F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Loran Update

Mitchell Narins (US FAA)

G. Thomas Gunther (Booz Allen Hamilton)

Sherman Lo (Stanford University)

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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)

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Loran Technical Evaluation Report March 2004

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

The Evaluation Team’s The Evaluation Team’s ConclusionConclusion“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.”

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Loran Modernization

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

North American Loran SystemNorth American Loran System

New SSX Installed!

George, Washington;

Dana, Indiana;

Fallon, NV;

Searchlight, NV; and

Middleton, CA

New TFE also Installed! Baudette, MN; Seneca, NY;

Boise City, OK; Malone, FL; Havre, MT; and Jupiter, FL

TTX Stations: 66 US, 11 Canadian

Control Stations

New SSX Stations:New SSX Stations: 55 US

LSU

SSX Stations: 77 US, 44 Canadian

SSX Stations w/New TFE: 6 USSSX Stations w/New TFE: 6 US

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Loran Working Groups

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Detecting Early Skywave

Baudette – Dunbar Forest

Boise City – Little Rock

Boise City – Little Rock

From Dunbar Forest, MN & Little Rock, AK (8970 Alpha 1 monitors) 02-03 NOV 2003

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Early Skywave Detection Network: Path Midpoints for Early Skywave

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Test Locations

University of Minnesota

Oklahoma University

Langmuir Laboratory

Middletown

Loran-C TowerMiddletown, CA

University of MinnesotaMinneapolis, MN

Langmuir LabSocorro, NM

University of OklahomaNorman, OK

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Atmospheric Noise Front End

35 KHz BW @ 100kHz BPF

200 Hz BW @ 100kHz BPF

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

University of Oklahoma

Locus Loran Antenna35kHz & 200Hz

True Time AntennaTiming

Wide-band Flat Plate Antenna250kHz BW

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Flight Route for ASF Validation Testing

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

FAA Van for Collection of ASF data

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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.

38.85 38.9 38.95 39 39.05 39.1 39.15 39.2 39.25

-2.8

-2.7

-2.6

-2.5

-2.4

-2.3

-2.2

-2.1

-2

-1.9

Lat

AS

F

Seneca

300m300m

600m

600m

1200m1200m

1500m

1500m

3000m3000m

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Airship Test for Altitude Variation

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Loran Timing Performance Panel

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Loran Testing and Applications

Boston Harbor Testing (PIG)

NYC Testing (Volpe)

NM GPS Jamming Tests (Volpe)

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Testing of Loran in an Urban Environment

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Testing in GPS Jamming Environment

Jamming Begins

Loran & Integrated Loran DR

DR

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

User Equipment Development

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

Certified Receiver Development

Freeflight Locus

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

FreeFlight/LocusFreeFlight/LocusGA Multi-Mode ReceiverGA 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

F E D E R A L A V I A T I O N A D M I N I S T R A T I O N • A I R T R A F F I C O R G A N I Z A T I O N

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