Transcript No Slide Title

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
Outline
• Background
• Requirements
• Integrity Analysis
Hazards
Fault Tree
• Other Loran Issues
• Conclusions
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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
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March 2002 Loran Murder Board
• Main FAA Loran issue is whether it can support nonprecision 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 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.?
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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
proof and system design
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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, allin-view receivers
• Time of Transmission
control of secondaries
However, the bar has been raised!
(both the requirements and their proof)
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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%
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Phase & Cycle Error
Envelope
Tracking
Point
Phase
Tracking
Point
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Integrity Hazards
Atmospheric Noise
Skywave
Interference
Local Noise, P-static,
Receiver Noise & Bias
Transmitter
Bias& Jitter
Propagation Prediction Errors

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TOT & TOA Monitor Network
Secondary TOT – Operating
TOA – Operating
TFE – Jan 03
Secondary TOT – Planned near term
TOA – Planned near term
Master TOT – Operating
TOA - Planned Phase 2
No current plans
(SAMs & LORSTAs)
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Loran Cycle Integrity
• Uses redundant information to verify cycle integrity
• Similar to GPS RAIM
0.2
0.15
No Fault
0.1
0.05
0
0
5
Threshold
Fault
15
25
10
Pmissed_detection
20
WSSE
30
35
40
Pfalse_alarm
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Horizontal Protection Level
• Provide user with a guarantee on position
Horizontal Protection Level > Horizontal Position Error
HPL  
K a  K b   K g
i
i
i
i
i
i
i i
i
• ai is the standard deviation of the normal distribution
that overbounds the randomly distributed errors
• bi an overbound for the correlated bias terms
• gi an overbound for the uncorrelated bias terms
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Integrity Fault Tree
Probability (HPE >
HPL) > 10-7/hour
Phase Error
Cycle Error
+
At least 1
Cycle
Incorrect
All Cycles
Correct
+
Propagation
+
All Unbiased &
Independent
Range Errors
ai > ai
All Completely
Correlated
Range Errors
bi > bi
All Potentially
Uncorrelated
or Biased
Errors
gi > gi
+
+
+
Transmitter
Interference
at Receiver
Propagation
Transmitter
Interference
at Receiver
Propagation
Transmitter
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One Cycle
Incorrect
Two or More
Cycles Incorrect
Interference
at Receiver
15
Continuity Fault Tree
Continuity
99.9%
+
Loss of
Signal
No Cycle
Integrity
+
+
No Critical
Transmitter
N or less
Critical
Transmitters
+
+
Two
Transmitter
Out
More than 2
Transmitter
Out
+
+
Transmitter
Off Air
Receiver
Not Track
Transmitter
Off Air
Transmitter
Off Air
Fail Slip
Detector
Fail Cycle
Integrity
Receiver
Not Track
Receiver
Not Track
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Other Loran Issues
• Loran Data Channel
Data Channel for RNP 0.3 Integrity
• Station ID – Time Tag
Data Channel for Increased Accuracy
• Differential Loran
• Loran Accuracy Performance Panel (LORAPP)
• Loran Accuracy
RNP 0.3
Harbor/Harbor Approach
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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
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Acknowledgements, etc.
• Funded by Federal Aviation Administration
Mitch Narins – Program Manager
• For additional info:
loran.stanford.edu
Contacts
• [email protected]
• [email protected]
• -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 .
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