WESTON was one of the few Program 989 satellites that had a communications intelligence mission, designed “to intercept, recognize, and record Mercury Grass and Dawn Rose communications signals in the 60 to 70 MHz and the 360 to 420 MHz frequency bands,” according to a mission summary. WESTON would “measure the frequency and power of the intercepted signal,” but would not geolocate the targets. [14]
Mercury Grass was a NATO reporting name for a truck-mounted communications system used by the headquarters of SA-2 Guideline surface-to-air missile emplacements to communicate with their battalions, and much more importantly,
used by Soviet field units to communicate back to Moscow. It was apparently a very clever and sophisticated communications system that Western intelligence agencies had discovered almost by accident. The Soviet Dawn Rose communications system’s purpose is unknown, but it operated in the 360–410 megahertz frequency band.