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Semi-Automatic Ground Environment (SAGE)

The Semi-Automatic Ground Environment (SAGE) system, completed in the early 1960s, revolutionized air defense. The integrated radar and computer technology that was developed for SAGE also contributed significantly to the development of civilian air traffic control systems. With the increasing possibility of a large-scale bomber attack on the United States in the mid-1950s, it became evident that further improvements in the nationís defense capability were needed. As the air defense system matured, the Air Force pursued the development of advanced command, control, and communications systems. The the Massachusetts Institute of Technology's (MIT) Lincoln Laboratories was commissioned to develop an automated nationwide computer-based air defense system. At Hanscom Field, the Massachusetts Institute of Technology's new Lincoln Laboratory (1951) and its spinoff, the MITRE Corporation (1958), worked to bring the SAGE system to completion. The end result of MITs efforts was the Semi-Automatic Ground Environment System, which consisted of a network of computerized control centers throughout the United States.

The Air Force completed the installation of SAGE in the early 1960s, with a total of 22 of these advanced command and control nodes installed. The first SAGE Division became operational in Syracuse NY on 26 Jan 1959. Groundbreaking for the first SAGE complex at McChord AFB, began in 1957. In December 1957, the US Air Defense Command activated the Grand Forks Air Defense Sector of NORAD. The sector became operational with the SAGE system on December 15, 1959, covering the air space of three states and one Canadian province. The Air Force inactivated the Grand Forks Air Defense Sector on July 1, 1963. In 1958 Air Defense Command established a Semi-Automatic Ground Environment (SAGE) sector at Minot AFB, which was activated in June 1961. However, as SACís mission continued to grow at Minot, ownership passed from ADC to SAC, and the SAGE center was deactivated in May 1963.

SAGE systems were located at Sector Direction Centers. The SAGE automatic data-processing capability substituted for manual GCI systems in observing, plotting, transmitting information and assigning targets for air defense weapons. SAGE facilities processed air surveillance information and sent the data to Air Defense Command units. IBM engineers installed two large, 275-ton computers in the basement of each SAGE facility, which were huge, windowless blast-resistant concrete buildings. The heart of the SAGE system, known affectionately as "Clyde", provided weapons controllers of the 60's and 70's with data which facilitated the intercept of unknown aircraft by Air Force fighters. These nodes were tied directly to NORAD's Combat Operations Center, which moved to Cheyenne Mountain from Ent Air Force Base in 1966, and maintained surveillance, identified aircraft, selected and directed intercepting aircraft, coordinated air defense responses and disseminated air defense intelligence.

In 1979, the SAGE control centers were replaced by Regional Operations Control Centers (ROCC), as new high-speed digital computers replaced the old "Clyde" systems.

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