In early August 2017, North Korea announced plans to launch four intermediate-range ballistic missiles towards the waters surrounding Guam — perhaps 30 or 40 kilometers from the island’s coast. This short video, co-produced with the CSIS Aerospace Security Project, shows how U.S. missile defense systems might respond if a launch was detected.
The United States would first detect the missiles’ heat signatures with infrared satellites such as the Defense Support Program or the newer space-based infrared system. These satellites would then cue terrestrial radars, such as the TPY-2 X-band radars in Japan and South Korea, which can track the missiles over longer distances. The missiles would be within the radars’ field of view for perhaps six minutes. The Navy’s Aegis BMD ships might also be in position to track the missiles’ flight.
The trajectory of the missiles headed to Guam would take them over the southern part of Japan, flying just south of Hiroshima at an altitude of over 700 km. If the U.S. determined these missiles were a threat to Guam, what systems would be called upon to respond?
If the U.S. military determines the missiles to be a potential threat, the United States might attempt to employ missile defense interceptors to shoot them down. Available systems include sea-based SM-3, launched from an Arleigh Burke-class destroyer, or a land-based THAAD battery based on Guam, or some combination of the two
Although both systems have an excellent testing record, neither of the two have ever been used in against ballistic missiles in an operational context.
All of this would happen within a relatively short period of time. North Korea has suggested it take about 17 minutes, others have said it could be as little as 14. It depends on the trajectory used. A more lofted trajectory would take longer and rise to a higher altitude in space, while a more shallow trajectory would take less time and stay lower.
If attempted, an intercept would occur either before the missiles reach their apogee or during their downward descent.
Guam is an unincorporated island territory of the United States, located 3,400 kilometers southeast of Pyongyang. The island hosts 160,000 inhabitants, including a combined 7,000 U.S. troops stationed at the Andersen Air Force Base and Naval Base Guam.
See also:
Missiles of North Korea | Missile Threat
Hwasong-12 Intermediate-range ballistic missile | Missile Threat
Video: Midcourse Discrimination | Missile Threat
Terminal High Altitude Area Defense System | Missile Threat
Aegis Ballistic Missile Defense | Missile Threat