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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 - Model X (ASDE-X)
a. The Airport Surface Detection Equipment -
Model X (ASDE-X) is a multi-sensor surface
surveillance system the FAA is acquiring for airports
in the United States. This system will provide 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 sys-
tem 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 transponders.
2. Interfaces. ASDE-X contains an automa-
tion interface for flight identification via all
automation platforms and interfaces with the
terminal radar for position information.
3. ASDE-X Automation. A Multi-sensor
Data Processor (MSDP) combines all sensor reports
into a single target which is displayed to the air traffic
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
Surveillance Systems 4-5-7