The AIM-120 seeker does not select a random target in the terminal phase,...
Gambit
How does a Active Radar guided missile prioritizes its target in terminal phase . In layman terms how it sees and decides - "bang this is my target" .
When it's onboard radar goes active , there will be more than 10 RF emitter in a given area .
Two to three targets would be giving same radar return in dB .
A relatively low RCS design(Say Jet A) at 10Km range would be reflecting same energy as a slightly large figure (Say Jet B) at 20 Km distance + plus it might be possible that Jet A has just entered Theater field when missile is switching to Active terminal mode
Is it only based on
TWS/AACQ/STT/RWS information ; meaning Track while scan data which firing platform transmitted to missile - aka aspect angle, heading, airspeed and closure .
Or it has something to do with Pulse train / PRF sequence of reflecting surface which may be unique to hostile radar/jet .
Not necessarily. And yes...An actively guided missile does not perform any target selection.
Any body is essentially a radar reflector and the more complex the body, the greater the variability in producing an RCS value. The aircraft's radar will have a greater electronic view of the area than the missile because the missile does have a much smaller and less capable radar system, that mean if there are 10 reflectors in view, the missile may not see all 10. It is up to the pilot to 'deconflict' the available targets and prioritizes for the missile. Once a target has been assigned to the missile, it is supposed to maintain radar lock on that target. At this point it is the missile's design that will give the series its reputation. Target characteristics, aspect angle, heading, airspeed and closure rate, are independently calculated by the missile itself after acceptance from the parent aircraft. These information are incorporated into the type of guidance the missile is founded upon.
For example...
Other forms are pure pursuit navigation (PPN), command line of sight (CLoS) or plenty of hybrids. All air-air missiles today are hybrid in their guidance algorithms. Probably only MANPAD-types are still using simple guidance algorithms like PPN.
If the target deploys chaff, then it becomes a matter of sensor-guidance fusion sophistication if the missile is able to maintain target lock. The issue here is the distance between the missile and target at the moment of chaff deployment. Remember the property of beam dispersion or widening over distance.
NWS JetStream - NWS Radar on the Web
The beam of energy transmitted from the Doppler radar is no different. A conical shaped beam is formed as the energy moves away from the radar. And it is near the center line of the beam where most of the energy is located with the energy decreasing away from the centerline.
If the missile is able to distinguish the chaff cloud from the target, then it is a matter of programming on whether or not the missile is programmed to head for the largest radar return and be misled. The odds of distinction increases with distance because of that beam widening property. At the moment of chaff discharge the pilot will execute violent maneuvers. Go back to the noaa.gov source above and mentally place the aircraft and the chaff cloud any point inside a radar beam cone. The closer to the missile they (aircraft and chaff cloud) are to the missile, the better the odds that those violent maneuvers will take the aircraft outside of that cone. The further away from the missile, the better the odds are that the missile can see both. There are no guarantees here. If the missile is programmed to head for the largest radar return, then this point is irrelevant. But if the missile is sophisticated enough to remember the target's radar signature, heading, airspeed, altitude and even flight mechanics as chaff will have different aerodynamic behaviors than an aircraft, then the missile should be able to ignore the chaff and remain focused on the aircraft. But once again, if aircraft and chaff cloud are close enough to the missile, meaning deep inside the radar cone, then this sophistication is not of any use simply because the violently maneuvered aircraft is no longer inside the missile's radar view.
