Loran Integrity Performance Panel Loran Integrity & Performance Panel (LORIPP) Per Enge, Stanford University, November 2003 Based on the work of: Federal Aviation Administration, U.S. Coast Guard, Peterson Integrated Geopositioning, Booz Allen Hamilton, Ohio University, JJMA, ITT, University of Wales, Reelektronika & Stanford University But the opinions may be mine alone & and the mistakes certainly are!

Loran Integrity Performance Panel 2 RNP 0.3 Requirements Performance RequirementValue Accuracy (target)307 meters Monitor Limit (target) (HAL)556 meters Integrity for all users in the coverage area (cannot average Boulder against Colorado Springs) at all times (cannot average solar peak against quiet times) under all conditions (in the presence of hazards) /hour Time-to-alert10 seconds Availability at primary or alternate airport (minimum/target) 99.9/ 99.99% Continuity (minimum/target)99.9/ 99.99%

Integrity Hazards (from Sherman Lo) LORIPP work is organized around these hazards with a system engineering group predicting coverage.

Loran Integrity Performance Panel ? means: Use the best available engineering to think through the corner cases. Find the data that describes the hazard. If the right data does not exist, collect some. Design monitors to address any real integrity issues. Remember, over design hurts continuity, availability and coverage.

Loran Integrity Performance Panel 5 Error Bounds, Not Accuracy One or more cycle errors: Envelope TOA at short ranges Residuals test at long ranges Prob(HPE > HPL) < per hour transmitter receiver noise & RFI temporal ASF residual of temporal ASF spatial ASF

Loran Integrity Performance Panel 6 Integrity Analysis is best taught by example. My favorite example (hazards) are: Q evil waveforms for GPS Q early skywave for Loran Q remember these are only two examples from two long hazard lists.

Loran Integrity Performance Panel 7 DGPS Position Error Measured by Trimble at the 1993 Oshkosh Air Show SV19 Visibility Period Altitude (meters) Local time of day Differential vertical error up to 8.5 meters

Loran Integrity Performance Panel 8 C/A and P(Y) Measurement from Camp Parks

Loran Integrity Performance Panel 9 C/A and P(Y) Measurement from Camp Parks

Loran Integrity Performance Panel 10 Modeling Evil Waveforms (from Eric Phelts) Correlation Peaks Code Offset (chips) Normalized Amplitude C/A PRN Codes Chips Volts   1/f d

Loran Integrity Performance Panel 11 Signal Quality Monitoring (from Eric Phelts) SQM2b SQM2b E-L Spacings: 0.1 chips* 0.15 chips 0.2 chips Spacing (chips) Correlator Receiver Spacings Normalized Magnitude

Loran Integrity Performance Panel 12 WAAS Safety Processor WREs, level D SV orbit determination & corrections Iono. correct. & GIVE UDRE Range Domain Position Domain + CNMP UDRE Safety Processor DO 178 level B L1/L2 Biases GIVE Corrections Processor DO 178, level D

Loran Integrity Performance Panel 13 Error Bounds, Not Accuracy (from Sherman Lo) LORAN WAAS with Latency Removed

Loran Integrity Performance Panel 14 Back to Loran – Early Skywave

Loran Integrity Performance Panel 15 ECD Perturbations at Fairbanks (from Bob Wenzel) Large solar proton event on Jan. 10 time in days UT (n.0 is early afternoon on n-1 in Western Alaska)

Loran Integrity Performance Panel 16 TD Perturbations at Fairbanks (from Bob Wenzel) 300 nsec time in days UT (n.0 is early afternoon on n-1 in Western Alaska)

Loran Integrity Performance Panel 17 Previous plots blown up Caribou (9960W) to Sandy Hook 463NM or 857 km from Bob Wenzel

Loran Integrity Performance Panel 18 Monitor Using 228 Paths < 900 NM (from Ben Peterson)

Loran Integrity Performance Panel 19 Early Skywave Cures Monitor at LorStas and SAMs (not at airports!) Range limits Sample earlier (at 20 or 25 microseconds) & maybe speed the rise time of the pulse. Channel sounding pulse Receiver autonomous detection See talks by Peter Morris, Bob Wenzel, Frenand Le Roux & Ben Peterson for much more.

Loran Integrity Performance Panel 20 Summary means: Use the best available engineering to think through the corner cases. Find the data that describes the hazard. If the right data does not exist, collect some. Design monitors to address any real integrity issues. Remember, over design hurts continuity, availability and coverage. For Loran We are well underway. We have the right people, working the right issues. But it is a big job

Loran Integrity Performance Panel 21 Backup Viewgraphs

Loran Integrity Performance Panel 22 Major Hazards 1.Temporal Variations of Groundwave including ASF, ECD and SS 2.Spatial Variations of ASF, ECD & SS 3.Weather related noise (p-static & atmospheric) 4.Early skywave 5.Aircraft dynamics 6.Man-made RFI 7.Transmitter Hazards LORIPP work is organized around these hazards with a system engineering group predicting coverage.

Loran Integrity Performance Panel 23 Typical Distributions of TOA Measurement (from Ben Peterson) Probability Density of TOA Accuracy = fn(Phase uncertainty) Pcycle error = fn(Envelope uncertainty) Blue - Low SNR, Red - High SNR

Loran Integrity Performance Panel 24 Threat Flow from GPS Work Ground control segment upload GPS satellite nav. message signal dist. ionosphere & troposphere Airborne radio environ. RFI multipath Ground radio environ. RFI multipath Ref. rcvr. Level D code cycle slips Fault detection Data broadcast Data faults Airborne rcvr. Airborne fault detection

Loran Integrity Performance Panel 25 Monitor Performance nominal prob. density function faulted prob. density function Pr(false alarm) Pr(miss detect)

Loran Integrity Performance Panel 26 Simulation Data for Locus LRS IIID (from Bob Wenzel)