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AIM

10/12/17

4−5−7

Surveillance Systems

4−5−3. Surveillance Radar

a. Surveillance radars are divided into two general

categories: Airport Surveillance Radar (ASR) and

Air Route Surveillance Radar (ARSR).

1. ASR is designed to provide relatively

short−range  coverage in the general vicinity of an

airport and to serve as an expeditious means of

handling terminal area traffic through observation of

precise aircraft locations on a radarscope. The ASR

can also be used as an instrument approach aid.

2. ARSR is a long−range radar system designed

primarily to provide a display of aircraft locations

over large areas.

3. Center Radar Automated Radar Terminal

Systems (ARTS) Processing (CENRAP) was devel-

oped to provide an alternative to a nonradar

environment at terminal facilities should an ASR fail

or malfunction. CENRAP sends aircraft radar beacon

target information to the ASR terminal facility

equipped with ARTS. Procedures used for the

separation of aircraft may increase under certain

conditions when a facility is utilizing CENRAP

because radar target information updates at a slower

rate than the normal ASR radar. Radar services for

VFR aircraft are also limited during CENRAP

operations because of the additional workload

required to provide services to IFR aircraft.

b. Surveillance radars scan through 360 degrees of

azimuth and present target information on a radar

display located in a tower or center. This information

is used independently or in conjunction with other

navigational aids in the control of air traffic.

4−5−4. Precision Approach Radar (PAR)

a. PAR is designed for use as a landing aid rather

than an aid for sequencing and spacing aircraft. PAR

equipment may be used as a primary landing aid (See

Chapter 5, Air Traffic Procedures, for additional

information), or it may be used to monitor other types

of approaches. It is designed to display range,

azimuth, and elevation information.

b. Two antennas are used in the PAR array, one

scanning a vertical plane, and the other scanning

horizontally. Since the range is limited to 10 miles,

azimuth to 20 degrees, and elevation to 7 degrees,

only the final approach area is covered. Each scope is

divided into two parts. The upper half presents

altitude and distance information, and the lower half

presents azimuth and distance.

4−5−5. Airport Surface Detection

Equipment (ASDE−X)/Airport Surface

Surveillance Capability (ASSC)

a. ASDE−X/ASSC is a multi−sensor surface

surveillance system the FAA is acquiring for airports

in the United States. This system provides high

resolution, short−range, clutter free surveillance

information about aircraft and vehicles, both moving

and fixed, located on or near the surface of the

airport’s runways and taxiways under all weather and

visibility conditions. The system consists of:

1. A Primary Radar System. ASDE−X/

ASSC system coverage includes the airport surface

and the airspace up to 200 feet above the surface.

Typically located on the control tower or other

strategic location on the airport, the Primary Radar

antenna is able to detect and display aircraft that are

not equipped with or have malfunctioning transpond-

ers.

2. Interfaces. ASDE−X/ASSC contains an

automation interface for flight identification via all

automation platforms and interfaces with the

terminal radar for position information.

3. Automation. A Multi−sensor Data Proces-

sor (MSDP) combines all sensor reports into a single

target which is displayed to the air traffic controller.

4. Air Traffic Control Tower Display. A high

resolution, color monitor in the control tower cab

provides controllers with a seamless picture of airport

operations on the airport surface.

b. The combination of data collected from the

multiple sensors ensures that the most accurate

information about aircraft location is received in the

tower, thereby increasing surface safety and

efficiency.