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Loran Update

Loran Update. Mitchell Narins (US FAA) G. Thomas Gunther (Booz Allen Hamilton) Sherman Lo (Stanford University). Key Points. Loran technical evaluation report March 2004

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Loran Update

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  1. Loran Update Mitchell Narins (US FAA) G. Thomas Gunther (Booz Allen Hamilton) Sherman Lo (Stanford University)

  2. Key Points • Loran technical evaluation report March 2004 • Loran can technically satisfy the aviation, maritime, and timing requirements allowing users to retain most benefits of GPS • While no decision has been made on Loran, work is progressing to implement enhanced Loran (eLoran) • Loran modernization • Loran working groups • Loran timing panel • Loran user equipment development • Loran testing and applications

  3. Loran & its Role in the US • Loran is currently: • A hyperbolic radionavigation system… • …operating between 90 kHz and 110 kHz… • …that uses a very tall antenna… • …that broadcasts primarily a groundwave • …at high power… • …that provides both lateral position… • …and a robust time and frequency standard • A supplemental system for enroute navigation in the US National Airspace System (NAS) • A system for maritime navigation in the coastal confluence zone (CCZ) • A Stratum 1 frequency standard (i.e., 1 x 10-11) that also provides time within 100 ns of UTC (USNO)

  4. Loran Technical Evaluation Report March 2004

  5. The Evaluation Team’s Conclusion “The evaluation shows that the modernized Loran system could satisfy the current NPA, HEA, and timing/frequency requirements in the United States and could be used to mitigate the operational effects of a disruption in GPS services, thereby allowing the users to retain the benefits they derive from their use of GPS.” “This conclusion is based on an analysis of the applications’ performance requirements; expected modification of radionavigation policies, operating procedures, transmitter, monitor and control processes, and user equipment specifications; completion of the identified Loran-C infrastructure changes; and results from numerous field tests. Collectively, these create the architecture for the modernized Loran system.”

  6. Loran Modernization

  7. Loran Modernization • Current accomplishments • All stations upgraded to new TFE • All CONUS stations upgraded to SSX • 11 stations upgraded to Legacy SSX: Baudette, Boise City, Havre, Malone, Seneca, Jupiter, Carolina Beach, Nantucket, Caribou, Grangeville, Raymondville, Gillette, Las Cruces • New SSX INSTALLS: George, Dana, Fallon, Searchlight and Middletown • New Loran Command and Control System (NLCCS) installed & operating at NavCen East (NavCen West soon) • Developing • Testing TOT Operations • Loran Enhanced Monitoring System (LEMS) • Loran Information Control and Operations System (LICOS) • Transmitter equipment necessary for eLoran is installed in CONUS

  8. New SSX Stations:5 US TTX Stations: 6 US, 1 Canadian SSX Stations w/New TFE: 6 US SSX Stations: 7 US, 4 Canadian LSU Control Stations North American Loran System New TFE also Installed! Baudette, MN; Seneca, NY; Boise City, OK; Malone, FL; Havre, MT; and Jupiter, FL New SSX Installed! George, Washington; Dana, Indiana; Fallon, NV; Searchlight, NV; and Middleton, CA

  9. Loran Working Groups

  10. Loran Working Groups • Continued assessment and development of Loran for aviation & maritime operations • Standards: Receiver MOPS and system safety assessment • Refinement of hazard models: noise, variations in ASF, ECD, etc. • Development of system infrastructure and design: Early skywave detection network, ninth pulse messages, ASF & dLoran grid, dLoran monitor • This work prepares the necessary assessments, analyses, and documents for certification

  11. Example 1: Early Skywave Testing • Early skywave is a major integrity hazard since it interferes with the desired groundwave • Analogous to GPS multipath • Develop monitor receiver & tests to determine if an event occurred • Develop network to detect event and determine affected area • Develop protocols and message design to warn users

  12. Detecting Early Skywave Boise City – Little Rock Baudette – Dunbar Forest Boise City – Little Rock From Dunbar Forest, MN & Little Rock, AK (8970 Alpha 1 monitors) 02-03 NOV 2003

  13. Early Skywave Detection Network: Path Midpoints for Early Skywave

  14. Early Skywave Network Simulator • Simulator tests network design against potential early skywave events • Worst case failures • False alarms • Also test warning algorithms • Plot shows early skywave detection points if all transmitters and SAM used in monitor network • Red areas are where early skywave could exist • Highlighted points are detected locations

  15. Example 2: Atmospheric Noise Testing • Atmospheric noise is the major source of noise in the Loran band • CCIR is the standard model • Validation and refinement of CCIR models used for coverage predictions • Development of processing to reduce the effect of noise and improve coverage

  16. Test Locations University of Minnesota Minneapolis, MN Loran-C Tower Middletown, CA University of Oklahoma Norman, OK Langmuir Lab Socorro, NM University of Minnesota Middletown Oklahoma University Langmuir Laboratory

  17. Atmospheric Noise Front End 35 KHz BW @ 100kHz BPF 200 Hz BW @ 100kHz BPF

  18. University of Oklahoma Wide-band Flat Plate Antenna 250kHz BW Locus Loran Antenna 35kHz & 200Hz True Time Antenna Timing

  19. Preliminary Results • Confirms both CCIR noise levels & amplitude distribution • CCIR suggestion for translation to Loran band seems valid • Suggests that high noise (> 100 dBuV/m) levels are possible for Loran • Suggests that nonlinear processing could produce significant gain CCIR predicts the above median APD values for our bandwidth! Predicted and Actual Amplitude Probability Distribution

  20. Example 3: ASF Testing • Validation of ASF models used for integrity and coverage predictions • Test effects of hazards • Preliminary development of procedures for airport survey and generating government supplied ASF for aviation • Preliminary development of ASF grid and monitor density necessary to support HEA

  21. Flight Route for ASF Validation Testing

  22. FAA Van for Collection of ASF data

  23. Variation of ASF with Altitude • Plane flew back and forth between 2 points at various altitudes: 300m, 600m, 1200m, 1500m, 3000m • ASF variation may be due to antenna directionality, measurement error, etc.

  24. Airship Test for Altitude Variation

  25. Loran Timing Performance Panel

  26. Loran Testing and Applications Boston Harbor Testing (PIG) NYC Testing (Volpe) NM GPS Jamming Tests (Volpe)

  27. Example 1: Land Mobile Testing • Test the use of Loran, Loran & DR, integrated GPS/Loran/DR in urban environments • Test the use of Loran, Loran & DR, integrated GPS/Loran/DR in GPS jamming conditions • Demonstrate when using Loran is effective in an integrated navigation system

  28. Testing of Loran in an Urban Environment

  29. Jamming Begins DR Loran & Integrated Loran DR Testing in GPS Jamming Environment

  30. User Equipment Development

  31. Freeflight Locus Certified Receiver Development

  32. FreeFlight/LocusGA Multi-Mode Receiver • Phase I Prototype (Two-box initial solution) similar to GPS/WAAS/Loran Rockwell Collins MMR/Locus development • Phase I Prototype testing of Integrated GPS/WAAS/Loran receiver testing progressing at this time • Phase II Prototype will be available for testing Spring 2005

  33. Summary • Loran Modernization Proceeding: CONUS completed • Loran Working Groups working to prepare Loran for certification in aviation RNP 0.3 and maritime HEA applications • User equipment and receivers that can support eLoran currently being developed and tested

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