At 12:38 a.m., T-branchers picked up the whoop of an air defense radar from a SAM site, just outside Mariel. They turned on their recorders and got out their stopwatches, measuring the interval between the buzzing sounds and consulting a bulky manual that contained the identifying characteristics of all known Soviet radar systems, including frequency, pulse width, and pulse repetition rate. The manual confirmed what they already suspected. It was a Spoon Rest radar.
