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First data from Venus Express !
djellison
post Dec 19 2006, 08:39 AM
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QUOTE (Phil Stooke @ Dec 19 2006, 02:00 AM) *
The key here is to look for differences between measured and modelled temps,


Or even the changes over time in the differences between measured and modelled - that would be more of a clincher.

Doug
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edstrick
post Dec 19 2006, 09:42 AM
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The trick will be to minimize interference from variable cloud opacity and any specrtral color imparted to the surface emitted near IR filtering up through the clouds by varying cloud properties. The more data the accumulate, the more they will be able to cherry-pick data with the lowest cloud interference. For precise searches for thermal hotspots, they'll have to convolve the surface emissions with the blur-function of the atmosphere, and then the blur-and-sampling of the Venus Express observations before decisively detecting a thermal anomaly.
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remcook
post Dec 19 2006, 09:56 AM
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QUOTE
But to me it looks like the second map shows even more topographic effects than the first. For instance, in the center of both maps is a bluish region, which overlies a region of high mountains called Phoebe Regio. In the right-hand map, its temperatures seem even colder than they do on the left side, so it would seem that the effects of topography have been accentuated rather than removed. It would seem I don't quite understand their topography correction.


some people already noted the thing about the 'second' image being a modelled map of topography. Just one note: in order to retrieve temperature, a correction is needed to account for topography. If you have high topography, you'll have less atmosphere in the way, so less atmospheric absorption. I think this is the correction you mention. However, the actual surface temperature is ALSO correlated to altitude, since the atmosphere is colder at higher altitudes.
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elakdawalla
post Dec 19 2006, 05:43 PM
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QUOTE (volcanopele @ Dec 18 2006, 02:48 PM) *
Nice write-up about this on your blog, Emily. However, I think that the release image shows both the actual data from VIRTIS, as well as a simulated view of temperatures based on altimetry data from Magellan, not VIRTIS data corrected for altitude.

QUOTE (Phil Stooke @ Dec 18 2006, 06:00 PM) *
Yes, the Magellan map is modelled temperature based on topography and some assumed lapse rate. The key here is to look for differences between measured and modelled temps, which might reveal hot spots - active volcanism. And Emily - your map of the Venus hemisphere is - alas - wrong! You are looking at Ovda Regio, not Phoebe. You're about 180 degrees off. Mixed up east and west longitudes?

Ooopss.... no wonder I was having a hard time finding the spots on the ESA release on that globe. I apologize for the mistakes. Not my best work at all. sad.gif Thanks for the corrections, guys.

--Emily


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scalbers
post Dec 20 2006, 04:35 PM
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QUOTE (Phil Stooke @ Dec 19 2006, 02:00 AM) *
Yes, the Magellan map is modelled temperature based on topography and some assumed lapse rate. The key here is to look for differences between measured and modelled temps, which might reveal hot spots - active volcanism.

And Emily - your map of the Venus hemisphere is - alas - wrong! You are looking at Ovda Regio, not Phoebe. You're about 180 degrees off. Mixed up east and west longitudes?

Phil


Greetings,

Oooops, I wonder if this errant globe posted for a while in Emily's blog was the same one I had sent her last week or so? I had imported the Venus map that Emily and I had put together into Celestia. I now see there was a 180 degree shift in the way I had imported the map. So when I get the chance I'll try to make a new globe in Celestia - though it'll be a couple of weeks until I'm back to my computer and email. The previous globe I made was just of the radar reflectivity. I also have a shaded/colored relief map of topography on my web site that would also be of interest to compare with the VIRTIS data. If anyone has access to Celestia in the meantime, feel free to give these maps a try.


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Phil Stooke
post Dec 20 2006, 05:37 PM
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The VIRTIS map from ESA is labelled with negative longitudes, with -90 at center. If you just enter 90 without noticing the sign you get your 180 shift. Curse the backwards rotation of Venus!

Phil


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edstrick
post Dec 21 2006, 08:06 AM
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"... Curse the backwards rotation of Venus!"

I'm having fun thinking of worse.. how about a planet with an IMAGINARY rotation. (sqrt(-1))

We apparently have small riged-body asteroids with 2 spin axes, I think Toutatis is one. Does a tumbling spin, like an American Football.
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