I worked on a project that happened to have some spy satellite data as noise...

You can hide them. A common practice is to do an orbital maneuver when the satellite is directly between the Sun-Earth line-of-sight, where attempts to use instruments are pretty well saturated/destroyed.

With that said, it is still possible to see where the satellites go after such a boost if you are able to look really close to the limb of the sun with the right kind of equipment :)

Not every hobbyist had access to 1m+ mirrors, though. I imagine you could take a reasonably revealing picture of eg an Orion: https://en.m.wikipedia.org/wiki/Orion_(satellite)

I don't understand this thread. Sure with enough effort and manpower you can prevennt your own civilians from discovering these. How would the US government stop civilian entities in say Russia or China from discovering these? I still see a marginal potential utility though: not showing adversaries that you have noticed their satellites (in order to prevent them from improving their stealth).

People have done a lot with less than 1m.

http://www.satobs.org/telescope.html

https://satelliteobservation.net/2017/04/20/observing-satell...

I gasped when I read their main antenna is 330’ wide.

Not as easily if they're equipped with this: http://www.bisbos.com/space_misty.html

Wouldn't that also obscure the camera? I don't actually know what spy sattelites would be used for besides visual imaging aimed at Earth.

Could easily be intended not for visual surveillance but for gathering electromagnetic signals, where an inflatable dome would not be a problem.