Venera-13, Venera-14 Lander Images, Images generated from raw digital telemetry |
Venera-13, Venera-14 Lander Images, Images generated from raw digital telemetry |
Guest_DonPMitchell_* |
May 5 2006, 07:40 PM
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#1
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Guests |
Here are images I generated from the 9-bit Venera-13 and Venera-14 data. Most of the work was spent combining three or four transmissions from the spacecraft, each with an independent set of digital noise. In some cases, scrambled regions of images were restored by recalculating the 10th parity bit, and shifting the bit stream. In particular, I resurrected a new section of the image on Venera-14 Camera II on the left side. I managed to distill out one very high quality copy of the full transmission from each of the four cameras.
Next, there is the problem of linearizing the camera response. The camera response curves published in Cosmic Research are wrong, or at least they do not extend into the darker range where a lot of the actual Venus imagery lies. You can prove they are wrong from the calibration wedges, viewed through the four different filters. Correct generation of true log response would result in wedge profiles that are exactly offset from one another. Some recent work on camera self-calibration in the computer-vision community points the way to reconstructing response curves, and when applied to the Venera images, the result is very pleasing. Round objects, like the elbow joint of the penetrometer, look round, not flat, details in shadows appears out of the blackness of the original Russian images, and some additional hills on the horizon appear out of the formerly white sky. The full transmission consisted of several passes of the camera scanner, back and forth, across the scene. These four panoramas are combinations of up to five black-and-white images (clear filter), and a number of red, green, and blue-filter images. In Lab color coordinates, I extracted the ab channels from the red/green/blue images, and added them to the much higher quality B/W images. You can see that when making scans through the clear filter, the camera covered a wider area, the uncolored regions are just where the RGB data did not exist. Most of the blue images are black, due to a sudden drop-off in the camera response. There are probably a few areas near the bright horizon where the real RGB ratio can be extracted...a project for someone someday. I've been too busy with my book and my company in Seattle to completely finish what I wanted to do. The color is still not correct on any Venera surface images. But the color filters in the camera were balanced with gray filters to be somewhat correct. I am awaiting one last key piece of data -- the spectral response of a color filter that was in front of the calibration wedge. With that in hand, an absolute color calibration would be possible. Venear-13, Camera I (short program): Venera-13, Camera II (long program): Venera-14, Camera I: Venera-14, Camera II: |
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Guest_BruceMoomaw_* |
May 10 2006, 02:58 AM
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#2
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The next Venus's visit time by any other spacecraft would be Messenger's flyby on October 26, 2006. This spacecraft is carrying seven scientific playload, which are specially designated to study Mercury. However, some of its scientific instrument would be useful during its Venus' fly-by short time:
There will be no science observations from Messenger during its first Venus flyby because, by bad luck, this occurs near solar conjunction and its radio signals will be blocked -- but they have a massive science campaign planned during the second Venus flyby, including the use of several instruments which you predicted would not be used: http://www.lpi.usra.edu/vexag/Nov2005/MESSENGER_VEXAG.pdf |
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May 12 2006, 07:36 AM
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#3
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
There will be no science observations from Messenger during its first Venus flyby because, by bad luck, this occurs near solar conjunction and its radio signals will be blocked Again, I have to say that's a pretty lame excuse for skipping science on the first flyby. The s/c is performing pre-recorded observations anyway and I don't get it why they simply don't choose to delay the science playback a week or two? But the disk of the Sun is never visible at the surface of Venus or am i wrong? If, as Bruce suggests, even the small pebbles have sharply defined shadows, that implies a well defined, point-like light source. So yes, the sun should be clearly visible as a round disk from the surface, though it's likely the rest of the sky is pretty bright as well. -------------------- |
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Guest_DonPMitchell_* |
May 12 2006, 12:08 PM
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#4
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So yes, the sun should be clearly visible as a round disk from the surface, though it's likely the rest of the sky is pretty bright as well. No, I do not believe so. Take a look at the overhead-view projection I posted. The illumination on the surface is form the uniformly bright hemisphere of the sky, no point source. Between clouds and rayleigh scattering, I do not believe the disk of the Sun is ever visible on the surface of Venus. I'm planning to do a multiple-scattering montecarlo simulation of this soon, because I want to see if the color of the sky might be different. The spectrum of the Zenith was measured, and the panoramic cameras see some of the horizon, but it is not obvious that the two parts of the sky are the same color. [attachment=5558:attachment] I generated this image a while ago, simulating scattering effects with data from Venus Standard Atmosphere. The image of Venus is rendered with 5 % of the actual density! That is because at full density, at this scale (200 km x 200 km squares), the true Venus atmosphere looks almost opaque near the surface. |
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May 12 2006, 12:23 PM
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#5
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
No, I do not believe so. Take a look at the overhead-view projection I posted. The illumination on the surface is form the uniformly bright hemisphere of the sky, no point source. Between clouds and rayleigh scattering, I do not believe the disk of the Sun is ever visible on the surface of Venus. I was merely following on Bruce's assumption. It did strike me a bit odd the sun would be visible through the thick cloud cover and enormous atmosphere. I generated this image a while ago, simulating scattering effects with data from Venus Standard Atmosphere. The image of Venus is rendered with 5 % of the actual density! That is because at full density, at this scale (200 km x 200 km squares), the true Venus atmosphere looks almost opaque near the surface. This is awesome! This is the sort of rendering I see a lot of space simulation programs struggle to achieve (Celestia, Orbiter...). How did you produce this result and how computationally expensive was it? -------------------- |
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Guest_DonPMitchell_* |
May 12 2006, 12:42 PM
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#6
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This is awesome! This is the sort of rendering I see a lot of space simulation programs struggle to achieve (Celestia, Orbiter...). How did you produce this result and how computationally expensive was it? Thanks. Actually, computer graphics research is my "day job". This was a special purpose renderer done in C++. It's a steadily growing program called "BookGraphics", which contains a large number of totally unrelated subroutines, each of which makes a figure for my book. :-) |
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May 12 2006, 01:44 PM
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#7
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Senior Member Group: Members Posts: 2488 Joined: 17-April 05 From: Glasgow, Scotland, UK Member No.: 239 |
Don:
You mentioned your book - can you tell us more about it, please? I'm sure it's one I *need* to buy! Bob Shaw -------------------- Remember: Time Flies like the wind - but Fruit Flies like bananas!
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Guest_DonPMitchell_* |
May 12 2006, 04:21 PM
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#8
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Don: You mentioned your book - can you tell us more about it, please? I'm sure it's one I *need* to buy! Bob Shaw I decided to write a book instead of just updating my website about the Soviet Exploration of Venus. I have a lot more material, photos and interviews with scientists, etc. I won't make back the money I've spent, which wasn't the point anyway. A problem with websites is they are not acknowledged officially, never reviewed, discussed or cited in the literature. You can't inject your work into the arena of public discourse unless you write a book, made out of paper and ink. Just a weird fact even in our modern times. |
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May 12 2006, 04:34 PM
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#9
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Member Group: Members Posts: 444 Joined: 1-July 05 From: New York City Member No.: 424 |
Verba volant, scripta manent.
TTT |
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