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Photos from the Surface of Venus
Mean_Nishka writes "I was surprised to learn that the Soviets sucessfully landed a number of probes on the surface of Venus (the probes were given the name 'Venera') in the 70's and early 80's. NASA has a small collection of images from four of the missions. The images aren't much, but offer a stunning view of the surface of Venus. You can view surface photos at this NASA site. Space.com has a great summary of the Venera program here."
I thought everyone knew about these. It's almost like never hearing that Neil Armstrong was the first man on the moon. And hey! We've got Space Shuttles now! Or at least had them.
Everyone should know all they can about space exploration. Start at the beginning. Look up the list of early launches (back in the 1960's) to the moon, Venus, and Mars. Find the first closeup. photograph of Phobos ever taken. Learn what happened to the spacecraft. Investigate the technology behind the first photo of the backside of the moon. (a portable film development laboratory and a fax machine!!!). Marvel at the precision landing of a LEM near a Surveyor. Ooogle at the footage of a Ranger crashing into the Moon.
There's a lot of shit out there, and it's important enough that any geek should be ashamed to admit they'd never heard of Venera.
If tits were wings it'd be flying around.
Venus fact sheet is here http://nssdc.gsfc.nasa.gov/planetary/factsheet/ven usfact.html
Refraction of light only occurs when it passes from one material to another and the index of refraction of the two materials is different. So, the atmosphere of venus would not distort anything.
The real answer is the cameras on the Veneras were panoramic rotating slit cameras. Nothing more complicated than that.
If tits were wings it'd be flying around.
When Russian speakers borrow foreign words, they usually keep the original gender (feminine in this case, despite the fact that the Latin nominative plural ends in -us which usually means masculine), and they usually take the root form of other cases rather than just the nominative singular ("Vener-" rather than "Venus"). In Russian, feminine nouns usually end in "-a" (or "-ya", which is a different letter). So to borrow the word Venus from Latin, Russian took the base form "Vener-" and tacked an "-a" on the end of it because it was feminine to make "Venera".
I believe genus/generis (pl. genera) is declined (has grammatical endings tacked on) in the same way as "Venus", so yes, if she were cloned there would be two Venera. (But in Russian Venera is the singular.) Penis is declined in a different way; the Latin plural would be penes.
Not that anybody's life is really improved by knowing this, of course. :-)
I am wrong. I just looked up Venus through the English->Greek dictionary, and it came back as Afroditi. I guess Venera is the plural of Latin Venus, and not Greek as I have speculated.
Here is the dictionary link:
http://www.kypros.org/cgi-bin/lexicon
Paul.
You assume the atmosphere is homogenous. Thermal differences between blocks of the atmosphere on Earth can produce refraction. It's how you get mirages.
It's also how you can sometimes "see" heat rising off objects. Warmed air rising off a hot object can have a perceptibly different index of refraction from the ambient air surrounding it. This produces optical distortion of objects viewed through the warmed air.
But then again, I could be wrong.
In a medium which is isotropic this corresponds to a straignt line since the shortest path between two points is a straight line. In a inhomogeneous medium the path of a ray of light corresponds to the path integral of the index of refraction. In the case of discrete boundaries this corresponds to straight lines between bounadries with refraction occuring at the boundary according to Snell's law (which corresponds to a minimization of the path integral).
In the case of smoothly varying indices of refraction, such as in a heated gas or a medium of varying concentration the light follows a curved path described by a minimization of the path integral, resulting in a curved path. This is not only the basis for mirages but also "lineless" bifocals. The atmoshere of Venus at one point was believed to be so dense that the curvature of these rays would make an observer think that he was within a bowl. see http://www.cosmographica.com/gallery/portfolio/po
As for light travelling in straight lines through water check out http://faraday.physics.uiowa.edu/optics/6A40.40.h
in this case the varying refraction is achieved by varying concentrations of sugar (although brine will work as well).
This gradient index effect is commonly employed within CD-rom lenses: http://www.sinopt.com/software1/usrguide54/exampl
So an example of bending rays of light is probably within arm's reach of you.
All this being said the primary source of the distortion is probably the line scan optics.
Basically, they had no idea how much light was reaching the surface. The probe wouldn't have lived long enough for manual gain control (it would have to take a picture, send it to Earth, the Russians would have to process it, adjust the gain, send the gain adjust command to the probe, repeat until a usable image comes back), so they gave the probe's on-board camera automatic gain control.
Once they got the image from the probe, they converted the raw logarithmic data into a more usable format. Then it was adjusted to be viewable by a human.
Automatic gain control:
The electronics in the camera automatically adjusted for brightness.
Logarithmic quantization:
The image data had to be digitized in order to be sent back, which requires quantization. But if you don't know ahead of time the brightness characteristics of the pictures you're taking, you don't know how subtle a difference in brightness the your digitization scheme should be able to handle, while still being able to capture the full range of brightnesses in the images. So when they digitized, which basically means that they made a table of integers and assigned a brightness value to each integer, the assignment scheme made each brightness value be some constant multiple K of the preceding value. In this way a brightness range of K^N, where N is the table size, can be captured in the digitization. This is opposed to a linear quantization scheme (like is used in digitized audio), where only a range of K*N can be represented.
Optical density:
Don't know what this means.
Linear radiance:
This is where they undid the logarithmic stuff to get numbers that their software was expecting, so they could massage their image data to get something suitable for human eyes.
Windowed sinc filter:
This is part of the massaging they had to do. It's hard to explain without going into some deeper concepts. It's basically what the smooth filter in Photoshop does.
Correcting the modulation transfer function:
I don't know. I'm an audio guy.
Gamma-corrected values:
Different displays show colors differently. The gamma value has to do with some curve that maps between brightness values and display brightness. Or something like that.
Gravity is insurmountable. It is directly related to the mass of the planet. While simulation of gravity by "centrifugal force" may be possible in space-craft it is not remotely practical for planet exploration and habitation. Most medical problems experienced by cosmonauts and astronauts are directly related to weak gravity conditions.
There are two types of planets in our solar systems, small rocky planets and gas giants. Bringing in Jupiter as an analogue to Venus is just plain silly
Solved in the short term by structures that are structurally engineered to resist extreme pressure and heat on the outside while maintaining liveable conditions on the inside. As I noted, the Earth's oceans constitute a valuable test environment for such structures, as does space itself.
Solved in the long term by climate engineering and terra-forming. This is more achievable than changing the mass of the planet.
Highly debatable. For evidence of life on Venus see the recent New Scientist story "Venus' Atmosphere Implies Life" discussed here on slashdot.
The puerile mindset of the poster demonstrated by this ad hominem attack immediately reduces the respect paid to any counter-argument the poster may choose to put up. I was highly reluctant to pay respect to such a comment by replying. I won't do so for any future replies from this poster.