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Future Venus Missions
vjkane
post Nov 29 2019, 06:17 PM
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QUOTE (scalbers @ Nov 28 2019, 04:51 PM) *
What's the story with disulfur oxide as a possible UV absorber as in this publication? Then we have this thread.


CUVE



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vjkane
post Nov 29 2019, 06:22 PM
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QUOTE (rlorenz @ Nov 23 2019, 07:29 PM) *
<personal opinion only>
The Venera/VEGA/Pioneer Venus generation are basically all retired, the Magellan generation (i.e. those
professionally active while the mission was in operation) still has a reasonable fraction of people in the field that can offer direct experience to missions developed and launched
in the 2020s, but if it takes until 2030 to go back, much of the intellectual heritage of the earlier missions and questions will be lost.
</opinion>

The ESA/NASA EnVision mission, if selected, would as I remember, begin to deliver data from it's low orbit in something like 2033 to 2035 (don't have time to look up actual date). So another half generation plus of scientists would retire before data begins to flow.

A NASA mapper mission, if selected for the ~2024 Discovery launch date, would presumably deliver data beginning a year or two later (flight time to Venus plus aerobraking).


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JRehling
post Nov 29 2019, 10:11 PM
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The OSSO abstract and CUVE proposal are both very interesting. I think what has allowed the identity of the UV absorber to remain indeterminate is the fact that the physical manifestation of the absorber is a wildcard: If it's not in a simple gaseous state, then the spectral properties of grains and droplets introduce complexity that is hard to account for. For example, if a solid particle has liquid droplets condense upon it, the resulting spectrum might be very hard to duplicate in the lab without knowing which permutation to look for. The lab work and something like CUVE are certainly positive steps forward, though. As the chromophores in the clouds of Jupiter and Saturn are also still unknown suggests how difficult something like this is to resolve.

It sticks in my mind that Venera 11 and Venera 12 found large amounts of chlorine in the clouds while Pioneer did not. That seems odd if chlorine were not part of what varies spatially and temporally in Venus' clouds. It seems to me like a clincher would be to have in situ cloud sampling measuring elemental composition occur at locations that are known to be, respectively, UV bright and UV dark would be the most definitive way to resolve the question. It would be nice to know, in retrospect, what the UV albedo was at the time and place of the Venera and Pioneer in situ measurements, but that information may be irretrievable.
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rlorenz
post Nov 29 2019, 11:13 PM
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QUOTE (JRehling @ Nov 29 2019, 05:11 PM) *
I think what has allowed the identity of the UV absorber to remain indeterminate is the fact that the physical manifestation of the absorber is a wildcard: If it's not in a simple gaseous state, then the spectral properties of grains and droplets introduce complexity that is hard to account for. For example, if a solid particle has liquid droplets condense upon it, the resulting spectrum might be very hard to duplicate in the lap without knowing which permutation to look for. The lab work and something like CUVE are certainly positive steps forward, though. As the chromophores in the clouds of Jupiter and Saturn are also still unknown suggests how difficult something like this is to resolve.


<opinion>
I don't doubt that UV spectroscopy so far is inadequate to identify the UV absorber, nor that it is an important element of the Venus climate. But I havent seen a persuasive case that a better UV spectrum would be able to unambigously identify it (your chromophore analogy is a good one), nor that a UV spectrometer is the best payload for a smallsat Venus orbiter. I could be wrong about both these things, but havent seen it yet.

I do believe that a UV spectrometer able to yield a better spectrum *could* be implemented on a smallsat, so in the context of SIMPLEX (i.e. 'what could you do at a planet with a smallsat that might be scientifically interesting? : the overall data volume needed is modest) a proposal like CUVE makes sense.

On the other hand, LUVOIR claims to be able to do good UV spectro-imaging at Venus too (see https://asd.gsfc.nasa.gov/luvoir/reports/LU..._2019-08-26.pdf ). And/or maybe the Indian mission will have a decent UV spectrometer.

Even identifying the absorber from an in-situ mission will be challenging, but I'd venture that has a better chance (if it can sample the relevant altitudes) of providing a more definitive answer than any remote sensing would.
</opinion>
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