“How do they know this is Grad and Uragan and not a Smerch or a 9A52-4 Tornado?”
From the rocket types, identified by the fragments, I’m sure. Different launchers use different types of rockets, different ranges, etc.
Okay, but these seemed to be identified rather quickly... apparently they judged from the size of craters/explosions or something.
I guess they have seen enough of this to recognize them.