# Presentation: 055522

## 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***
***ION-GPS 2002***
***Portland, OR September 24-27, 2002 ***

## Outline

***Background***
***Requirements***
***Integrity Analysis***
***Hazards***
***Fault Tree***
***Conclusions***

## Loran Basics

***100 kHz (350-1400 kW) ***
***Groups of 8 pulses @ 1 kHz ***
***Hyperbolic, 2D ***
***Groundwave***
***Configured in chains of a master & 2-5 secondaries ***
***Chains characterized by Group Repetition Intervals (GRI) of 59.3-99.9 ms***
***Masters synchronized to UTC***

## Background

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

## March 2002 Loran Murder Board

***Main FAA Loran issue is whether it can support non-precision approach ***
***Preferably Required Navigation Performance 0.3 (RNP 0.3)***
***Focus on the development of tools and sensitivity analysis to demonstrate meeting RNP 0.3 requirements****** ***
*What are the most critical criteria 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.?*

## LORIPP

***Membership from academia, government, and industry ***
***Operating under the direction of the FAA’s Loran program office***
***Expertise 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***
***If Loran can meet RNP 0.3, provide the necessary system design***

## Why we feel this will work when it didn’t a decade ago

***Previous problems***
***Precipitation static***
***Momentaries (up to 59 sec transmitter off-air) due to coupler switches and loss of commercial power ***
***Triad based solution  ***

***Current solutions***
***H field antennas***
***Reduce coupler switches to 3 sec off air***
***Transmitter UPS***
***Master independent, all-in-view receivers***
*Time of Transmission control of secondaries*

- However, the bar has been raised!
- (both the requirements and their proof)

## RNP 0.3 Requirements

| Performance Requirement | Value |
| --- | --- |
| Accuracy (target) | 307 meters |
| Monitor Limit (target) | 556 meters |
| Integrity | 10-7/hour |
| Time-to-alert | 10 seconds |
| Availability (minimum) | 99.9% |
| Availability (target) | 99.99% |
| Continuity (minimum) | 99.9% |
| Continuity (target) | 99.99% |

## Phase & Cycle Error

- Phase Tracking Point

- Envelope Tracking Point

## Integrity Hazards

##  Example: LORAN Cycle Integrity 

- Algorithms similar to GPS RAIM use redundant information to verify cycle integrity

## Integrity

***Provide user with a guarantee on position***
***Horizontal 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***
***Determine comprehensive list of integrity hazards/faults***

## Integrity Fault Tree

- Phase Error

- Cycle Error

## Conclusions

***LORIPP tasked with investigating the ability of Loran to meet RNP 0.3***
***LORIPP tasks:***
***Identifying and analyzing hazards that may affect integrity, availability, etc.***
***Data collection, analysis and proofs on major Loran hazards***
***Development of procedures that will permit RNP 0.3***
***Current investigation leads us to believe that Loran can meet RNP 0.3***
***LNAV/VNAV with baro aiding***

## Acknowledgements, etc.

***Funded by Federal Aviation Administration***
***Mitch Narins – Program Manager***
***For additional info:***
***BenjaminPeterson@ieee.org***
***-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 . ***