Aerodynamics & engineering dictates that not many things can move at the speed/agility of a stealth fighter.
If you've got a radar system already in place, "Stealth" is just the ones that don't also pop up on the radar.
Presumably scattered radar receivers can detect faint reflections using similar correlation.
Is there a background microwave radiation at shorter wavelengths that could be made into a camera that could see through clouds too? microwave is too long wavelength to make a small camera.
> Presumably scattered radar receivers can detect faint reflections using similar correlation.
Yes, multistatic radars are already in service. An advance on the concept is that the active transmitter can be placed outside anticipated weapons range and those within range are merely passive receivers.
There have been proposals to build such systems that use 'oblivious' transmitter sources such as commercial radio broadcasts.
There was a project to extend/enhance the Kraken multi-SDR system that got yanked from GitHub, etc, because it tripped over ITAR in that it enabled passive radar.
ITAR assumes the US leads the world in technology, and actively prevents us from catching up if we don't.