Agreed. Fabulous stuff. Thanks for sharing.
Paul
On Jun 1, 2009, at 6:27 PM, Cotty wrote:
On 1/6/09, Joseph McAllister, discombobulated, unleashed:
This discussion has triggered my earliest digital camera memories,
back when TV studios were still using tubes to image.
My camera was about the size of the Hubble, flew in orbits between
250
and 175 miles depending on requirements, and could image items on
earth as small as 40 inches (one meter +). In 1976. By the time I
left
the project in 1987, it could image items as small as a loaf of
sliced
American bread. Some said as small as a golf ball, but that's a
contrast thing, not resolution. You could tell if someone had a hat
or
helmet on, and if their shirt was long sleeved or short.
The sensor consisted of three overlapping strips of CCD sensor about
2" long and 1/4 inch wide.
_________________
______________ _____________
Like that. They could image either in "still mode" or "strip mode".
In
either case they were capturing the image as it crossed the sensors
and the satellite cruised by overhead. In strip mode you could take
in
a 10 to 60 mile wide area (vertical or oblique) by as long as you
wanted. The bird was stabilized and pointed (positioned) quite
rapidly
if need be by a series of Control Motion Gyros (CMG) that had brakes
on each. CMGs were spinning rapidly, and to reposition the satellite
the brakes were applied to one or more of the CMGs for a bit to start
the motion, then again to the opposite CMG to stop it. Six CMGs were
employed, in various orientations, though I believe three were
primary, and the other three were cut in as backups if one of the
primaries failed. Because it was in space, and weightless, it didn't
take as much energy as you think, but you were starting and stopping
several tons, and the laws of inertia still applied.
The latest generations are still up there, so always smile and wave
when you look up at the clouds
Joseph that was a fascinating read, thanks mate.
--
Cheers,
Cotty
(sat in Terminal B near Gate 67 waiting for the 9pm redeye to London)
___/\__
|| (O) | People, Places, Pastiche
||=====| http://www.cottysnaps.com
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