Suppose that once I win a lottery I can build a small, modest SEM column and put it in a 6U cubesat that opens one side to allow the electron optics to be open to the vacuum of space rather than providing any cumbersome vacuum pumping.
The cubesat is released from the ISS so it's exposed to the environment at 400 km. It's equipped with a big 100m x 1 cm loop of kapton or thin metal foil on a motor so that it collects micrometeorite (or Andromeda strain) impacts and then studies them, at least that's my excuse for launching it, hopefully they'll let me navigate it around the ISS to study damage to the various materials on the outside of the ISS.
Question: Just how good is the vacuum at 400 km for a SEM. Can it be expressed in Torr? In other words, 1E-03? 1E-06? 1E-10? How high can it rise during a period of high solar activity?
My little SEM has mostly encapsulated solenoid electromagnets (100 gauss to say 1 kG) along with some small scan coils for imaging and electrostatic lenses in the gun. Will that be a problem in terms of charged particles up there or the Earth's field?
What about the hot tungsten filament in the electron gun? Will that be a problem?
Will my secondary electron detector be swamped by electrons in space?
Even if the vacuum turns out to be pretty good, are there species that will attack materials in my SEM?