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Aviation Use of Radar

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					Aviation Use of Radar

 WP8B/8D Radar Seminar
    September 2005
                   Radar Types
• Ground-based
  • Surveillance
     • Long Range
     • Terminal
  • Others
     • Precision approach
     • Surface detection
     • Weather
• Airborne
  • Radar altimeter
  • Weather
                      WP8B/8D Radar Seminar -   2
                             Aviation
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 @ 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
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                             Aviation
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
                  WP8B/8D Radar Seminar -             4
                         Aviation
        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
                       WP8B/8D Radar Seminar -                    5
                              Aviation
         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.

                         WP8B/8D Radar Seminar -                           6
                                Aviation
             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

                 WP8B/8D Radar Seminar -        7
                        Aviation
 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.
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                                    Aviation
      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

                  WP8B/8D Radar Seminar -   9
                         Aviation
 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

                    WP8B/8D Radar Seminar -               10
                           Aviation
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 controller’s 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


                   WP8B/8D Radar Seminar -                  11
                          Aviation
  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.

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                              Aviation