Future Venus Missions Options

[JRehling]

One also needs to know if "high" and "relatively high" are referring to the same altitudes or if there's some important difference there. I would guess that anything above the clouds, encountering direct solar UV, qualifies equally well as "high" for these purposes, but I never received a paycheck for studying Venus.

[rlorenz]

I suppose one would need a great deal more expertise to know whose argument is stronger.

Expertise, maybe. But as humans, we can also employ our heuristic tools of caricature, profiling and prejudice.

Therese Encrenaz has been in *planetary* spectroscopy a long time. I think (and my Planetary Climate book gives many examples) in planetary science there are many instances of spectroscopic detections being disproved by in-situ or other data, which make some people (like her) cautious. In stellar astronomy (which seems to be where the Cardiff group has more pedigree), I could imagine there are fewer disproved 'discoveries' just because there are fewer ways to confirm or refute initial announcements.

So, IMHO, if Therese says it isnt in her data, then it isnt in her data... (and knowing her, she wouldnt say it wasnt there on Venus, only that there wasnt evidence for it in her data).

It may be non-PC to consider such meta-factors, but at the hairy edge of detectability, one is obliged - Bayeswise - to weigh all the information.

There are sadly a lot of incentives in the journals and the media to talking up anything that could bear on life in the universe - indeed Nature Astronomy even had an editorial congratulating itself on how much press the paper had generated and how this was only possible because of their media embargo policy. Cui bono....

All this said, Venus deserved the attention.

[Greenish]

For what it's worth, this is new on the arxiv, not yet refereed:
Re-analysis of the 267-GHz ALMA observations of Venus: No statistically significant detection of phosphine
I.A.G. Snellen, L. Guzman-Ramirez, M.R. Hogerheijde, A.P.S. Hygate, F.F.S. van der Tak
https://arxiv.org/abs/2010.09761

"...The reported 15σ detection of PH3 1−0 is caused by a high-order polynomial fit that suppress the noise features in the surrounding spectrum. ...Low-order spectral baseline fitting shows a feature near the expected wavelength at a signal to-noise of only ∼ 2."

It does come with a front page caveat that there has since been an update to the ALMA processing pipeline [while this re-analysis was in work], that they haven't fully analyzed. It notes that though many of the "spurious ripples" are gone, they still see no clear PH3 feature.

[antipode]

Here's a Venus mission concept I hadn't seen before (apologies if its been covered further back).

https://www.hou.usra.edu/meetings/vexag2020/pdf/8045.pdf

Its a fascinating idea with potential high return, but I worry about that long cable and any shear/turbulence in between the baloon and the descent module.

P

[vjkane]

Here's a Venus mission concept I hadn't seen before (apologies if its been covered further back).

https://www.hou.usra.edu/meetings/vexag2020/pdf/8045.pdf

Its a fascinating idea with potential high return, but I worry about that long cable and any shear/turbulence in between the baloon and the descent module.

P

Fixed URL link

This abstract discusses a similar idea:

VENUS CORONA AND TESSERA EXPLORER Investigating the Surface of Venus from Beneath the Clouds [#8031]
VeCaTEx would use an aerobot to descend repeatedly beneath the dense clouds for imaging targeted area of the surface in the near infrared spectral region to address six of the prime investigations prioritized by VEXAG.[color="#FF0000"][/color]

[vjkane]

Moderators: I obviously had problems editing my previous reply and don't see a post delete button (sure I'm just missing the obvious). Please delete duplicates.

This is the correct link for the other poster at the recent VEXAG meeting for a mission concept that would go beneath the clouds for a more detailed examination of the surface.

Venus Corona and Tessera Explorer (VeCaTEx) Mission ConceptVisit My Website: Investigating the Surface of Venus from Beneath the Clouds [#8031]
VeCaTEx would use an aerobot to descend repeatedly beneath the dense clouds for imaging targeted area of the surface in the near infrared spectral region to address six of the prime investigations prioritized by VEXAG.

[JRehling]

As a non-mechanical engineer, I nonetheless share antipode's sense that a cable more than 20 km long seems to introduce some serious worries about practicality. I can't even picture something like that working on Earth, much less being transported to Venus.

Here's an informative analysis of aerobot architectures. I'd never heard of nor thought of some of these architectures.

https://dartslab.jpl.nasa.gov/References/pd...TitanVeinus.pdf

We are, apparently, about three months away from finding out whether Venus will prevail in the upcoming Discovery mission selection, and the ESA decision on Envision was said, in 2018, to be expected "in 2021." So the next few months will have profound impact on the course of Venus exploration, with anywhere from zero to three missions in the balance depending on those decisions.

[mcaplinger]

As a non-mechanical engineer, I nonetheless share antipode's sense that a cable more than 20 km long seems to introduce some serious worries about practicality.

To put it mildly. At any rate, most of the concepts are just for a balloon that can change altitude by various means (see https://www.lpi.usra.edu/vexag/reports/Venu...ssion_FINAL.pdf sections 3.2.3 and B.2.8.1 for one such concept).

[Gerald]

I was wondering whether any fiber is known to be strong and heat-resistant enough, and found aramids, e.g. M5, possible candidates. I'm just not sure whether thin fibers would also be sufficiently weathering resistant under the harsh environmental conditions in the Venus atmosphere.
This is before thinking about the dynamics of such a tether in a dense and stormy atmosphere.
In space in Earth orbit, at least, some tether experiments were already performed in the 1990s (SEDS-1 and SEDS-2).
(More space tether missions.)

[mcaplinger]

In space in Earth orbit, at least...

I've talked with people who worked on TSS-1 and -1R and they had quite a few stories about it. Let's just say that I don't think tether technology is quite ready for a Venus mission.

[JRehling]

Reading the afore-linked reports, I think I've been disabused of the notion that an idealized aerobot, allowing for mobility at the surface, would be implemented anytime soon. It's possible in principle, but isn't part of the VEXAG report, and the complexity of more modest aerobot concepts implies the greater complexity of surface-to-clouds-and-back aerobots.

One important pragmatic consideration: Descent is more expensive than ascent, requiring energy to compress the helium and generally being rate-limited, while ascent is comparatively cheap and easy. For hypothetical missions that would cool at height and then descend and operate quickly, this would be a problem because there would be substantial thermal load accumulating during the slow descent.

The most modest aerobot/balloon missions would be, like the Soviet Vega balloons, operating only at high altitude, studying only the "local" atmosphere with no surface science. A more ambitious option is to perform surface science from "afar", observing in IR from altitude, but here there's a tangle of tradeoffs as cooler temperatures keep the aerobot in the clouds. Operating below the clouds, for better surface visibility, means higher temperatures. The clouds themselves entail a harsh chemical environment. And altitude control entails engineering complexity with added mass and points of failure.

There are a variety of possible aerobot missions at Venus, but there isn't going to be a be-all end all option that can visit the surface multiple times anytime soon.

Airplanes create other options, with some of the same tradeoffs. One possibility, unique to Venus, is an airplane that would operate in perpetual sunlight, flying east against the atmosphere's rotation, as the planet rotates beneath it. The clouds, again, create the unfortunate tradeoff: You get solar radiation for solar power or a view of the surface, but not both.

[antipode]

Here's another Venus mission proposal from LPSC 21 that uses a long tether on a spool of some sort.

https://www.hou.usra.edu/meetings/lpsc2021/pdf/1425.pdf

While I love these designs are they doable? - we are talking about tethers 10s of km long,
being unrolled across zones with radically different temperatures and possible wind shear. I believe
wind speeds are expected to be low, but as pressures are so high....?

Would anyone like to comment on how feasible this is?

P

[stevesliva]

That would be quite a lot of tether mass. It also doesn't mention if it's a gas balloon... does that go without saying?

[vjkane]

That would be quite a lot of tether mass. It also doesn't mention if it's a gas balloon... does that go without saying?

From the abstract: "Current estimates for tow-body mass, incorporating the phase-change material, rechargeable battery power, pressure/temperature sensors, airspeed sensor, accelerometer, the near-infrared imager and a topmounted CCD camera for balloon and sky/cloud viewing on deployment and retraction, is ~2-3 kg. The tether, comprised of high-strength tensile fibers, a Gbspeed optical comm link, and a protective coating for the abrasive atmosphere, is planned to extend ~ 9 km to account for its downwind drift in the prevailing relative wind. The estimated tether mass is 3.6 kg, while the deployment/retraction system on the balloon gondola has an estimated mass of ~ 1 kg. "

[bobik]

The EnVision Assessment Study Report is now out! Selection between Theseus and EnVision not earlier than June 2021.