What Is Radar The word "radar" was invented by scientists of the United States Navy during World War II. The word comes from the first letters in the term "radio detection and ranging.""Detection," as used here, means finding an object or target by sending out a radio signal that will bounce back off the target as a radio echo. "Ranging" means measuring the distance to the target from the radar set(the device tat sends out the radio signal and picks up the returning echo). Radar set on the ground uses radio echoes to locate aircraft, ships, and other objects. Radar sets can locate artificial satellites and spacecraft thousands of kilometres from