Air Traffic Control Radar Ruofei Fu EECS 725

Air Traffic Control (ATC) During peak air travel times in the United States, there are about 5,000 airplanes in the sky every hour. How do aircraft avoid each other? AIR TRAFFIC CONTROL (ATC)

Air Traffic Control (ATC) Zones The United States airspace is divided into 21 zones (centers), and each zone is divided into sectors. The shape and size of zones is determined by the volume of air traffic.

Air Traffic Control (ATC) TRACON (Terminal Radar Approach CONtrol) airspaces •In each zone there are portions of airspace, about 50 miles in diameter, called TRACON airspaces. • In each TRACON airspace there are a number of airports, each has its own airspace with a 5-mile (8-km) radius.

Air Traffic Control System Facilities Flight Service Stations Provides information (weather, route, terrain, flight plan) Assists pilots in emergencies Airport Traffic Control Towers(ATCTs) Located at every airport Handle all takeoff, landing, and ground traffic Terminal Radar Approach Controls(TRACONs) Handles departing and approaching aircraft separation and sequencing. Air Route Traffic Control Centers(ARTCCs) It provides ATC services outside TRACON airspace Air Traffic Control System Command Center(ATCSCC) Oversees all air traffic control

Two main types of radar in ATC Primary Surveillance Radar(PSR) Secondary Surveillance Radar(SSR)

Primary Surveillance Radar(PSR) First used in WWII Aircraft reflects electromagnetic radiation Radar and antenna move in a circular sweep

Primary Surveillance Radar(PSR) The radar sends a signal and times how long it getting back, and calculated the distance of objective. slant range antenna - aim:

Primary Surveillance Radar(PSR) Block Diagram:

Secondary Surveillance Radar(SSR) A secondary Radar system is a cooperative target identification system in which the interrogator transmits an encoded signal to a aircraft. The transponder on board receive the interrogation and reply by transmitting in 4-digit transponder code back to SSR. Identify Friend or Foe(IFF) is the first identification system used by military during WWII. The SSR antenna usually stand on top of PSR, and sweeping with PSR

Secondary Surveillance Radar(SSR) Transponder: An electronic device, that let ATC to identify aircraft position and altitude ATC gives a specific squawk code for the aircraft Pilot enter identify-code into transponder, so ATC can recognize the aircraft

Secondary Surveillance Radar(SSR) Block diagram:

Secondary Surveillance Radar(SSR) Circular Direction Narrow Beam

Secondary Surveillance Radar(SSR) Aircraft Transponder Control Unit(in cockpit): The 4 digits are octal numbers, which means that each number has the options from 0 to 7. There are 4096 possible code combinations. Pilot uses the combination to send message to identify their aircraft Two main modes of Transponder: Mode A - ON: It transmits beacon code without altitude information Mode C - ALT: It transmits altitude information to ATC with beacon code

Secondary Surveillance Radar(SSR) Radar screen for ATC Controller:

Secondary Surveillance Radar(SSR) SSR-Special Transponder Code 7500 -Hijack(taken alive) 7600 - Lost Comm(technical glitch) 7700 - Emergency(going to heaven) Every radar facility in range would receive these alert from pilot.

Secondary Surveillance Radar(SSR) Primary Radar(PSR) Aircraft is a passive element Aircraft reflects electromagnetic energy back to radar antenna Secondary radar (SSR) Aircraft is as active element Aircraft answers by send signal back to SSR

PSR and SSR Comparison PSR SSR A Primary Radar transmits high-frequency and power signals toward the targets. It doesn't require any co-operation primary radar is more like seeing something in the distance with eyes Requires much less transmitting power to provide coverage Transponders receive the interrogation and reply by transponder code secondary radar is more like sending a text to the crew of the aircraft, and them sending back an SMS with their position and a lot of other information.

Reference Craig Freudenrich, Ph.D, How Air Traffic Control Works http://science.howstuffworks.com/transport/flight/modern/air-traffic-control3.htm Preeti Jain, Classification of RADARs,http://www.engineersgarage.com/articles/types-of-radars Radar Basics, http://www.radartutorial.eu/02.basics/Pulse%20Radar.en.html Fact Sheet – Co-Located TRACONS (Terminal Radar Approach Control), http://www.faa.gov/news/fact_sheets/news_story.cfm?contentkey=4009

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