Death by ICBM was a near constant threat to both sides during the Cold War. America's answer: a long-range, phased-array early warning system designed to find, identify, and track these sea-launched ballistic missile threats. It worked so well, the Air Force still uses it.

The United States Air Force Rome Air Development Center (RADC), with the help of Raytheon, began designing the system in 1975 and by 1980, the PAVE PAWS (in reference to PAVE, the Air Force program name, and Phased Array Warning System), came online at both Otis AFB in Massachusetts and Beale AFB in California. Two more PAVE PAWS systems were later installed in Robins AFB, Georgia, and Eldorado AFB, Texas, but they were decomissioned in 1995 at the end of the Cold War. The Robins AFB system was moved to Clear AFB, Alaska, and restarted in 2001 to provide full coverage defense to the whole of the western US. And combined with the BMEWS system, all but a small fraction of the South West is protected from attack.

There Isn't an ICBM Around that Can Sneak Past This Radar ArrayS

The PAVE PAWS radar has two primary objectives. First, watch for, spot, ID, track, and determine the attack characteristics of incoming ICBM and SLBM threats. Once the system spots a missile, it continuously tracks the threat until eliminated, even if the warhead separates from its booster rocket. Secondly—and even more important now that the Cold War has ended—PAVE PAWS tracks satellites in support of the USSPACECOM Space Surveillance Network. All of the information that the system generates, as well as the supplemental data from the BMEWS system, flows into NORAD at Peterson Air Force Base and U.S. Strategic Command's Missile Correlation and Space Control Centers at Cheyenne Mountain Air Station, Colorado.

Each radar installation is a 72.5-foot wide array comprised of 1,792 solid state 325W transponder modules. Unlike mechanical radar sites, which have to physically move a dish around, the PAWS array shifts its focus by modifying the phase timing of the electromagnetic pulses each produces. A pair of arrays are seated in five story tall, three-sided buildings. Each array wall is 102 feet wide and tilted back 20 degrees so as to allow the beam to elevate between 3 and 85 degrees over the horizon. Together the arrays can create a narrow-but-precise 2.2 degree wide beam capable of tracking a 10 square meter object with a practical limit of 3,000 nautical miles and a 240-degree area of coverage.

There Isn't an ICBM Around that Can Sneak Past This Radar ArrayS

To spot objects, the PAVE PAWS first erects a surveillance fence (which requires 11 percent of its processing power) wherein it continuously scans the entirety of its coverage range, spending just ten micro seconds on any given point. If it does spot an inbound, the radar will allocate another 7 percent of its resources to actively tracking the object in addition to continuing to monitor the rest of the sky for a maximum resource usage of 18 percent. This allows the system to track fleets of inbound ICBMs while discerning the make, model, and destination of each—automatically. In fact, the only human input required is that of monitoring the system and signing off on the final validity warning.

The system is very effective, so much so that Taiwan has been clamoring for one of its own for nearly two decades. However, after a $1.4 billion dollar outlay, Raytheon did recently build one for the tiny island nation. Taiwan plans to employ the system as an early warning device in case China decides to lob a small part of its massive ballistic missile stores in that general direction. Many security analysts have also speculated that the US is being allowed access to the satellite monitoring data that the new installation generates as tribute for proliferating the technology.

"I would expect the U.S. would have made a deal that the U.S. gets satellite surveillance from the Taiwan radar," former CIA weapons analyst Allen Thomson told Wired. "Most of time it's sitting there watching satellites, and that's about it. The U.S. could certainly could use that information."

The system could also easily track any potential North Korean nuke launch 1050 nautical miles to the North East.

[Wired - Wikipedia - USAF - FAS - Military Aerospace]