Galileo images and mosaics of Europa |
Galileo images and mosaics of Europa |
Aug 22 2005, 04:03 AM
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
I have worked on sprucing up some global views of Europa from Galileo. There are a few more global views I hope to get to eventually. But the best two at nearly full phase benefited a lot.
[Moderator note: There are several more threads containing Galileo Europa images but they all contain several inactive image links. The main threads are: http://www.unmannedspaceflight.com/index.php?showtopic=2016 http://www.unmannedspaceflight.com/index.php?showtopic=2174 http://www.unmannedspaceflight.com/index.php?showtopic=2222 http://www.unmannedspaceflight.com/index.php?showtopic=2082 http://www.unmannedspaceflight.com/index.php?showtopic=2142 ] -------------------- |
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Feb 3 2006, 07:30 PM
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Junior Member Group: Members Posts: 37 Joined: 20-November 05 Member No.: 561 |
edstrick's explanation made me think of a question of spaceprobe construction:
Why even use filter wheels at all? Now that 1000 x 1000 pixel sensors are so cheap, we can load probes with as many cameras as we want. Look how many the MERs have. So instead of possibly-sticky mechanical wheels, or prism arrangements (imagine a gigantic 8-prism for 8 filters!), why not just have an array of 8 separate cameras all pointing the same way, each with its own dedicated filter? Granted, for landers or other close-up features the parallax would be unacceptable, but for planetary flyby/orbits, parallax would be too tiny to see. (Wouldn't it?) Then it could take pictures with ALL the filters all at the same time--no motion shift between them! And you wouldn't even have to worry about 8x the data coming back, because you could still transmit them sequentially, or even decide which filtered pictures are worth sending. How come they're not being built this way now? |
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Feb 3 2006, 08:08 PM
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Member Group: Members Posts: 562 Joined: 29-March 05 Member No.: 221 |
QUOTE (jrdahlman @ Feb 3 2006, 07:30 PM) edstrick's explanation made me think of a question of spaceprobe construction: Why even use filter wheels at all? Now that 1000 x 1000 pixel sensors are so cheap, we can load probes with as many cameras as we want. Look how many the MERs have. So instead of possibly-sticky mechanical wheels, or prism arrangements (imagine a gigantic 8-prism for 8 filters!), why not just have an array of 8 separate cameras all pointing the same way, each with its own dedicated filter? Granted, for landers or other close-up features the parallax would be unacceptable, but for planetary flyby/orbits, parallax would be too tiny to see. (Wouldn't it?) Then it could take pictures with ALL the filters all at the same time--no motion shift between them! And you wouldn't even have to worry about 8x the data coming back, because you could still transmit them sequentially, or even decide which filtered pictures are worth sending. How come they're not being built this way now? Because the cost of the sensor isn't the limiting factor, it is the size and weight of the camera(s). Mass and volume constraints are very tight on space craft. A filter wheel is a far more elegent solution to capturing a variety of wavelengths than duplicating the entire camera. A filter wheel weighs very little and occupies very little space, far far less than duplicating the sensor, optics and camera body multiple times. The problem of motion shift is an interesting one for orbiters/flyby craft. There has been recent discussion regarding the use of 'sport mode' on the MER PANCAM. This cuts the interval between frames to 3 seconds from 10-20. While the interval between frames for Cassini is longer, one wonders wheather the use of subframe images or better routines will be able to squeeze a higher frame rate from the camera. It is important to remember that spacecraft are primarily scientific instruments. Thus when spacecraft are designed, and choices made between returning scientifically calibrated data or pretty pictures the former must take priority and thus we should be thankfull that the latter is so often acheived as well. |
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