the missile is capable of low altitude flight and thus has the ability to fly under ground-based radar systems of all missile defense systems. air-borne radar systems like the awacs can detect cruise missiles within a relatively constrained area. this is usually done during active military engagements due to cost and limited numbers of planes. additionally any system capable of detecting the launching or take off of aircraft (eg surveillance satellites) can be used to identify that a cruise missile has been launched, which can give a responding military force time to get effective airborne surveillance aloft.