1. Air Traffic Control Radar
Ruofei Fu
EECS 725

2. 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)

3. 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.

4. 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.

5. 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

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

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

8. 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:

9. Primary Surveillance Radar(PSR)
Block Diagram:

10. 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

11. 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

12. Secondary Surveillance Radar(SSR)
Block diagram:

13. Secondary Surveillance Radar(SSR)
Circular Direction
Narrow Beam

14. 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

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

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

17. 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

18. 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.

19. Reference
Craig Freudenrich, Ph.D, How Air Traffic Control Works
Preeti Jain, Classification of RADARs,
Radar Basics,
Fact Sheet – Co-Located TRACONS (Terminal Radar Approach Control),

20. Air Traffic Control Radar
Thank you