Regarding the few images released after the 6/5/2007 Messenger flyby of Venus:
http://photojournal.jpl.nasa.gov/catalog/PIA10124
The image caption states that 614 images were acquired. Are these available?
After all these missions, there is still a lack of (available) visible-light (non-UV) images of the 2nd rock.
The best one I've seen is this Mariner 10 attempt at a true-color image from its Venus flby. It was produced by Ricardo Nunes from Mariner's clear and blue filters.
Here's the URL for this and other Mariner 10 images by him:
http://www.astrosurf.com/nunes/explor/explor_m10.htm
That version did not correct for the nonsquareness of the pixels, so looks oval (and yellow). I like http://www.planetary.org/multimedia/space-images/venus/global-view-of-venus-from.html. Also, http://www.planetary.org/multimedia/space-images/venus/venus_messenger_3447783055_7201387b94_o.html.
That orange version is some derivative of my original image.
The original shows a gibbous Venus (Mariner 10 doesn't have that much distortion, the camera system is similar to Voyager's) and colors closer to Malmer's version.
Mariner color data comes from Clear and Blue filters only.
I subtracted the Blue data from the Clear (panchromatic) channel, thus creating a synthetic yellow chanel.
Some interesting results also come from Venus Express ( http://www.astrosurf.com/nunes/explor/explor_vex.htm ):
I feel that all those images hold up quite well.
Some overall brightness and color variations are visible.
The general tone is yellowish, but it depends a lot on the actual processing, image gamma etc.
Thanks everyone for the images and links. But this:
Interesting. I hadn't seen that Messenger image myself. Had any comment been made about ground visibility with that image? Fascinating!
You can't see the surface in visual wavelengths.
The "atmospheric windows" are on the IR bands.
To view details on the clouds, simply use images on the UV band. Much better than trying to process visible images.
An interesting mission for that was Pioneer Venus.
I've tried to put together a small image library of full disk UV images:
http://www.astrosurf.com/nunes/explor/explor_pvenus.htm
On this case there might be some geometric distortion, since the "camera" was a Photopolarimeter, just like on P10 and P11.
As 4throck says, that image is not showing the surface.
If somebody wanted to convince me otherwise, I would want to know exactly which part of the planet was facing the spacecraft at that time. A general resemblance to one small feature is not nearly enough.
Sorry!
Phil
Very much appreciate the Messenger color Venus picture, Emily. The sharp edge of the limb emphasizes the featurelessness nature of the upper cloud deck very effectively. If there was something to see, it would be there.
Thanx very much for all your help here.
Here's my best image of Venus, taken with a Celestron 6se last month:
Amateurs have turned up some very impressive results in UV and IR, but in visible light, there's not much difference between so-so, pretty good, and the best efforts.
I've played around with projecting this into a map, then projecting the map back into a sphere to create a full Venus image, but one has to make a good model with Hapke parameters to do that right. And then, you could get a nice full Venus image. Which, to spoil the surprise, is going to be a white circle. You may as well take a Voyager image of Uranus and desaturate the color away and you'll get almost the same result.
Nice image!
Again I agree. You can get good earth based images of Venus. Measure of quality is sharpness of the limb.
For that you should image when the planet is high, during the day :-)
Here, an amateur used IR to image Venus's night side. Whether or not surface features are visible, I'm not sure.
http://www.skyandtelescope.com/astronomy-news/amateur-images-venuss-surface/
Galileo used IR to map Venus topography - not leading to any useful improvements on the mapping of the planet, I don't think, but rather a nice demonstration that it's possible. Then Venus Express certainly improved on that work, collecting possible evidence of an active volcano.
http://sci.esa.int/venus-express/46816-surface-warmth-on-a-volcano-on-venus/
If you like those linear features, you'll love these! Venus by Percival Lowell, 1896:
http://www.skyandtelescope.com/wp-content/uploads/spokes_l.jpg
Phil
the lack of details in the "Human visible" and the over all unidirectional flow in the UV
is the reason i use a 100% synthetic ( fractal based ) cloud map for Venus
the Pioneer Venus images in PDS
http://pds-atmospheres.nmsu.edu/Venus/venus.html
and on
http://www.astrosurf.com/nunes/explor/explor_pvenus.htm
are great ,-- but rather OLD
I suspect that with the right filters, some details on Venus would be visible to a human observer appropriately located, but a human looking at Venus from nearby with no filters at all would be on the verge of pain from the intense brightness. I suppose you could simulate it by using a mirror to reflect sunlight onto something white on a bright, sunny day so that there was a spot with double sunlight. It's bad enough looking at snow on a sunny day, and Venus sunlit clouds are about twice as bright.
But, there is contrast at the violet end of the spectrum, just barely in the visible range, and so a person with the right "sunglasses" could see detail. But without those, the SNR would be problematic due to the greater luminance in the rest of the spectrum. And, as I mentioned above, it would be somewhere between blinding and painful.
It might be interesting to consider what polarizing filters could achieve. When I'm wearing sunglasses, I often see sun dogs in the sky and notice that without the shades, the sun dog is essentially invisible.
Lowell was too creative on his drawings and interpretations.
On that illustration he was seeing the Y shaped pattern, and that is real.
But he interpreted the shadings as linear features, and put those into the sketch.
As always, one should never over interpret low SN data :-)
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