with 4 and pare the numbers back as margin gets eaten up, maybe 2 would end up flying, then the other two ready to go for a New Frontiers Galileo II or a discovery class Enceladus mission?

trs-new.jpl.nasa.gov/dspace/bitstream/2014/39393/1/06-0829.pdf
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angel1801
post Sep 3 2006, 04:27 PM
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Has anyone thought of putting an Europa Lander at about 180W longitude? This is the point that always faces away from Jupiter. With much less or no radiation from Jupiter, a lander might last for a little bit longer!


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ugordan
post Sep 3 2006, 06:37 PM
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I would think the landing site will be determined from orbital imagery as potentially most interesting, not which longitude it's on.


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Roly
post Sep 4 2006, 03:01 AM
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Any chance that the launch vehicle for the Europa Explorer/Europa Geophysical Explorer could be uprated between now and the hypothetical late 2010s launch date? I seem to remember some speculation that Delta IVH had potential configurations with additional CBCs and SRBs. Maybe an Al-Li spacecraft bus ?

Given that it will be a flagship mission if it is ever launched, a few tens of millions more to ensure that there is enough mass available for a lander seems prudent.
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edstrick
post Sep 4 2006, 11:07 AM
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The radiation is not FROM Jupiter. The radiation is in circum-jupiter space, in the form of ion-rich plasma in the plasma torus, and very high energy charged particles spiraling around the magnetic field lines, bouncing from one of jupiter's poles, out past the equator, to the other. The leading edge of moons orbiting slower than jupiter's rotation gets a plasma-shadow from the torus, but no areas are shielded from the belt radiation.
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JRehling
post Sep 4 2006, 05:15 PM
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QUOTE (angel1801 @ Sep 3 2006, 09:27 AM) *
Has anyone thought of putting an Europa Lander at about 180W longitude? This is the point that always faces away from Jupiter. With much less or no radiation from Jupiter, a lander might last for a little bit longer!


The least radiation would be on the leading face, not the far face. Jupiter doesn't emit radiation, but traps it in belts that, in part, rotate along with Jupiter's magnetic field. Because it rotates faster than Europa, it hits heavily on Europa's trailing side, and less heavily on the leading side.
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Julius
post Sep 5 2006, 08:03 PM
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Being modest,I'd still say that 3 days lifetime for a Europa lander is too short!With Mars we can launch every 2 years and it takes about 7 months to get there.I'm sure we wont be having so frequent missions to Europa so each mission to Jupiter has to be ambitious compared to Mars missions.And yes I like your suggestions regarding seismometers and observing Jupiter from close up.Realistically,we have to find a way how to deal with radiation.That I think should be the limiting factor.
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