By Sharon Watkins Lang, USASMDC/ARSTRAT Historical OfficeNovember 18, 2015
What factors need to be considered when developing a radar? Can the radar detect, identify and track its targets? Can the data be processed in a timely manner and transmitted to the necessary systems? Can the radar communicate with its missiles to guide them effectively to the target?
At the same time it is necessary to ensure that the radar does not interfere with the equipment already in place. To be a valued addition to the network, the radar should do no harm. From Nov. 12-26, 1973, the Safeguard commands conducted a series of electromagnetic compatibility, or EMC, tests on the Missile Site Radar, or MSR, to prove this point at the Safeguard complex in North Dakota.
Located on a 430-acre site amidst the plains and farmlands of North Dakota, electromagnetic issues would not seem to be an issue. As one of the tallest buildings in North Dakota, the turret of the MSR, at 123-feet above ground, was nevertheless a potential issue.
Equipped with four radar antenna arrays, the MSR was an S-band single-beam, phased array radar. The radar was designed for continuous operations, with each antenna, used to both transmit and receive data, measuring 13 feet in diameter equipped with over 5,000 phased-array elements.
Of particular concern was the potential threat to the Air Force's Minuteman launch facilities and transporters deployed at Grand Forks Air Force Base, North Dakota, as well as specialized equipment found on military aircraft and the Canadian microwave communications system which also operated in the region. Would the radar beams disrupt, diminish or destroy these networks?
Following negotiations with the Canadian government and the Air Force, test parameters were determined and a series of joint Army-Air Force tests were conducted, between 7 a.m. and 2 p.m. on Nov. 12, 15, 16 and 17, to assess the situation.
In newspaper articles throughout the area, officials explained that in these tests, the MSR's radiation beam would be "intentionally depressed below the minimum elevation at which it normally operates."
To achieve this mode of operation, radar operators would have to override the built-in safety features. The test area would extend two miles from the northwest and southeast radar faces. They also advised that during the test periods all access would be restricted with both ground and air patrols.
In these announcements, Army officials added that they expected no significant electromagnetic interference with commercial power systems or television. They also equated the power broadcast by the radar outside the test zone "to that produced by appliances in the average household and would be less than a person would receive standing under an electric power line."
To test the Minuteman system, the MSR beam, in elevation failure mode, was directed toward launch complexes in the vicinity. In addition, Minuteman missiles were transported along roads "in the immediate proximity to the MSR." On other occasions, the Air Force performed flyby tests to assess the effect of the electromagnetic environment upon aircraft electro-explosive devices, or EEDs and communications equipment.
Aircraft included in the test program included the B-52h, F-106a and F-4d. In conjunction with these efforts, officials with the Canadian Department of Communications and American observers collected data at various locations around Winnipeg and the Manitoba Province.
The command formally received the results of these tests in April 1974. The "Safeguard/Minuteman Electromagnetic Compatibility" report revealed that "the Minuteman system is compatible with the electromagnetic environment generated by the Safeguard radars without imposing unduly restrictive constraints on the operation of either system." Ground transportation should be restricted to specific routes and EEDs should be transported in closed metal containers in the vicinity of either the MSR or the Perimeter Acquisition Radar, or PAR.
Similarly, aircraft were advised to maintain a specific separation distance to ensure EEDs and communications were not affected. The reports from Canada of the Spectrum Signature Measurements were also positive.
They concluded that "no abnormal radar out-of-band emissions were being radiated … and no interference has or is being reported from harmonic or spurious emanations." As a result of these tests, engineers found "no restrictions need be imposed on any designed operating parameters of the PAR and MSR systems."
The MSR and Safeguard were ready to proceed in the next step toward full deployment.