Secondary surveillance radar (SSR) is a radar system used in air traffic control (ATC), that not only detects and measures the position of aircraft i.e. range and bearing, but also requests additional information from the aircraft itself such as its identity and altitude. Unlike primary radar systems that measure only the range and bearing of targets by detecting reflected radio signals, SSR relies on targets equipped with a radar transponder, that replies to each interrogation signal by transmitting a response containing encoded data. SSR is based on the military identification friend or foe (IFF) technology originally developed during World War II, therefore the two systems are still compatible. Monopulse secondary surveillance radar (MSSR), Mode S, TCAS and ADS-B are similar modern methods of secondary surveillance.
Famous quotes containing the words secondary and/or radar:
“The prime purpose of being four is to enjoy being fourof secondary importance is to prepare for being five.”
—Jim Trelease (20th century)
“So I begin to understand why my mothers radar is so sensitive to criticism. She still treads the well-worn ruts of her youth, when her impression of mother was of a woman hard to please, frequently negative, and rarely satisfied with anyoneleast of all herself.”
—Melinda M. Marshall (20th century)