The First Europa Lander, What can be done first, cheapest & best? Options

[nprev]

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

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...

[nprev]

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

http://www.unmannedspaceflight.com/index.p...t=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...

[RNeuhaus]

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.

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

[ljk4-1]

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)

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[ljk4-1]

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

[PhilHorzempa]

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

[Guest_Richard Trigaux_*]

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.

[JRehling]

Why to limit the life time of a surface lander?

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?

[nprev]

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?

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.

[Guest_Richard Trigaux_*]

...the seismic environment on Europa might be quite complex indeed...

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.

[RNeuhaus]

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

[JRehling]

an astronamic telescope to observe closer to Jupiter changing clouds would be a MUST!

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.

[djellison]

A panoramic camera plus an astronamic telescope to observe closer to Jupiter changing clouds would be a MUST!

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

[algorimancer]

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.

[djellison]

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