Aviation Use of Radar

1
Aviation Use of Radar

• WP8B/8D Radar Seminar
• September 2005

2
Radar Types

• Ground-based
• Surveillance
• Long Range
• Terminal
• Others
• Precision approach
• Surface detection
• Weather
• Airborne
• Radar altimeter
• Weather

3
Ground Surveillance Radar (1 of 2)

• Long Range Radar 130 sites in US
• Band 1240-1370 MHz, in ARNS (5.331, 5.334)
• Sensitivity 1-2 m2 target _at_ 200 to 250 nmi
• Mission Detection and tracking of aircraft at
  long ranges for ATC use.
• Secondary weather detection function
• Backup for terminal radar (w/ increased
  separations)
• 12 second scan
• Vertical polarization for tracking circular for
  weather
• Shared with Defense Department and Department of
  Homeland Security

4
Ground Surveillance Radar (2 of 2)

• Terminal Radar 300 sites in US
• Terminal area coverage
• 4.8 second scan
• Normally sited at airports with traffic above a
  certain level
• Some are mosaiced allowing multiple radars to
  form a single picture of the airspace
• Integral part of procedural response to
  navigation aid outages

5
Ground Others (1 of 2)

• Precision Approach Radar (PAR)
• Band 9.0-9.2 GHz
• Allows controller to direct precision approaches
• Primarily military use in the US civil back-up
• Surface Detection
• Band 9.0-9.2 GHz (ASDE-X), 15.7-16.2 GHz
  (ASDE-3)
• ASDE-X for small/medium airports currently 30
  systems, however expected to increase
• ASDE-3 installed at 40 large airports
• 1 second scan

6
Ground Others (2 of 2)

• Weather
• NEXRAD 150 sites in US
• Band 2700-3000 MHz
• 200 nmi coverage volume
• Sited off-airport
• Series of scans in increasing altitudes, 6 minute
  repeat period
• Single frequency, circular polarization
• Terminal Doppler Weather Radar (TDWR) 45 in US
• Band 5600-5650 MHz
• Detects wind shear and local weather phenomena
• 45 nmi coverage
• Located at major airports with history of severe
  thunderstorms
• Single frequency, multiple waveforms, multiple
  scan options depending on local conditions.

7
Airborne Radar

• Radar altimeter
• Band 4200-4400 MHz in ARNS
• Integral part of precision landing systems
• Also integrated into terrain-warning sensors
• Weather Radars
• Bands 5350-5470 MHz, 8750-8850 MHz, 9.3-9.5
  GHz, 13.25-13.4 GHz
• Used for weather detection, windshear and
  turbulence detection and ground mapping

8
Radar Hardware Characteristics

• Ground-based Surveillance
• Two frequency, paired with fixed delta-f (limits
  assignable channels)
• Diplexed for increased performance, or
  hot-standby (use alternate frequency if
  interference detected)
• Some use of chirped or compressed waveforms
• Fan beams newer versions with beam forming array
  to help provide target altitude discrimination
• Sector blanking not allowed on commissioned
  radar, 360 degree coverage required
• Ground-based Other
• PAR/ASDE-X implement 4 frequencies, however can
  meet performance objectives with 2.
• ASDE-3 has 16-frequency hopset, 2 assignable
  hopping patterns.
• Multipath and rain attenuation offer significant
  challenges.
• Weather radar is generally single frequency with
  multiple waveforms
• Waveform selection tailored to prevailing
  weather patterns.
• Sector scans can be implemented to focus
  attention on developing problem areas.

9
Airborne Radar Characteristics

• Radar Altimeters
• Frequency Range 4200-4400 MHz
• Center Frequency 4300 /- 25 MHz
• Transmit power 20 mW to 500 mW
• Range up to 1526 Meters
• Pulse width 200 ns
• Antenna Beamwidth 70 degrees

10
Airborne Radar Characteristics

• Airborne Weather Radars
• Band 9300-9500 MHz
• Avoidance Range 340 nm
• Transmit Power to Antenna 35 W 12 kW
• Pulse Width (microseconds) 1 to 28.8
• Antenna Pattern type pencil beam
• Antenna flat plate and flat plate slotted array

11
Radar Processing Characteristics

• Radar design depends on operational environment
  and performance goals. Some offer some form of
  screen clutter removal
• Does not mitigate interference, simply keeps it
  from showing on the controllers screen
• Ground clutter mapping If certain range bins
  keep getting reflections from a fixed target
  (e.g., a building), will notch-out those bins.
• Moving Target processing Will not show targets
  moving slower than a set threshold rate

12
Automatic Dependant Surveillance (ADS)

• Aircraft periodically provides own-ship position
  and intent information (broadcast or on a
  contract basis)
• Some question if ADS reduces need for radar
• Issues
• Requires all aircraft to be equipped
• Reduces possibility of procedural workarounds
  for navaid outages
• Requires all aircraft to participate
• How address a 9/11-like situation?
• Bottom line Many issues need to be addressed,
  studies continue.