Space weather effects on airnavigation and utilization ofspace weather information
Susumu Saito
Electronic Navigation Research Institute✤ ENRI (Electronic Navigation Research Institute) is a public research
institute for aeronautical CNS (Communications, Navigation andSurveillance) and ATM (Air Traffic Management).

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Outline

Aeronautical navigation and GNSS
- Requirements for air navigation- GNSS-based air navigation
Ionospheric effects on GNSS and mitigation- Ionospheric disturbances and mitigation- Ionospheric threat model development in the Asia-Pacificregion for air navigationPotential use of space weather information for airnavigation- Five-year research program of ENRI

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Requirements of air navigation
Different levels of requirements for different flight operations
Phase
En route
En route,
Terminal
Initial,intermediate,
NPA*(1)
APV*(2)-I
APV*(2)-II
Precision
Approach(Category-I)

Horizontal Vertical
Accuracy Accuracy
(95%)
(95%)
2.0NM
0.4NM
720ft
52ft
52ft
52ft

Integrity-

1-1x10-7/hr-

1-1x10-7/hr-

1-1x10-7/
hr

66ft
26ft
26-13ft

1-2x10-7
in anyapproach
1-2x10-7
in anyapproach
1-2x10-7
in anyapproach

Time-to-alert

Continuity

Availability

5min

1-1x10-8-4to 0.99-0.99999
1-1x10 /hr

15sec

1-1x10-8-4to 0.99-0.99999
1-1x10 /hr

10sec

1-1x10-8-4to 0.99-0.99999
1-1x10 /hr

10sec

1-6x10-6 per 0.99-0.99999
15sec

6sec

1-6x10-6 per 0.99-0.99999
15sec

6sec

1-6x10-6 per 0.99-0.99999
15sec[Annex 10 to the International Civil Aviation Convention]*1 NPA: Non precision approach*2 APV: Approach operations with vertical guidance

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3

GNSS-based air navigation
ICAO*(1) promotes migration to GNSS*(2)-based navigation fromconventional (ground-based)
Requirements defined by ICAO
- Very high safety (integrity) requirements- All the requirements (accuracy, integrity, continuity, andavailability) must be fulfilled together for operational systems
Augmentation systems are required to meet the requirements- SBAS (Satellite-based Augmentation System): Wide area
- GBAS (Ground-based Augmentation System): Local area
- ABAS (Aircraft-based Augmentation System): Aircraft standalone
Currently only L1 frequency signal can be used for air navigation- GPS L2 signal is not in a frequency band protected for aviation- L5 signal will be available for air navigation in the future*1 ICAO: International Civil Aviation Organization*2 GNSS: Global navigation satellite system

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Errors in GNSS measurements
Clock offset(receiver, satellite)
sPseudo-range ρ = r + c [δtu − δt ] + Iρ + Tρ + �ρIonospheric Troposphericgeometric range
delay
delay

Carrier-phase φ = λ−1

Ionospheric delay is the largest
one and the most difficult tocorrect for single-frequency
users�
Iρ

==Multipath, thermal
noise, etc.

cs
[r + Iφ + Tφ ] + [δtu − δt ] + N + �φ
λ Clock offset Initial phaseRe2
ne (l)dl
228π me �0 f S
� R
40.3
ne (l)dl
2f
S

total electron
content (TEC)(receiver, satellite) ambiguity

1.0

16 cm/TECU@L10.8

Delay [m/TECU]

Measuredvalues0.6

0.4
L5 (1.17645 GHz)
L2 (1.22760 GHz)
0.2
L1 (1.57542 GHz)00.75

1.01.251.5

1.75

2.0

Frequency [GHz]AOSWA-3, Fukuoka, 2-5 March 2015
5Ionospheric impacts on GNSS-based airnavigation
SBAS and GBAS are based on differential GNSS technique- Spatial decorrelation of ionospheric delay is the major
error source
Number of available satellites is an important factor- More satellites, better satellite geometry and- Better position accuracy with smaller error boundSatellite
Ionosphericdelay

Spatial difference inionospheric delay andGBAS

Ionosphericdelay
difference

erroneousposition solution
Aircraft

ObservationCorrection
information
VHF data
broadcastGround reference
statoin
Airport

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6Ionospheric disturbance with large spacial
decorrelation

6050

8.040

6.4

30

4.8Delay (m)TEC (1016m-2)

SPS
Equatorial
anomaly

SPS/SED
Plasma bubble[Foster et al., 2002]

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Ionospheric threat model
Ionospheric threat model describes how the ionosphericparameters relevant for a specific GNSS-based systems

Velocity [m/s]Ionospheric delay gradient andvelocity in disturbed conditions (US)Ionospheric delay gradient in the nominal
condition (Japan)

Tailbounding

Ionospheric delay gradient at
L1 rfrequency [mm/km][Lee et al., ION GNSS 2006][Yoshihara et al., Japan Inst. Nav., 2010]
AOSWA-3, Fukuoka, 2-5 March 2015
8Prototyping and validation
GBAS airborne experimental
subsystem and flight experiment

New Ishigaki
AirportNGBAS ground subsystem prototype
RR1

IFM

399 m

RR4

Plasma bubbles
W

ERR2
175 m
RR3
122 m
S

Plasma bubble monitoringby all-sky imager for GBAS
experiments
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9Mitigation efforts in Asia-Pacific region
Ionospheric Studies Task Force (ISTF)- Established in the ICAO Asia-Pacific Region in 2012
- Objectives• Facilitate ionospheric data collection and sharing• Study the need for development of regional
ionospheric threat models for GBAS and SBAS,• Develop them if the need is identified.
Observation data have been contributed by member States
5th meeting was recently held in Japan (16-18 February 2015)- 16 participants from 6 States- 7 observers from industries and air navigation service
providers- Need of regional ionospheric threat model for GBAS wasidentified.
ENRI is leading this activity.
AOSWA-3, Fukuoka, 2-5 March 201510Space weather information and air navigation
Ionospheric phenomena are important part of spaceweather.
ICAO 12th Air Navigation Conference recommended- to study optimum ways of utilizing space weather information tofacilitate global use of GNSS
- to work on the ionospheric issues in a coordinated mannerSpace Weather Concept of Operations (ConOps)- Under development- Define how space weather information should be utilized for
mitigation of impacts on- Navigation- Communication- Radiation dose
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Research program of ENRI for space
weather information utilization
Development of ionospheric threat mitigation algorithm forGNSS-based air navigation-

Five-year program from April 2015 to March 2020
Utilize space weather information✦Not limited to self-contained systems✦Integrity consideration-

Development of concept of space weather utilization suitable
for the low latitude region-

Development of ionospheric anomaly mitigation technique for
GNSS with space weather information-Feed back to ICAO Space Weather ConOps
Ionospheric observations to understand characteristics ofionospheric and space phenomena that have impact on GNSSAOSWA-3, Fukuoka, 2-5 March 201512Summary

GNSS is expected to be a main enabler of next generation airnavigation
High safety (integrity) is required for air navigation at the sametime as accuracy, continuity, and availability
Mitigation of Ionospheric impacts (ionospheric delay gradient,scintillation) is the key point to facilitate GNSS implementation
for air navigation- Ionospheric threat assessment and threat model development
undertaken by ICAO Ionospheric Studies Task Force in theAsia-Pacific region- ENRI will launch a five-year program for development ofionospheric threat mitigation algorithm for GNSS-based airnavigation
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ENRI International Workshop on CNS/ATMVisit http://www.eiwac2015.jp !

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