A Moving Target Detection Radar in Vietnam

The spring of 1966 marked a year since the first US combat troops (Marines) had entered Vietnam. By March 1966 there were 215,000 American troops in country, and several hundred were being killed in action each month. The jungles, swamps, rivers, and the intractability of the enemy made the struggle very difficult for the Allies. In addition, anti-war sentiment was already strong back home, and Communism was on the rise around the world, leading to tough decisions about America’s involvement.

Given the battlefield conditions and tactics of the enemy, the US needed to leverage its vast technological advantage as much as possible to try to gain the upper hand over Viet Cong insurgents. Radar had been deployed since the 1930s, and the technology had vastly improved by 1966. One of the radars used in Vietnam then was the AN/TPS-25 (“Tipsy-25”), which in Army equipment nomenclature stands for Army-Navy System (AN); Ground, Transportable (T); Radar (P); Detecting, Range and Bearing, Search (S); Model (25).

The AN/TPS-1 began to see service in WWII as a long-range search radar. Model 25 was a ground surveillance radar which could detect the presence of moving targets and supply range, azimuth, and target type information. It used a rotating half-square-meter-area parabolic reflector antenna and could be mounted on a tripod or mast to a maximum height of 25 feet. The operator would listen to a tone, which he would use along with automatic and manual control to pinpoint the location and distinguish between different types of moving target (dismounted person, tracked vehicle, truck). The location was lit up on a paper map plotting board, and the appropriate action could be taken against the target. The crew consisted of seven men. Equipment included a shelter with electronics, the radar and mast/tripod, and three vehicles which carried the Tipsy-25 and other components, including a teletypewriter set, radios, and power units.