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Jairo
2005-Jul-10, 12:03 AM
The Lunar Orbiter probes were unusual because, instead of using TV transmission, thew used a combination of photograph and scanning to achieve better resolution.

I saw it was better than the TV images from the Ranger probes, but the TV images from the Surveyor probes donīt seem to be much worse.

I suppose this is because they were landed and the image wasnīt moving, giving more time transmit it. But do you know any other motive?

Thanks.

01101001
2005-Jul-10, 05:32 AM
Just a guess: photogrphy had much more dynamic range than video with vidicon tubes. My 20th-Century rule of thumb was that chemical photography had about 10 times the dynamic range of video, and eyeballs about 10 times the dynamic range of photography. (I have no idea where modern CCD devices fit, nor HD video, nor LCD displays.)

If you could image things photographically, and had the time to slowly and carefully scan the image to convert it to electrical signals for transmission, you got a lot more data.

ngc3314
2005-Jul-10, 12:32 PM
If you could image things photographically, and had the time to slowly and carefully scan the image to convert it to electrical signals for transmission, you got a lot more data.

Indeed. There is no comparison between a TV image and the Lunar Orbiter products. You could take a 20-by-24-inch enlargement (umm, 50x60 cm), a pretty standard LO data product, and still need a magnifying glass to see the detail it would deliver. Just the thing for mapping, particularly when the primary mission was surveying potential landing sites for bounders and small-scale surface roughness. And the technology was already available from the classified world.