Upgraded Early Warning Radars

The U.S. Space Force maintains Upgraded Early Warning Radars (UEWR). These radars are capable of detecting ballistic missile attacks and conducting general space surveillance and satellite tracking. They are located across both the United States and United States European Command.
The UEWRs have 240 - 360 degree coverage. These sites are designed primarily to detect and track intercontinental Ballistic Missiles (ICBMs) and Sea Launched Ballistic Missiles (SLBM), while conducting general space surveillance and satellite tracking. Missile Warning and attack characterization data is sent to the United States’ Missile Warning and Space Control Centers, the U.S. National Military Command Center and U.S. Strategic Command. Satellite tracking data is sent to the Combined Space Operations Center (CSpOC) for processing.
Two of the former Ballistic Missile Early Warning System Radars, and one PAVE Phased Array Warning System (PAWS) have been modified to support the Missile Defense mission through the UEWR program. The UEWR upgrades modernized 80 percent of the radar/computer subsystems and a complete re-write of software to improve midcourse BMDS sensor coverage by providing critical early warning, tracking, object classification, and cueing data.
All systems are operated by U.S. and Canadian personnel with the exception of one system, which is operated by the British Royal Air Force. The UEWR systems have a co-primary missions to provide Missile Warning Data to the Integrated Tactical Warning and Attack Assessment (ITW/AA) system while simultaneously providing missile tracking data to the U.S. Ground based Mid-Course Defense (GMD) Fire Control Center (GFC/C).
The unique aspect of the radars is their phased array antenna technology. The systems differ from mechanical radars, which must be physically aimed at an object for tracking and observation. The phased array antenna remains in a fixed position. Phased array antenna aiming, or beam steering, is done in millionths of a second by electronically controlling the timing, or phase, of the incoming and outgoing signals.
Controlling the phase through the many segments of the antenna system allows the beam to be rapidly projected in different directions. This allows interweaving of tracking pulses with surveillance pulses, allowing tracking of multiple targets while maintaining the surveillance responsibility.
A phased array antenna, as with any other directional antenna, will receive signals from space only in the direction in which the beam is aimed. To provide surveillance across the horizon, the building housing the entire system and supporting the antenna arrays is constructed in the shape of a triangle.
The radar system is capable of detecting and tracking multiple targets that would be indicative of a massive missile attack. The system must rapidly discriminate between vehicle types, calculate their launch and impact points, and perform scheduling, data processing and communications requirements. The operation is semi-automatic and requires highly trained personnel for monitoring, maintenance, prioritization, scheduling, and as a final check of the validity of warnings. Different computers communicate with each other from the heart of the system, which relays the information to Colorado Springs, Colo., and missile defense forward users.
(Current as of Oct 2020)