RADaR

a system for detecting the presence, direction, distance, and speed of aircraft, ships, and other objects, by sending out pulses of high-frequency electromagnetic waves that are reflected off the object back to the source.

• an apparatus used for radar.
  plural noun: radars

• used to indicate that someone or something has or has not come to the attention of a person or group.
  "the band has been kind of off the radar these past few years"