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Why no VeRa images from VEX ?, I remember Magellan's radar pics
GravityWaves
post Apr 12 2007, 08:21 AM
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See lots of stuff about Atmosphere, Wind, Clouds but nothing on the surface of Venus
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djellison
post Apr 12 2007, 09:13 AM
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The clue is the word radar.... VEX is not equiped with radar to see through the clouds of Venus. VIRTIS (the IR camera) can infer surface properties at some wavelengths, but direct observations of the surface and virtually impossible. VEX is there to study the Atmosphere, Wind and Cloud, not map the surface with radar.

Doug
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cndwrld
post Apr 12 2007, 10:13 AM
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A couple things on this.

VeRA can't image the surface, but it can do bi-static radar (BSR) observations of the surface. You point the big antenna at the surface, push out as much energy as you can, collect the reflection on Earth, and then puzzle over the results. It gives information on surface roughness and electrical properties, but no cool pictures. It also requires a very exact geometrical relationship between the spacecraft, the point on the surface of interest, and the receiver on Earth. On Venus Express, that orientation doesn't occur very often, so only about three or four BSR observations have been done so far. None of the results have been published so far, and the data is said to be under evaluation. The team is really understaffed, so planning observations takes up almost all their time, with nothing left for processing. They're looking into ways to improve that.

BSR experiment #1 (Maxwell Montes): successfully conducted despite VEX survival mode shortly before the experiment. The observation was only accomplished because the flight control team did an exemplary job of recovering from the safe mode the day before the BSR.
BSR experiments #2, #3: cancelled because of sun interference with other experiments.
BSR experiment #4: scheduled for 18 and 20 March 2007
BSR #5: planning completed for mid-June observation
BSR #6, 7: in the planning list for August and November


As was mentioned, the imaging spectrometer VIRTIS is being used to get images of the surface. More at:
http://www.esa.int/SPECIALS/Venus_Express/SEM4KXPJNVE_0.html

This is done in the IR, through a very dense atmosphere, by indirect methods. So the resolution is extremely low, and the method is still being worked on. But it gives the possibility of detecting large scale thermal events, such as volcanic activity. From this one can get cool pictures, but without great detail. Given that no active volcanism has been detected before, finding it would be really important.

The PFS instrument was properly designed to do this surface thermal analysis, but unfortunately it is not working. The work with VIRTIS is attempting to make up for some of what was lost.

Hope that helps.


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tedstryk
post Apr 12 2007, 11:57 AM
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Will it simply be spectral analysis of the reflection, or will some altimetry be possible? I know some basic profiles were made using Venera 9 and 10 bistatic radar. I figure that, especially for Maxwell Montes, being able to compare the radar's spectral and reflectance characteristics to altitude would be important.

Ted


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cndwrld
post Apr 12 2007, 01:07 PM
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I can't speak with ANY authority about what they can get out of it. But I've never seen any mention, in anything that came across my desk, about references to altimetry. Doesn't mean they won't do it, though. I just don't know. Sorry.


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Littlebit
post Apr 12 2007, 05:36 PM
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QUOTE (cndwrld @ Apr 12 2007, 04:13 AM) *
None of the results have been published so far, and the data is said to be under evaluation. The team is really understaffed, so planning observations takes up almost all their time, with nothing left for processing. They're looking into ways to improve that.

mmmmm Venus Express at-home rolleyes.gif
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