i'd go so far as to say i'm 90% sure that there are no film based satellites
in orbit.
SPOT has ~1m ground resolution as i recall the most detailed of the
commercial satellite fleet and it is digital, it can cover the same point on
the earth every 3 days though at different angles.

if the CCD sensor has more resolution than the optics then it isnt hard to
do. I havent heard of anybody shooting video from space, though it would
probbly be possible you would need to be in very low orbit with a mirror
around the size of hubble to make it actually worthwhile.

using film would be horribly inefficent, rather than spending 500 million
dollars 3 or 4 times a year to launch a new satellite because your old one
ran out of film, spend 500 million dollars on a CCD, it will be far more
sensitive than film (QE of ~1 vs 0.2) and far higher resolution.
put a BigAss (TM) ground station somewhere you controll, and download the
data every day or so.
with a few ground stations you could download every 90 minutes or so. rather
than film where if something goes wrong you have to go chasing this film
canister somewhere in the arctic while the people you are spying on are
doing the same.


> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
> Of Philip Stortz
> Sent: Thursday, October 21, 2004 02:27
> To: Microcontroller discussion list - Public.
> Subject: Re: [OT:] Whoops
>
>
> it definitely was done that way on some satellites at one time.  i
> suspect it's still being done for high resolution work, video is still
> much lower resolution.  some of these satellites film the entire planet
> every day or so, and then eject a film container on a parachute etc.
> which is then developed and studied both manually and by computer
> imaging looking for any change.  of course for more real time
> surveillance video type techniques are used, but they are limited in the
> area and resolution trade offs available, i.e. with film you can image
> the whole planet with high resolution film and optics and enlarge it
> later, concentrating on the areas that are interesting or that show a
> significant change over time.  i'm sure many of the satellites still use
> film for these reasons, while others don't, and there may be some that
> have both capabilities.  spy satellites are pretty sophisticated and a
> great deal is spent on them, some can even change their orbit on
> command, requiring a significant fuel reserve.  the limits shrink
> rapidly when nearly infinite money is available, as it often is for
> these types of projects.
>
> Dave VanHorn wrote:
> >
> > At 06:48 PM 10/17/2004, Philip Stortz wrote:
> >
> > >yeah, and it would almost have to be a surveillance satellite in the
> > >first place, returning the whole thing just as we recover film packs
> > >being parachuted back to earth (i'm sure we're still doing that with
> > >some of our spy satellites).
> >
> > I don't think so, but they don't always tell me these things.
> > My father worked on some of those systems back in the late 60's
> and early 70's.
> >
> > The film capacity would be a pretty severe limitation.
> > AFAIK, there isn't anything that they can't do without film these days.
> -------
>
> --
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