SAGE (Semi-Automatic Ground Environment)

SAGE (Semi-Automatic Ground Environment)

SAGE demonstrated pioneering solutions to the problem of the user interface. Courtesy: The MITRE Corporation.

Jay Forrester and George Valley from MIT's Lincoln Lab conveived of a continental air-defense system that integrated radar, communications and computers designed to track and intercept hundreds of incoming aircraft. This became the SAGE (Semi-Automatic Ground Environment) system, the largest computer project ever.

SAGE is a landmark in the history of both radar and computing. The SAGE air-defense system was actually built by the United States in the 1950s. It used radar on land, at sea, and in the air and was a major advance in telecommunications. A network of 23 control centers was built, each center receiving information from some 100 sources, principally radar stations. The surveillance and communications demands were met by real-time computerized processing of information. The computer for SAGE, the AN/FSQ7 built by IBM, was the first full-production machine with a magnetic core memory and the first to have a standby computer in case of machine failure. Each AN/FSQ7 weighed 250 tons and contained 49,000 electron tubes.

Most of the human-machine interaction took place at large radar screens with light pens, rather than with punched cards or teletype terminals. The first test of SAGE—directing an interceptor plane to a target—occurred on 20 April 1951. The system performed well. However, it was not until 1 July 1958 that the first SAGE center went into regular operation.The system was fully operational by 1963.