Future Venus Missions Options

[Phil Stooke]

Oh well, might as well start that new topic since it's already well advanced in the Juno area...

My perspective on landers is as follows. All the landers we've had so far were dropped blind onto an essentially unknown surface. Any future landers can be targeted for specific terrains. It really is not true that we have had representative landings. Even a descent image or two, a panoramic photo plus a bit of surface composition, from a simple Venera-class lander just updated a bit, would be useful if we could put several down at well chosen targets. My choices would be:

Examples of the main plains units (smooth, fractured, ridged)

tesserae

high elevation radar-bright tesserae

large fresh lava flow unit ('fluctus')

crater dark parabola

crater ejecta outflow unit

dunes area.

And I have always assumed, rightly or wrongly, that it would be relatively easy to put these down, so they ought to be fairly inexpensive as planetary landers go.

Phil

[Guest_BruceMoomaw_*]

Actually, this type of mission -- a balloon using "reversible fluids" to achieve controllable variable buoyancy with a surprisingly low use of both gas and power, spenjding most of its time in the clouds but dipping periodically all the way to the surface briefly -- has been studied by JPL for years as the "Venus Geoscience Aerobot". I've just found two very detailed descriptions of it that I wasn't even aware were on the Web (including Martha Gilmore's article, of which she privately sent me a less developed version YEARS ago. Apparently it took her that long to get Acta Astronautica to publish the damn thing.)

http://techreports.jpl.nasa.gov/1999/99-0750.pdf
http://www.planetary.brown.edu/planetary/documents/2056.pdf

If this balloon design is workable, then obviously this has tremendous merit as a New Frontiers or Small Flagship mission. (One can easily conceive of an improved version, which uses LIBS and Raman spectrometers for its brief surface analyses rather than an X-ray spectrometer as she suggests -- or which actually deploys a core tube or scoop to snatch a surface sample for later leisurely onboard analysis, like JPL's recent Titan Organics Explorer concept: http://www.lpi.usra.edu/opag/feb_05_meetin...resentation.pdf .)

Unfortunately, that seems to be a a very big "if", judging from Kerzhanovich's recent LPSC piece ( http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1223.pdf ), in which he says flatly: "A key problem is that at the time the decadal survey
was published, no high temperature balloon technology existed to implement either mission. Prior technology development efforts had concentrated on a
single balloon that could operate across the entire 0-60 km altitude range, tolerating both the sulfuric acid aerosols and the extreme temperatures of -10 to +460 ºC. However, this problem was unsolved because no combination of sufficiently lightweight balloon material and manufacturing (seaming) technology was ever found to tolerate the high temperatures at the surface." If, as this implies, polybezoxasole can't be adequately seamed after all, then we're stuck with his suggestion for a near-surface steel-bellows ballon whose instrument package must endure Venusian surface tempartures for o very long periods -- which will require new electronics technology, as the Solar System Roadmap says.