An effective layered defense incorporates a wide-range of sensors to detect and track threat missiles through all phases of their trajectory. Satellites and a family of land- and sea-based radars provide worldwide sensor coverage.

Upgraded Early Warning Radars (UEWR)

Three Air Force Early Warning Radars (UEWR), located in Beale Air Force Base, Calif.; RAF Fylingdales, United Kingdom; and Thule Air Base, Greenland, were upgraded and integrated into the Ballistic Missile Defense System (BMDS). The upgrades modernized the hardware and software to improve midcourse BMDS sensor coverage by providing critical early warning, tracking, object classification and cueing data. All three UEWRs were transferred to the U.S. Air Force for sustainment in FY14. The Early Warning Radars in Clear, Alaska and Cape Cod, Mass. began the UEWR modernization in FY12 and FY13, respectively.


The U.S. Air Force COBRA DANE radar in Shemya, Alaska has been upgraded to include the missile defense mission and has been integrated into the Ballistic Missile Defense System (BMDS).
The upgrade improved midcourse BMDS sensor coverage by providing acquisition, tracking, object classification, and data that can be used for cueing, launch of interceptor missiles, and course updates of interceptors while retaining the site’s legacy intelligence and space track missions. The Air Force is responsible for the COBRA DANE Upgrade system operations, maintenance, and sustainment.

Army Navy / Transportable Radar Surveillance (AN/TPY 2)

The Army Navy/Transportable Radar Surveillance and Control Model 2, or AN/TPY-2, is a transportable X-band, high-resolution, phased-array radar designed specifically for ballistic missile defense. The AN/TPY-2 is capable of tracking all classes of ballistic missiles and identifying small objects at long distances. In the forward-based mode, this radar plays a vital role in the Ballistic Missile Defense System (BMDS) by acting as a forward based sensor for the system, detecting ballistic missiles early in their flight and providing precise tracking information for use by the system. Use of multiple sensors provides overlapping sensor coverage, expands the BMDS battle space, and complicates an enemy's ability to penetrate the defense system. In the terminal mode, the same radar provides surveillance, track, discrimination and fire control support for the Terminal High Altitude Area Defense (THAAD) weapon system.

Sea-Based X-Band Radar

The Sea-Based X-Band (SBX) Radar acquires, tracks and discriminates the flight characteristics of ballistic missiles. The SBX provides an advanced capability to the Ballistic Missile Defense System (BMDS), increasing the Missile Defense Agency’s ability to conduct operational and realistic testing of the BMDS, while providing an operational capability to the combatant commands.

Space Tracking and Surveillance System (STSS)

The Missile Defense Agency (MDA) operates the Space Tracking and Surveillance System-Demonstrators (STSS-D). STSS-D constellation consists of two satellites orbiting at 1350 km, 58 degree inclination, with 120 minute orbital period. STSS-D uses sensors capable of detecting visible and infrared light and serves as the experimental space layer of the Ballistic Missile Defense System (BMDS).

SPY-1 Radar

Used aboard Aegis cruisers and destroyers, the SPY-1 Radar is part of the Initial Missile Defense Capability. Planned improvements to existing phased-array S-band radars will enhance the system’s capability to track short-, medium- and long-range interceptors.

Near Field InfraRed Experiment (NFIRE)
The Near Field Infrared Experiment (NFIRE) technology project is operated by the Missile Defense Agency (MDA) from the Missile Defense Space Center at Schriever AFB, Colo. The satellite collects near-field phenomenology data for use in plume-to-hard body handover algorithms, navigation, guidance and control, and endgame homing algorithms for boost-phase interceptor programs. This data is used to validate models and simulations that are fundamental to developing guidance and homing algorithms.
The satellite also uses a commercial off-the-shelf Laser Communications Terminal (LCT) to conduct laser communication proof-of-concept experiments. These experiments test low-earth orbit satellite-to-satellite, satellite-to-aircraft, and satellite-to-ground communication capabilities by providing an extremely high data rate at a low cost. Additionally, the LCT provides a secure communications link with a low-probability-of-intercept as compared with other communication techniques.

Selected Sensors Images

Sea-Based X-Band Radar (SBX) STSS Image Beale Early Warning Radar
FBX_T Sea-Based X-Band Radar (SBX) STSS Image
Beale Early Warning Radar STSS Image Sea-Based X-Band Radar (SBX)

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SBX April 2005 (3.1 MB WMV*)