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Venus Express
tedstryk
post Apr 12 2005, 06:56 PM
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If all goes well, Venus Express will be a major topic for discussion in this forum a year from now. Does anyone know how good the surface coverage will be from VIRTIS and VMC? My understanding is that VIRTIS will obtain low resolution multispectral maps, and that VMC will, in addition to cloud monitoring, have one channel that can see the surface, but I don't know at what resolution or at what quality. It will be nice to have some non-radar images of Venus' surface besides the Venera snapshots and the shadowy images from Earth and Galileo's NIMS.

Ted


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Guest_BruceMoomaw_*
post Apr 20 2005, 10:31 AM
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See my new note on the "Radar on Venus Express?" thread, Ted. I may be able to get you some more precise resolutional data later on if I can find the time. (However, VMC -- unlike VIRTIS -- cannot see the surface; it's entirely for UV cloud top patterns.)
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tedstryk
post Apr 21 2005, 03:16 AM
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Actually, VMC will have some limited capabliity to detect the surface. My source on this is the ESA mission documentation. See below:

3.7 VMC (Venus Monitoring Camera)
Precursors. Imaging of the Venus disc at different wavelength was carried out by the Pioneer Venus orbiter, during the fly-bys of Mariner-10 and Galileo, and from the ground. These data was used to study the atmospheric dynamics at the cloud tops (UV), to investigate the thermospheric dynamics (UV, visible, and near-IR airglow), to map the surface brightness and to study cloud opacity variations (near-IR). However, these observations lacked global spatial and temporal coverage as well as spatial resolution. At the same time they demonstrated the power of the global imaging in the study of dynamical processes in the Venus atmosphere.
VMC/Mars Express. The Video Monitoring Camera (VMC) onboard the Mars Express is a monochrome wide-angle CCD camera that was designed to take the video sequence of Beagle-2 lander leaving the Mars Express spacecraft at Mars.
VMC/Venus Express. The Study Team has recommended to modify the Mars Express camera into a wide-angle multi-channel Venus Monitoring Camera. The modification will consist of adding several narrow band filters in the UV, visible, and near-IR spectral ranges that would allow the camera to provide support imaging for the whole mission, achieve additional science goals, and contribute to the public outreach programme. Preliminary study showed that the modification of VMC will not specify additional requirements to the Mars Express bus and will be fully compatible with spacecraft interfaces. More detailed elaboration of the technical, programmatic, and financial issues related to the VMC modification and accommodation on the spacecraft will be done by the VMC team, Astrium, and ESA during the pre-Phase B study in the beginning of 2002 if the mission is approved. The modified VMC will be prepared in parallel with available VMC/Mars Express in order not to jeopardize the schedule of the mission. In case of failure to modify VMC in time VIRTIS will be able to cover significant part of the VMC goals so that the achieving of the mission objectives would be secured.
The VMC camera will be capable of achieving scientific goals in atmospheric dynamics and surface studies by means of global multi-channel imaging. An example of UV image expected from VMC at Venus is shown in Figure 2.2. Sequence of such images would allow one to visualize the motions of the cloud tops and to study the general circulation and wave phenomena at the altitude of ~70 km. Images of the Venus disc taken every 30 min will be used to create movies of the cloud motions and propagating waves that would be extremely valuable for investigation of the atmospheric dynamics. Figure 2.6 shows an example of image that VMC will take in the visible at night. The monitoring of airglow patterns that originate at 90-110 km is an efficient tool to study the dynamics of the Venus upper atmosphere. The VMC observations in the 1 m transparency “window” will give the images similar to those shown in Figures 2.5 and 2.9. These images have two types of features. Some of them belong to the surface and result from the temperature and emissivity variations. Second type of markings originates in the main cloud deck and indicates cloud opacity variations. The movies based on such imaging will be used to study global atmospheric dynamics at ~50km.
To summarize, VMC will fulfill the following scientific goals:
• Support imaging, i.e. global imaging context for the whole mission;
• Observations of the global cloud motions in the UV and near-IR spectral ranges;
• Study of distribution of the unknown UV absorber at the cloud tops;
• Monitoring the UV and visible airglow and its variability as dynamical tracer;
• Mapping the surface brightness temperature distribution and search for volcanic activity.
Besides important scientific goals the VMC imaging and movies will significantly contribute to the public outreach programme.


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Guest_BruceMoomaw_*
post Apr 21 2005, 05:34 AM
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You've caught me -- I was completely unaware of VMC's near-IR sensitivity. Very embarrassing.
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Mode5
post Apr 21 2005, 05:53 AM
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To the powers that be, thank you for creating this forum. It is the first I heard of this mission.

I am fascinated by Venus and looking forward to it now. It sounds like they are interested in studying the atmosphere extensively. Some of the questions they want to answer:

"What are the global characteristics of the atmosphere?"
"How does it circulate?"
"How does the composition of the atmosphere change with depth?"
"How does the atmosphere interact with the surface?"
"How does the upper atmosphere interact with the solar wind?"

The understanding and possible control/conversion of greenhouse gasses on Venus could directly benefit us on Earth. Terraform Mars? Too easy; I say we go for Venus! wink.gif

Here are some excellent Magellan images of the surface.
http://www2.jpl.nasa.gov/magellan/images.html
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Gsnorgathon
post Apr 21 2005, 07:08 AM
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Ted - do you have a link for the ESA mission doc(s)?
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tedstryk
post Apr 21 2005, 09:17 AM
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http://megasn.obspm.fr/VEX_MDR51.doc

It is a bit dated in terms of VENSIS still being listed, but I don't think anything lese has changed.


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djellison
post Apr 21 2005, 09:26 AM
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I wonder if the effects of looking thru narrow spectral bands will result in the sort of quality we get at Titan - or something a bit better than that

Doug
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tedstryk
post Apr 21 2005, 09:51 AM
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Hard to tell. It is sort of like Pre-Cassini Titan, in that the limiting factor in all images we have is the resolution of the detector, so we don't know just how well we will be able to see. I will research this a bit more and see if I can dig up any speculation. Still, if Venus Express can take images at Cassini/ISS Titan resolution, they will look even more spectacular, because Venus is so much larger. And at last we will have some global multispectral data (although some data to this effect has been assembled from different Radar systems (PVO, Magellen, Venera, and the earthbased collection).

Anyhow, it seems the VMC, while it is a clone of the "Beaglecam" on Mars Express, seems to be hav converted in to quite a good little science instrument. Here is the info from the regular Venus Express website:
http://sci.esa.int/science-e/www/object/in...bodylongid=1448


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Guest_BruceMoomaw_*
post Jun 23 2005, 12:06 AM
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I can dig up some stuff on this for you, given a little more time (sorry it took me so long to even notice the question). As I recall, they're hoping for a resolution of roughly 30-50 km in VIRTIS' near-IR surface maps at Venus' poles, where it will be best -- but that may be just for its possible mineral maps, with the resolution of its actual albedo maps being a lot better.
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remcook
post Jun 25 2005, 08:28 PM
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I believe the spectral 'windows' are much less clear than for Titan, but for Galileo NIMS, some people have made temperature maps of the surface, clearly showing topography. quite cool cool.gif
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edstrick
post Jun 26 2005, 07:02 AM
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My understanding is that the topographically related infrared brightness variations seen by Galileo at Venus were diffused through the lower atmosphere and then the dense middle cloud deck.

VIMS' middle infrared visibility of Titan's surface is quite good, compared with poor visibility and high amounts of diffuse scattering of reflected light in the 1 micrometer 'window" as seen by the Cassini imaging system.

My understanding is that at Venus, the atmosphere has no non-scattering transmission till you reach microwave wavelengths. Basically, imagine holding a sheet of blotchy waxed paper 50 km above the planet's surface and examining the diffuse patterns on the waxed paper from variable amounts and colors <spectral emissivity variations> of the surface below. The blotches will be constantly varying with time and location, but the color and brightnesses of the glow from beneath will be constant, and the color especially, can be separated from the blotchy cloud patterns <which themselves are interesting>
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Guest_Richard Trigaux_*
post Jun 26 2005, 08:06 AM
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QUOTE (tedstryk @ Apr 21 2005, 09:51 AM)
It is sort of like Pre-Cassini Titan, in that the limiting factor in all images we have is the resolution of the detector, so we don't know just how well we will be able to see.


I think the main limiting factor in Cassini was not the instruments themselves, but the radio bandwidth available, together with very brief observation opportunities. This was all the more true for Huygens, which images were ridiculously small and tremendously compressed.

With Venus we have more solar power, and a much shortest distance. And, in orbit, we have the possiblity to take hundreds of images of the same surface part, and so to statistically eliminate the effects of cloud features.
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edstrick
post Jun 26 2005, 10:31 AM
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On Cassin, the VIMS is the best instrument we could design with early 90's mid-infrared imaging technology.

We now have real mid-infrared imaging detectors. Not 10 megapixel, but still real camera chips, that can take quality images with really good resolution in the mid-IR (1 to 5 micrometers, more or less). We just @#$@# didn't back then.
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maycm
post Jul 8 2005, 12:49 PM
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An update....though not much new information.

http://www.spacedaily.com/news/venus-05a.html
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