PSR is primary Surveillance Radar. Primary radar is ? classical" radar which reflects all kind of echoes, including aircraft and clouds. A radio detection system that transmits short bursts (pulses) of RF energy and detects their echoes from objects (targets) such as aircraft or ships. The round - trip propagation time for the echo return may be used to determine the target's range (distance from the radar's antenna). This type of radar (now called primary radar) can detect and report the position of anything that reflects its transmitted radio signals including, depending on its design, aircraft, birds, weather and land features.