Venus Express Radar? Options

[Bubbinski]

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?

[remcook]

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/in...fobjectid=33964

[djellison]

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

[Guest_BruceMoomaw_*]

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.

[Mode5]

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.)

[remcook]

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.)

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.

[djellison]

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

[Guest_BruceMoomaw_*]

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.

[djellison]

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.

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

[Guest_BruceMoomaw_*]

[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).

[JRehling]

________________________________________

[...]

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).

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

[Guest_BruceMoomaw_*]

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.)

[Mode5]

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

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)

[Guest_BruceMoomaw_*]

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.

[Guest_BruceMoomaw_*]

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 .