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The Loran Integrity Performance Panel (LORIPP)

The Loran Integrity Performance Panel (LORIPP). The LORIPP Team Loran Team Meeting McLean, VA July 30, 2002. LORIPP Background. What is LORIPP and why does it exist? Determine Requirements (System Engineering) Identify Threats to Loran and Determine Threat Allocations (Fault Tree)

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The Loran Integrity Performance Panel (LORIPP)

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  1. The Loran Integrity Performance Panel (LORIPP) The LORIPP Team Loran Team Meeting McLean, VA July 30, 2002

  2. LORIPP Background • What is LORIPP and why does it exist? • Determine Requirements (System Engineering) • Identify Threats to Loran and Determine Threat Allocations (Fault Tree) • Bound/Mitigate Effects of these Threats • Develop Threat Models • Provide Substantiated Information on Loran Capabilities • What will we accomplish? • Prove Stand Alone Loran Can Act as a Redundant Navigation System (RNP 0.3 or 0.5)

  3. Threats to Loran Integrity • Transmitter • Propagation Effects • Interference (Atmospheric Noise, P Static, Sky Wave) • Ground Wave Propagation Phenomena (ASF, ECD, SNR) • Receiver

  4. LORIPP Work Plan • Transmitter Performance (LSU, PIG, Tom G., NAVCEN) • Receiver Algorithms & Performance (PIG, Stanford, USCGA) • Fault Tree (Stanford, Kevin B., NAVCEN) • System Engineering (PIG, Bob W.) • P-Static Evaluation (Bob E., Bob T., Bob L., Bob W., Frank G., Kevin B.) • Atmospheric Noise (Stanford, PIG, Kevin B., Bob W.) • Ground Wave Propagation: ASF, ECD and Signal Strength (Bob W., USCGA, NAVCEN, LSU, PIG, Tom G., OU, FAATC) • Loran Communications (Stanford, PIG, Frank G.) • Sky Wave (Bob W., USCGA) • Documentation & Meeting Logistics (Tom G., Stanford, NAVCEN)

  5. System Engineering • Development of Coverage Analysis Tools • Calculation of Continuity & 95% Accuracy • Reliability, i.e., Mean Time between Failures, etc. • Avionics • New Transmitter Equipment (validate assumptions)

  6. Fault Tree • Integrity Fault Tree • Continuity Fault Tree • Determine Allocations in Error Budget • ECD (propagation, receiver calibration, receiver noise) • TOA (receiver noise) • Tails of the distributions

  7. Preliminary Integrity Fault Tree Probability (HPE > HPL) > 10-7/hour Probability Transmitter Caused HMI Probability Propagation Caused HMI Probability Receiver Caused HMI Transmitter Timing Evil Waveform CW RFI Sky Wave ASF Effects ECD Cross Rate

  8. Transmitter Performance • Determine ABS Threshold, Time to Blink from Onset of Fault, Probability of Out of Tolerance w/o blink • Determine Transmitted ECD Tolerance, Blink on transmitted ECD? *** • Determine Threat Monitor Requirements at transmitter, Certification Requirements for Monitors • Calibration re UTC • Chain Operations • TOE verus SAM • Analysis of coverage under each situation • Control of TOE to UTC vs measurement of TOE to UTC and transmission of measured offset

  9. Receiver Algorithms & Performance (1/2) • Determine the probability of false alarm & missed detection of blink/off air at given SNR (given time to alarm requirement) • Establish SNR Threshold (for reliably identifying the correct station & cycle) with 7 9s of confidence • Master independent, multi-chain navigation • Resolution of 200 usec cross chain lane ambiguities • Identification of secondary w/o master • Loran Cycle Integrity Calculations • Weighted Sum Squared Error vs Sum Squared Error • Analysis of probability of cycle slips after verifying cycle integrity

  10. Receiver Algorithms & Performance (2/2) • Input from Potential Manufacturers – Validate Assumptions of HMI Analysis • Determine ECD Requirement • Determine Loop Time Constants • Develop Simulator • Averaging time • HPL calculation

  11. Cycle Resolution Verifies that the correct cycle is being tracked Determine Pwc (probability of being on the wrong cycle) HPL Calculation Determines the 99.99999% confidence bound on horizontal error Determine HPL HPL < 0.3 NM HPL < 0.5 NM Pwc < 1x10-7 Cannot meet RNP 0.3 or 0.5 Requirements HPL > 0.3 NM (RNP 0.3) HPL > 0.5 NM (RNP 0.5) Pwc > 1x10-7 Basic Receiver HMI Algorithm

  12. P Static • Educate LORIPP via tutorial paper and briefing. • Determine how P static fits into Fault Tree • Different faults caused by P static and Allocations • What would the continuity allocation be? • What is max level of P static • Developing H-field Antenna Test Plan and, at a minimum, determine a figure for SNR drop outdoors

  13. Atmospheric Noise • Determine the necessary analysis level, i.e., 95%, 99%, or 99.9%, worst time period or averaged over time? • Determine and Develop Applicable Databases • Time Domain Model for Simulation • Determine the credit that can be claimed for non-linear processing • Implement Results in Simulator and Receiver

  14. Ground Wave Propagation: ASF, ECD and Signal Strength • Data Collection • Guidance/requirements definition for data collection effort (also collecting ECD & SNR data) • Coordinate with Atmospheric Noise Threat Model • Data Analysis • 99.99999% bounds on remaining errors • Correlated vs. Uncorrelated terms • Mathematical modeling & prediction including terrain of SS, ECD, & ASF?

  15. Sky Wave • Quantify effects on TOA bias • Quantify effects on ECD bias • Receiver technology for mitigation • Integrity Allocation & Threat Model

  16. Loran Communications • Effects on Navigation if Signals are Modulated • Impact on Availability, Integrity, Accuracy, & Continuity if Loran Data is Transmitted • What data? • And at what rates? • Quantify the benefits provided by the data channel in improving Loran Nav. performance (Availability, Integrity, Accuracy, & Continuity)

  17. Documentation & Meeting Logistics • Collect White Papers from Briefings • Loran/LORIPP Web resource? • Meeting Minutes • Organize Project and Arrange Priorities • Determine Documentation Methodology

  18. Summary • The LORIPP just had its first meeting this past week • The major (critical) issues for Loran RNP 0.3 were discussed • A work plan was developed to gather the data and perform the analysis necessary to prove Loran performance • Future meetings are planned to further develop the integrity analysis – late September

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