[geepytee]

On the transponders off point, I imagine soon we will have enough satellites such that we can map every object on the surface of the earth (specially something as large as a boat).

Could even see it through clouds using radar.

[preisschild]

The soviets did exactly that so they can attack large US convoys with long-range Anti-Ship Missiles

They had to use a fission reactor onboard those satellites to power the radar array

It consisted of 2 satellite types. US-A (active) and US-P (passive). US-A used radar and US-P used passive antennas so they can "see" signals from ships.

https://en.wikipedia.org/wiki/US-A

Late Cold War AShM's (SS-N-19 Shipwrecks) could use those satellites directly to update the target location in-flight

https://en.wikipedia.org/wiki/Legenda_(satellite_system)

[rcxdude]

The usual issue with satellites is they'll see the whole surface of the earth _eventually_, but it takes some time before they're back over the same spot, so tracking moving objects isn't really what they are best at.

[yencabulator]

This changes with Starlink-style constellations, and US spy industry is already doing that with SpaceX.

https://www.space.com/space-exploration/launches-spacecraft/...