Airport surveillance radar
[1] The primary radar typically consists of a large rotating parabolic antenna dish that sweeps a vertical fan-shaped beam of microwaves around the airspace surrounding the airport.
[1] The positions of the aircraft are displayed on a screen; at large airports on multiple screens in an operations room at the airport called in the US the Terminal Radar Approach Control (TRACON), monitored by air traffic controllers who direct the traffic by communicating with the aircraft pilots by radio.
They are responsible for maintaining a safe and orderly flow of traffic and adequate aircraft separation to prevent midair collisions.
The primary surveillance radar (PSR) consists of a large parabolic "dish" antenna mounted on a tower so it can scan the entire airspace unobstructed.
It transmits pulses of microwave radio waves in a narrow vertical fan-shaped beam about a degree wide.
The dish is rotated at a constant rate about a vertical axis so the beam scans the entire surrounding airspace about every 5 seconds.
The primary radar displays a "return" indiscriminately from any object in its field of view, and cannot distinguish between aircraft, drones, weather balloons, birds, and some elevated features of the terrain (called "ground clutter").
Due to its crucial safety purpose, extreme uptime requirements, and need to be compatible with all the different types of aircraft and avionics systems, the design of airport surveillance radar is strictly controlled by government agencies.
[2] It is a relocatable, solid-state, all-weather radar with dual-channel, frequency diversity, remote operator controls, and a dual beam tower mounted antenna.
The antenna covers an elevation of 40° from the horizon with two feedhorns which create two stacked overlapping vertical lobes 4° apart; the lower beam transmits the outgoing pulse and is used to detect distant targets near the horizon, while the upper receive-only beam detects closer higher elevation aircraft with less ground clutter.
It has a remote monitoring and maintenance subsystem; if a fault occurs a built-in test detects and isolates the problem.
Like all airport surveillance radars it has a backup diesel generator to continue operating during power outages.
The DASR system detects aircraft position and weather conditions in the vicinity of civilian and military airfields.
The older radars, some up to 20 years old, are being replaced to improve reliability, provide additional weather data, reduce maintenance cost, improve performance, and provide digital data to new digital automation systems for presentation on air traffic control displays.
Functions include aircraft separation, weather advisories, and lower level control of air traffic.
[5] Airport Surveillance Radar is beginning to be supplemented by ADS-B Automatic dependent surveillance-broadcast in the US and other parts of the world.
