First, early warning satellites detect launch of a missile and track it until burnout, using IR devices. Data on the estimated trajectory are passed to early warning radars In Alaska, Greenland and Britain. These radars gather track and threat assessment data and pass them to the X-band radars for more refined assessment. Following passge of this information to Grand Forks, an interceptor is launched. Then its inboard sensor acquires the target and determines which is the re-entry warhead and manoeuvres to intercept.
Ground radars perform kill assessment.
It should be noted that placement of the NMD missile and X-band radars at locations other than Grand Forks probably violates the ABM treaty and Russia may agree only to part of the US proposal. In that case, deployment of a a partial NMD would be of questionable value. This is a US-Israel development and first deployment is scheduled for the year 2000. A joint program involving the US, Germany and Italy. Additional partners will be sought.