Describe the function of the Ground-Based Midcourse Defense (GMD) system and its components.

The Ground-Based Midcourse Defense (GMD) system is a critical component of the United States' missile defense network. The primary function of the GMD system is to intercept and destroy incoming intercontinental ballistic missiles (ICBMs) during their midcourse phase, which is the longest and most vulnerable phase of their flight.

The GMD system consists of multiple components, including sensors, interceptors, and a command and control network. The sensors are used to detect and track incoming missiles, and they include both ground-based and space-based systems. Ground-based sensors include radar and optical systems, while space-based sensors include satellites equipped with infrared and other sensors.

Once a missile is detected and tracked, the GMD system uses interceptor missiles to destroy it. These interceptors are designed to collide with the incoming missile and destroy it through kinetic energy. The GMD system uses two types of interceptors: the Ground-Based Interceptor (GBI) and the Standard Missile-3 (SM-3) Block IIA. The GBIs are launched from underground silos in Alaska and California, while the SM-3s are launched from Navy ships.

The command and control network is responsible for coordinating the sensors and interceptors and providing situational awareness to operators. The network includes a variety of ground-based and airborne assets, including the Joint Tactical Ground Station (JTAGS), the Cobra Dane radar, and the Airborne Infrared (ABIR) system.

While the GMD system is a critical component of the United States' missile defense network, it has some limitations. One limitation is its reliance on interceptors that use kinetic energy to destroy incoming missiles. This approach requires a high degree of accuracy and can be vulnerable to countermeasures by an attacker. Additionally, the GMD system is limited in the number of missiles it can intercept at once, which means that a large-scale attack could overwhelm the system's capabilities.