Ok, so I just looked over the recent posts about a Venus-blimp-lifting-body proposal. It occured to me that Venus might be a good topic for wild ideas -

The surface temperatures and pressures on Venus are brutal, it is more like an ocean than an atmosphere. So, what if we treat exploration of Venus more like bathymetry, with a bundle of instruments on a tether. Drop it down, get the data, pull it back up before it melts.

So, here's one. I just read about New York skyscrapers saving power by making ice at night to store cooling power. Occurred to me that something similar might work well on a Venus blimp/flying wing. Solar powered refrigeration units create dry ice. Vent the blimp, drift down to the surface, get your measurements while CO2 evaporation cools the probe. Have the CO2 fill a couple of high temp weather balloons to lift you back up.

I'd be highly interested to see this seriously explored but I would expect the miniaturization, low power requirements and low mass requirements would prevent this type of mission at this time. However, with enough money, anything is possible in a short time.

I like the idea of using a phase change to drive raising and lowering through the Venusian atmosphere. Water would be another possible material for this purpose. Perhaps we are in for a new age of steam . . I think we can leave constraints like cost and mass at the door and just think about ideas, as long as they don't require fantasy science. The best ways of exploring Venus will be unique to that world. If the idea's good enough it will be paid for, and hefted. It's time for Venus!

Ok, following up on earlier idea about a Venus probe, a sort of stratospheric diving bell.

If you happen to be 50 kilometers above Venus, it appears to be rather comfortable.
Standard earth pressure, standard earth temperatures, a bit of sulfuric acid rain, but tolerable.

Recent suggestion include a solar powered flying-wing-blimp,

and brain-ship loitering in the cool air, controlling a dumb but heat tolerant rover by radio...

I figure its' about time to think about what other ideas might work?

Lets consider "off the shelf" technology- specifically military cluster bomb tech. We now have cluster bomblets that use rotating laser and infrared scanners to survey the battlefield, identify targets, prioritize targets, and then navigate there.

I would suggest a similar layout, but to deliver science, not semtex.

There's a blog post with additional information on the Discovery finalists. You can follow links for more detail for several of the proposals.

You may be right. We will probably know more as more info on the mission is released.
BTW, I remember that Magellan too took 15 months and one and half orbit around the Sun to arrive at Venus. In that case, however, the orbit design was due to NASA opting not to launch two back-to-back Shuttle+IUS missions (Magellan and Galileo) on the same Venus launch window.

It's curious that the landing sites already visited and photographed (Veneras 9, 10, 13, and 14) were in each case close to tessera or highland units, which seems very unlikely given how much of the planet is wide-open flat planitia. They are also in a very narrow band of longitudes due to the combination of the unexplained synchrony between Venus' revolution and the Earth-Venus synodic periods; the re-use of minimum-energy trajectories in every case; and, the desire to have a day-lit landing site. The aforementioned Veneras as well as the Pioneer Day and Large probes all landed within about 30° of longitude. If one of those variables changes (namely, length of cruise), then a totally different band of longitudes will be selected, potentially a wider one if Venus is gibbous rather than crescent at arrival.

Tesserae are pretty widely distributed. Most 60° bands of longitude would give you 1 or more tesserae landing sites to choose from.

Well, it might only be necessary for raising.
Just occurred to me, after considering the spinning cluster bombs, that probes shaped like maple spinners could make a controlled descent.

If the probes had a camera pointed off-axis, you could naturally build up a spiral image, getting higher and higher resolution as you descend.

Seems that Venus has enough atmospheric diffraction that solar panels on the top and bottom of a wing can provide almost equal power.
So, perhaps a bunch of cube-sats tucked into a maple spinner enclosure, floating at 50km and using solar power to replenish a dry-ice cooling system, then fluttering down to the surface, use CO2 gas to inflate and lift back to 50 km, start all over again.

The other idea, that literally floated in, is to copy orb-spiders. When spiders hatch, they spin a thread, catch a breeze and fly away.
Even heavier adult spiders fly this way although they actually create a 2d "sail" rather than a 1d string.

So, anybody have ballpark energy requirements for probes floating in Venus's CO2 atmosphere, making dry ice to cool a lander, or fabricating polycarbonate sails?

Great writeup, Van, as always!

Well, the only hope for a Venus mission in the next decades rests with the Venus in situ Explorer now

I'm listening to Jim Green's program update at SBAG. He has now said several times that the asteroid missions were selected because they were "most technically ready" and "best fit into a cost capped program".

If you look at Lucy and Psyche, the spacecraft are straightforward, the instruments are all near copies of existing instruments, and the data return rates are likely pretty modest. The latter is one of the key drivers of spacecraft cost.

DAVINCI had the challenge of having a carrier probe (simple in itself, but another element), a high pressure vessel, and expensive composition instruments that had to be modified to work with high pressure, high temperature gasses.

VERITAS was using a modification of radar systems used at Earth, but I don't know if any modifications were required. The biggest challenge, I suspect, was the data return rate which would have driven the cost and complexity of the entire spacecraft system. (Ralph Lorenz published a great paper on how data rate is the driver of planetary mission costs.)

Following the cost overruns of the last decade following the selection of more ambitious missions, NASA's managers appear to have become more conservative. While surprises happen (InSight, for example), in general this has worked.

The Huygens probe used spin to build up images. I can't remember if the spin was created by the parachute design or vanes on the probe.

The European community has united behind the EnVision Venus mapping mission for the M5 (fifth medium) class mission. It is similar to VERITAS with the biggest difference being the addition for EnVision of a subsurface radar instrument. We will know if it made the list of finalists mid year this year. Launch target is the very late 2020s.

There's also a joint Russia-US Venera-D mission in early discussion that would include an orbiter (I think without a radar unit) and an atmospheric probe/lander. However, the Russian space program is strapped for cash and has an ambitious lunar program in the queue ahead of any Venus mission.

There's also been vague (in the public press) talk about other space agencies such as China doing some kind of Venus mission.

Such winged seeds are called 'samaras', and have been proposed for planetary atmospheric sensing, but typically would give you higher angular rates than you would want for imaging. (They are discussed at some length, as well as the spin vanes on Huygens, spinning parachutes, rifled bullets etc in my book "Spinning Flight : Dynamics of Frisbees, Samaras, Boomerangs and Skipping Stones"

Achieving slow descent on Venus is not usually a problem with conventional vehicles, however, since the atmosphere is so dense.

Small vehicles (like the 'cubesat') do not work well in the deep Venus atmosphere as they would warm up very quickly - active cooling doesnt scale down efficiently.

Latest Venus mission news:

There was a selection of candidates for the next New Frontiers mission, and for the many-th Discovery/NF selection opportunity, Venus was not selected.

However, a Venusian silver lining: The VICI mission program led by Lori Glaze was one of two non-finalists to receive funding for future mission development.

Among the many Venus proposals in recent years, VICI is distinguished by its plan to send two landers to two different areas of tessera terrain. This is likely the oldest terrain on Venus, and includes the possibility of landforms that were created before Venus had its current climate, dangling the possibility of evidence of a cooler, perhaps even wet, past.

For now, Venus isn't at the front of the queue for New Frontiers missions, but that's one piece of encouraging news.

If VICI or another comparable mission flies in the next few NF missions, it could become the first designated U.S. surface science lander on Venus, only sixty years after the first Soviet lander arrived!

Interesting article about future missions and capabilities.

https://www.sciencenews.org/article/what-wi...go-venus?tgt=nr

The EnVision Venus mapping mission was just selected as a finalist for ESA's M5 call (flight in late 2020s or early 2030s?)

Press Release

Webpage

Venus exploration is at an interesting crossroads, because it now has a hand in three different competitions, and could win big if it is selected in two of those, or be neglected yet again if it is selected in zero.

EnVision plus VICI or any of the Discovery options with a lander, for example, would do a great job of revolutionizing the state of Venus science, undoubtedly leading to quite different possibilities for any subsequent mission to advance things further. In the best case, we could be at that status in the mid 2030s. In the worst case, we could reach the 100th anniversary of Mariner 2 with the last U.S. mission to Venus being Magellan and the last lander being Venera 14.

Right now, Venus is in just one competition I'm aware of: EnVision in ESA's M5 competition (launch target appears to be early 2030s). I suspect that there will be proposals in the next Discovery competition, beginning next year if I recall with flight in mid-2020s.

That's right, and more precisely, that is the only competition in which a Venus mission is alive for this cycle. I was referring to the ongoing presence of Venus missions in the Discovery and New Frontiers competitions which seems likely to continue until the alternatives are exhausted. The Venus concept VICI also has technology development funding (for the laser spectrometer, such as currently working on Mars) in hand from New Frontiers, which isn't a mission, but is a small start towards one. I'm not sure if that technology development could be used to strengthen the DAVINCI concept, like VICI led by PI Lori Glaze, in upcoming Discovery competitions. DAVINCI was more of a descent atmospheric probe with some surface imaging and a laser spectrometer whose goals only mention the atmosphere, not the surface, although the similarity to the Mars Curiosity instrument is mentioned. I'm curious if the atmosphere-only limitation on DAVINCI's laser spectrometer was due to expectations that it would fail before reaching the surface. If so, the technology development funding for a surface laser spectrometer on VICI could make DAVINCI a significantly more capable mission than in the last competition. One could imagine a very busy surface science mission of an hour or two while it composition-zapped nearby rocks.

It seems like Venus could win the second, third, or fourth -next New Frontiers mission competition (after Dragonfly or CAESAR), and/or the next Discovery mission competition (after the two asteroid missions fly). Nothing is guaranteed, but the competition would seem to be getting thinner every time Venus loses.

From other readings on LIBS/Raman spectroscopy on Venus' surface, there are challenges to both the transmission of the pulses and interpreting the resulting spectra under the very dense atmosphere. I don't think that there were any questions about its survival to arrive on the surface (and it wouldn't operated except on the surface).

An atmospheric probe (VICI - Discovery) and an orbiting radar/thermal spectral mapping orbiter (VOX - New Frontiers; VERITAS - Discovery) were judged at Category 1 (fully selectable by meeting all scientific and programmatic requirements) in the last Discovery and New Frontiers competitions. (Despite being Cat 1, VOX was not selected as a finalist, which was noted by the Venus community.) I would expect that both will be re-proposed for the next Discovery selection which will begin next year.

Between them, VICI and VOX/VERITAS would meet the high priority scientific goals laid out by the last Decadal Survey for Venus. (The VOX team apparently successfully argued that the surface study goals could be met by an orbiter, replacing the previous assumption that a lander was required.)

Interestingly, the time period for selecting the M5 mission (for which EnVision is a competitor) and the next Discovery mission will be similar. I hope that the two agencies don't select a Venus orbiter in the hopes that the other will.

Venus Landed Platform Working Group

NASA has convened a Venus Landed Platform Working Group to assess high priority science investigations that are needed on the surface of Venus. Topic areas include Venus surface geology and geochemistry, atmospheric chemistry and dynamics, interior processes, and surface-atmosphere interactions. This includes investigations that may be enabled by new technology approaches, such as extended duration landers via active cooling or high temperature electronics, or using surface mobility. Individuals who would like to suggest important science investigations should please send a short description of the science question being addressed, the measurements required to answer the science question, and key technical requirements such as measurement duration or mobility requirements. Please send this input to the following individuals:

Martha Gilmore, mgilmore@wesleyan.edu
Natasha Johnson, natasha.m. johnson@nasa.gov
Walter Kiefer, kiefer@lpi.usra.edu
Jonathan Sauder, jonathan.sauder@jpl.nasa.gov

The Working Group’s first meeting begins on June 19.

This has been online for months now, and I'm just taking a look.

https://link.springer.com/article/10.1007/s11214-018-0528-z

Very exciting plans… but of all the proposed missions and architectures, not many are on a solid path towards implementation. The Indian orbiter seems likely. Otherwise, we have Venus as being no better than second in line for a New Frontiers mission and the Envision orbiter (which would be a grand all-purposes Venus orbiter) one of three candidates for a future ESA mission.

The Indian orbiter will carry a number of instruments, but it appears to have some severe limitations on payload mass and data rates.

The proposed ESA EnVision radar and infrared mapping mission wouldn't launch until the early 2030s if selected. It is facing severe cost and mass limitations. NASA is investigating whether it could provide the major radar mapping instrument.

The Venera-D joint Russian (lead) & US lander and orbiter could fly in the mid-2020s, but Russia is strapped for cash.

That leaves the two Discovery missions to be selected (as I remember) in 2021 for flight in the mid and late 2020s as the only other opportunity.

It's interesting to me that EnVision and VOX both propose the same instrument to probe emissivity in the IR, as does the Discovery proposal VERITAS. I think that Venus Express' PFS instrument would have returned some of the same value, except that it failed and returned no data at all (the Wikipedia page erroneously reports that it did, probably a hasty editor converting original plans into the past tense after the mission ended). In a nutshell, this is similar, for Venus, to what VIMS on Cassini accomplished at Titan, making use of haze-penetrating bands to observe the surface. It would be great to have an orbiter in a low circular orbit provide this or a resolution of radar superior to that of Magellan or, as both EnVision and VOX propose, both.

It seems not impossible that VOX or another Venus mission could be the second or third next New Frontiers mission, which looks like the 2030s, as would be EnVision.

The Discovery missions have seemingly chosen every conceivable non-Venus mission that anyone can propose with Venus almost inevitably getting to the front of the queue eventually. Proposals for the next Discovery missions are due at the end of this month. If VERITAS were chosen, that could likely knock EnVision and VOX down in value, and make VICI a candidate for a future New Frontiers mission in the 2030s.

Our company recently hosted Dr Jean Anne Incorvia from the UT Integrated Nano Computing Lab for a lecture on Magnetic RAMs. Of course, I asked a bunch of space-focused questions. She said they are very robust at high temperatures (tested up to 250C) and radiation environments, and are well suited to space operations. The transistor part of the structure is vulnerable to damage, but the memory element itself is very tough. Endurance testing is over 10^15 modify cycles. Time to rewrite a bit is on the order of 1-10ns. I also brought up Silicon Carbide as the semiconductor substrate for the ferro structures, but nobody is looking at that. (Potential opportunity there!) With Curie temps in the 1000C range, I am hopeful we have a perfect memory for an upcoming Venus lander/rover!

http://www.utinclab.com/

You were right to ask about SiC. The MRAM junction might be high temp tolerant, but the associated FETs are not.

MRAM does have its own sort of soft error rate (bits flipping randomly, not necessarily radiation induced.) So I would wonder if that rate increases with temperature. MRAM, though, seemingly has a lot less complex circuitry to fail than Flash does. Density is years behind, though. The stuff they do with Flash now is insaaaane. Very far removed from zeroes and ones.

Probably some quantum tunnel magic I suppose. The Dr mentioned that as the temperature rises your speed would increase since it is easier to flip bits but your error margin would decrease. Dealing with bad bits is NAND bread&butter though so it should be easy enough to mitigate.

Yeah modern flash memory now is MLC, basically instead of just reading a straight 0 or 1, it reads mid-level voltage levels and translates that into 000 001 010 011 etc. That makes it extremely susceptible to disturbs (reading bits at X,Y has a chance of messing up their neighbors), lowers the lifetime of the cell when turned off as the electrons slowly drain, and much more vulnerable to radiation induced damage.

MRAM is still fairly young tech for semiconductors (original Space Shuttle used ferrite cores, so the concept has been around a long time!), but based on her talk there is plenty of run room and the potential for very high densities.

A German lab has been developing an IR emissivity instrument for over a decade or so. They have done extensive work on the instrument development and on interpreting the multispectral results in terms of composition. This instrument has been included on every post-Venus Express mission that I know of except possible the planned Indian mission.

Here's a link to an LPSC 2019 abstract:

VEM

A nice summary! I've seen other write-ups of the specs and it's a phenomenal instrument design for a specific case of interest.

Now the pity would be if the Indian mission is the only planned Venus orbiter that doesn't include it and ends up being the first to fly, which it could be by a margin of years. If we have to wait ~15 years to get this data back, it will be a pity when it could easily be done within 4 years if Venus were a higher priority.

Just read the Russians gave agreen light and will send a new lander before 2023. Hoping to use some experimental tech to allow the probe to operate in extreme temperatures. Nasa is interested in helping develop this technology

I know roscosmos says alot and doesnt follow through. But Venus is definitely something they are capable of.

or at least they were capable of. I doubt that almost 35 years after the most recent successful Russian planetary mission they are retaining any of the know how

The Phase II Report of the Venera-D Joint Science Definition Team calls for a launch in 2026 at the earliest.

thanks for that. Glad I can count on this place to be accurate.

Yahoo later corrected the article to 2026.



Man Russia needs a win so bad. The last somewhat successful interplanetary mission was....what ? ..Phobos II....somebody?

in today's Nature:
Venus is Earth’s evil twin — and space agencies can no longer resist its pull

Phobos2 though unfortunately not fully successful, did get some great images, yet it seems to be the most recent Russian exploration mission to at least make it beyond Earth orbit. The most recent success seems to be Vega which after a couple of as-yet unmatched firsts in deploying landers and balloons to Venus, continued another first visiting Halley in 1986 according to this wikipedia page. After the breakup of the USSR, other than the Russian's fine and clockwork Soyuz activities and contribution to ISS, its unfortunately been crickets as far as exploration is concerned. It looks like Luna25 in 2021 is their next hope in a long line of false starts, found this article on the space review.

new Wired article on the LLISSE is interesting once you bat away all the adverts.
The 20cm cube is designed to stay operational for 60 days capturing day/night transition, but likely have no camera, is hoping to hitch a ride on Venera-D.
Also found an old PDF and another older? paper mentioning a possible wind-powered battery option for demonstration in 2023. Wind speeds are so fast at altitude it speeds the planets rotation by 2 minutes per day, wind slows at the surface to apparently a few km/hr so seems workable, solar cells should be considerably less mass but im not sure what the status is now though ive also heard due to high albedo Venus actually receives less energy at the surface than Mars does.. here's more fun.

https://www.space.com/possible-nasa-venus-f...ip-mission.html

This article discusses the possibility of a flagship-class mission to Venus sometime after 2023.
One may argue that recent Venus proposals have failed because they are too cautious, so perhaps a multifaceted
approach on the scale of Cassini would stand a better chance of success.
Mentioned are multiple orbiters, long and short-term landers, and a balloon-based aerial platform with, (sic) a seismometer.
Despite its ambitious nature, the proposal strategy seeks to be cheap relative to other flagship-class contenders.
I guess that means we'll have to wait a few more decades for a sample return.
,

Interesting timing, given that three Discovery proposals aimed at Venus are now being evaluated with an announcement of selection for Step 1 targeted for January 2020, only weeks from now. Any of those three would satisfy the flagship aims partially, so the proposal of a flagship mission puts some (more) people/programs at cross purposes, and the community has to have a lot of overlap; there can't be very many people who would be investigators for the flagship mission who aren't involved with some of those Discovery proposals.

Orbital studies of the surface and orbital/descent studies of the atmosphere are both addressed by the Discovery proposals, in addition to the descent imaging of tessera terrain. The flagship mission includes a lot more in situ surface focus.

The timing feels off unless the people proposing the flagship mission have a strong sense that the Discovery proposals are all going to be rejected. Otherwise, the flagship goals could descope and focus with the satisfaction of some of those goals.

I don't recall any precedent for gathering together several discovery-scale proposals with the same destination and consolidating into a single flagship-scale mission. But there could be some efficiencies in launch, data return, shared infrastructure. Politically it would be difficult to persuade the individual would-be PI's to report to a single overall head, but I suppose they might be willing to settle for a piece of the action with high probability, in place of a low-probability shot at being the sole focus.

Anyway, I am just imagining that; the article mentions no such consolidation. It seems to describe a top-down effort by someone who wants to design the whole venture from scratch.

<personal opinion only>
Despite being a proponent of Venus exploration (I am associated with one present Discovery proposal, as well as having involvement in international missions)
I find the case for a Venus flagship somewhat uncompelling : I wonder if it essentially was the result of the architecture of the Decadal Survey
(i.e. the (non-Mars) terrestrial planets could get one Flagship into consideration, and that's what popped out)

There is definitely a need for higher-resolution radar observations (Magellan's stated purpose was to map Venus as well as Mariner 9 mapped
Mars, so there's a little catching up to do...) with an emphasis on change detection (e.g. multiple revisits, interferometry etc.) and for in-situ measurements on and near the surface.

The synergy of combining these into a single mission (for which there are surely *some* advantages) is IMHO less strong than at more remote targets (I led the
science definition team for the first Titan Flagship study in 2007, which advocated a lander, a balloon and an orbiter - at the large Titan-Earth distance, the
orbiter really improved the data return from the in-situ elements) - the data relay enhancement of return from a lander is not so critical for non-mobile
landers which develop new information at a much lower rate than rovers/balloons etc., and for the smaller Earth-Venus distance.

The capability for near-surface in-situ missions (high P,T) used to be within the purview of the USA and USSR. It isn't clear that Russia today really has that capability, so
I'd expect the USA to be the lead behind any future lander.
(Balloons etc near the 1-bar cloud tops are less demanding : although the entry challenges are non-trivial, they are comparable with Earth entry, that
ESA, China, Japan etc. can handle)
Unless surface mobility, multiple (>2) landers, or sustained longevity is introduced, near-surface in-situ measurements are within Discovery/New Frontiers scope

Beyond their propulsive demands, orbiters require attentive thermal design, but are otherwise not terribly different from Earth orbiters. So the pool of countries /agencies
that could 'bite off' the radar/gravity/near-IR mapping job is not small. We have already seen promise that India may enter this arena (although I am skeptical that the
downlink bandwidth will allow an Indian mission - if anything like MOM - to do justice to radar mapping)

If an Indian mission happens (even just an orbiter with a range of payloads), and a 'proper' radar mission (ESA's Envision and/or a US Discovery class like VERITAS) and
an in-situ mission (e.g. Discovery or New Frontiers and/or Venera-D [but Im not holding my breath on that, V-D's been nothing more than vugraphs for about a decade now]
start development in the next few years, then Venus science in the next decade will be in decent shape. In which case I'd find it hard to argue for a Flagship, and I'd suggest that
such a 'coalition' of smaller missions is more likely to happen than a Flagship.

If India+Envision only, that'd be good, but there are some major questions still not being answered (surface/atmosphere chemistry for one, probably the noble gas abundances)
If only one of those, it amounts to 'life support' for Venus science at best. 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.

There are doubtless aspects of the Venus climate whose understanding can be refined, but IMHO (see my book 'Exploring Planetary Climate') the basics were pretty well figured-out by Pioneer Venus and the Veneras. There is
new appreciation of time variability from VEx and Akatsuki, but again, good traction of much of that science can be made from smaller missions. I just don't see a Flagship.

Akatsuki is great (but its near-IR cameras ceased operation after a year in orbit, so it's just doing UV, thermal IR, lighting/airglow and radio occultations). The Bepi-Columbo
and Solar Probe flybys are cool and all, but don't provide a lot of data or answer any major questions.

</opinion>

Your opinions are gold, Ralph – very informative.

One thought on the engineering side that you didn't mention: Obtaining circular orbits via aerobraking or otherwise. Magellan began with a relatively low-eccentricity orbit attained with chemical propulsion, then used aerobraking to circularize the orbit for the gravity mapping phase. Since then, three U.S. orbiters and one ESA orbiter have used aerobraking to obtain a circular orbit at Mars.

Veritas and Envision would be the first mission(s) to use aerobraking to attain a circular orbit around Venus for a spacecraft's primary mission.

What I wonder is whether other space programs would have the capability to achieve this or if this seems like USA/ESA capability only for the time being. I realize that the question is potentially speculative, but seeing as the USA and ESA missions plan on it and the Indian mission does not it seems like a potentially significant distinction between proposed orbital surveys of the planet's surface.

For atmospheric science, this seems much less significant as time variation is important and a wide perspective is not a bad tradeoff.

Ill second that, but...

...What would be the most cost effective way to get more information on the mysterious 'unknown UV absorber' in Venus' clouds?
Does this need in situ sampling, or can it be done remotely, and if the latter, is it in the reach of a larger cubesat?

(I'm assuming there wont be megabucks around for Venus missions in the near-mid term)

P

What's the story with disulfur oxide as a possible UV absorber as in this publication? Then we have this thread.

CUVE

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).

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.

<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>

Until the other day, I had assumed that the DAVINCI proposal (now called DAVINCI+) in the current set of Discovery proposals was basically DAVINCI from last time around with a modest change. The reality is dramatically different. What they have added since last time is arguably larger than what was proposed before.

In a nutshell, the new mission proposal is more like a Messenger for Venus with an entry probe rather than just an entry probe. It would flyby Venus twice while holding the probe, make significant scientific observations in IR and UV, of both the atmosphere and the surface, before releasing the probe, then the carrier would enter Venus orbit and continue making observations long after the probe's mission was complete.

Many details here. I'm not sure how the IR emissivity science would relate to that collected by VERITAS, should both of them be selected. It seems almost certain that VERITAS would collect more and better IR emissivity science, but each of them is doing a lot more than that.

https://www.hou.usra.edu/meetings/lpsc2020/pdf/2599.pdf