Experimental SAGE Subsector

 (D) 42.36145, -71.09669, MIT's Digital Computer Laboratory (D) 42.46059, -71.26733, ESS Lincoln Labs Direction Center (L) 41.97575, -70.02398, South Truro MITRE Test Radar Site (L) 41.06254, -71.87417, Montauk Point MITRE Test Radar Site (L) 42.64612, -71.09377, Boston Hill MITRE Test Radar Site (L) 43.90167, -69.84556, West Bath Mitre MITRE Test Radar Site (G) 42.68897, -70.63243, Halibut Point (Rockport) MA Gap Filler (G) 42.17944, -70.72306, Scituate Gap Filler Radar Site (G) 41.35528, -70.73467, Marthas Vineyard Gap Filler Radar Site (G) 42.06199, -71.28608, Foxboro Gap Filler Radar Site (G) 42.37792, -71.69611, Clinton Gap Filler Radar Site (G) 41.72889, -71.06750, Fall River Gap Filler Radar Site (G) 41.86577, -71.820911, Chestnut Hill Gap Filler Radar Site (G) 41.69735, -69.97958, Chatham Gap Filler Radar Site (G) 42.03417, -70.05417, North Truro Gap Filler Radar Site (G) 41.70861, -70.56583, Pine Hill Gap Filler Radar Site (G) 41.28381, -70.05086, Nantucket Gap Filler Radar Site (G) 42.88989, -71.36925, Londonderry Gap Filler Radar Site (G) 42.91846, -70.79594, Hampton Beach Gap Filler Radar Site

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Experimental SAGE Subsector (ESS) (1955-1958) - Simultaneously with the development of the manual Permanent System radar network, separate efforts were made to automate as much of the air defense process as possible using fledgling digital computer and data transmission technology. This experimental project run by MIT's Lincoln Laboratory resulted in the SAGE System.

The research project phases included: the Cape Cod System I (1953), the Cape Cod System II (1954), and the Experimental SAGE Subsector (ESS) (1955-1958). The research project ended in 1958 with the deployment of the first SAGE System direction center at McGuire AFB, McGuire SAGE Direction Center DC-01.

The deployment phase began in 1958 with a new organization spun off of Lincoln Laboratory, the MITRE Corporation. The Rand Corporation had already assumed software responsibility in 1955. Lincoln Laboratory returned to their research role and that continues to this day.

Cape Cod System I (1953)
This phase connected the MIT Whirlwind I computer to a small radar network of 13 sites that included a long range serach radar, several height finder radars and the majority being gap-filler radars. Proof of concept was the major goal of this phase.

Cape Cod System II (1954)
The Cape Cod System II expanded Cape Cod System I with more sites and changes in the operating positions within the Direction Center. The primary objective was to supply statistical results on system capacity and accuracy.

Experimental SAGE Subsector (1955)
The Experimental SAGE Subsector (ESS), direction center was located in Building F, Lincoln Laboratory, Hanscom Air Force Base, Massachusetts. The building was completed in 1955 and equipped with a prototype FSQ-7 Direction Center computer. While production model FSQ-7s contain two identical computers the prototypes had only a single computer. Two single computer prototypes were contracted for with IBM in 1953 and delivered in 1955. One was installed at Lincoln Laboratory for the ESS and designated as FSQ-7 (XD-1). The other prototype FSQ-7 (XD-2), remained at IBM in Poughkeepsie, New York, for training, programming support and as a hardware test bed.

Also contracted for were three prototype FST-2 coordinate data transmitters for installation at the three long range radar (LRR) sites. The FST-2s connected the LRR to the prototype FSQ-7 (XD-1). The Gap-Filler radars were connected to the prototype FSQ-7 (XD-1) by a Slowed Down Video (SDV) mechanism that would later become the FST-1. An Air Force ground-to-air data link was connected to the output of the prototype FSQ-7 (XD-1) for experiments with data-link-equipped aircraft, this function would evolve into the Ground-Air Transmit-Receive (GATR) radio site concept.

The experimental SAGE Subsector provided data on reliability, computer programs, and operating procedures. The prototype FSQ-7 (XD-1) in Building F at Lincoln Laboratory was organized to define and support the regular functions of a Direction Center with the computer on the first floor, the operations area on the second floor and the power equipment in the basement.

The original Whirlwind I computer was also connected to the prototype FSQ-7 (XD-1) to validate the computer to computer cross-tell functionality that would allow adjacent direction centers to communicate and allow the direction center to communicate with the combat centers.

Almost concurrently with the ESS testing, IBM received production contracts for the systems to be deployed and eventually manufactured twenty-four FSQ-7s dual computer systems and three FSQ-8s dual computer systems plus the two single computer systems (XD1) and (XD2).

Notes:
 * 1) As each radar was brought up it included a Mark X - IFF capability and the interrogation replies were multiplex with the radar data.
 * 2) Cape Cod System fully operational by September 1953, trials began in October 1953 and concluded 15 Jun 1954 with highly favorable results.
 * 3) "The Experimental SAGE Subsector (ESS) was essentially an expansion of the Cape Cod System. But, unlike the Cape Cod System, ESS was a fully operational prototype."

See Also:
 * US Radar Sets

Sources:
 * Lincoln Laboratory - Cape Cod SAGE Prototype
 * ESS - Cape Cod Radar Sites Planned List (with activation dates)
 * ESS - Cape Cod Radar Sites Planned List (with activation dates)