[overfeed]

> A typical satellite will orbit once every 100 minutes or so (military spy satellites more often because they fly lower,

Constellations (like Star Shield or the Chinese equivalent) solve this problem; there is always a dozens of satellites overhead, and they don't need a lot of resolving power to detect contrails, I vet even cubesats with repurposed phone-camera sensors would suffice.

[Tor3]

contrails can be detected, at least when they disperse a bit. And as they linger it's even easier. What's difficult anyway you look at it is to detect the actual airplane, at the point where it's at at the moment.

Note that the Starshield satellites aren't able to cover all of the earth all of the time, far from it.

[overfeed]

> What's difficult anyway you look at it is to detect the actual airplane,

Contrails tell you when and where to look with more paranoia than usual, and temporarily lower the noise floor and not to disregard the some signals that you'd normally classify as a small bird.