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Posted by: nprev Dec 31 2005, 12:08 AM

I think that many people in this forum would agree that somebody's going to have to land on Europa someday before the rather elaborate schemes to penetrate the outer ice layer will ever fly, if for no other reason than to get some relevant ground truth before committing to such an elaborate, expensive, and risky mission.

EO seems to have ruled out any surface science package for that mission (though it would be nice to change their minds! ), but I think that there is a valid requirement at some point to directly assess the surface properties of Europa in an inexpensive yet creative way. Some candidate instrument payloads might be:

1. A sonar transducer/receiver set embedded within a penetrometer to determine crust density and examine the uniformity of the ice layer within the operational radius of the instrument (looking for cracks and holes, in other words).

2. A conductivity sensor again embedded inside a penetrometer to measure the native salinity of the surrounding material and possibly derive some constraints on the composition of metallic salts in the European crust (saltiness has a major effect on ice properties, in addition to the obvious need to derive the salt content of any underlying ocean).

3. A seismometer for all sorts of reasons.


How does this sound? Any critiques, additions, or subtractions? I omitted a surface imager not only because of bandwidth/extra complexity considerations but also because it seems desirable to penetrate the crust in order to minimize as much as possible reading any contaminants from Io during surface measurements. The orbiter data could be used to sense and subtract this from the penetrometer readings.

Posted by: Steve G Dec 31 2005, 02:40 AM

The all ice surface would facilitate the use of penetrators instead of more complex landers. Ideally, look for vented material that came to the surface from a fissure, and maybe there would still be some organics left over. But yes, I would want a seismometer!

Posted by: BruceMoomaw Dec 31 2005, 03:33 AM

JPL's study of useful instruments for a small Europa lander listed, in order of priority:

(1 & 2): A surface GCMS (or, better, a mass spectrometer combined with some kind of liquid chromatography) to look for organics and other interesting compounds; and a seismometer to try to sound the thickness of the total ice layer.

(3) A magnetometer to make induced-field measurements simultaneously with an orbiter to obtain data on the thickness of both the ice layer AND the underlying liquid-water layer.

(4) A surface panoramic camera.

There was, as I've noted, a knockdown debate on this subject at the November COMPLEX meeting -- including an unbelievably dreary and nitpicking debate over the usefulness of seismometers and magnetometers, culminating in the general conclusion that you'd need at least 1 or 2 weeks of data from them, which requires powering the lander with a small RTG rather than batteries.

But the trouble, again, is that the most important measurement by far would be a search for possibly biological organic compounds buried deeply enough in the ice that Jupiter's radiation won't have scrambled them unrecognizably -- and such a small lander probably can't drill the 1 or 2 meters necessary for that purpose. Any of the other measurements that a small lander could make can just as well be delayed and then put on the first dedicated larger Europa Astrobiological Lander mission to look for near-subsurface organics, at a site selected by Europa Orbiter.

The obvious possible solution to this problem would be a penetrator, and in fact at the meeting I spoke up and suggested just that. (It has other major advantages, too -- elimination of the need for a heavy final braking or shock-absorption system, shielding of the lander from Jupiter's destructive radiation by the ice itself, and better coupling of the seismometer to Europa's surface.) Unfortunately, Torrance Johnson was one step ahead of me. He said that just this possibility was examined in depth by the JIMO science definition team, and it turned out that penetrators on airless worlds have one huge Achilles heel -- there's no airflow to keep their nose pointed straight in their direction of travel when they hit the surface. So you need to add a big and complex attitude-control system to do this, or your penetrator will hit the surface slightly skewed, at which point you're screwed.

Still, Paul Lucey of the University of Hawaii is proposing "Thunderbolt" -- a Europa penetrator to look for subsurface organics (a descendant of his "Polar Night" Discovery proposal that would launch three small penetrators from a lunar orbiter to look for polar ice). The COMPLEX people actually suggested that I should get in touch with him to see if he's found a possible solution to the attitude-control problem, and while I haven't been able to contact him yet I intend to do so after New Year.

By the way, I'm telling you guys all this because every crumb of it had to be cut out of the shortened version of my upcoming article on the COMPLEX meeting for "Astronomy".

Posted by: JRehling Dec 31 2005, 04:38 AM

An interesting factoid is that penetrating into lunar ice would be operationally very similar to penetrating into Europan ice -- if there is lunar ice on the surface of comparable purity (I suspect it's dirtier). That is, the orbital-->impact delta-v would be very similar. The main difference is that a lunar ice mission would end up in darkness. Of course, the instrument selection might be quite different as well.

Posted by: edstrick Dec 31 2005, 12:17 PM

as Bruce points out.. hit the surface slightly off dead-on, and you're screwed.. and slightly off is very damn little, I think. NOT trivial.

Regarding the lunar polar ice. I think the best evidence is fairly clear. Despite the weak claims of a signal of ice in bistatic-radar data using the prospector or clemantine (forget which) data, earthbased radar reveals no trace of depolarized backscattered signals from low attenuation, thick ice deposits in the lunar cold-traps. They see it on Mercury's polar ice, the martian poles, and icy galillean satellites. Not the Moon.

This agrees with (I dont' remember who's) model for lunar volatile sources and sinks, combined with models for loss mechanisms from polar ices, including radiation sputtering, UV photodissociation (interplanetary and interstellar Lyman Alpha), impact gardening etc. The conclusion was that the most plausible model had many percent but not tens of percent ice mixed with regolith in the polar cold traps to depths of meters or more. This would be rather hard to spot optically, except maybe by scanning with infrared lasers, one in a strong ice absorption band, the other just outside the band.

A real resource, but not one you'd want to squander as hydrogen for rocket fuel, etc., except on the shortest term.

Posted by: Bob Shaw Dec 31 2005, 12:40 PM

There are *natural* penetrators as well as man-made ones. All we do, is look for a nice fresh impact, fissure, mini tiger-stripe or whatever, and land there. Turn a few ice boulders over, and there's your reasonably deep, reasonably fresh sample.

An orbiter with *good* imaging would be required, plus a smallish lander (perhaps attached to the orbiter, or not - the orbital dynamics might make it cheaper to have survey orbits/descent profiles which are best served by two vehicles).

Bob Shaw

Posted by: gpurcell Jan 1 2006, 05:01 PM

I think it is going to be pretty difficult to argue for/design a complex lander on Europa without establishing ground truth with a simpler lander. If there is no lander on the next mission, then I suspect it will be two missions beyond before we see a very capable lander.

Posted by: nprev Jan 1 2006, 09:11 PM

Re the penetrometer descent alignment problem: Wouldn't a "nose-heavy" penetrometer with an elongated body tend to align itself to local vertical during descent regardless of the presence of an atmosphere? If I'm not mistaken, a variation of this sort of tidal stabilization is used on terrestrial comsats for attitude stabilization up at GEO. Even though Europa's gravity gradient is much gentler, a penetrometer launched with a sufficiently low delta-V with respect to Europa should therefore have enough time to align itself properly during the descent.

Posted by: BruceMoomaw Jan 1 2006, 09:42 PM

Uh-uh. An object that short would take weeks -- and maybe months -- to align itself, and then it would point itself straight downward instead of in the direction of motion. There is no simple solution to this problem.

As for a smaller lander to provide ground truth for the later bigger ones, there are two possible ways in which this could be useful -- but there are cheaper alternatives to both. First, of course, we need really high-resolution pictures of Europa's surface to see what kinds of landing hazards exist -- especially since the data we have up to now suggests that the surface may be extremely rugged, laced with crevasses and small ridges. But Europa Orbiter is now virtually certain to carry a big MGS-type camera for very high-res photos of some patches of the surface from orbit.

Second, it might be wise to get a measure of the salt content of the ice before sending a big lander that would probably obtain its data by releasing a short-distance Cryobot to melt its way 100 meters or more into the surface. (We want to be sure of getting below the upper layer of radiation-modified surface material -- which may have been gardened by impacts a fair distance into the surface if we're unlucky -- and Chris Chyba has also pointed out that a Cryobot may be the only way of gathering and filtering enough meltwater to have a good chance of detecting small amounts of biochemicals.) But high salt content might jam up a Cryobot by causing it to build up more and more concentrated brine in front of its nose until you had a block of salt which it could not melt through -- so it may be necessary to add a mechanical grinding head to chew down through this at the same time that you melt the ice. However, EO is virtually certain to carry a good near-IR spectrometer -- and a mass spectrometer to analyze the molecules of Europa's surface sputtered into the space above it by Jupiter's intense radiation -- and these together should be able to answer that question. (They may even add an X-ray spectrometer for direct element measurements.)

I've wondered, though, if it might be worthwhile to put a small sterilized impactor on EO, equipped with a camera, to be released during the last flyby of Europa which the craft will make to almost match orbits with the moon before it finally fires its rocket engine on the next pass to enter orbit around it. This could provide us with very close-up pre-impact photos that might provide more data on surface roughness -- and the Orbiter might be able to fly through the cloud of debris thrown up by the impact (Ice Clipper-style) to do a better mass spectrometric analysis of Europa's main surface constituents. And such an impactor would of course be much lighter than a flat-out lander, especially since EO wouldn't need to carry the fuel to brake its mass into Europa orbit. I still imagine the data from this would not be worth the monetary and mass cost, but I DO intend to ask the mission's designers about the possibility.

Posted by: nprev Jan 1 2006, 10:22 PM

Hmm. How about a "semi-hard" lander al a Ranger instead? (...without the balsa wood, of course!)

Seriously, if the velocity differential is small enough during the final flyby, maybe something like a minature version of the MER EDL system without chutes but augmented by a retro could drop a nice little instrument suite on the surface with a high probability of success.

Posted by: tty Jan 1 2006, 11:04 PM

Two wild ideas:

1) Europa has an atmosphere though it is extremely thin. Might some kind of large drag chute or balloon give enough drag to stabilize a penetrator? A penetrator would be long and thin, so it would not require much drag to align it.

2) Armor piercing projectiles use a "sleeve" of softer material (e g lead) to hold and align the penetrator on contact with the armor.
However the ice may be to soft to "strip" the sleeve and in any case I think it would only work if the penetrator comes in more or less vertically.

tty

Posted by: ermar Jan 1 2006, 11:52 PM

Europa's atmospheric pressure is something like 10^-7 bar... which, according to http://en.wikipedia.org/wiki/Outer_space, is 10 times less than the pressure on Earth at which aerodynamic surfaces cease to function. (Europa's atmosphere is oxygen gas, so density for a given pressure should be similar). The drag is enough that you couldn't orbit at 1 m above the surface for too long, but methinks it would be a little low for penetrator alignment.

Posted by: tasp Jan 2 2006, 03:42 AM

Perhaps a future mission would drop an impactor at high velocity to vaporize some ice and a carefully timed following craft would decel in the plume . . . .


{dramatic to watch, but would it work?}

Posted by: ljk4-1 Jan 3 2006, 03:49 PM

It was called the Europa Ice Clipper:

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

Posted by: tty Jan 3 2006, 06:19 PM

It's too bad there is no GPS system on Europa. The new US/Swedish Excalibur guided artillery shell actually has a miniaturized GPS/INS guidance package and solid rocket attitude control system that is not only ruggedized to survive being shot out of a 155 mm gun and small and light enough to fit inside a 155 mm shell, it's also dead cheap compared to normal space hardware and built to stand long-term storage without maintenance.

tty

Posted by: nprev Jan 3 2006, 08:40 PM

I don't know how much GPS would really help, but a good, cheap minaturized INS is a must-have, along with that solid-rocket attitude control system...maybe add a radar altimeter in the nose of the penetrometer & have the steering algorithm just hunt for the max rad alt return amplitude that's closing in correspondence with the descent rate, which would presumably wash out side-scatter....? Hmm, this sounds more do-able...

Posted by: nprev Jan 3 2006, 11:59 PM

AlexBlackwell posted the fact that the 2006 Discovery Ao window is now open:

http://www.unmannedspaceflight.com/index.php?showtopic=1970&st=0&#entry34412

Anybody feel brave enough to submit a proposal for a Discovery ridealong penetrometer for EO based on what we've chewed over so far? I have no academic or industry affiliation, nor am I a scientist, so all I can do is instigate...

Posted by: RNeuhaus Jan 5 2006, 05:06 PM

I think it is the best solution. A mission of two steps: 1) simpler lander to ascut the surrondings in order to identify the required characteristics for the second mission. 2) The second mission will be properly designed according to the 1st mission to get the a more detailed mission such as a kind of penetrator.

The best experience is : Advance slow but as firm as possible.

Rodolfo

Posted by: ljk4-1 Mar 29 2006, 07:47 PM

Tell me this wouldn't be useful for an Europan ocean probe:

A SUBMERSIBLE HOLOGRAPHIC MICROSCOPE. A new device allows
scientists to form 3D images of tiny marine organisms at depths as
great as 100 m. The device allows the recording of behavioral
characteristics of zooplankton and other marine organisms in their
natural environment without having to bring specimens to the
surface for examination. Scientists at Dalhousie University in
Halifax, Canada, used the hologram arrangement originally invented
by Denis Gabor: light from a laser is focused on a pinhole that acts
as a point source of light if the size of the hole is comparable to
the wavelength of light. The spherical waves that emanate from the
pinhole illuminate a sample of sea water. Waves scattered by
objects in the sea water then combine at the chip of a CCD camera
with un-scattered waves (the reference wave) from the pin hole to
form a digitized interference pattern or hologram. The digital
holograms are then sent to a computer where they are digitally
reconstructed with specially developed software to provide images of
the objects. The Dalhousie researchers packaged their holography
apparatus in such a way that the laser and digital camera parts are
in separate watertight containers, while the object plane is left
open (see figure at http://www.aip.org/png/2006/255.htm ). One
difficulty was to get container windows of optical quality that are
thin enough for high resolution imaging but thick enough to resist
sea pressure. The new submersible microscope can also record the
trajectories of organisms in the sample volume so that movies of the
swimming characteristics of micron size marine organisms can easily
be produced. Holograms with1024 x 1024 pixels can be recorded at 7
to 10 frames/s. This requires a large bandwidth for data
transmission to a surface vessel and was accomplished with water
tight Ethernet cables. Imaging volumes can be several cubic
centimeters depending on the desired resolution. The Gabor geometry
allowed the Dalhousie researchers to design a very simple instrument
capable of wavelength limited resolution of marine organisms in
their natural environment. Past generations of submersible
holographic microscopes had lower resolution, weighed several tons,
had to be deployed from large ships, and used high-resolution film
as the hologram recording medium. This meant that only a small
number of holograms could be recorded. In contrast, the Dalhousie
instrument only weighs 20 kg, can be deployed from small boats or
even pleasure vessels, and can record thousands of holograms in a
few minutes so that the motion of aquatic organisms can be captured
in detail. (Jericho et al., Review of Scientific Instruments,
upcoming article; contact M.H. Jericho, Dalhousie University,
jericho@fizz.phys.dal.ca, and also the Universidad Nacional de
Columbia)

***********
PHYSICS NEWS UPDATE is a digest of physics news items arising
from physics meetings, physics journals, newspapers and
magazines, and other news sources. It is provided free of charge
as a way of broadly disseminating information about physics and
physicists. For that reason, you are free to post it, if you like,
where others can read it, providing only that you credit AIP.
Physics News Update appears approximately once a week.

Posted by: ljk4-1 May 1 2006, 06:55 PM

Karl Hibbitts describes a proposed hyper-velocity impactor that would
smack right into Europa’s outer ice shell.

http://www.astrobio.net/news/article1944.html

Posted by: PhilHorzempa Jun 27 2006, 04:07 AM

It seems that at the November 2005 COMPLEX meeting there were
4 options presented for a Europa Lander that could be included as part
of the Europa Explorer mission.

Each of these options assumes the same plan for initial descent.
First, the lander arrives, eventually, with the Orbiter in a circular 100-km orbit
around Europa.
Second, after separation, the lander fires a thruster to
decrease velocity by 22 m/sec. This puts the lander into a 100 x 1.5 km orbit
around Europa.
Third, a large rocket burn takes place at periapsis to decrease velocity by 1,500 m/sec.
This essentially stops the lander cold and it begins to free-fall the last
1.5 km to the surface. This is the Stop and Drop maneuver. The remainig descent
to Europa's surface is where the designs diverge.

These are details of each of the 4 proposed lander designs.

1. JMI - Jovian Moon Impactor - This probe falls all the way to the
surface, impacting it at 62 m/sec. It is designed to withstand 5,000 - 10,000 g's and
looks to heritage from the Deep Space 2 Mars penetrators. This is where a precursor
mission like DS-2 has its payoff.
JMI Mass = 65 Kg

2. EPF - Europa PathFinder - After the Stop and Drop, EPF free falls to the surface, but
cushions its landing with 3 airbags, similar in size to the Beagle 2 design. The EPF itself
is desinged to withstand 600 g's and is saucer-shaped.
EPF Mass = 220 Kg

3. ESSP - Europa Surface Science Package - After the Stop and Drop, the ESSP utilizes
thrusters to slow its descent. The thusters cut-off at about 10 meters and ESSP freefalls
to semi-soft landing at about 40 g's or somewhat greater.
ESSP Mass = 350 Kg

Each of these first 3 landers is designed to have payload masses of about 7 - 8 Kg,
a lifetime of 3 days, power levels of about 10 W,
with a total science data transmission of 200-300 MBits.


4. IML - Icy Moon Lander - A true soft lander, using thrusters all the way to the surface
after Stop and Drop. Landing at less than 40 g's and using an RTG.
TMI Mass = 825 KG
The TMI is designed to last for 30 days, to have a power level of 100 W, to have a payload
mass of 40 Kg, and to transmit a total of 7 Gbit of data.

I think that the IML and/or the ESSP may use crushable materials to cushion the
landing on Europa. Also, these landers are able to be considered since the new
mission design for the Europa Explorer envisions using the Delta 4 Heavy as the launch
vehicle and the use of a VEEGA trajectory. The VEEGA trajectory design utilizes 1 Venus
and 2 Earth flybys and enables 7,000 Kg to be sent on the way to Jupiter.
This contrasts with the original Europa Orbiter design that contemplated
a payload of only 1,500 Kg to Jupiter.




Another Phil

Posted by: Richard Trigaux Jun 27 2006, 07:16 AM

Why to limit the life time of a surface lander? if it has no RTG, it is understandable that the battery limits the lifetime (when it is exhausted). But a RTG has a theoretical lifetime of 30 years or more.

I know what the limiting factor is: radioactivity, which will quickly destroy any electronics. However there would be some strong interest into having a long lived probe on Europa surface:

-long run seismometre recording (a lone seismometre is not very useful, but a further mission may bring another one, so that they could work as a network and explore inner Europa structure, provided that the first is still working 10 or 20 years later).
-use it as a beacon or GPS emitter for a further mission or landing
-detecting underground SOUNDS on Europa, which may help to understand the oceanic properties.



So what I propose would be that the lander may have a pod, which would use the excess RTG heat to bury a small emitter/seismometre deep enough into the ice, so that it would be protected against radiations and could work for 20 or 30 years.

Could there be alternative power sources other than RTG?

-solar panels could still have some efficiency on Europe, but they would quickly degrade with radiations.

-a long wire left on the ground may gather enough electricity to feed a small circuit, with an emitter working in burst mode. On Earth, during magnetic storms, continuous currents can appear into power lines, strong enough to disturb their normal operation. On Europe, which moves into Jupiter magnetic field, a large copper loop laid on the ground may gather enough energy to feed a small aparatus, without all the hassle and problems of a RTG, insensitive to radiations, and for a virtually infinite time. A large capacitor battery would store the energy for emission bursts, of during magnetic storms (the current may be sometimes zero), without a limited lifetime like batteries.

Posted by: JRehling Jun 27 2006, 07:04 PM

Mainly with an eye towards the mass budget. There are time-varying phenomena on Europa, and there are non-time-varying phenomena (at least, on cycles of greater than 30 Earth days). Only a magnetometer and seismograph would be useful over long time scales; other than the diurnal changes in light and those two experiments, the only requirement for a long lifetime will be to grab samples near the craft... and that might be rather homogeneous itself. Some of the time variation the magnetometer will go looking for would repeat many times in 30 days anyway. So the question is how much mass is it worth (taking it away from surface composition instruments, or orbiter instruments) to get a long life out of a seismometer?

Posted by: nprev Jun 28 2006, 01:30 AM

I would say that a long-lived seismometer would be worth quite a bit. Consider all the variables (potentially) involved: sub-shell oceanic tidal effects on the crust, undersea vulcanism, crustal structural failure events, resonance flexing from the other big moons...the seismic environment on Europa might be quite complex indeed, and thus would require long-term data acquisition.

Of course, you really need a lot more than one seismometer in one location to get a really useful dataset.

Posted by: Richard Trigaux Jun 28 2006, 07:42 AM

and also very difficult to read, as whatever comes from the rocky core would have to pass through a liquid layer (eventually not continuous) and an ice layer (eventually not heterogenous). Worse, the water layer would play as a wave guide, bluring the origins of vibrations.

So with my opinium we should send a simple mission with one seismometre which would:

1) give an idea of rocky quakes (long term), to give an idea of how do do for a future cluster.

2) estimate the depth of ice and water layers. (a very useful step for a further lander/driller)

The best place on Earth to test the 2) would be on Ross ice shield, which is freely floating over water.

1) would work with a small lander,using a wire loop to sustain a long-term activity.

2) would be a one-shot, in the litteral meaning: a small shell impacts the surface at a (relatively) high speed, which produces seismic waves. Then it waits for the return from the ice bottom and ocean floor. Shortest mission than on Venus! This seems to be the simplest mission we can imagine, with yet an important result: the thickness of ice and water. Only hitch: it seems that most of Europa surface would rather be a layer of rubbles than plain ice. So this shell should aim at places where ther is plain ice, in the chaotic regions. This is a problem of a homing missile relying on a stored image of the target.

Posted by: RNeuhaus Jun 28 2006, 10:49 PM

A panoramic camera plus an astronamic telescope to observe closer to Jupiter changing clouds would be a MUST! It is for observating for any change phenomena that might happen on Europa moon.

Rodolfo

Posted by: JRehling Jun 29 2006, 12:31 AM

I don't see that reasoning. Europa is in the thick of radiation belts, and any telescope would be a lot of mass that would have to be gently landed on Europa. You would get better and longer-term imagery of Jupiter by having a bigger telescope orbiting Jupiter outside the radiation belts. There's no reason to take a Jupiter-aimed instrument and waste rocket fuel putting it on the surface of Europa.

Just in terms of Jupiter distance, there must be an optimal radius for a telescope in terms of fuel needed to put it into orbit vs. resolution vs. radiation-limited lifetime. I don't expect that optimum to be at Europa, where anything not underground is going to die in months from radiation.

Posted by: djellison Jun 29 2006, 07:23 AM

Why? If you want to observe jupiter - have a jupiter orbiter. Spending the time, volume, mass, energy and data to do it from the very very very harsh surface of Europa is just stupid.

Doug

Posted by: algorimancer Jun 29 2006, 12:49 PM

Considering the deliverable mass potential, and our recent experiene with MER, I think it would be silly to send a fixed lander rather than a rover. Seems like the MSL design ought to be nearly ideal for Europa, and it already has radioisotope generators integrated. I suspect that mission planners are assuming that the surface will be dull and homogeneous, so that one spot is as interesting as another. This may be a mistake, so why not use off-the-shelf technology and provide some options. At the very least, a rover would be a handy means of deploying a seismic network.

Posted by: djellison Jun 29 2006, 01:00 PM

I'm sure everyone would love a massive long life rover on the surface of Europa....who wouldn't. Every scientist, every engineer would LOVE to have a rover on Europa.

And we'd all like New Horizons to be a Pluto Orbiter, and DAWN to be sample return, and Messenger to be a lander......

But you have to do what is feasable given time, money, and in this case technology. 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 )

A comparatively simple impactor / hard lander, perhaps with a decent imager, short life etc...that's currently feasable in a sensible time frame and budget and would tell us a hell of a lot about Europa.

MSL will be ( hopefully ) the 7th succesfull landing on Mars. 4 of those were/will be static landers.

If we were talking out 4th Europan lander..I'd be going 'hell yeah - let's go for wheels' - but for our first effort....one needs to be modest in requirements.

As Alan has said w.r.t. NH.....better is the enemy of good enough.

Doug

Posted by: Myran Jun 29 2006, 03:36 PM

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.

Posted by: JRehling Jun 29 2006, 05:51 PM

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?

Posted by: JRehling Jun 29 2006, 05:55 PM

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.

Posted by: RNeuhaus Jun 29 2006, 08:14 PM

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

Posted by: djellison Jun 29 2006, 09:07 PM

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

Doug

Posted by: nprev Jun 30 2006, 12:50 PM

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! --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.

Posted by: algorimancer Jun 30 2006, 01:13 PM

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...

Posted by: Bob Shaw Jun 30 2006, 01:50 PM

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

Bob Shaw

Posted by: JRehling Jun 30 2006, 05:52 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.

Posted by: Bob Shaw Jun 30 2006, 07:26 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

Posted by: 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.

Doug

Posted by: DDAVIS Jul 1 2006, 01:16 AM

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

Posted by: RNeuhaus Jul 1 2006, 02:45 AM

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

Posted by: Richard Trigaux Jul 1 2006, 06:01 AM

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.

Posted by: edstrick Jul 1 2006, 08:50 AM

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.

Posted by: Bob Shaw Jul 1 2006, 01:55 PM

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...

Bob Shaw

Posted by: Myran Jul 1 2006, 02:26 PM

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.

Posted by: 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.

Posted by: djellison Jul 3 2006, 07:36 AM

Pushbroom?

Doug

Posted by: Richard Trigaux Jul 3 2006, 09:52 AM

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.

Posted by: Stephen Jul 3 2006, 11:20 AM

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...)

======
Stephen

Posted by: Richard Trigaux Jul 3 2006, 11:44 AM

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.

Posted by: nprev Jul 4 2006, 01:09 AM

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.

Posted by: Roly Sep 3 2006, 07:07 AM

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

Posted by: angel1801 Sep 3 2006, 04:27 PM

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!

Posted by: ugordan Sep 3 2006, 06:37 PM

I would think the landing site will be determined from orbital imagery as potentially most interesting, not which longitude it's on.

Posted by: Roly Sep 4 2006, 03:01 AM

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.

Posted by: edstrick Sep 4 2006, 11:07 AM

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.

Posted by: JRehling Sep 4 2006, 05:15 PM

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.

Posted by: Julius Sep 5 2006, 08:03 PM

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.

Posted by: nprev Sep 6 2006, 01:43 AM

I still think a hard-lander, a penetrometer, or some variation of the Pathfinder/MER EDL system is the way to go for the first landing. There are WAY too many unknown unknowns at the 10 cm-10m scale on Europa's surface, and the close flybys of Enceladus by Cassini make me suspect that Europa might be rough indeed... ...better to send out something with max survival potential rather than a traditional soft-lander given that the host orbiter will also be the primary means of determining surface topography at this scale.

It would be both a tragedy and a first-class fiasco to send a lander out there only to find out that its probability of surviving the landing is vanishingly small.

Posted by: algorimancer Sep 6 2006, 12:55 PM

Something like the MER's autonomous navigation system could solve the landing-in-rough-terrain problem. Just need a fast computer to do a quick 3D model/analysis of the surface prior to landing, and be prepared to adjust the position as needed to avoid particularly troublesome areas. The low gravity ought to be helpful as well.

Posted by: ugordan Sep 6 2006, 01:27 PM

Still, the biggest problem is soft landing via powered descent. The fuel allocation would be huge, you still need to kill some 1.5 km/sec orbital velocity + lower the altitude + propellant margins. IF you had plenty of fuel, you could easily hover above the final descent area searching for a nice spot. By the time we get a Europa lander flown, autonomous navigation will surely mature, but propellant will still be the limiting factor on what you can do.

Posted by: algorimancer Sep 9 2006, 09:24 PM

I just had one of those Aha! moments and came up with an interesting means of aerocapture. We launch a combination lander/impactor. Sometime prior to arrival at Europa (or any other ice world) the lander/impactor separate, and the lander portion decelerates slightly to allow the impactor to arrive in advance. The impactor (could be a big ball of ice) impacts the surface, vaporizes itself + a substantial volume of surface ice/volatiles. The lander portion arrives just in time to aerobrake on the explanding impact plume, possibly landing within the crater or somewhere beyond.

Variations on this theme might involve diverting a small near-earth asteroid or Jupiter Trojan asteroid (using some of that creative low-delta-v chaotic orbital mechanics that's come into vogue lately) to act as the impactor - get a big enough impactor and penetrate Europa's ice shell, so that the lander can drop directly into the ocean below.

Details of plume size as a function of impactor mass, as well as how to ensure that the plume is predominantly gaseous or fine particles (rocks would be bad), are left as an exercise for the mission planners

Odds are someone will drop a link to some paper somewhere that pre-invented this notion decades ago.

Posted by: Myran Sep 10 2006, 07:42 AM

Thats a wild idea algorimancer.

But regardless how I scrutinize it from front and the rear I cant get it to work.
If we think of the gas released by one such impact, it would be in such one limited area that the breaking you get from that are extremely limited. When aerobreaking you need to break around a halfcircle of a world at least and sometimes dipping into the atmosphere many times.

Then about the dust plume. Without an atmosphere you cant count on the fact that bigger boulders fall back faster so you can get your lander down on finer dust since it wont be supported by any air molecules.
They will in fact fall with almost exactly the same speed. Since the 'atmosphere' or Europa are thinner than the diluted remants of one homeophatic ghost.

Posted by: algorimancer Sep 10 2006, 01:05 PM

Yeah, it is pretty wild. Timing would be critical, and it would demand a lot of the hardware. On the other hand, it could be the difference between a 500 million dollar mission and a 2 billion dollar mission.

The intent here is not a traditional aerobraking approach, but somewhere between a hard impact and traditional aerobraking. The idea is to aerobrake into the expanding plume from above, orthogonal to the surface, rather than from the side as in a traditional aerobraking maneuver (though that may work as well or even better). The deceleration would be heavy (orbital speed to near zero in no more than tens of kilometers, if not less than a kilometer), but still something which robust hardware can be designed to accomodate. A tough ablative heat shield would be helpful. Consider that natural impacts can toss intact rocks from Mars or the Moon to Earth.

Most of the deceleration would occur within a fraction of a second, but it's a dramatically more survivable proposition than simply impacting the surface. You wouldn't want to ride along though I think the biggest challenge here would be to generate a sufficiently large plume.

Posted by: nprev Sep 10 2006, 09:00 PM

Hmm. Given that the Galileo data was a bit limited due to the comm restrictions implicit in the antenna deployment failure, what do you suppose the odds are that there are some natural plumes that a lander could use for aerobraking?

I know that there have to be some severe constraints on Europan vulcanism already from the Galileo data set, but still...I would be very surprised if there aren't a few geysers somewhere on the surface.

Posted by: Drkskywxlt Sep 11 2006, 01:32 PM

I think any such impact with the surface of Europa would create so many large fragments (even very small fragments would be damaging at the speed the lander would be going) that a some very heavy protection would be required. That would add further weight and complexity to an already complex mission. I imagine that the fuel required to slow the lander or orbiter to reasonable speeds would be much lighter than any ablative shield to protect the lander from ice and debris thrown up by the impactor.

Posted by: AndyG Sep 11 2006, 03:34 PM

The (admittedly ill-fated) penetrators of Deep Space 2, the Mars' impactors carried with MPL in '99, had electronics designed to survive up to 60000g of deceleration.

Assuming a Europa lander hits the surface of Europa at around the local escape velocity (2.02 km/s), then it would need "only" 7m of decelerant in order to bring it to a halt and not exceed that deceleration.

Compressible "somethings" like LEM legs? An airbag? A controlled explosive device fired under the lander when <4 milliseconds from touchdown?

I saw the original animations for the MER entry and landing sequences, and had to laugh at the unlikelihood of everything working just so. These days I wouldn't rule anything out.

Andy

Posted by: remcook Sep 11 2006, 04:12 PM

Most importantly IMO is the whole uncertainty of the plan: noone knows exactly what happens when you impact Europa. Designing a mission with these enormous uncertainies will give you a mission that is overly robust and thus too heavy and too costly. And that without a good idea if it even works! I'd spend my money on something else...

Posted by: algorimancer Sep 11 2006, 05:47 PM

The nice thing about Europa is that, of all the icy satellites out there, it is the one with the least uncertainty about material composition. Essentially we're looking at a surface which, to considerable depth, and beyond reasonable doubt, is predominantly water ice with contamination from salts and sulfur compounds. Rocky material should be virtually non-existent. This is the sort of material which can be (relatively) neatly modeled in a laboratory or a computer, and engineering feasibility determined with confidence. (yes, I'm simplifying a great deal here)

The implicit tradeoff in this notion is that between the mass of the fuel and hardware needed for traditional deceleration, versus the mass of an impactor and shielding for impact-assisted aerobraking [IAA]. This leaves open a lot of unanswered engineering questions, such as whether it is possible to design an impactor which will do a good job of vaporizing a volume of Europan ice rather than simply fragmenting it (I like the notion of an impactor which splits into many small pieces prior to impact, perhaps a bag of water with a small explosive charge which detonates shortly before impact). If the mass balance tradeoff is in favor of IAA then it might be worth testing a prototype.

Certainly you'd want to test a notion like this prior to sending a full-scale rover. If you're sending several penetrators anyway, why not replace one or two of them with IAA technology demonstrators.

One more thing, any Europa orbiter/lander might benefit from aerobraking at Jupiter prior to arrival at Europa, which could substantially reduce the approach velocity to something like AndyG's figure. The impactor component of an IAA package could do the opposite and use Jupiter for a gravity assist so as to impact Europa with maximum velocity.

Lot's of unanswered questions. I too initially thought the Pathfinder/MER airbag approach was pretty outrageous, but it worked rather well. Heck, they designed a manned vehicle (Orion) designed to be powered by H bombs, and demonstrated a prototype. Just at the moment I think IAA is outrageous but might still work, and I'll leave it at that.

Posted by: Julius Sep 12 2006, 07:37 PM

Main objective should be to get a Europa lander safely with a technique that has been proved to work (in the case of Mars).I believe the airbag system should be the solution if so many uncertainties exist on the characteristics of the Europan surface.One should opt for simpler ways rather than be complicated.

Posted by: rasun Nov 29 2007, 05:35 PM

Hi!

Apparently, NASA's Astrobiology, Science and Technology for Exploring Planets program funded the DEPTHX, an autonomous underwater robot.
(See Depthx home here:
http://www.frc.ri.cmu.edu/depthx/
many images here:
http://www.jsg.utexas.edu/news/rels/030807b.html
and here:
http://geology.com/zacaton/
or many links at NASA:
http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=10644

DEPTHX and it's follow-up, ENDURANCE are "advertised" as robots that are largely developed so that their next version would be operating in the oceans of Europa, at least that's what I get from the articles. But the Europa Explorer, if approved, will at best fly around 2015, and then a first Europa lander, if approved, probably not before 10 years later; and THEN probably a submarine (but this still sounds very optimistic)

So isn't it too early to start to develop a submarine 20-30 years before it can be launched? Of course it's never too early, and i'm no way against it, but it still sounds strange...? Is this project really seriously meant to have anything to do with Europa?

Posted by: JRehling Nov 29 2007, 08:36 PM

NASA does a lot of low-levels-of-funding exploration of new technologies. I used to work one building over from the robotics building at NASA Ames, and I saw stuff in development over there that doesn't remotely resemble anything that's ever flown, or is scheduled to soon.

Whether or not it actually speeds exploration, it also has public outreach value, encouraging interest in exciting ideas that may one day be put into effect.

I think a real key is that most of this stuff costs almost nothing compared to an actual mission.

One of the interesting things (in a sense, a very uninteresting thing) about a submarine is that remote sensing would be very limited. It would be mainly about analyzing the water immediately in/around the submarine. And maybe the floor, but visual/IR imaging would be limited to meters. There probably wouldn't be much point in wandering horizontally anywhere above the floor.

Posted by: DDAVIS Dec 3 2007, 11:17 AM

This discussion is of particular interest to me as I am doing an animation sequence soon of a Europa lander. I have visualized such a thing in the past for the PBS show 'Life Beyond Earth' as a surveyor type lander carrying a probe underneath which would be weighed at the bottom with a plutonium 'lens', with the instruments above this. This probe resembes a blunt version of the Galileo probe entry shell. When released the heat from the lower probe lining melts a hole below it and the probe merrily tunnels its way to the liquid far below.
Any thoughts about this general means to get to the deep ocean with a probe as opposed to other spacecraft schemes being contemplated?

Don

Posted by: nprev Dec 3 2007, 12:46 PM

Wow.

Don, only thing I can think of is that the penetrator/melter should be fluted in some way to allow water vapor to escape to space around it instead of re-freezing in the tunnel. (Exactly how long would it take that thing to melt its way through several kilometers of ice, anyhow?)

Posted by: JRehling Dec 3 2007, 07:05 PM

One of the worries is that impurities in the ice would accumulate at the bottom of the hole, eventually creating an obstruction. Even if the fraction of impurity were very low, accumulating one meter of it after ten thousand meters of ice could be a show stopper.

I'm curious about what would happen when you actually hit the water. Would it gush out and rocket your sub into a geyser far above the surface -- which, obviously, would disable it as well as prevent access to the ocean. One of the problems I see with Enceladus is that if what we're seeing are geysers, then it may be pretty well impossible to push into the ocean, since it's trying to get out with considerable force. Which makes sense -- there must be nonzero pressure in water under a shell of ice, whereas the pressure above is the vacuum of space.

Maybe the saving grace would be if the hole re-freezes above the craft, and then when it reached the ocean, there'd be nowhere for it to go up. Somehow, it would have to handle that pressure transition, though, from surface to ocean.

Another issue is how to maintain radio contact. Leaving a chain of repeaters has been mentioned, but that sounds like a lot of mass, not to mention one heck of a lot of failure points.

And once the craft got to the ocean, there'd be a lot more to accomplish. A vertical descent to the rocky mantle would be fascinating, but might entail rather tremendous pressures.

I think realizing this vision is, however, one of the most exciting goals in solar system exploration, and finding the best location (if there is a best location) to make this descent is the real imperative of the next Europa exploration from orbit. Alternately, if a lander were only to sit on/near the surface and analyze the crust, it's still important to pick a good spot.

Good spots Galileo looked at include these:

http://photojournal.jpl.nasa.gov/catalog/PIA01405

http://photojournal.jpl.nasa.gov/catalog/PIA01640

http://photojournal.jpl.nasa.gov/catalog/PIA01177

But given how little of the surface Galileo imaged very well, it's imperative to do a more comprehensive survey.

Posted by: dvandorn Dec 4 2007, 07:54 AM

I would say that not only is it imperative that a melt-hole reseal itself, it's really unavoidable. The extreme cold of the ice surrounding the melt-hole will refreeze any liquid water very quickly, for the first 80% of the hole at least, so if you don't keep re-heating the walls of the hole, it'll freeze solid again within hours of the passage of the ocean probe.

I'm tempted to think that the first 20 or 30 meters of the hole might have to be drilled "dry", the probe dropped in, and the whole thing filled in with the excavated shavings. You then very *slowly* melt out enough liquid water around the probe to *seep* up through the shavings, consolidating them and establishing a pressure-tight seal.

You think that's going to be an engineering feat? That's not even the biggest challenge -- the biggest problem is how to maintain communications through the ice crust between the probe as it descends (and of course after it reaches the ocean) and the lander on the surface, which is of course the comm link between the probe and the outside Universe.

You can't just lower the thing on a cable -- the cable would probably have to be a few km long at the shortest, which would be pretty massive on a spacecraft which will likely have an extremely tight mass budget. Not to mention avoiding snag and jam issues on whatever payout device you design, and the fact that 99% of your cable would be frozen into the resealed hole for most of the descent. You'd have to keep the cable heated for its entire length for it to move through the ice as it pays out, and that wouldn't let you truly seal the melt-hole and avoid that nasty geyser that will otherwise spray your entire mission into a Europan sub-orbital trajectory.

The best design I've seen (and it's likely been discussed here) was one in which the descending probe would leave relays every few tens of meters, each relay capable of talking with the two above it and the two below it. (It's easier to transmit across 30 meters of ice than it is to transmit across a few km... and you want to be able to lose one or two and, as long as they're not next to one another, you still maintain your overall link to the surface.)

The bigger issue, of course, is that any such ocean probe is going to have to literally sink the entire way through the ice crust. That means that the probe is going to have to create a bubble of superheated (for its environment) liquid water that will unfailingly *sink* through the entire crust. Given the likelihood (almost certainty) that the ice is likely not homogenous but will have impurities (such as, oh, I dunno, maybe house-sized rocky boulders), this is going to be very, very difficult to pull off. The whole descent process is going to be extremely energy-intensive, and the probe will have to take that energy down with it -- no cables, remember? And each comm relay is going to have hefty power requirements, too. (And, of course, in such an eternally dark ocean, we'll need to bring some awfully bright lights all the way down into it, just to see what's there...)

The odds are that this isn't going to work the first time we try it. It may not work the first several times we try it. It may be almost impossibly difficult to do.

Whatever the odds, though -- we simply must try.

-the other Doug

Posted by: nprev Dec 4 2007, 12:19 PM

Nihilistic, but IMHO painstakingly plausible, oDoug...

Convinced me utterly that we gotta do a VERY thorough search for cracks, weak spots, whatever sort of (relatively) easy access points there may be...

Posted by: Cugel Dec 4 2007, 01:06 PM

Why would you go all the way down to the liquid water (if any is present at all)?
All that ice has to come from somewhere and it didn't come falling out of the blue sky.
It's the same ocean that everybody is looking for, just in a frozen state!
Now, the top 1 meter or so might be seriously altered by Jupiter's radiation,
but just 2 or 3 meters down and you're in the ocean.
Melt it, pump it up to the lander and analyse it for organics and other ingredients.
It will probably cost you a billion or 3 but at least it is technically doable.

Posted by: JRehling Dec 4 2007, 03:02 PM

I hadn't thought about this angle before, but of course if it's much denser than water, it's going to descend very rapidly (and without much controlled mobility) once it hits water. If it's not, then then it's not going to be a lot of force driving the descent through the ice. Unless the heated front end is jettisoned (or, I should say, flotsomed) at that point. Another failure point.

Posted by: JRehling Dec 4 2007, 03:06 PM

Icebergs on Earth also come from the ocean, but I bet they don't contain many squid, clams, or blue whales.

The "3 meter down" lander may have to be the next step, but it will leave a lot to be desired.

Posted by: centsworth_II Dec 4 2007, 03:55 PM

But do icebergs contain detectable evidence of the existence of squid, etc. ?

Posted by: marsbug Dec 4 2007, 04:35 PM

I dont know about squid but there are many studies ( these two are a random selection) showing that microorganisms can survive entombed in ice, which would at least tell us there was something down there. Europas ice sheet might prove to be an interesting habitat in its own right, and much more accesible than the ocean itself. Investigating the ice at increasing depths first would give us a chance to test out various approaches, giving us a better chance when we feel ready to, er, take the plunge into the ocean itself. Although if we could come up with an approach that would let us do it tomorrow I'd say go for it, even if it were a shot in the dark!

Posted by: hendric Dec 4 2007, 04:55 PM

I always thought the "heated front end" would be the RTG you take down with you to get power. After all, the only source for energy would be the RTG, and the waste heat has to go somewhere! Unless you plan to throw away your RTG and run on batteries the rest of the mission? Be a real shame to limit yourself to a few days in the ocean. Besides, as the probe gets closer to the bottom I think it will run into water bubbles and caves within the ice. Dumping your drill the instant you hit free water might not get you to the open ocean. You'll want active bouyancy control once in the ocean anyways, so a slightly larger ballast tank should take care of any "falling like a stone" concerns.

Would the water refreeze before it sublimates? Speaking of which, how will the motherprobe handle being on top of a geyser? Could it get encrusted in ice? Maybe the motherprobe needs to have wheels, or a crane, so that it doesn't need to be directly over the probe hole. Just a couple of sensor ports so it can sample the outflow.

A precursor mission could be a connected hot drill, just a 20cm 100W RHU that gets lowered on a wire. Being on a wire, you can control your descent rate so that the hole stays as clear as possible, without water refreezing above you. There would still be problems with dirt/rocks/pebbles, but you could probably go for dozens of meters minimum. Just put a KM on the spool in case of an extended mission. If you put it on an arm (I know, KISS), or rover, you could probe in multiple locations. Of course, money and UMSF being what it is, I doubt even a simple lander that just drops an RHU on the ground could be made for a New Frontiers budget.

Here's a thought: What if the lander WAS an RHU? Basically, a hard lander that had a very large RHU with a minimal a la Deep Impact camera. Make your own instant geyser for a dedicated orbiter to sample over the following months. A 250-500kg hard lander with mostly plutonium could make one hell of a hole over time. Could it reach the ocean itself turning into a mini cryo-volcano? The mind boggles!

Anyways, enough of the random ramblings. Back to work!

Posted by: centsworth_II Dec 4 2007, 05:58 PM

I think it's safe to say that the first Europan lander will not attempt to reach
the ocean, but will hopefully attempt to reach un-radiated ice.

Posted by: dvandorn Dec 4 2007, 07:12 PM

I don't think I'd be good with just opening up a hole and creating a geyser to study. There is a whole wide range of assumptions we can make about what's in that ocean -- but if there are living organisms, I think it's incumbent on us to explore without endangering them.

After all, we don't want UMSF to get the bad reputation that the military had at one point -- you know, the reputation reflected in the old slogan, "Join the Army, go to strange new places, meet strange and interesting people -- and kill them."



-the other Doug

Posted by: Cugel Dec 4 2007, 07:30 PM

At least, a water sample from 3 meters down would tell you the saltness and acidity of the ocean, which could be bad enough to make any form of biology impossible. And if we're lucky and some organics are found in the water it would be a lot easier to get the funding for the real thing. Here's a bit from Bruce about this topic: http://www.spacedaily.com/news/life-00p5.html

Posted by: tty Dec 4 2007, 07:42 PM

Couldn't that possibly be related to the fact that the ocean water has been evaporated (=distilled), then fallen as snow, lain around at subzero temperature in an icecap for thousands of years before finally being calved back into the Ocean?

If you analyzed sea-ice that has actually frozen in/on the ocean you wouldn't have any problems finding organic material and even an occasional small squid frozen into it. Clams are bottom animals and whales sink after death so I wouldn't expect finding them.

Posted by: charborob Dec 4 2007, 08:03 PM

A probe melting its way all through Europa's ice crust? That would demand an enormous amount of heat. Much more than a small RTG can supply, I'm sure. Unless you land on thin (a few meters at most?) ice.

Posted by: dvandorn Dec 4 2007, 08:58 PM

My thoughts exactly -- it's going to be a very energy-intensive process. Just bringing on a few electric heaters isn't going to get it done. We're talking about *extremely* cold ice here, for the most part. Ice, like any other material, needs to be raised all the way to its melting point before it will melt. You can't just ignore the hundred-plus degrees of heat that you have to apply just to get the ice up to its liquifaction point.

This is going to be harder and more energy-intensive than, say, melting ice cubes that are already within 10 degrees of their melting point.

-the other Doug

Posted by: hendric Dec 5 2007, 01:41 AM

Well, RTGs actually put out quite a bit of heat, and it wouldn't be unreasonable to send one capable of 2-5kW of heat (100-200We of electricity) as part of the descending module. Should be plenty to get down as deep as you'd like. Plus, you don't need to melt the ice, per se, sublimating it away is just as good. Also, your heat source never goes away, it's working all day, every day.

Besides, look at what simple dirt/dust does with comets and Iapetus. I think a 5kW RTG would be more than able to get a reasonable descent speed.

Posted by: nprev Dec 5 2007, 01:45 AM

I wouldn't be too quick to discount life even if the water chemistry is more hostile than that of a http://rydberg.biology.colostate.edu/Phytoremediation/2003/Boczon/Home_Page.html...the durability & adaptibility of life on Earth surprises us rather frequently...

Like this idea a LOT, though. Heck, don't forget a microscope; could be some tiny critters like plankton frozen in there as well! In fact, if we found any degree of biodiversity in frozen microorganisms, that would be a very strong indicator that macrofauna (macro-somethings, anyhow) were quite possible...and watch that funding flow!!!

Posted by: DDAVIS Dec 5 2007, 07:10 PM

Wow, this discussion is great!
I am imagining an RTG mounted vertically at the bottom with the radiating fins shaped so as to taper like a blunt harpoon pointed down. The narrower parts of the radiators may be hotter than the wider upper parts which should, along with the weight of the RTG itself, send the probe tunneling more or less straight down. The probe would be a modest cylinder mounted atop the RTG and slightly narrower, with various 'windows' for admitting water samples, and various sensors. Two aspects which intrigue me are what direction to mount the camera or to have multiple cameras. The other is the data return question. I wonder about having the probe unreel a long durable cable as it drops. What is the smallest size a cable spool a few km long can be made? How thin is the thinnest ice on Europa? Can the figures for the thinnest ice and the longest cable overlap?

Don

Posted by: tty Dec 5 2007, 07:23 PM

Let's do some order-of-magnitude calculations here. Let's say that a sinking probe needs to melt a 0.5 square meter hole in ice at an average temperature of 173 K.

The density of ice at 173 K is 925 kg/m3. The specific heat of ice goes from about 2.0 kJ/kgK at 273 K to 1.4 kJ/kgK at 173 K. I'll assume 1.7 as an average. To melt 1 kg of ice at 273 K requires 333 kJ. Melting your way one meter into Europan ice would thus require 463 (333 + 100x1,7) = 233 000 kJ = 233 000 kWs. That means that an 5 kWT RTG would need about 13 hours to melt its way through one meter of ice at 100% efficiency.

However efficiency will be very far from 100%. While the specific heat of ice goes down with temperature the thermal conductivity goes up, from 2.2 W/mK av 273 K to 3.5 W/mK at 173 K, so a lot of heat will be wasted in heating ice well away from the probe. Also the RTG will need to keep the entire outer surface of the probe at >273 K, otherwise it will almost immediately get stuck (at 173 K that water will re-freeze fast).

If we rather optimistically assume 50% total efficiency then a 5 kWT RTG will be able to melt its way about 3 feet per day. Melting your way through, say, 50 km of ice is clearly not on. Even a couple of kilometers would take several years.

Another big problem is communications. Even if the hole does not re-freeze behind the probe, the pressure will almost certainly close it, unless it is lined in some way, long before the probe is through it. Radio communications are probably out, particularly as there is likely to be some electrically conductive materials mixed up with the ice. However sound conducts pretty well through ice, so some kind of sonar link would probably be possible. It would require leaving a relay station on the surface though.

Posted by: mchan Dec 6 2007, 04:20 AM

That and the time it takes for an RTG (even a 5kW one) to melt its way thru 10's of Km of ice brings back to mind an old UMSF thread:

http://www.unmannedspaceflight.com/index.php?showtopic=1783

Back closer to reality:

http://www.jpl.nasa.gov/releases/2002/release_2002_6.htmlhttp://www.jpl.nasa.gov/releases/2002/release_2002_6.html

Before sending these fancy gizmos to Europa, can we even get a submarine robot thru 3 Km of ice here on Earth:

http://en.wikipedia.org/wiki/Lake_Vostok

Posted by: nprev Dec 6 2007, 07:14 AM

Gotta say that I'm pretty sold on the pristine ice-sampling concept; that could conceivably tell us most of what we want to know, plus it's a million times more technically feasible.

TTY's calcs convince me that unless we find some really thin ice, a Europan sub mission is a hundred years off or more, awaiting highly advanced hypothetical technologies like high-efficiency directed energy or fusion generators.

Hmm...slightly OT here, but if there are weak spots at all on the surface, they must pop open from time to time. A future orbiter should look REALLY hard for very transient geysers. (I suspect that, if they exist, they don't last very long at all due to freezing/self-sealing).

Posted by: edstrick Dec 6 2007, 09:39 AM

Both from a science and an engineering perspective.. ultra-high priority from a Europa orbiter or multi-flyby mission <much less good at this> is to map the global ice thickness, and search for thin spots.

Posted by: centsworth_II Dec 6 2007, 05:02 PM

At the least, a first Europa mission should map the global ice thickness,
at the most, it would include a lander that could drill a meter into the surface.
Discussion of getting a probe into the ocean is way off topic for a first mission thread.

Posted by: hendric Dec 6 2007, 05:47 PM

That's an 80cm diameter hole. I'm thinking a 20cm probe, with a hole maybe ~25cm diameter. More like .05 square meters.

So to purely melt the ice would now require only ~23,300 kWs, about 1/10th the previous number.

But, some of the ice will directly sublimate before reaching 273K, reducing the heat needed, and also any contaminants will depress the melting point as well.

Assuming 50% efficiency, that gives us ~10 meters a day. So a 90 day mission would get you almost a kilometer down. Plus I bet the ice gets warmer as it gets deeper, accelerating the rate of descent.

I was using the 5kW RTG number for a suspended probe from a wire. For a dumb-hot-rock, I think you could get 50kWt or more and only slightly increase the volume of ice you need to melt.

For a real submarine probe, I actually agree with you, it's probably not going to happen because of the time to get to the ocean would fry any relay left on the surface. Let's say you got a spiffy cool melting drill that went twice as fast, 1 km in 45 days would still take over a year to get to 10km. Your surface relay will likely be toast well before that.


Let's try working it backwards. Say you want 30 days in the ocean, and 60 days descent through 10km of ice. that's 1 km every 6 days, or almost 7m/h of ice. Given a .5 m^2 borehole (reasonable for a sub), your numbers give 1.6 MWt/h. You'll need to bring along a small nuclear reactor, apparently, to make it through the ice!

Posted by: tty Dec 7 2007, 07:48 PM

Your point on impurities lowering the melting point is well taken. However I don't think sublimation will have any effect on the energy required. The melting will happen in a thin water film around the probe and I can't see how sublimation could work in this environment. There may be some sublimation behind the probe if the hole stays open, but that does not do you much good. Also the ice is actually going to be a lot colder than 173 K at least to start with. Another complication is that several of the (at least) 12 phases of ice may be present at depth on Europa, and I'm very uncertain how this would affect the energy requirements and how they would react to heating.

As for the surface relay being fried by radiation, how about this: the complete probe lands on Europa and deploys a dumb rad-hardened antenna that anchors itself to the surface (easy, you turn on a little heater in each leg for a while, and then turn it off again). Then the complete probe starts melting itself into the ground unwinding the antenna cable. When it has gone several meters into the ice the probe separates into two parts. The relay section (which has a small (or well-insulated) RTG) freezes into place while the deep-sinker section with a big, hot RTG keeps on going down and unwinding either a thin metal wire or a an optical filament to keep in contact with the relay. Note that the bobbin must be on the sinker since the filament will inevitable get frozen in.

Using a long thin wire for communication may sound outlandish, but both missiles and torpedoes use this kind of wire for guidance over very considerable distances (tens of kilometers) and at very high speeds. The Swedish Navy even has a variety of the TP61 torpedo that can be used for reconnaissance/intelligence gathering. A submarine launches it and then lies doggo on the bottom while the torpedo runs in slowly and quietly towards e. g. a harbor. Then the torpedo also puts itself on the bottom and starts listening and sends what it hears back through the wire quite indetectably.

The main problem with using wire communication is that if there is much internal movement in the ice it will probably break the wire. However the amount of movement in ice can be determined seismically, so in addition to measuring the thickness of the ice and the composition, we will need to land at least one seismometer on Europa.

Posted by: JRehling Dec 8 2007, 01:39 AM

The home run we've got to try for is to find a place where the crustal integrity is considerably less than average and where we can get a much greater descent for the same effort. There is a lot of evidence in the geomorphology that some places on Europa's crust get more interaction with the subsurface than others, on time scales that are sub-geological. The hope is that we could get our probe into the right place at the right time -- which may range in difficulty from pretty easy (if there's a warm slushy spot overlying some permanent, active volcano) to absolutely impossible (if, say, such eruptions usually do not take place, and the mean time between them is measured in centuries or worse). And this is exactly why we have to commit to serious reconnaissance of Europa sooner rather than later. If we get the negative result, then the rest of the jovian system "wins" and can enjoy receiving the next /n/ missions. If we get the positive result, then Europa deserves the preferential (Marslike) treatment.

On the surface-relay issue, I think as long as we're burrowing down, a worthwhile goal would be to at least "countersink" the relay so that it faces open sky, but is surrounded by europan ice on five sides. That would a priori seem to cut the radiation load by 75-80% of what would be experienced by a Europa orbiter, and perhaps more if the landing site is not on the trailing side (which gets the most radiation pummeling). Imagine a relay sunk a few meters in with a skyward hole that sweeps past the Earth's location in the sky once each orbit. If a good landing site were near the center of the leading face, the radiation exposure might be cut an order of magnitude or more thanks to the shielding provided by Europa itself.

Posted by: brellis Feb 25 2008, 10:28 PM

http://www.space.com/businesstechnology/080212-technov-europa-robot.html is to be tested in the next few weeks. An untethered robotic submarine. It's a followup to http://www.space.com/businesstechnology/070307_techwed_depthx.html.

Posted by: Vultur Sep 13 2008, 02:49 AM

This might well be too hard to pull off, but what about this:

The lander falls toward Europa, firing retrorockets at low impulse. At some point close enough to the ice surface where the trajectory is very predictable (less than a meter or so of error, hopefully), the lander fires an explosive-tipped impactor. The explosive goes off on contact with the ice, making a crater down into the levels of unirradiated ice. The lander lands in the crater; if you're lucky, there'll be pulverized bits of unirradiated ice to put in your analyzers even before you rasp it off the crater wall!

Posted by: djellison Sep 13 2008, 07:04 AM

Sound more dangerous, unpredictable and dynamic than it needs to be. A sub-surface drill is a far better idea.

Posted by: centsworth_II Sep 13 2008, 10:58 AM

Also, the ice being rock hard, it would take quite an explosive charge to get any depth.
In fact, the ice will be so hard, http://www.space.com/scienceastronomy/080828-am-thermal-drill-ice.html

Posted by: nprev Apr 18 2009, 05:36 AM

Should have posted this earlier, but our friend & fellow forum member vjkane has a very good recent post covering a January Europa hard lander/penetrator conference on his excellent http://futureplanets.blogspot.com/2009/04/europa-hard-landers-and-penetrators.htmlblog.

Posted by: Paolo Aug 30 2009, 08:51 AM

http://www.tsenki.com/NewsDoSeleFed.asp?NEWSID=7247

Babelfish translation:

30-08-2009 Russia can send research mission to the satellite of Jupiter - Europe - in 2020-2021
Russia can send research mission to the satellite of Jupiter - Europe - in 2020-2021, transfers [ITAR]- TASS. On this reported at the sixth international aerospace congress the deputy director of the Institute of Space Research of/[IKI]/of the Russian Academy of Sciences Oleg [Korablev]. On Thursday he made a report “landing apparatus to the satellite of Jupiter - Europe”.
[Korablev] reminded one that Europe and the three additional satellites of Jupiter were opened by Galileo by Galileo. Contemporary concepts about Europe were formed after through Jupiter system they flew several American automatic spacecraft. In particular, it is established that in Europe are water of the glacial on the basis of these data they appeared different models of the thickness of ice cover. According to [Korableva], “in all these models general “raisin” - under ice is liquid water, ocean”. According to the estimation Of [korableva], “Europe is the model of the icy peace, where there can be life”.
The representative of IKI reported that the scientific research work on the mission to Europe conducts [NPO] of the name Of [lavochkina] and IKI. “Is assumed that in the composition of mission they will be orbital module and landing apparatus, it refined [Korablev]. - Orbital module will remain in orbit of Europe for relaying of data from the landing apparatus. With the production of these modules will be used the reserves of the previous missions - “Phoebus- ground” and “Moon- resource”. It is assumed that the mass of landing apparatus will be 550 kgf”. [Korablev] noted that the developers of mission were forced to calculate large limitations on the basis of radiation, since powerful radiation belts of Jupiter can negatively influence onboard equipment.
“Scientific research works on the mission to Europe it is planned to complete in 2010, reported [Korablev]. - The tentative date of starting - 2020-2021. Under this mission will be used the carrier rocket “proton”. According to [Korableva], the overflight into the system of Jupiter and the output to Europe will engage seven years. Landing apparatus works on the surface of Europe of 60-90 days.
“By the primary task of mission - the search for the tracks of extraterrestrial life and the study of the structure of Europe, noted [Korablev]. - The flight of Russian mission will be carried out in parallel with the analogous missions of European Space Agency and American agency of NASA (National Aeronautics and Space Administration). In the opinion [Korableva], in the case of the success of these missions by the following direction of studies of the distant planets of the solar system, most likely, will become Saturn.

Posted by: Hungry4info Aug 30 2009, 11:53 AM

While I love the whole idea of a USA + Russia + ESA invasion of the Jupiter system, I don't expect Russia will actually go ahead with this.

Posted by: vjkane Aug 31 2009, 08:01 PM

They would need to be working hard on the radiation tolerant electronics and design techniques now for this schedule. So far as I know, they are not.

Posted by: Hungry4info Sep 3 2009, 11:14 AM

If the Russian lander lands on the anti-Jupiter hemisphere of Europa (the 'far side' of that moon), would that still be a problem?

If so, would some cooperation between NASA and Roscosmos enable that process to be sped up? Surely NASA has experience in such issues from Galileo.

Posted by: ynyralmaen Sep 3 2009, 06:39 PM

It'd still be a problem on the anti-Jupiter hemisphere - the energetic charged particles that are the problem are guided by Jupiter's magnetic field, and strike the entire surface of Europa. There are probably variations in particle flux over the surface (and these are probably responsible for some of the colour variations in the surface ices), but the flux is high everywhere; being out of sight of Jupiter doesn't really help.

Posted by: vjkane Sep 4 2009, 12:43 AM

My understanding is that the trailing edge of each moon gets the brunt of the energetic particles. The Jovian radiation fields rotate in the same direction as the moons but at a much faster rate. Therefore, the energetic particles are slammed into the trailing hemisphere.

The leading hemisphere, therefore, has a lower radiation environment, but it is still a high radiation environment. If good landing sites could be found on the leading side, that would be good, but you still need a very radiation hardened lander.

Posted by: dvandorn Sep 4 2009, 01:54 AM

Here's a thought -- Europa's surface is mostly water ice, right? Ice is an excellent radiation shield, right? And we need to learn how to melt our way down into the ocean below somehow, right?

You could greatly increase the lifetime of a Europa lander if you could effectively bury most of it in ice soon after it lands...

-the other Doug

Posted by: Paolo Jan 5 2010, 08:15 PM

Pure science fiction but interesting anyway, a Russian Fobos-Grunt based Europa lander
http://www.iki.rssi.ru/conf/2009elw/presentations/presentations_pdf/session2/martynov_ELW.pdf

Posted by: Juramike Jan 5 2010, 08:28 PM

2 years in Jupiter system orbit before lander release.

Is there a chance that that much radiation exposure would be bad for the lander electronics?

Posted by: nprev Jan 5 2010, 09:10 PM

No detail on instruments; guess the purpose is to present a method to land 70 kg of instrumentation on the surface. Also no mention of nominal surface mission duration, though the lander appears to be RTG powered.

Re radiation: I wonder how much of the mass budget represents shielding.

Posted by: djellison Jan 5 2010, 09:34 PM

Most of Juno's electronics are in a titanium 'safe house' that's about 1 x 1 x 0.8m, and is something like 130kg - JUST for the box - not the electronics inside.

Posted by: nprev Jan 5 2010, 09:43 PM

Hmm. Looks like that might mean that the actual science payload would be no more than 20 kg at a WAG; don't have a good sense of scale for this thing.

Posted by: helvick Jan 5 2010, 09:55 PM

Titanium seems like an odd choice to me (given it's density) but I assume this is actually some sort of ceramic\alloy construct. I recently discovered (to my surprise) that depleted uranium is one of the most effective and efficient (in terms of mass) x-ray\gamma-ray shielding materials - I can see many reasons for not using it (cost for starters) but I'm wondering whether it's ever been used or considered for radiation protection enclosures on spacecraft.

Posted by: ugordan Jan 5 2010, 10:03 PM

There's more to radiation shielding than x-rays and gamma rays. In fact, I'd wager the primary damaging mechanism of Jupiter's radiation belts is directly via charged particles trapped in the belts (not secondary photons they produce when braking) and secondary particles. A low-Z material would be better suited for slowing down those suckers. In that vein it doesn't strike me as odd titanium would be used. In the end, it's always a tradeoff between different characteristics like primary absorption cross-section, secondary radiation production, etc.

Posted by: nprev Jan 5 2010, 10:16 PM

Low-Z also means low weight. Ti's got a number of excellent, complementary properties.

Posted by: hendric Jan 5 2010, 10:24 PM

I'll bet these guys have some good pointers on choosing radiation tolerant electronics

http://bura.brunel.ac.uk/bitstream/2438/1470/1/iprd06_hobson.pdf

Posted by: helvick Jan 5 2010, 10:29 PM

Which is a very fair point - casual scanning of the usual sources didn't yield anything that indicated Titanium was often used for radiation shielding but that's not a surprise - most of the tech\materials stuff that crop up here tends to be in the "hard to find on google" category and I resisted the temptation to dig into the NTRS - anytime I do that months seem to disappear.

I was just looking at Doug's other point - the 1x1x0.8m safe masses 130kg - if that was _just_ titanium it would only be about 5.5mm thick plate. Making things out of solid metal, even a fairly low density one like Titanium, pushes total mass up awfully quickly.

Posted by: djellison Jan 5 2010, 10:33 PM

http://opfm.jpl.nasa.gov/files/Y-McAlpine-Lessons%20Learned.pdf - big pdf containing a flash based presentation from http://opfm.jpl.nasa.gov/europajupitersystemmissionejsm/instrumentresources/ - they talk all about it.

Posted by: helvick Jan 5 2010, 11:28 PM

Ah no, I've been sucked in - see you guys sometime in February. At least I've found the high-Z vs low-Z discussion points and why high-Z has some particularly bad downsides for Juno which seems to explain the choice of Titanium rather than the Tungsten\Tungsten Copper that crops up in the bits I've found so far.

Posted by: Marz Dec 10 2011, 12:34 AM

http://opfm.jpl.nasa.gov/europajupitersystemmissionejsm/jupitereuropaorbiterconcept/ launch in 2020 land in 2026! let's light this candle!

"NASA is considering dropping two robotic landers on the surface of Jupiter's moon Europa..."
http://news.yahoo.com/jupiters-moon-europa-target-possible-nasa-lander-212201869.html

Posted by: centsworth_II Dec 10 2011, 03:33 AM

I take it this is a vote for an orbiter mission over a lander mission.

While the lander mission is exciting, the much longer lived and broader ( multiple moon flybys) orbiter mission is more interesting and will provide plenty of excitement in its own right.

Posted by: SFJCody Dec 10 2011, 07:56 AM

Agreed that a broad reconnaissance would be preferable. But a short lived lander with a similar mission scope to MSL might well be able to find enough through detailed in-situ analysis as to make the case for a super-duper flagship very strong indeed, whereas an orbital only mission might merely find suggestive/ambiguous evidence.
Might being the operative word of course...

Posted by: Paolo Dec 10 2011, 09:31 AM

the problem is: without an orbital reconnaissance you don't even know what are the most suitable sites where to land and make in situ analyses

Posted by: Drkskywxlt Dec 10 2011, 01:15 PM

The bigger problem right now, Paolo, is there's no money for this unless a Europa lander can be proposed for a Discovery mission.

Posted by: MarcF Aug 8 2013, 07:46 AM

NASA Discusses Future Robotic Lander Mission To Europa
http://www.redorbit.com/news/space/1112917950/jupiter-europa-mission-nasa-robotic-lander-080713/

The paper by Pappalardo et al. is published in Astrobiology Journal:
http://online.liebertpub.com/doi/full/10.1089/ast.2013.1003

Best Regards,
Marc.