Long-term Ionospheric Anomaly Monitor(LTIAM)

Overview

ICAO ISTF/516 – 18 February, 2015

Threat: Severe Ionosphere Disturbances

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11/20/2003, 20:15:00 UT

• Ionosphere spatial gradients as large as 412 mm/km have been observed in the United States since April 2000.

• A worst-case ionospheric threat model was developed for LAAS in CONUS based on study of about 10 severe days.

Front Speed

Airplane Speed

Width

LAAS Ground Facility

SlopeLGF IPP

Limitations of the CAT I LAAS Ionospheric Anomaly Threat Model

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0 10 20 30 40 50 60 70 80 900

50

100

150

200

250

300

350

400

450

Elevation [deg]

Slop

e [m

m/k

m]

Dual-frequency and L1 CMC verifiedL1 CMC

Flat 425 mm/kmLinear bound (mm/km):y = 375 + 50(el - 15)/50Flat 375

mm/km

• CAT I Ionospheric Anomaly Threat Model

• Limitations:– Constructed based on a small number of ionospheric storm events– Receiver separations within the CORS network (typically 40 – 100

km) do not reflect the LAAS architecture

S. Datta-Barua, J. Lee, et.al., (2010). Ionospheric Threat Parameterization for Local Area Global-Positioning-System-Based Aircraft Landing Systems . AIAA, the Journal of Aircraft.

Need of Long-Term Ionospheric Anomaly (LTIA) Monitor

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• Long-term ionospheric anomaly monitoring is needed to build an Ionospheric threat model, monitor ionospheric anomalies over the system life cycle, verify CAT I threat model, and trigger updates if needed.

Ionospheric Threat Space with Newly Validated Ionospheric Anomalies

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Newly Verified AnomaliesThreat points in the current threat model

All 10 severe days of data from

the CONUSionospheric

storm archive were processed

0 10 20 30 40 50 60 70 80 900

50

100

150

200

250

300

350

400

450

Elevation [deg]

Slop

e [m

m/k

m]

Flat 375mm/km

Linear bound (mm/km):y = 375 + 50(el - 15)/50 Flat 425 mm/km

0 10 20 30 40 50 60 70 80 900

50

100

150

200

250

300

350

400

450

Elevation [deg]

Slop

e [m

m/k

m]

Flat 375mm/km

Linear bound (mm/km):y = 375 + 50(el - 15)/50 Flat 425 mm/km

Overview of LTIA Monitor

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LTIA Monitor Inputs

•External Data-Space weather databases (Dst, Kp)

•GPS Observation Data

LTIA Monitor Outputs

• Manual Validation (MV)- Re-examination of potential anomalies output

LTIA Monitor Processing

•Ionospheric Event Search (IES)-Select periods and areas deserving further study

•Ionospheric Delay/Gradient Estimation (IDGE)-Process ionospheric data of interest

•Ionospheric Anomaly Candidate Screening (IACS)

• Periodic Report- Processor statistics- Manual validation results- Ionospheric statistics

• Safety Assessment- Follow-up as needed

Data Collection Processing

Ionospheric Anomaly Search Processor Reporting

Automated Procedures

Manual Procedures

Overview of LTIA Monitor

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LTIA Monitor Inputs

•External Data-Space weather databases (Dst, Kp)

•GPS Observation Data

LTIA Monitor Outputs

• Manual Validation (MV)- Re-examination of potential anomalies output

LTIA Monitor Processing

•Ionospheric Event Search (IES)-Select periods and areas deserving further study

•Ionospheric Delay/Gradient Estimation (IDGE)-Process ionospheric data of interest

•Ionospheric Anomaly Candidate Screening (IACS)

• Periodic Report- Processor statistics- Manual validation results- Ionospheric statistics

• Safety Assessment- Follow-up as needed

Data Collection Processing

Ionospheric Anomaly Search Processor Reporting

Automated Procedures

Manual Procedures

Internal Processing

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Internal Processing

Iono. Event Search

• Search for periods/areas of interest

• Automated daily processing

• Event selection criteria

Iono. Delay & Gradient

Estimation

• Create “simple truth” data using dual-frequency data

• Estimate iono. gradients using station-pair method

Iono. Anomaly

Candidate Screening

• Search for unusually large gradients (e.g., > 300 mm/km)

• Automated screening to remove receiver faults, data errors

Kp >Kp_th

Dst <Dst_th

Overview of LTIA Monitor

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LTIA Monitor Inputs

•External Data-Space weather databases (Dst, Kp)

•GPS Observation Data

LTIA Monitor Outputs

• Manual Validation (MV)- Re-examination of potential anomalies output

LTIA Monitor Processing

•Ionospheric Event Search (IES)-Select periods and areas deserving further study

•Ionospheric Delay/Gradient Estimation (IDGE)-Process ionospheric data of interest

•Ionospheric Anomaly Candidate Screening (IACS)

• Periodic Report- Processor statistics- Manual validation results- Ionospheric statistics

• Safety Assessment- Follow-up as needed

Data Collection Processing

Ionospheric Anomaly Search Processor Reporting

Automated Procedures

Manual Procedures

Manual Validation

• Validate that the observed events are actually due to the ionosphere and not receiver faults or data errors using L1-only measurement

10

20 20.5 21 21.5 22-100

-50

0

50

100

150

200

250

300

350

400

Time (hour of 11/20/2003)

Iono

Slo

pe (m

m/k

m)

Comparison of Slopes, ZOB1 and GARF, SVN 38

DF SlopeL1 CMC Slope

Example of LTIAM Plots for Anomaly Candidate (Brazilian TM Study: SAVO-SSA1 PRN 21)

ICAO ISTF/50 5 10 15 20 25

10

15

20

25

30

35

40

45

Hour of Day (UT)

Ele

vatio

n (d

egre

es)

SAVO-SSA1 Elevation Angle of PRN21

SAVOSSA1

20 21 22 23 24

0

100

200

300

400X: 23.86Y: 459.6

Hour of Day (UT)

Slo

pe(m

m/k

m)

SAVO-SSA1PRN21 (dist=9.97km)

21 21.5 22 22.5 23 23.5 24

2

4

6

8

10

12

14

X: 23.86Y: 3.201

Hour of Day (UT)

Sla

nt Io

nosp

heric

Del

ay (m

)SAVO-SSA1 ... PRN21

SAVOSSA1

20 21 22 23 24-100

0

100

200

300

400

500

Hour of Day (UT)

Slo

pe (m

m/k

m)

Manual Validation SAVO-SSA1 (9.97 km) PRN21

I

ICMC

501.2 mm/km

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Distribution of LTIAM software tool

• Version 2.1 was made available to IGWG participating members (2012)

• The same version of the tool and supporting documents are available to the ISTF group members (an approval from FAA is obtained) – LTIAM-2.1 (zip file)

– LTIAM Algorithm Description Doc v2.1

– LTIAM User Manual v2.0

• Application form for LTIAM software package

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References

• “User Manual for the Long-Term Ionospheric Anomaly (LTIA) Monitoring of the Ground-Based Augmentation System,” KAIST, Version 2.0, June 20, 2012

• “Algorithm Description Document and User Manual for Long-Term IonosphericAnomaly Monitor (LTIAM) of the Local Area Augmentation System,” Tetra Tech AMT, Inc., Stanford University, KAIST, Version 2.1, August 13, 2012.

• S. Jung and J. Lee, “Long Term Ionospheric Anomaly Monitoring for Ground Based Augmentation Systems.” Radio Sci., 47, RS4006, July 2012, doi:10.1029/2012RS005016.

• J. Lee, S. Jung, M. Kim, J. Seo, S. Pullen, and S. Close, “Results from Automated Ionospheric Data Analysis for Ground-Based Augmentation Systems,” Proceedings of the Institute of Navigation International Technical Meeting (ION ITM 2012), Newport Beach CA, January, 2012

• J. Lee, S. Jung, and S. Pullen, “Enhancements of Long Term Ionospheric Anomalies Monitoring for the Ground-Based Augmentation System,” Proceedings of the Institute of Navigation International Technical Meeting (ION ITM 2011), San Diego, CA, January 24-26, 2011

• J. Lee, S. Jung, E. Bang, S. Pullen, and P. Enge, “Long Term Monitoring of Ionospheric Anomalies to Support the Local Area Augmentation System,” Proceedings of the 23rd International Technical Meeting of the Satellite Division of the Institute of Navigation (ION-GNSS 2010), Portland, OR, September 2010.

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