From: virker@ikke.invalid.retro.com   
      
   > I have a question and I hope its not too silly.   
      
   There are no such things as silly questions (almost).   
      
   > Are there standard (optical) cameras on space probes, and, if so, how   
   > do they see the planets?   
      
   Well, "standard" is probably not the right word, as far as I know, all space   
   probe cameras so far has been more or less tailor-made. But it's a camera   
   employing largely the same techniques as any off-the-shelf digital camera.   
      
   > OK, like I said, its silly.  I know that there are all sorts of   
   > infra-red/etc instruments on spacecraft that pick up all kinds of   
   > radiated materials from a planet.   
      
   What's radiated is usually not "materials" but rather energy, usually in the   
   form of electromagnetic radiation (radio waves, microwaves, infrared light   
   [heat], visible light, ultraviolet light or X-rays).   
      
   > But some of the still photos I've   
   > seen appear to be plain old regular photos.   
      
   They are. A photo is a detection of the visible light radiated from an   
   object.   
      
   > What I want to know is,   
   > if this is the case, where does the light come from?  I mean, when   
   > taking pictures of Uranus, for example, is there really enough light   
   > from the sun to fully illuminate the surface?   
      
   Depends on what you mean by "fully" :-) But yes, images taken by space   
   probes show us what the planets look like in reflected sunlight.   
      
   > Or does the aperature   
   > on the camera stay open for long periods of time to collect a lot of   
   > light?   
      
   Good guess! Out by Uranus, or even worse, Neptune, the Sun looks so small,   
   that it's hard to distinguish it from all the other stars. Now, I don't know   
   for how long time Voyager 2 exposed the images of e.g. Neptune, but I don't   
   think it was taken on 1/500 sec.!   
      
   > Or do the atmospheres of the planets themselves give off some   
   > sort of illumination?   
      
   Probably not in visible light. I believe Jupiter and Saturn give off some   
   UV- and X-rays of their own, and Jupiter radiates some in the radio bands as   
   well, but that's it.   
      
   Hope that cleared up a few things :-)   
      
   /steen   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)