Ahhh right, I didn’t recognize it from a photo but I’ve read of it.
It’s annoying that so many sources are calling VERA-NG a “radar” when it’s specifically not a radar: it’s a fully passive system, it only receives and doesn’t emit. Hell, even the Wiki article is titled VERA passive sensor
Radar can totally be passive, and if you’re flying above enemy territory, it’s a really good idea to use passive radar and not active radar (the latter of which is used for some guided missile platforms).
In fact, active radar means everyone with passive radar knows where (and probably, what) you are.
Radiolocation can be passive radar can not. Radar requires one or more transmitters and one or more receivers.
One of the primary sensors on F16 (simulators in the early 1990s) was a passive radar — called that — that detected and pointed at those things trying to ping my plane.
Since it detected transmissions outside effective range, it meant I tracked them sooner than they tracked me, much the way automotive radar detectors have different warning sounds for when they sense radar around somewhere and when the car is being pinged directly.
Technically (the best kind of correct!) There is a transmitter in these cases, just not controlled by the same source as the detector.
I suspect radiolocation isn’t restricted to radar signals but can track stars and radio stations. Though they too transmit.
