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Russia Plans "long-lived" Venus Probe
ljk4-1
post May 12 2006, 08:29 PM
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QUOTE (DonPMitchell @ May 12 2006, 04:22 PM) *
It's a clever mission plan. The Venera spacecrafts were 6 tons, and required a Proton rocket to launch. This proposal is basically the Vega lander stuck on a Fregat. It can be launched by a Soyuz, and the pieces are probably all sitting in a warehouse at NPO Lavochkin.

But it's Not Invented Here. :-)


Those are probably the very landers mentioned in Omni magazine in 1991
that Russia tried to sell for just $2 million.


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

- Henry David Thoreau, November 15, 1853

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Guest_BruceMoomaw_*
post May 12 2006, 11:05 PM
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Actually, the first and second "SAGEs" never even had the chance to become rival concepts. The first one was an idea for a possible Discovery mission mentioned back in the early 1990s, a couple of years before the first AO for any Discovery mission even went out. It never even became an actual proposal.

Esposito's "SAGE", on the other hand, was a proposal for the first AO for the new New Frontiers program, which was released a decade later. The only thing they have in common is their name.

Really, though, if ever I saw an opportunity for a possible US/Russian collaboration that might actually work, this is it. The Russians just might be able to build a copy of their old Venera spacecraft without screwing it up. (Mars 96 -- based on the Phobos design, which they had never been able to get to work -- was so complex and built on such a shoestring that, even had its launch succeeded, insiders thought the chances that the spacecraft itself would work were virtually nil. They were building the thing by GASLIGHT, for God's sake, because the Russian space agency couldn't pay its electric bills!) Have the Russians build and launch 1 or 2 Venera landers equipped with good American (or European) instruments and you might really have something -- and at this point Russia might actually be able to afford to build them properly.

I have a bit more information coming on Esposito's SAGE later today.
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Guest_BruceMoomaw_*
post May 13 2006, 10:58 AM
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And here it is. One of the primary investigators on SAGE was Bruce fegley of Washington university (located, oddly, in St. Louis); and in 2003 he put a Powerpoint rpesentation on the Web regarding the desirable goals for such a Venus lander (keeping in mind that his own Venusian specialty is chemical interactions between the surface and atmosphere). That presentation no longer seems to be there -- but, once again, I recorded it at the time. It was nicely detailed, but here are what seem to me to be his most important spefications:

(1) The key atmspheric measurements include temperature and pressure profiles from the surface to the clouds. (Oddly, he says that not only did the Pioneer probes fail to get data below 12 km, but so, for some reason, did Vega 1 -- and since the 1970s Veneras were of questionable accuracy, Vega 2 sems to have provided us with our only good low-altitude T and P profile so far.) They also include composition, using a GCMS -- in order of priority:
Overall abundance of H2O, CO, SO2, N2 and the noble gases
Vertical profiles of the first three
COS, H2S, HCl and HF
Isotopic ratios for H, C, N, O, S and the noble gases
H2, H2SO4
CO2 abundance below the clouds

(2) The top priority surface analysis site should be a big representative region for average Venusian chemistry and mineralogy. Second priority is an anomalous region -- either a tessera ("some propose these are metamorphic"), or one of the high-altitude high radar-reflectivity regions. Both primary rocks and phases that have reacted with the atmosphere are needed -- preferably a depth profile using a drill core, and including if possible an examination of the atmospheric gases at different depths in it (here his own biases show).

The top-priority measurements are element and mineralogical composition together (elements by themselves are not worthwhile). The best mineralogical instrument is an X-ray diffractometer; element analyses should include elements from C through Na, which X-ray and gamma-ray spectrometry can't detect. Then, in order of priority, come:
Color imaging of the surface and the drill core
Fe oxidation state (he recommends Mossbauer for this)
Visible/IR reflection spectra
Oxygen fugacity in the surface (using a ceramic O2 sensor)

SAGE's payload, as indicated by the JPL description, doesn't include all Fegley's desired measurements, but it would include most of them.
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Guest_Myran_*
post May 13 2006, 12:14 PM
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QUOTE
BruceMoomaw mentioned: ......the high-altitude high radar-reflectivity regions.


Oh yes those are really interesting, and might be really wortwhile to investigate. Whatever it is that covers high peaks of Venus, it certainly cant be anything we're used to. Especially interesting if it turns out those areas are covered by semiconducting metal salts as some have proposed as one explanation for the data.
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Guest_DonPMitchell_*
post May 13 2006, 12:41 PM
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QUOTE (BruceMoomaw @ May 13 2006, 03:58 AM) *
Oddly, he says that not only did the Pioneer probes fail to get data below 12 km, but so, for some reason, did Vega 1 -- and since the 1970s Veneras were of questionable accuracy, Vega 2 sems to have provided us with our only good low-altitude T and P profile so far


Why does he think Venera-9 - 14 had questionable readings? Their platinum-wire thermometers are not as good as our platinum-wire thermometers?
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Guest_BruceMoomaw_*
post May 13 2006, 10:41 PM
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Damned if I know, except that his slide says that there was "low accuracy P and T data from the old Veneras". Nor does he say why he has more faith in the results from Vega 2 (or, for that matter, why there apparently were no good measurements from Vega 1), but he wonders whether the Vega 2 data was "representative". I should add that he wants really accurate data: "Measure T and P with ~0.01% accuracy. At the surface, this is +0.1 K and +0.01 bar."
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edstrick
post May 14 2006, 07:20 AM
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Accurate measurements of stability and convective power of an atmosphere that is marginally stable or unstable against convection, like the sub-cloud Venus atmosphere, require extremely high precision. Unfortunately, the Net Flux radiometers on the Pioneer Venus small probes had a design defect that put poorly calibratable biasses and errors in the science results. Venera 7 and 8 temp data were very crude. Later Venera data were better, but maybe not as accurate as the Pioneer data.
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Guest_Richard Trigaux_*
post May 14 2006, 08:03 AM
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QUOTE (BruceMoomaw @ May 13 2006, 10:58 AM) *
.... They also include composition, using a GCMS -- in order of priority:
Overall abundance of H2O, CO, SO2, N2 and the noble gases
Vertical profiles of the first three
COS, H2S, HCl and HF
Isotopic ratios for H, C, N, O, S and the noble gases
H2, H2SO4
CO2 abundance below the clouds
....


If there are measurable abundancies of such gasses as HF, H2S, HCl and the like, at a temperature of 450°C, it is expectable that the surface rock are completelly rotten, see metamorphized, as are rocks around earth fumaroles. As sulphates or carbonate could not from at such temperatures, we may find a lot of other salts, sulphides and sulphites, chlorures and fluorures. Many of them could be semi-conducting.
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Guest_DonPMitchell_*
post May 14 2006, 02:24 PM
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It looks like the accuracy of the Venera-9 to 13 and the Pioneer atmosphere probes were about the same, on the order of 2 to 5 degrees C. The Vega-2 probe had an accuracy of about 0.5 degrees.

The standard atmosphere is still based on a combination of Pioneer and Venera-10 data, fit to a thermodynamic model. Keep in mind that when you fit hundreds of measurements to a model, you get much better statistical accuracy than the error of the individual measurements.
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JRehling
post May 15 2006, 12:59 AM
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QUOTE (BruceMoomaw @ May 12 2006, 01:57 AM) *
Good description of the original Russian/American "SAGE" can be obtained indirectly at
[...]
Descent Imager and Spectral Radiometer -- Uwe Keller, Max Planck Institute (a member of the Titan DISR team)

X-Ray Fluorescence and Diffraction -- David Blake, ARC (PI for the "CheMin" instrument on MSL)

Gas Chromatograph/Mass Spectrometer -- Paul Mahaffy, GSFC (PI for the "SAM" instrument on MSL)

UV Imaging Spectrograph -- Bill McClintock, LASP (U. of Colorado)


Hopefully, the Venus DISR would return more data than the Titan DISR. The bottleneck seems to be less restrictive, since there is no relay necessary. I think the Huygens DISR did a fine job, even with half the data, of returning a full overhead panorama at reasonable resolution (although it was hell in terms of processing on the ground). But that one x-axis-narrow surface view aside, DISR returned nothing whatsoever from below a certain ceiling.

I think the imaging goals would be:

1) To locate the landing site in context (registering descent images with Magellan data).
2) To provide high-resolution (cm-order resolution) imaging of the immediate landing site.
3) To produce resolved multispectral imaging at a variety of altitudes.
3a) ...for its own scientific value.
3b) ...to benchmark the usefulness of such imaging to evaluate the worthwhileness of including such imaging in future high-mobility (aerobot) missions.

Per 3b, the benchmarking could potentially be performed with a much smaller mission before SAGE. If multispectral imaging has any use in making mineralogical discrimination on Venus, a dream mission would be one or more aerobots that spun around the planet returning imaging noodles that crossed many different types of surface unit, "coloring" in representative terrains that are mapped comprehensively by radar, giving us a pretty good inference of the mineralogy of the whole planet. If an aerobot could return this data while flying a Vega-like trek across Venus (~9000 km), one or two well-chosen entry locations could sample all the major terrain types.

GCMS could also be flown on a smaller mission; unless Venus is being washed in new volcanic eruptions on a colossal scale, this only needs to be flown once, ever.
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Guest_BruceMoomaw_*
post May 15 2006, 02:14 AM
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The same thing is true of the UVIS, whose main purpose is obviously to identify the cloud UV absorber. In fact, Esposito proposed a "Venus Composition Probe" for the first Discovery AO (I don't know whether he repeated it) that would have been split into two modules: a vented one just for upper-atmospheric analyses carrying mass and UV spectrometers, and an armored module to survive until impact carrying atmospheric structure sensors and an IR spectrometer to proofile reactive trace gases.

As for Rehling's proposed composition-mapping high-altitude balloons: it might well be possible for them to get acceptable near-IR spectra of the local surface (at least through the limited spectral sunlight windows allowed by Venus' atmosphere and clouds); but it's more open to question as to whether they could get useful images. Tjhere have been quite a few studies of that, reaching differing conclusions:

http://www.sciencedirect.com/science?_ob=A...eb2b26976a8d59f (I ahve Moroz's complete 2002 article, but it's no longer available for free on the Web.)

http://www.lpi.usra.edu/meetings/LPSC98/pdf/1646.pdf

http://www.aas.org/publications/baas/v35n4/dps2003/376.htm

The 1998 one was done in connection with the "VEVA" Discovery proposal for droppable imaging probes ( http://trs-new.jpl.nasa.gov/dspace/bitstre...6/1/00-0365.pdf ), which actually reached quite optimistic conclusions: "Venus’ atmosphere has an opaque cloud deck above ~47-km altitude. Our simulations show that by imaging below the cloud deck in a window in the CO2 absorption at about 1 pm, interpretable images can be obtained even from 47 km altitude (images from this altitude will show primarily surface elevation differences due to the differing optical path lengths to the surface; lower areas will appear brighter). We also simulated the effects of near-isotropic lighting on aerial photographs and found that roughness-induced differences in apparent surface brightness (self-shadowing) provide good contrast between units even under these conditions."
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Guest_DonPMitchell_*
post May 17 2006, 06:05 PM
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With regard to long-life missions, the Russians developed quite a few techniques, some of which you see copied in the Pioneer Venus probes.

1. Phase-change materials to absorb heat. Venera-8 used Lithium Nitrate Trihydrate, a substance that has almost the latent heat of fusion of ice, but melts at 30 C instead of 0 C. In the Venera-9 to Vega landers, a small internal fan circulated the air through a "heat battery" of this material. Instruments that extended outside the insulated hull were also packed in a layer of LiNO3.3H2O, the cameras and x-ray soil spectrometer, and external instruments like the IR/Visible spectrometer.

2. Insulation. They did a lot of research on this, developing some special high-temperature organic polymer foams and ceramic foams for the landers. Their early long-life lander proposal was to be insulated with aerogel. Alternating sheets of fiber quartz and metal foil was also used in places.

3. High-temperature lubricants. Molybdenum Sulphide mixed with metal flakes was developed for things like the Venusian soil drill. The used MoS2 instead of graphite (used by NASA) in space and on their Lunokhod rovers, based on some automated fiction tests onboard the early Zond probes.

4. Connectors. Russians are fascinated by connector technology for some reason, and special ones were developed for the external electrical systems on Venera landers. Given that the Pioneer probes shorted out, perhaps this is not a problem to be underestimated.

5. Coatings. Polysiloxane was popular, as an enamel paint for some parts. An almost indestructable polymer, semiorganic on a Silicon-Oxygen-Silicon clain.

6. Hardened electronics. I'm amazed by the amount of external instrumentation on the later Veneras, Ksanfomality's seismograph for example. I'm not sure what the technology was, Silicon MOSFET or possibly even miniaturized vacuum tubes.

7. Power sources. The Venera landers were powered by batteries (Silver Zinc are extremely energy dense). But they did some research on radioisotope thermopiles, windmills and solar cells. The surface is too dim for solar cells as it turns out. Small windmills did operate some of the Venera experiments that requried mechanical action during descent. And the Venerokhod rovers were to be wind powered.

Of course, they also took advantage of heat. Many "timed" events were activated by links designed to melt at specific altitudes on Venus. This included things like parachute reefing and covers on instruments to keep cloud goop off.
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Bob Shaw
post May 17 2006, 06:50 PM
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Don:

Venerokhod?

Do tell!

Bob Shaw


--------------------
Remember: Time Flies like the wind - but Fruit Flies like bananas!
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Guest_DonPMitchell_*
post May 17 2006, 06:54 PM
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QUOTE (Bob Shaw @ May 17 2006, 11:50 AM) *
Venerokhod?


Yep. They developed a couple working models. Was used wind-powered electric motors, and another powered the wheels by direct drive from the mill.
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Guest_Richard Trigaux_*
post May 17 2006, 07:47 PM
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Is there really some wind on Venus ground? Not sure, it seems a very quiet environment. At least dunes were not detected. If most of the sun heat is absorbed into the clouds, it is expectable that all the convection will happen into these clouds, not on the ground.

External connectors shorted on Venus probes? Possible explanations into this exotic environment:

-droplets of sulphuric acid
-action of other gasses, like HF (which attacks nearby everything)
-oxydation/sulphurization of insulators

eventually a very thin layer of sulphide forming on the surface of an insulator can be enough to turn it conductive, especially on Venus temperature.
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