Sigint/elint satellites

[totoro]

So those trios of sigint/elint sats that US and China have in droves, what sort of signals can they detect?

Infantry Battalion level Comms?
Long range Comms (hundreds of km distance)?
SAM battery targeting radar?
Radar of a maritime patrol helicopter?
Fighter jet radar?
Large shipborne air search radar?

All of the above? Just some of the above?

 

[Flyaway]

Fairly recent video from the NRO about SIGINT

View: https://www.youtube.com/watch?v=1o9b_3kYVh4&t=3s

 

[Grey Havoc]

The Space Review: Stars in the sky: The top secret URSALA, RAQUEL, and FARRAH satellites from the 1970s to the 21st century

 

[Josh_TN]

So those trios of sigint/elint sats that US and China have in droves, what sort of signals can they detect?

Infantry Battalion level Comms?
Long range Comms (hundreds of km distance)?
SAM battery targeting radar?
Radar of a maritime patrol helicopter?
Fighter jet radar?
Large shipborne air search radar?

All of the above? Just some of the above?

If you are talking about the constellations that operate three to a formation in low earth orbit, those were referred to as Parcae or White Cloud in the U.S. and focus on gathering signals from ships (more generally they would be referred to as NOSS satellites). These would probably focus on navigation and air search radars, but might include HF and VHF communications as well. Modern versions might include AIS info as well, but it might be easier to coallate that on the ground after the fact. We do not know anything specific about what they gather; we can only assume. If they can detect ship based air search radars, it stands to reason they might have some utility against land based models as well.

Note that U.S. satellites of this type now operate in pairs, not trios, for almost the last dozen iterations.

We know nothing about the Chinese models; their purpose is inferred from their altitude and formation.