Loran Integrity Performance Panel The Loran Integrity Performance Panel Sherman Lo, Per Enge, & Lee Boyce, Stanford University Ben Peterson, Peterson Integrated Geopositioning Tom Gunther & Bob Wenzel, Booz Allen Hamilton Lt. Kevin Carroll, US Coast Guard Loran Support Unit Kevin Bridges & Mitch Narins, FAA International Loran Association 2002 Washington DC, October 27-30, 2002

Loran Integrity Performance Panel 2 Outline Background Requirements Integrity Analysis QHazards QFault Tree Other Loran Issues Conclusions

Loran Integrity Performance Panel 3 Loran Basics 100 kHz ( kW) Groups of 8 1 kHz Hyperbolic, 2D Groundwave Configured in chains of a master & 2-5 secondaries Chains characterized by Group Repetition Intervals (GRI) of ms Masters synchronized to UTC

Loran Integrity Performance Panel 4 Background The U. S. DOT has accepted the findings and recommendations of the VNTSC Report on GPS Vulnerability Qspecifically the need for a backup to GPS in safety critical applications. Qthe various components of the DOT will be making recommendations to Secretary Mineta on how they propose to meet this requirement For the FAA QSufficient navigation infrastructure for sustaining the capacity and efficiency to continue commercial flight operations with dispatch reliability. QContinuing operations by air transportation in the presence of interference is the best deterrent to deliberate jamming

Loran Integrity Performance Panel 5 March 2002 Loran Murder Board Main FAA Loran issue is whether it can support non- precision approach QPreferably Required Navigation Performance 0.3 (RNP 0.3) QFocus on the development of tools and sensitivity analysis to demonstrate meeting RNP 0.3 requirements What are the most critical conditions that will have to be met to satisfy the requirement? For example, do we need better ground wave propagation models, better user receiver performance, tighter specifications on the signal in space, more transmitters, etc.?

Loran Integrity Performance Panel 6 LORIPP Membership from academia, government, and industry QOperating under the direction of the FAAs Loran program office QExpertise in safety and integrity analysis; fault tree analysis; digital signal processing and all-in-view receiver development; Loran infrastructure modernization; etc. Investigating Loran ability to meet RNP 0.3 QIf Loran can meet RNP 0.3, provide the necessary proof and system design

Loran Integrity Performance Panel 7 Why we feel this will work when it didnt a decade ago Previous problems QPrecipitation static QMomentaries (up to 59 sec transmitter off-air) due to coupler switches and loss of commercial power QTriad based solution Current solutions QH field antennas QReduce coupler switches to 3 sec off air QTransmitter UPS QMaster independent, all- in-view receivers Time of Transmission control of secondaries However, the bar has been raised! (both the requirements and their proof)

Loran Integrity Performance Panel 8 RNP 0.3 Requirements Performance RequirementValue Accuracy (target)307 meters Monitor Limit (target)556 meters Integrity10 -7 /hour Time-to-alert10 seconds Availability (minimum)99.9% Availability (target)99.99% Continuity (minimum)99.9% Continuity (target)99.99%

Loran Integrity Performance Panel 9 Phase & Cycle Error Phase Tracking Point Envelope Tracking Point

Loran Integrity Performance Panel 10 Integrity Hazards

Loran Integrity Performance Panel 11 TOT & TOA Monitor Network Secondary TOT – Operating Secondary TOT – Planned near term Master TOT – Operating TOA – Operating TOA – Planned near term TOA - Planned Phase 2 TFE – Jan 03 No current plans (SAMs & LORSTAs)

Loran Integrity Performance Panel 12 Verifying Integrity Cycle Resolution Verifies that the correct cycle is being tracked Determine P wc (probability of being on the wrong cycle) HPL Calculation Determines the % confidence bound on horizontal error Determine HPL Cannot meet RNP 0.3 Requirements P wc < 1x10 -7 P wc > 1x10 -7 HPL > 0.3 NM (RNP 0.3) HPL < 0.3 NM

Loran Integrity Performance Panel 13 Loran Cycle Integrity No Fault Fault P missed_detection P false_alarm Uses redundant information to verify cycle integrity Similar to GPS RAIM

Loran Integrity Performance Panel 14 Horizontal Protection Level Provide user with a guarantee on position QHorizontal Protection Level > Horizontal Position Error i is the standard deviation of the normal distribution that overbounds the randomly distributed errors i an overbound for the correlated bias terms i an overbound for the uncorrelated bias terms

Loran Integrity Performance Panel 15 Integrity Fault Tree Phase Error Cycle Error

Loran Integrity Performance Panel 16 Continuity Fault Tree

Loran Integrity Performance Panel 17 Other Loran Issues Loran Data Channel QData Channel for RNP 0.3 Integrity Station ID – Time Tag QData Channel for Increased Accuracy Differential Loran Loran Accuracy Performance Panel (LORAPP) Loran Accuracy QRNP 0.3 QHarbor/Harbor Approach

Loran Integrity Performance Panel 18 Conclusions LORIPP tasked with investigating the ability of Loran to meet RNP 0.3 LORIPP tasks: QIdentifying and analyzing hazards that may affect integrity, availability, etc. QData collection, analysis and proofs on major Loran hazards QDevelopment of procedures that will permit RNP 0.3 Current investigation leads us to believe that Loran can meet RNP 0.3 QLNAV/VNAV with baro aiding

Loran Integrity Performance Panel 19 Acknowledgements, etc. Funded by Federal Aviation Administration QMitch Narins – Program Manager For additional info: Qloran.stanford.edu QContacts -Note- The views expressed herein are those of the authors and are not to be construed as official or reflecting the views of the U.S. Coast Guard, Federal Aviation Administration, or Department of Transportation.