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Posted by: Bubbinski Apr 20 2005, 03:16 AM

Ah, I notice there's a bunch of new forums on this site. So I figure I might as well inaugurate at least one of them.

I see that the Europeans are going to launch a sister ship to Mars Express, only this one's going to Venus. I've checked out the ESA web site and it mentions that the probe will study the atmosphere of Venus as well as measure the surface temperatures. But the site didn't say much more, nor did I see a breakdown of what instruments the craft had. Is there going to be a radar on that spacecraft as well, to make follow up observations of targets Magellan caught? Or is there going to be a camera similar to Mars Express, only targeted toward the atmospheric clouds? And are there going to be any atmospheric or surface probes launched from the main craft, a la Beagle 2?

Posted by: remcook Apr 20 2005, 08:33 AM

the answers are no and no.

Venus express has instruments that are 'copied' from the Mars Express and Rosetta missions. Here's a list:

http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=33964

Posted by: djellison Apr 20 2005, 08:46 AM

(PS - i moved this into the Venus Express subforum )

Posted by: BruceMoomaw Apr 20 2005, 10:25 AM

Nope, no entry probe and no radar. The original design DID call for a copy of Mars Express' subsurface sounding radar on Venus Express. While there's no subsurface water to be found on Venus, this instrument could probe several km below the surface and identify lava flows and other strata, which could be extremely valuable in understanding Venus' still-puzzling geological history. But JPL would have had to provide part of the cost of this "VENSIS" instrument -- and NASA said no. So, no radar.

However, the single most important instrument on Venus Express -- the VIRTIS near-IR mapping spectrometer -- may provide a really surprising amount of information on Venus' surface geology, thanks to the existence of 6 narrow near-IR spectral windows that allow the orbiter to peer through the clouds all the way down to the surface. These will allow it to obtain really high-resolution surface temperature maps and also maps of near-surface trace gases, thus allowing a search for volcanic activity. Moreover -- although there are still uncertainties about the technical feasibility of these two moves -- it may also allow some surface compositional mapping of Venus, at least near the poles (allowing a search for four or five scientifically important minerals); and (most remarkably) an attempt to carry out Venusian seismology FROM ORBIT, since calculations indicate that modestly large quakes may produce pressure waves in Venus' very dense atmosphere big enough for VIRTIS to detect, and even allowing some geographical localization of the quake epicenters. We'll see.

VIRTIS, by the way, will definitely provide fairly high-quality images of Venus' cloud patterns in a number of different wavelengths, which in turn will allow the patchy patterns of its middle-altitude clouds below the solid upper cloud top to be observed. Indeed, that is one of its major science goals -- because, by precisely tracing the wind-driven movements of such clouds at various altitudes, it may finally provide enugh detailed information on Venus' winds to solve the still puzzling question of exactly what the mechanism is that drives its atmosphere's high-speed "superrotation". It will also look for lightning, although the evidence now points strongly against the latter. And Venus Express also carries "VMC", a little camera -- a copy of the one on Mars Express that got that last shot of the ill-fated Beagle drifiting away from the craft -- which has been modified to image the UV cloud patterns at the top of the cloud deck for comparison with VIRTIS' lower-altitude observations. Really, this could be a very interesting mission, thanks mostly to that one instrument VIRTIS.

Posted by: Mode5 Apr 21 2005, 06:12 AM

Isn't radar imaging far more accurate than that of infra-red? I don't really expect to see too much from a layman's point of view. I hope I am completely wrong. It's a great idea they have to use some of the left over equipment from the Mars Express mission. I wonder if we have a little radar sitting in a back room some where we can "loan" them. (I know it's too late for that now.)

Posted by: remcook Apr 21 2005, 08:32 AM

MAghellan was a massive spacecraft and the only thing it had was a radar. So, yes it is far more accurate, but also much more power consuming. But, the information you get from a radar is limited. You can get great topography and that kind of thing, but it is hard to say something about for instance temperature. Infrared will give complementary information about the surface, maybe even determine it composition better.

Posted by: djellison Apr 21 2005, 08:36 AM

Essentially we HAVE the radar dataset and unless we go back with some enormous power-eating SAR to remap venus - it makes more sense to go back and start looking in other ways.

Doug

Posted by: BruceMoomaw Apr 21 2005, 01:09 PM

There is very serious consideration being given by the US to a mission -- not a wildly expensive one, either; it may be flyable within a Discovery Program budget -- to aerobrake a US orbiter into a low circular orbit around Venus sometime during the next decade and map it radarwise with really high resolution (maybe 30 meters or less), and with emphasis on obtaining 3-D topographical data. If Bruce Campbell's concept for a similar SAR mapper of Mars (rejected last time as a Mars Scout proposal) can be made to work, it could be extremely easily adapted for this mission.

The reason Venus Express doesn't include any such system is simply that it was selected precisely because the ESA saw an opportunity to fly a very low-cost science mission of some sort using a clone of Mars Express in 2005 and put out proposals as to possible scientific uses for such a craft, with this being the chosen one. Minimizing costs in this way, however, requires an absolute minimum of modification to the original Mars Express spacecraft and mission design. And even then, VEx actually got cancelled once and reinstated -- and it was reinstated, in a programmatic form that made it harder to cancel, just before the ESA discovered new budget problems that forced them to cancel their planned Eddington astronomy mission (a higher-priority mission scientifically) and certainly would have killed VEx instead had they been discovered just a few months earlier. In short, this is a very lucky mission.

Posted by: djellison Apr 21 2005, 01:21 PM

And then - in a backwards ESA move - I suppose a clone of the Venus vehicle could be flown to mars at a later date - or vice versa. Are Mars mission precluded from Discovery money?

Doug

Posted by: BruceMoomaw Apr 21 2005, 03:14 PM

[quote=djellison,Apr 21 2005, 01:21 PM]
[quote=BruceMoomaw,Apr 21 2005, 01:09 PM]If Bruce Campbell's concept for a similar SAR mapper of Mars (rejected last time as a Mars Scout proposal) can be made to work, it could be extremely easily adapted for this mission.
[/quote]

And then - in a backwards ESA move - I suppose a clone of the Venus vehicle could be flown to Mars at a later date - or vice versa. Are Mars missions precluded from Discovery money?
________________________________________

Yes, they are -- including missions to the moons of Mars (a fact about which there have been complaints). There is, however, nothing to keep a similar spacecraft from being proposed separtely for Discovery and Mars Scout missions -- in fact, VESPER (one of the recent finalists for a Discovery mission) would have explored Venus using a mildly modified copy of the MCO/Odyssey Mars orbiter (which is also used for the MARVEL Mars Scout finalist concept and for Campbell's Mars SAR orbiter).

VESPER, by the way, was also proposed again for the last, abortive round of Discovery selections (with a small "VAMP" entry probe added for atmospheric composition data) despite the fact that Venus Express has now stolen a lot of its scientific clothes -- and it will, I imagine, be proposed again for the imminent next round of Discovery selections (which will have a new $450 million cost cap to correct the problem that prevented selection of any Discovery mission last time).

Posted by: JRehling Apr 21 2005, 05:48 PM

The unmentioned factor in Venus exploration is that a big New Frontiers mission is reserved for Venus, and it will probably be the third or fourth New Frontiers mission to fly. Any experiment which is an easy tag-along with this "VISE" mission is probably going to have no chance of making it through the Discovery door. The problem is, the scope of VISE is not yet determined, and because its main goals will squeeze tightly (if at all) through the New Frontiers cost cap, the hazard is that VISE's presence will stifle any initiative for pre-VISE Venus exploration, leaving some important goals un-met when VISE doesn't get around to them either.

What you can say for certain about VISE is that it will perform surface mineralogy in one or more sites on Venus's surface, with the plurality of visited sites due either to mobility of a single (balloon-lofted) craft or multiple stationary landers. It would be wonderful if VISE could also perform two other experiments: (1)multispectral imaging of the surface from altitude (but beneath the cloud deck) somewhat like Huygens's DISR did at Titan; (2) detailed measurements of isotopic abundances that could tell us a great deal about the evolution of Venus's (and Earth's!) atmospheric evolution.

A great, and new document online discusses Venus-related planning at NASA. See:

http://www.lpi.usra.edu/vexag/Venus_Roadmap.pdf

Posted by: BruceMoomaw Apr 22 2005, 02:07 AM

One thing to keep in mind about VISE is that it has already had to be drastically trimmed down from what the Decadal Suvey originally recommended -- which included a test of a balloon inflated on Venus' surface to lift it off the surface and back into the clouds. This would be a test of high-temperature balloon technologies that would be useful both for a repeated-landing Venus travelling aerobot and for a Venus sample-return mission (although the latter project will be so titanic in cost compared to its science return that I think it will be a very, very long time before we see it). This part simply could not be done within the current $700 million New Frontiers cost cap -- just as the Decadal Survey's recommended combination Jupiter polar orbiter and multiple entry probes can't be done within that cap and will have to be split into two separate NF missions.

Larry Esposito's "SAGE" concept for the VISE mission (although he's very close-mouthed about its details) called for 2 or 3 landers that would simply touch down and do their analyses on the surface without taking off again (plus at least one separate small cloud-layer balloon for wind pattern studies). And even SAGE didn't make it into the list of NF finalists, probably because the review board thought it too ambitious for the estimated cost. I think it very likely that the atmospheric part of VISE -- specifically, detailed analysis of atmospheric trace gases and isotopes on the way down -- can and will be split off from the surface studies part onto a separate Discovery-class entry probe (such as the Division of Planetary Sciences had recommended before the Decadal Survey report came out). A single mission of this sort could do an excellent job on Venus' atmosphere, after all -- whereas understanding its surface will take a number of separate landers, whose necessarily limited experiment payloads can then be focused entirely on surface compositional analysis and imaging. (One thing that would be nice to cram onto such landers -- if we can do it -- would be an in-situ age-dating instrument to confirm whether or not Venus really did undergo total catastrophic global resurfacing about half a billion years ago.)

Posted by: Mode5 Apr 22 2005, 07:33 AM

True; I was looking at the GOES I/R imaging, it definitely will capture the atmosphere's movement and should be be fairly detailed. I don't expect to see much of the surface features with the IR. Am I wrong about that? (hopefully)

Posted by: BruceMoomaw Apr 22 2005, 10:07 AM

You'll see them in a somewhat fuzzy way -- the 6 near-IR bands which reach all the way to Venus' surface (an amazing and totally accidental discovery of the early 1980s) allow photos that map the planet's nightside surface temperatures, and so clearly show its higher-altitude regions. (During its Venus flyby back in 1990, Galileo got some very nice global images of this type with its NIMS.) The open question is whether they will reveal anything else about the surface, such as allowing mapping of some of its minerals -- but at a minimum they'll allow a search for active volcanism.

Posted by: BruceMoomaw Apr 22 2005, 10:14 AM

One such Galileo image -- taken in the 2.3-micron window, and compared with a radar altitude map of Venus' surface -- can be seen at the VIRTIS webpage at http://solarsystem.dlr.de/TP/VIRTIS_en.shtml .

Posted by: BruceMoomaw Apr 22 2005, 10:26 AM

I haven't been keeping up with this mission at all well. The webpage I just mentioned also includes a link to the VIRTIS Surface Science Working Group's site ( http://irsps.sci.unich.it/~luciam/VEX/ ) -- which turns out to be brimming over with information on the observations they hope to make with it, including a list of its surface geological targets!

Posted by: JRehling Apr 22 2005, 04:23 PM

Good discussion in this thread...
I think having an atmospheric isotopic analysis will eventually become a desirable feature of a long-term lander, since it is still an open possibility that Venus undergoes major volcanic outgassing on a regular basis. (Namely, Pioneer Venus seemed to have detected a major change in SO2 levels during the course of its mission.) We ought to see if Venus Express can repeat that result (of course, a negative needn't mean that there is no such phenomenon -- if there are such events, they may not be decadal in frequency). WRT volcanism, a high-resolution radar mapping could be interesting from the standpoint of seeing changes since Magellan (finally, turning the long lag between Venus missions into a virtue), and an exciting follow-on to such a finding from radar or Venus Express would be to send a mass spectrometer downwind of any identified source of the gases (this might be quite easy to localize if it were a large volcano) -- follow the lava, so to speak.

Another goal that seems to me to be worthwhile is to learn just enough about Venus to be able to identify possible venusian meteorites on Earth. These are certainly possible in principle, although pending an acute analysis, it is possible that any would be so rare that we are unlikely to find any. (The friction an upward-bound ejected sample would experience passing up through Venus's atmosphere at escape velocity would be a considerable barrier, perhaps all but insurmountable.)

The current roadmap excludes any future radar orbiter. The other outstanding feature is that VISE has been so downscoped that I'm not sure I see the point, except as a demonstration of technology (and it's far too expensive to justify the mission on those grounds) or as a stopgap to provide an earlier quantum boost in our knowledge of Venus before the proposed geophysical network and venusian "MER" (rover or airborne), which would both surely duplicate any VISE findings, except to add one more surface point to spatial coverage. It's hard to call the next step in Venus science urgent timewise (the US has flown only two missions dedicated to Venus since Lyndon Johnson was president).

If this is the plan they are going with, I begrudgingly conclude they should skip VISE and move directly to a next-generation Venus mission, with considerable spatial and temporal coverage rather than waste a New Frontiers mission now.

If there is any way to have a nonnegligible groundtrack of a descending geophysical station, to add some panoramic coverage during a Huygens-like descent, it seems to me an all-things to all-people "single" mission would be to build three surface stations that can last on the surface, and come away with imagery of three descent tracks, long-term atmospheric and seismic science, and upclose looks at three stationary locations. I can't see but how that would provide better science for the buck than the current plan of three huge missions before VSSR (which will almost certainly not happen before I die -- and I'm not old).

Posted by: BruceMoomaw Apr 22 2005, 06:30 PM

John Rehling: "I think having an atmospheric isotopic analysis will eventually become a desirable feature of a long-term lander, since it is still an open possibility that Venus undergoes major volcanic outgassing on a regular basis. (Namely, Pioneer Venus seemed to have detected a major change in SO2 levels during the course of its mission.) We ought to see if Venus Express can repeat that result (of course, a negative needn't mean that there is no such phenomenon -- if there are such events, they may not be decadal in frequency). WRT volcanism, a high-resolution radar mapping could be interesting from the standpoint of seeing changes since Magellan (finally, turning the long lag between Venus missions into a virtue), and an exciting follow-on to such a finding from radar or Venus Express would be to send a mass spectrometer downwind of any identified source of the gases (this might be quite easy to localize if it were a large volcano) -- follow the lava, so to speak."

We don't necessarily need in-situ entry probes to monitor that sort of thing -- the two IR spectrometers on Venus Express will monitor SO2 (and a large number of other trace gas) levels very accurately over time and with high spatial resolution, and I believe they also have the ability to profile it at different altitudes. Nor do we need isotopic analysis, as opposed to
____________

"The current roadmap excludes any future radar orbiter."

The White Paper on Venus exploration provided by the DPS to the Decadal Survey said that such a mission can very likely be flown within the Discovery cost cap -- and the intriguing recent notes from the Venus Exploration Analysis group on that part of the developing Solar System Strategic Roadmap ( http://www.lpi.usra.edu/vexag/meetings.html ) indicate that such a mission might be an alternative to VISE as the top-priority Venus mission for the 2010s, depending on how much evidence of volcanic activity Venus Express and the later, smaller Japanese "Planet-C" orbiter turn up. (The DPS White Paper also said that such a high-resolution radar orbiter could have a microwave radiometer and a trace-gas IR spectrometer added to it as auxiliary instruments to further monitor and locate active volcanism.)
_________________________________

"The other outstanding feature is that VISE has been so downscoped that I'm not sure I see the point, except as a demonstration of technology (and it's far too expensive to justify the mission on those grounds) or as a stopgap to provide an earlier quantum boost in our knowledge of Venus before the proposed geophysical network and Venusian 'MER' (rover or airborne), which would both surely duplicate any VISE findings, except to add one more surface point to spatial coverage."

I wouldn't necessarily say that. Esposito's concept would involve 2 or 3 landers on a single launch, carrying out surface composition analyses on widely different types of Venusian terrain, and including fairly detailed mineralogy. (Although -- judging from my one brief look at the list of scientific instrument PIs for SAGE that he accidentally gave me before yanking it off the public Web -- age-dating is not one of them.) It may be quite a long time before we develop the technology for any kind of long-lived or long-distance-traverse Venus mission; and even if it isn't, the detailed surface geochemical data that VISE could provide would be very valuable in further selecting the destinations for such later missions.
_____________________________________

"If there is any way to have a nonnegligible groundtrack of a descending geophysical station, to add some panoramic coverage during a Huygens-like descent, it seems to me an all-things to all-people 'single' mission would be to build three surface stations that can last on the surface, and come away with imagery of three descent tracks, long-term atmospheric and seismic science, and upclose looks at three stationary locations."

VISE is definitely supposed to provide descent and surface imaging. (In this connection, note also the "VEVA" Discovery mission that was proposed a few years ago, which would drop four small dropsondes from a long-lasting cloud-layer balloon to provide multispectral descent imaging of different kinds of Venusian terrain before their impact -- and even had little parafoils to maximize their sideways gliding distance before impact. Moreover, one description of that mission among the JPL Technical papers says that the dropsondes might be augmented with "a laser altimeter and near-IR spot spectrometer", which I take to mean that a broadband laser might allow good detailed near-IR reflectance spectra of the local minerals from these probes as well. I've remarked elsewhere about the unique difficulties in obtaining good near-IR reflectance spectra of the dayside Venusian surface without an intermittent artificial light source, since the surface is so hot that it also glows thermally in the near-IR and the two types of near-IR spectra get mixed up together.)
___________________________


"I can't see but how that would provide better science for the buck than the current plan of three huge missions before VSSR (which will almost certainly not happen before I die -- and I'm not old)."

I question whether VSSR will happen before the General Sherman Tree dies. However, there are quite a lot of possible intermediate-level Venus missions that aren't all that "huge". (I myself have always found the problem of designing scientifically cost-effective missions to explore this savage place to be a fascinating engineering problem.)

Posted by: BruceMoomaw Oct 26 2005, 12:03 PM

It turns out that Dr. Bruce Campbell thinks VERY highly of the idea of a Venusian subsurface radar sounder -- in fact, he thinks it may be the only workable way to disentangle the planet's geological history, because its high temperature may actually make age-dating its rocks in any way impractical (the first I've heard of this). For that reason, he's about to propose a Discovery-class Venus orbiter to do just that, and I intend to try to find out more about it:

http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm05&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm05%2Ffm05&maxhits=200&="P23E-05"