Milestone-Proposal:SAGE (Semi Automatic Ground Environment)


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This Proposal has been approved, and is now a Milestone Nomination

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Is the achievement you are proposing more than 25 years old?

Is the achievement you are proposing within IEEE’s fields of interest? (e.g. “the theory and practice of electrical, electronics, communications and computer engineering, as well as computer science, the allied branches of engineering and the related arts and sciences” – from the IEEE Constitution)

Did the achievement provide a meaningful benefit for humanity?

Was it of at least regional importance?

Has an IEEE Organizational Unit agreed to pay for the milestone plaque(s)?

Has an IEEE Organizational Unit agreed to arrange the dedication ceremony?

Has the IEEE Section in which the milestone is located agreed to take responsibility for the plaque after it is dedicated?

Has the owner of the site agreed to have it designated as an Electrical Engineering Milestone? Yes

Year or range of years in which the achievement occurred:

1950 to 1958

Title of the proposed milestone:

SAGE (Semi Automatic Ground Environment)

Plaque citation summarizing the achievement and its significance:

In what IEEE section(s) does it reside?

Boston Section

IEEE Organizational Unit(s) which have agreed to sponsor the Milestone:

IEEE Organizational Unit(s) paying for milestone plaque(s):

IEEE Organizational Unit(s) arranging the dedication ceremony:

IEEE section(s) monitoring the plaque(s):

Milestone proposer(s):

Please note: your email address and contact information will be masked on the website for privacy reasons. Only IEEE History Center Staff will be able to view the email address.

Street address(es) and GPS coordinates of the intended milestone plaque site(s):

Lincoln Laboratory, Lexington Massachusetts

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Please give the address(es) of the plaque site(s) (GPS coordinates if you have them). Also please give the details of the mounting, i.e. on the outside of the building, in the ground floor entrance hall, on a plinth on the grounds, etc. If visitors to the plaque site will need to go through security, or make an appointment, please give the contact information visitors will need.

Main lobby of MIT Lincoln Laboratory in Lexington MA. Access by the public is available. Details will be provided later.

Are the original buildings extant?


Details of the plaque mounting:

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The main lobby provides entrance to public spaces such as the cafeteria and auditorium where IEEE meetings and other events take place.

Who is the present owner of the site(s)?

MIT Lincoln Laboratory

A letter in English, or with English translation, from the site owner(s) giving permission to place IEEE milestone plaque on the property:

A letter or email from the appropriate Section Chair supporting the Milestone application:

What is the historical significance of the work (its technological, scientific, or social importance)?

MILESTONE NAME: SAGE – Semi-Automatic Ground Environment

PERIOD: 1950 to 1958

SCOPE: The scope of this proposal encompasses the initial research, engineering and development of a large national defense project named SAGE. The period covered by this proposal is conception in 1950 to the construction of the first SAGE Control Center at McGuire Air Force Base, New Jersey in 1958.

ABSTRACT: Beginning in 1950, engineers, mathematicians, scientists and technicians, from the Massachusetts Institute of Technology's Digital Computer Laboratory, the Air Force Cambridge Research Laboratory, and MIT's Lincoln Laboratory, played the key role in the development of the Semi-Automatic Ground Environment (SAGE) system, the first major real-time, computer-based command- and- control system. Designed as a new air defense system to protect the United States from long-range bombers and other weapons, the SAGE system sent information from geographically dispersed radars over telephone lines and gathered it at a central location for processing by a newly designed, large-scale digital computer. As the system evolved, SAGE broke new ground in radar, communications, computer, information display, and computer programming technologies. SAGE not only revolutionized military command-and-controls, but led to landmark advances in online systems and interactive computing, real-time computing, and data communications using modems.

SYSTEM OVERVIEW The SAGE system used ground-based radars, sea-based radars on ocean platforms called Texas Towers, and airborne radars to detect enemy aircrafts. Digital communication links conveyed this information to command centers, where the first large real-time digital processors - novelties at the time – tracked the radar targets and guided fighter-interceptors to engage the intruding aircraft. Although Lincoln Laboratory’s primary responsibilities was to invent the needed command-and-control processes by using the newly emerging technology of digital computers, many development in radar technology were also needed to provide the “clean” data demanded by the computer.

AIR DEFENSE – THE FIRST YEARS (extracted from [1] pages 148 -151). “The first major Lincoln Laboratory effort in air defense, the Cape Cod System, was designed to integrate a surveillance net consisting of large search radars, height-finding radars, and gap-filler radars with a central digital computer (called Whirlwind) by using telephone lines for data transfer. The computer accepted target data from the radars and created tracks showing the positions and movements of the enemy aircraft. The computer then formulated a response and sent messages to the fighter aircraft so that they could intercept the target aircraft.

“The first version of the Cape Cod System was fully operational in September 1953, and it demonstrated that air battles could be managed with such a system. The next step was the augmentation of the Cape Cod System to form the Experimental SAGE Subsector, which covered more of New England. The Experimental SAGE Subsector included more radars, better data processing at the radar sites, a more capable central computer (the AN/FSQ-7), and improved display and control consoles for the human operators who were an integral part of the SAGE system. Figure 3 shows operations at a SAGE Direction Center at Lincoln Laboratory. The AN/FSQ-7 computer had a processing rate of about 100,000 instructions per second, which is much less processing power than today’s least expensive laptops.

“The first radar development needed to make SAGE work was to improve the performance of moving-target-indicator circuitry, which separates the echoes of the fast-moving objects of interest, namely, airplanes in flight, from echoes of slow-moving objects such as waves on the ocean and birds, and non-moving objects such as buildings and mountains. The second radar development came from an urgent need to strengthen the ability of radar to extract information despite radio-frequency interference and jamming. Both of these developments profited from enlarged understanding of communications theory, of which radar theory is a special case, that had flowered after the end of World War II.

Underlying these advances was the important development of processing devices to digitize data at the remote radar sites, and send it error-free to large central computers. SAGE was a large, distributed, digital, real-time, surveillance, communications, and command-and-control system. It was the world’s first such system, and the impact of its successful development spread far beyond its role in air defense of the United States. Some historians of science and technology consider SAGE to have been the launching pad of that economic marvel, the Boston-area electronics industry.” [1][2]

INSERT PHOTO FIGURE 3: Console operations at the Experimental SAGE Subsector Direction Center at Lincoln Laboratory in 1957.

1. An early warning radar searches for approaching aircraft.
2. The radar detects an enemy bomber approaching North America.
3. Telephone lines carry information from the radar to the SAGE Direction Center.
4. The SAGE Direction Center processes the information.
5. The Direction Center notifies interceptors of the target.
6. The Direction Center notifies higher headquarters.
7. The radar updates the position and course of the intruding aircraft.
8. The Direction Center notifies the appropriate surface-to-air missile batteries.
9. The Direction Center receives information from adjoining centers.
10. The Direction Center vectors interceptors to target.
11. The Direction Center receives status reports and other information.
12. The Direction Center provides final guidance to interceptors.
13. Interceptors destroy intruding enemy bombers.
14. The Direction Center receives raid assessment from interceptors.
15. The Direction Center apprises headquarters of status and results.
16. SAGE System maintains alert for additional hostile aircraft.


1. SAGE revolutionized air defense and also contributed significantly to advances in air traffic control systems. As the SAGE system matured, the Air Force pursued the development of a number of advanced command, control, and communications systems.

2. In peacetime SAGE was, for all intents, an air traffic control system. It influenced the design of the FAA’s automated control systems.

3. The system also gave IBM valuable insight, and it was not long after that the CEO of American Airlines met one of the IBM people involved in SAGE by accident on a flight, and soon the two companies were developing the SABRE airline reservation system.4. Other major SAGE developments included:
 CRT-based real-time user interface
.-use of wide-area communications via modems.


1. William P Delaney and William W Ward, “Radar Development at Lincoln Laboratory: An Overview of the First Fifty Years”, Lincoln Laboratory Journal, vol 12, 2000.

2. Thomas P. Hughes, Rescuing Prometheus: Four Monumental Projects That Changed the Modern World (Pantheon Books, New York, 1998). Chapter 2, pp. 15-67.

3. EC Freeman, ed., MIT Lincoln Laboratory: Technology in the National Interest” (Lincoln Laboratory, Lexington MA.1995). Chapter 2, “The SAGE Air Defense System” pp 14-33.

4. Robert Buderi, The Invention that Changed the World: How a Small Group of Radar Pioneers Won the Second World War and Launched a Technical Revolution (Simon & Schuster, New York, 1996).

5. Kent C. Redmond and Thomas M. Smith, From Whirlwind to MITRE: The R&D Story of The SAGE Air Defense Computer (MIT Press Cambridge, 2000).

6 MITRE Website.


Karl Wildes and Nilo Lindgren: A Century of Electrical Engineering and Computer Science at MIT, 1882-1982 and The Electron and the Bit: Electrical Engineering and Computer Science at the Massachusetts Institute of Technology, 1902-2002. Chapter 17, “From Whirlpool to SAGE”, pp. 280 -301.

Robert R. Everett, ed. Special Issue: “SAGE (Semi-Automatic Ground Environment,” Annals of the History of Computing, 5:4, 1983.

George E Valley, Jr., “How the SAGE Development Began,” Annals of the History of Computing, 7:3, 1985.

Robert Wieser, "The Cape Cod System," IEEE Annals of the History of Computing, 5:4, 1983.

John F. Jacobs, "The SAGE Air Defense System: A Personal History" (MITRE Corporation, 1986).

WEBSITES: wapedia: semi Automatic Ground Environment.

Mitre Photo Archives for Semi- Automatic Ground Environment (SAGE)

What obstacles (technical, political, geographic) needed to be overcome?

Two obstacles which we can identify have to do with organizational issues and lack of qualified personnel. Three non-profits institutions were created during the SAGE program. These organizational changes were amicably carried out and proved affective, allowing SAGE to progress smoothly in an orderly way.

The first big organization change was Lincoln Laboratory, which spun off from the main campus so that MIT could maintain its academic mission. The second was the creation of MITRE Corporation. MITRE was spun off from Lincoln Laboratory to complete SAGE weapons integration and implement the design. According to reference [3], this change prevented Lincoln Lab from “becoming over overwhelmed by its responsibilities”. The third was spinning-off the System Development Corporation (SDC), from RAND Corporation. SDC was created to handle the immense software requirements and to avoid a conflict within the research of the parent company.

Lack of experienced of qualified computer professionals was a problem and the solution was OJT - on-the-job-training.

As Bob Everett has noted, the SAGE program alone “trained hundreds of digital-system design engineers, thousands of computer programmers and thousands of digital-computer field engineers who gave great impetus to the new field of digital computers”. In the areas of hardware and computer operations, SAGE ‘s firsts included “computer-driven displays, on-line terminals, time-sharing, high-reliability computations, digital signal processing, digital transmission over telephone lines, digital track-while-scan, digital simulation, core memories, computer networking, duplex computers.”

What features set this work apart from similar achievements?

SAGE, or Semi-Automatic Ground Environment, was developed for the United States Air Force from 1950 to 1957 by the Massachusetts Institute of Technology's Digital Computer Laboratory, the Air Force Cambridge Research Laboratory, and MIT's Lincoln Laboratory. The work required scientific research in many different fields: computer hardware and software, radar, communications, and so on. During the period from 1950 to 1958, MIT and Lincoln Laboratory did much of the scientific research but others played important roles as well, for example, the Cambridge Research Laboratory (AFCRL), who’s work cannot be addressed at this time. Engineering is never a solo activity and as expected other companies were involved in successfully launching SAGE. The contract for manufacturing the AN/FSQ-7 computers was awarded to IBM. Western Electric Company provided buildings and internal power supply and communications. Phone lines were provided by the Bell System. System Development Corporation (SDC) was responsible for the software which consisted of 500,000 lines of assembly language.

SAGE was unique in that it was engineered in response to a specific contract. Its uniqueness is evident by the many innovations attributed to SAGE as follows: [3]

Magnetic-core memory.
Digital phone-line transmission.
Digital track-while-scan.

Multiple simultaneous users.
System data structures.
Structured program modules.
Global data definitions.
Table-driven software.
Software debugging tools.
Data description language.

Interactive graphic displays.
Light-pen input.
On-line common database.

Marginal checking.
Internal parity checking.
Built-in test data reduction.

References to establish the dates, location, and importance of the achievement: Minimum of five (5), but as many as needed to support the milestone, such as patents, contemporary newspaper articles, journal articles, or citations to pages in scholarly books. At least one of the references must be from a scholarly book or journal article.

Supporting materials (supported formats: GIF, JPEG, PNG, PDF, DOC): All supporting materials must be in English, or if not in English, accompanied by an English translation. You must supply the texts or excerpts themselves, not just the references. For documents that are copyright-encumbered, or which you do not have rights to post, email the documents themselves to Please see the Milestone Program Guidelines for more information.