RADAR stands for Radio Detection and Ranging, and is a system used to detect objects and measure their distance by using radio waves. PATHFINDER is an acronym for Pulse Airborne Targeting Radar, which is a type of RADAR used in aircrafts to detect and track targets. INUSE is an acronym for Identification of Uncorrelated Signals and Echoes, which is a technique used in RADAR systems to distinguish between multiple targets. Lastly, DOPPLER is an acronym for Doppler Effect, which is a phenomenon that occurs when the frequency of a wave changes due to the relative motion between the source and the observer. This phenomenon is used in RADAR systems to measure the velocity of a target.