WP8B/8D Radar Seminar - Aviation 3 Ground: Surveillance Radar (1 of 2) Long Range Radar ~ 130 sites in US Band: MHz, in ARNS (5.331, 5.334) Sensitivity: 1-2 m 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
WP8B/8D Radar Seminar - Aviation 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
WP8B/8D Radar Seminar - Aviation 5 Ground: Others (1 of 2) Precision Approach Radar (PAR) Band: GHz Allows controller to direct precision approaches Primarily military use in the US; civil back-up Surface Detection Band: GHz (ASDE-X), 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 - Aviation 6 Ground: Others (2 of 2) Weather NEXRAD ~ 150 sites in US Band: 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: 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 - Aviation 7 Airborne Radar Radar altimeter Band: MHz in ARNS Integral part of precision landing systems Also integrated into terrain-warning sensors Weather Radars Bands: MHz, MHz, GHz, GHz Used for weather detection, windshear and turbulence detection and ground mapping
WP8B/8D Radar Seminar - Aviation 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.
WP8B/8D Radar Seminar - Aviation 9 Airborne Radar Characteristics Radar Altimeters Frequency Range MHz Center Frequency /- 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 - Aviation 10 Airborne Radar Characteristics Airborne Weather Radars Band: 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 - Aviation 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
WP8B/8D Radar Seminar - Aviation 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.