Another question of course is that since it was impossible to load the cameras with new film, how much film did they carry when deployed? After using it all the camera was useless.
A modern digital camera would have been really valuable for these purposes.
BTW were those Corona satellites guidable, or did they just fly wherever they flew and operators could ask them to photograph what was under?
A useful way to decommission a satellite that is about to run out of its film storage would have been to guide it to a trajectory where it can take more accurate pictures from a lower position -- because once the satellite goes on such a trajectory, it will soon come down completely. But if you could use the last bit of film that way, and eject it for retrieval, then the dying of the satellite would at least have been utilized.
> Another question of course is that since it was impossible to load the cameras with new film, how much film did they carry when deployed? After using it all the camera was useless.
That's why both the US and Russians experimented with military space stations (US MOL, Soviet Almaz), so they could both resupply the cameras with more film, and in emergencies develop it directly in space and radio down scans of them.
However, both eventually figured out how do automate the latter and eventually developed fully digital cameras, rendering manned surveillance stations obsolete. The US never launched any, and the Soviet program was cancelled after three stations (that were masked as Salyuts).
> BTW were those Corona satellites guidable, or did they just fly wherever they flew and operators could ask them to photograph what was under?
Satellite orbits are largely fixed – changing your orbital plane is the single most expensive manoeuvre you can do, and too expensive in practice. (Even if we wanted to, we couldn't tilt the ISS' orbit by more than a degree or two, and if we did, Soyuz rockets couldn't reach it any more.)
That's why we instead just launch a whole lot of satellites that focus on different areas.
> A useful way to decommission a satellite that is about to run out of its film storage would have been to guide it to a trajectory where it can take more accurate pictures from a lower position
Even just lowering your orbit is expensive, fuel-wise, but the more important problem: The lower you go, the faster you are. This means lower exposure times and less image quality, not more.
Additionally, as far as I can tell, the film buckets were really dumb and used solid boosters hand-tuned to their original orbit. Launching them from a different trajectory would likely make them burn up during re-entry.
So how'd they get that film back down from space?
https://en.wikipedia.org/wiki/Corona_(satellite)#Recovery