As mentioned earlier by some Chinese analysts, THAAD can be effective in intercepting a North Korean short-range ballistic missile attempting to hit a South Korean target 300 km away, because its “terminal phase” matches the interception altitudes of THAAD. It is also known that the North Korean ballistic missile arsenal consists mainly of hundreds of modified Scud missiles with ranges between 300 and 700 km. Because these missiles can hit any South Korean target beyond the Seoul area (which is protected by Patriot PAC2/3 interceptors), the primary objective for deploying THAAD in South Korea is in all likelihood for defending against short-range ballistic missiles from North Korea.

One major concern of China’s security analysts is the X-band radar. While serving as the fire-control radar, Chinese analysts believe that it can be converted to an early-warning radar that could scan deep into China. While this may be true, it is important to understand that a fire-control radar is different from an early-warning radar in operational requirements. Fire-control radars are designed to quickly identify and verify the target, and initiate the launcher to shoot down the incoming missile. Because of the high demand for sensitivity and accuracy, fire-control radars scan a much narrower and closer area more frequently. In comparison, early warning radars scan a much larger and more distant area less frequently, because the demand for sensitivity and accuracy is less rigorous. Since a high level of sensitivity and accuracy is crucial for THAAD effectiveness in South Korea, it clearly needs a dedicated fire-control radar. So this radar is unlikely to be used interchangeably as both a fire-control and an early warning radar. The two X-band radars deployed in Aomori and Kyoto in Japan are dedicated to early-warning.

Chinese analysts believe that the X-band radar can gain more than ten minutes of early warning time compared to Alaska-based radars against Chinese strategic missiles flying toward the United States, which undermines the reliability of China’s already small strategic deterrent. Assuming this radar can easily be converted to an early-warning radar, however, whatever extra time it can contribute to early warning against Chinese missiles may become less significant for two reasons. One is that the two Japan-based X-band radars can also see the flight paths of Chinese missiles early and provide somewhat similar extra early warning time. The other is that the U.S. ballistic missile early-warning systems based on constellations of satellites, either deployed or under development such as the Space-Based Infrared System, may also be capable of provide early warning time sufficient to marginalize the contribution of the South Korea-based X-band radar.

Nan Li is a Visiting Senior Research Fellow at East Asian Institute of National University of Singapore.

Image: The first of two THAAD interceptors is launched during a successful intercept test. Wikimedia Commons/U.S. Army