Radar

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Radar
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Surveillance Systems

• Use of radio waves transmitted into air
• Waves reflected by an object in path of beam are
  returned
• Range determined by measuring time (SOL) for wave
  to go out to and return to receiving antenna.
• Direction determined by position of rotating
  antenna when reflected wave received.

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Limitations

• Amount of reflective surface determines size of
  radar return.
• Radio waves normally travel in continuous
  straight lines unless
• "Bent" by atmospheric phenomena (temperature
  inversions)
• Reflected or attenuated by dense objects (heavy
  clouds, precip, ground clutter)
• Screened by high terrain
• Stationary/slow moving targets eliminated by
  moving target indicator (MTI)
• Radar energy reflected blocks aircraft at same
  range and weakens or eliminates display of
  targets at greater range.
• Aircraft flying tangential may not be displayed.
• Low altitude aircraft screened by terrain or
  below radar (earth curvature)
• First priority vertical, lateral, or longitudinal
  separation between IFR aircraft
• VFR limited by traffic and workload

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Air Traffic Control Radar Beacon System (ATCRBS)

• Secondary surveillance radar, three main
  components
• 1. Interrogator. ground based unit transmits
  (scans) in synch with primary radar and transmits
  discrete radio signals to all transponders to
  reply.
• 2. Transponder. airborne unit receives signals
  from interrogator and selectively replies with a
  specific pulse group (code) only to those
  interrogations being received on mode to which
  set. Replies are independent of, and much
  stronger than a primary radar return.
• 3. Radarscope. displays both primary radar
  system and ATCRBS.

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Advantages of ATCRBS

• Reinforcement of radar targets.
• Rapid target identification.
• Unique display of selected codes. part of ATCRBS
  ground equipment is decoder. enables controller
  to assign discrete transponder codes to each
  aircraft.
• Beacon (transponders) and MTI combat ground
  clutter and weather
• Some Locations Secondary-Radar-Only

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4-5-3. Surveillance Radar

• Two general categories
• Airport Surveillance Radar (ASR) provides
  short-range coverage in general vicinity of
  airport to handle terminal area traffic. Can
  also be used as an instrument approach aid.
• Air Route Surveillance Radar (ARSR).
• long-range radar for large areas.

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4-5-4. Precision Approach Radar (PAR)

• A landing aid that displays range, azimuth, and
  elevation info
• Two antennas one scanning a vertical plane, and
  the other scanning horizontally.
• Range is limited to 10 miles, azimuth to 20
  degrees, and elevation to 7 degrees, only the
  final approach area is covered

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4-5-5. Airport Surface Detection Equipment -
Model X (ASDE-X)

• Provides high resolution, short-range, clutter
  free surveillance info about aircraft and
  vehicles, both moving and fixed, located on or
  near surface of airport's runways and taxiways

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4-5-6. Traffic Information Service (TIS)

• Provides info to cockpit via data link, similar
  to VFR radar traffic advisories over voice radio.
  
• Improves safety and efficiency of "see and avoid"
  flight through an automatic display that informs
  pilot of nearby traffic and potential conflict
  situations.
• Assists pilot in visual acquisition of these
  aircraft.
• Employs enhanced Mode S radar system, to "uplink"
  information to suitably-equipped aircraft
• Provides estimated position, altitude, altitude
  trend, and ground track information
• Up to 8 intruder aircraft within 7 NM, 3,500 and
  -3,000 feet vertically of client aircraft
• Indicates target a threat within 34 seconds
• Does not display an precise distance.
• Data derived from ATC radar uplinked to client
  aircraft on each radar scan (nominally every 5
  seconds).

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TIS Proximity Coverage Volume
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Terminal Mode S Radar Sites
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Concepts Capabilities

• Intruder aircraft must have operating transponder
  (Mode A, C or S).
• Provides following data on each intruder
  aircraft
• Relative bearing information in 6-degree
  increments.
• Relative range in 1/8 NM to 1 NM increments
  (depending on range).
• Relative altitude in 100-foot increments (within
  1,000 feet) or 500-foot increments (from
  1,000-3,500 feet) if intruder has Mode C
• Estimated intruder ground track in 45-degree
  increments.
• Altitude trend data (climbing/descending gt500
  fpm) if intruder aircraft has Mode C.
• A max of eight (8) intruders may be displayed if
  more than eight "most significant" intruders are
  uplinked.
• Closest proximity and/or greatest threat to TIS
  client.

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Status Messages

• Alert. Identifies a potential collision hazard
  within 34 seconds.
• TIS Traffic. TIS traffic data is displayed.
• Coasting. TIS display more than 6 seconds old.
  indicates missing uplink from ground. When TIS
  info more than 12 seconds old, "No Traffic"
  status indicated.
• No Traffic. No intruders meet proximate or alert
  criteria. may exist when TIS system functional or
  may indicate "coasting" between 12 and 59 seconds
  old (see (c) above).
• TIS Unavailable. No ground system is available.
  Displayed when TIS uplinks missing for 60 sec.
• TIS Disabled. The pilot has not requested TIS or
  has disconnected from TIS.
• Good-bye. The client aircraft has flown outside
  of TIS coverage.

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NOTE-

• Depending on avionics mfgr, some messages not
  available to pilot.
• client aircraft and display is oriented "track
  up," (12 o'clock the top)
• Rings indicate 2 and 5 NM.
• Each intruder depicted by symbol positioned at
  approximate relative bearing and range from
  client.
• Circular symbol near center indicates an "alert"
  intruder
• diamond symbols indicate "proximate" intruders.

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Limitations

• Does not relieve pilot responsibility to "see and
  avoid" other aircraft
• Shall not be for avoidance maneuvers during IMC
  or other times when there is no visual contact
  with the intruder aircraft.
• No recommended avoidance maneuvers are provided
  for, nor authorized, as a direct result of a TIS
  intruder display or TIS alert.