The U.S. Air Force maintains five PAVE Phased Array Warning System (PAWS) Early Warning Radars (EWR). These radars are capable of detecting ballistic missile attacks and conducting general space surveillance and satellite tracking. The acronym PAVE is a military program identification code.
They are able to detect and track both intercontinental and sea-launched missile threats. Early 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 Joint Space Operations Center (JSpOC) for processing.
Three systems have been modified to Upgraded Early Warning Radar (UEWR) status. They are located at Beale Air Force Base, Calif., Thule Air Force Base, Greenland and Fylingdales, England. The Fylingdales system is operated by the British Royal Air Force. The UEWR systems have a co-primary mission to provide missile tracking data to the U.S. Missile Defense Agency (MDA) GMD Fire Control Center (GFC/C).
The other two systems are located at Cape Cod Air Force Station, Massachusetts., and Clear Air Force Base, Alaska.
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. The maximum practical deflection on either side of antenna center of the phased array beam is 60 degrees. This limits the coverage from a single antenna face to 120 degrees. 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 two building faces supporting the arrays, each covering 120 degrees, 240 degrees of azimuth. The array faces are also tilted back 20 degrees to allow for an elevation deflection from three to 85 degrees above horizontal.
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. Four different computers communicate with each other from the heart of the system, which relays the information to Cheyenne Mountain Air Force Station and missile defense forward users.
(Current as of November 2015)
Point of Contact:
Air Force Space Command, Public Affairs Office
; 150 Vandenberg St., Suite 1105; Peterson AFB, Colo., 80914-4500; DSN 692-3731, or (719) 554-3731; Fax (719) 554-6013.