Terminal guidance comes into play during the Terminal phase of the flight.
Modern American ABM systems have the capability to intercept a Ballistic Missile during both Midcourse and Terminal phases of its flight and are also equipped with Terminal guidance system. The interceptor missiles do not just depend upon their onboard guidance systems to hone-in towards the target, they take cues from the entire surveillance setup (ranging from radar systems on the ground to satellites in space) to track the movement of the target in real-time.
So even if a Ballistic Missile is changing its direction mid-flight, it cannot escape or evade a modern interceptor unless it is relatively faster.
Change of course / trajectory is only relevant in terminal phase for evading terminal course intercept only... mid course intercept is a different scenario and that too has been problematic.. currently americans are unable to distinguish between rv and and an air filled balloon of same shape released with rv, as both travel through space at same speed.....
The modified PDV is an EXO-ATMOSPHERIC interceptor that can reach an altitude of 150kms- or at least thats what the DRDO research papers claim.It has already been tested upto an altitude of 120kms!
@amardeep mishra what would be the speed of shaheen rv at 150 + km altitude? Can you intercept that speed??