the motorola an/fps-23 was a short-range early warning radar deployed on the distant early warning line (dew line). it was used as a "gap filler", looking for aircraft attempting to sneak by the dew line by flying between the main an/fps-19 stations at low altitude. it could detect aircraft flying at 200 feet over land or 50 feet over water. the system was known as fluttar during its development at the lincoln laboratory, and this name was widely used.