How Missile Defense Systems Will Work

By: Kevin Bonsor

Anticipating Attacks

Artist's concept of SBIRS satellite
Artist's concept of SBIRS satellite
Image courtesy BMDO

­The NMD that is being developed now is a toned-down version of the missile-defense system proposed by President Reagan. Forget the lasers and high-speed projectile weapons. The current system will not be the impenetrable force-field that was envisioned in the Strategic Defense Initiative (SDI). Instead, the United States is working on a ground-based missile-defense system that can respond to a limited missile attack. There are five parts to this NMD system:

  • Upgraded Early-warning Radar (UEWR)
  • X-band/Ground-based Radar (XBR)
  • Space-based Infrared System (SBIRS)
  • Battle Management, Command, Control and Communications (BMC3)
  • Ground-based Interceptors (GBIs)

The first part of NMD will involve detecting the launch of enemy missiles and tracking them. Data gathered by a system of radar and satellites will be sent back to personnel at the BMC3, who then will take appropriate action. Let's take a look at the three components that make up the detection and tracking system of NMD.


  • Upgraded Early-warning Radar (UEWR) - This is a phased-array surveillance radar that can detect and track ballistic missiles. NMD will use upgraded versions of existing, ultra-high frequency early-warning radar. Hardware modifications, including the replacement of existing computers, graphic displays, communications equipment and the radar receiver/exciter, will also be made to the EWR. UEWRs will be used to detect and track missiles and other projectiles during their midcourse phase, before cueing the more precise X-Band Radar.
  • X-band/Ground-based Radar (XBR) - This consists of a multi-function phased array radar that uses high frequency and advanced radar-signal processing technology. The XBR will track missiles as they fly closer to the United States and assess which missiles are decoys and which are armed with warheads. It is equipped with high-resolution radar that allows it to accurately discriminate between closely spaced objects. XBR radar has a 50-degree field of view and can rotate 360 degrees to track targets. It will transmit a radiation pattern in a narrow beam made up of electromagnetic pulses. The radar site consists of the X-band radar mounted on a pedestal, a control and maintenance facility, a power generation facility and a 492-foot (150-m) protected area. The XBR site will cover 17.46 acres.
  • Space-based Infrared System (SBIRS) - Under development by the Air Force, the SBIRS satellites are on a 10-year development plan and are expected to be added to the system three to four years after NMD becomes operational. These satellites will replace the current Defense Support Program (DSP) satellites. There are three kinds of SBIRS satellites, including four geostationary earth orbit (GEO) satellites, two highly elliptical orbit (HEO) satellites and an unspecified number of low earth orbit (LEO) satellites. Eventually, there will be a 24-satellite constellation that will start tracking enemy missiles earlier than radar, allowing for quicker response.

Once radar has determined that an enemy missile has been launched and is targeting the United States, the next phase is to trigger one or more of the one-hundred interceptor missiles to destroy the enemy ballistic missile before it reaches U.S. air space. In the next section, you will learn how these interceptors will target and destroy enemy missiles.