Simultaneous Observations of EGNOS and GPS Amplitude Scintillations over Equatorial Africa · 2015....

Simultaneous Observations of EGNOS and GPS

Amplitude Scintillations over Equatorial Africa

Akala, A. O.

University of Lagos

[email protected]@unilag.edu.ng

Contributors: Doherty, P., Groves, K., Carrano, C., Bridgwood, C.,

1UNO ICG Experts Meeting, Vienna,

Austria, 14-18 Dec., 2015

Outlines

• Introduction

• Data Resources

• Results

• Conclusions• Conclusions

• Proposal

• Acknowledgements



IntroductionBased on its safety and economic benefits, GNSS/PBN is at the verge

of replacing the conventional terrestrial Nav infrastructures in the

aviation Industry (Akala et al., 2012, Radio Sci.).

For these reasons, ICAO has mandated all of its regions, under the

auspices of regional Ionospheric Studies Task Force (ISTF) to establish auspices of regional Ionospheric Studies Task Force (ISTF) to establish

a framework for understanding the phenomenology of ionospheric

effects on GNSS in each region, with

a view to proffering mitigation

strategies to their impacts on

GNSS aviation applications.



Group delay effect: It is currently being resolved by the dual frequency

(DF) mechanisms of modern GNSS receivers.

Scintillation effect: It is not yet resolved due to its temporal, daily, monthly,

seasonal, geomagnetic activity, solar activity, and regional variations that

have not yet been adequately addressed, particularly in the African region.

Ionospheric Effects on GNSS Aviation

have not yet been adequately addressed, particularly in the African region.

On a global scale, Burke et al., 2004; Gentile et al., 2006; 2011; Hei et al.,

2005; Kil et al., 2009; Akala et al., 2013 have reported more equatorial

scintillation events in the African longitude than other longitudes. Recently,

Tsunoda et al. (2015, JGR) suspected that orographic sources might be

responsible for these variations. Evidence is required for concrete

conclusions.4

UNO ICG Experts Meeting, Vienna,


0

30

60

90

Ge

og

rap

hic

La

titu

de

(d

eg

ree

)

DKRADD

NROILR

Data Resources

GPS Receivers

2012/2013

amp. scint data

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180-90

-60

-30

0

Geographic Longitude (degree)

Ge

og

rap

hic

La

titu

de

(d

eg

ree

)

NTA

NRO



Increasing

Mag. Lat

~3oS – 10oS

Variations of Equatorial African Amplitude

Scintillations (2010)

LOS

Mar Equi Jun Sols Sep Equi Dec Sols

~3oS – 10oSNOB

KPLAkala et al.

(2015, Astrophs.

& Space Sci.)



DKR

Mar Equi Jun Sols Sep Equi Dec Sols

Variations of Equatorial Amplitude

Scintillations (Dakar and Natal, 2013)

NAT

7

Akala et al. (Submitted, Space Weather)



Comparison of results of Akala et al. [2015] with the

Observed Scintillation Events at Dakar and Natal, BrazilStudy/

Data Coverage

Receiver location(s) Scintillations active

months

Non-scintillations

months

Post-sunset scintillations Diagonal features on

data

Akala et al. [2015]

2009–2011

Lagos (6.48oN, 3.27oE, Mag. Lat:

4.95oS), Nigeria

Nairobi (1.16oS, 36.80oE, Mag. Lat:

10.65oS), Kenya

Kampala (0.30oN, 32.50oE, Mag. Lat:

11.12oS), Uganda

Mar., Apr., Sep., and

Oct.

Active months of bubble

occurrences over the

stations [Burke et al.,

2004; Huang and

Hairston, 2015]

Jan., Jun., Jul., and Dec.

Non-bubble months

over the stations [ Burke

et al., 2004; Huang and

Hairston, 2015]

Evident in Nairobi and

Kampala data (mainly at

weak level)

(attributed to MSTID

propagating equator-wards

from the mid-latitude,

presence of sporadic E, and

neutral winds)

Evident in Kampala

data (attributed to

multipath noises due

to the antenna

environment)

Current study

2012–2014 (Jan. and Feb.)

Dakar (14.75oN, 17.45oW, Mag. Lat:

5.88oN), Senegal

Mar., Apr., Sep., and

Oct.

Active months of bubble

occurrences over the

station [Burke et al.,

2004; Huang and

Hairston, 2015]

Jun. and Jul.

Non-bubble months

over the station [ Burke

et al., 2004; Huang and

Hairston, 2015]

Climatology similar to

the report of Akala et al.

[2011]

Scanty occurrences (at weak

level)

Non-existent

Akala et al. (Submitted, Space Weather)



Ionospheric scintillations over Addis Ababa (2012)

25 30 35 40 45 50-5

0

5

10

15

20

PRN 9

PRN 12

PRN 29

PRN 17PRN 25

Mag.Equator

April 10, 2012

P120 P124

P126

PRN 218:21LT

20:04LT

18:35LT

18:00LT

22:24LT

21:01LT

00:21LT

01:31LT23:07LT

20:52LT

04:00LT

04:00LT

CNOFS ORB 21645

Addis Ababa

Geographic Longitude (deg)

Geog

raphic

Latitu

de (

de

g)

20

PRN 2

April 11, 2012

30

210

60

240

90270

120

300

150

330

180

0

9090

30

60

00

25 30 35 40 45 50-5

0

5

10

15

PRN 9

PRN 12

PRN 29

PRN 2

Mag.Equator P120 P124

P126

18:17LT

19:52LT

18:36LT

20:57LT

00:17LT

01:30LT03:01LT

04:00LTCNOFS ORB 21660

Addis Ababa

Geographic Longitude (deg)

Ge

og

rap

hic

La

titu

de

(d

eg

)

IPP traces of satellites that

experienced scintillations

and C/NOFS tracks over

Addis Ababa

Polar plots of high

elevation (≥ 30o)

scintillations (S4 ≥ 0.5)

over Addis Ababa during

2012

Akala et al. (Submitted, ANGEO)



Ion density and vertical ion drift velocity

measured on-board CNOFS

18 19 20 21 22 23 24 25 26 27 2810

4

105

106

107

LT (Hrs)

Ni (c

m-3

)

April 10, 2012 Orbit 21645

105

106

107

Ni (c

m-3

)

18 19 20 21 22 23 24 25 26 27 2810

4

105

106

107

LT (Hrs)

Ni (c

m-3

)

April 11, 2012 Orbit 21660

105

106

107

Ni (c

m-3

)

0 20 40 60 80 100 120 140 160 18010

4

10

Longitude (deg)

Ni (c

m-3

)

18 19 20 21 22 23 24 25 26 27 28-400

-200

0

200

LT (Hrs)

V-v

ert

(m

/s)

April 10, 2012 Orbit 21645

0 20 40 60 80 100 120 140 160 180-400

-200

0

200

Longitude (deg)

V-v

ert (m

/s)

0 20 40 60 80 100 120 140 160 18010

4

10

Longitude (deg)

Ni (c

m-3

)18 19 20 21 22 23 24 25 26 27 28

-400

-200

0

200

LT (Hrs)

V-v

ert (m

/s)

April 11, 2012 Orbit 21660

0 20 40 60 80 100 120 140 160 180-400

-200

0

200

Longitude (deg)

V-v

ert (m

/s)

April 11, 2012April 10, 2012 10UNO ICG Experts Meeting, Vienna,


IPP, Azimuth, & Elevation Coordinates of SBAS at the

Five Stations

STATIONS EGNOS EGNOS EGNOS WAAS

PRN 120 PRN 124 PRN 126 PRN 138

IPP LAT (o) IPP LONG (o) IPP LAT (o) IPP LONG (o) IPP LAT (o) IPP LONG (o) IPP LAT (o) IPP LONG (o)

ADDIS ABABA 8.49 34.15 8.55 37.79 8.55 38.01 - -

NAIROBI -1.19 32.64 - - - - - -

ILORIN 8.03 4.82 - - - - - -

DAKAR 13.89 342.65 13.85 345.25 13.83 345.65 - -

STATIONS EGNOS EGNOS EGNOS WAAS

PRN 120 PRN 124 PRN 126 PRN 138

Elev. Ang. (o) Azim. Ang. (o) Elev. Ang. (o) Azim. Ang. (o) Elev. Ang. (o) Azim. Ang. (o) Elev. Ang. (o) Azim. Ang. (o)

ADDIS ABABA 27.6 263.6 67.2 243.4 70.9 237.1 - -

NAIROBI 30.2 271.0 - - - - - -

ILORIN 64.5 248.2 - - - - - -

DAKAR 72.7 172.1 42.4 107.3 38.6 105.3 - -

NATAL 74.3 65.9 - - - - 9.3 271.9

DAKAR 13.89 342.65 13.85 345.25 13.83 345.65 - -

NATAL -5.53 325.9 - - - - -.5.4 314.39



Samples of Scintillation Observations at 5

Equatorial Stations during the equinox of 2012

-60

-30

0

30

60

90

Geogra

phic

Latitu

de (

degre

e)

17/10/12

-60

-30

0

30

60

90

Geogra

phic

Latitu

de (

degre

e)

16/10/12

0.4<=S4 > 0.7

(Mod. Scint.)

S4 > 0.7

(Int. Scint.)

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180-90


-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180-90


-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180-90

-60

-30

0

30

60

90


Geogra

phic

Latitu

de (

degre

e)

18/10/12

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180-90

-60

-30

0

30

60

90


Geogra

phic

Latitu

de (

degre

e)

19/10/12

04<=S4 > 0.7

(Mod. Scint.)

(Mod. Scint.)



-60

-30

0

30

60

90G

eogra

phic

Latitu

de (

degre

e)

10/10/13

-60

-30

0

30

60

90

Geogra

phic

Latitu

de (

degre

e)

11/10/13

Samples of Scintillation Observations at 3

Equatorial Stations during the equinox of 2013

0.4<=S4 > 0.7

(Mod. Scint.)

S4 > 0.7

(Int. Scint.)

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180-90

-60

-30

0

30

60

90


Geogra

phic

Latitu

de (

degre

e)

12/10/13

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180-90

-60

-30

0

30

60

90


Geogra

phic

Latitu

de (degre

e)

13/10/13

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180-90

Geographic Longitude (degree)-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180

-90


(Mod. Scint.)

0.3<=S4 > 0.4

(Weak Scint.)



GPS Scintillations over Addis Ababa, 10/04/12



EGNOS Scintillations over Addis Ababa, 10/04/12

EGNOSEGNOS

EGNOS



GPS & EGNOS Scintillations over Addis

Ababa, 19/10/12

EGNOSEGNOSEGNOS



GPS & EGNOS Scintillations over

Nairobi, 19/10/12

EGNOS



GPS Scintillations over Dakar, 19/10/12



EGNOS Scintillations over Dakar, 19/10/12

EGNOSEGNOS

EGNOS

EGNOS



GPS Scintillations over Natal, 19/10/12



SBAS Scintillations over Natal, 19/10/12

EGNOS WAAS



Conclusions1. Scintillation events recorded the highest daily distribution of

occurrences around 22–02 LT.

2. Scintillation occurrences were high during March and September

equinox, and low or non-existent during June solstice. Unlike Akala

et al. [2014; 2015], which reported January as off season for

equatorial scintillation occurrences in Africa, significant events were

recorded in January at Dakar. We observed that the climatology of

GNSS scintillations over Dakar is close to that of South America

(Natal).

3. During intense scintillations, SBAS signals are also vulnerable.



Longitudinal variability of equatorial

plasma bubbles

Burke et al. (2004), JGR23



Proposal for Communication and Navigation Lab

Africans need to work together to address the above state challenges

in order to design a robust GNSS technology for the African aviation

Industry.

At the University of Lagos, the Communication and Navigation Lab that

we are setting up solicits for support/collaborations from ICAO/Allied we are setting up solicits for support/collaborations from ICAO/Allied

Agencies and other scientist.

With such collaborations, we can develop a framework for ionospheric

data collections, analyses and interpretations for our understanding of

the morphology and climatology of scintillations over Africa. Overall, it

will lead to developing robust ionospheric scintillation models and

GNSS aviation for Africa. 24UNO ICG Experts Meeting, Vienna,


Objectives of the LabManpower development in GNSS technology: Currently, 4 Ph.D,

2 M.Sc, and 2 PGD students are being trained. 4 M.Sc students have

been earlier trained. All are Nigerian students, we shall be glad to

extend the trainings to other African students. We have expanded

our applications of GNSS to include aviation, maritime, and AIT

systems.systems.

We hope that the Lab will transform to an Institute in partnership

with our University in the future. Or, with the support of UNO, it

could be transformed to a Regional Centre for trainings on GNSS for

Africa.



AcknowledgementsBoston College and the United State Air Force Research

Laboratory (AFRL) for installing GPS receivers across Africa,

and the hosting scientists.

International Centre for Theoretical Physics (ICTP), Italy for

the Regular Associate Award. Parts of this work were carried the Regular Associate Award. Parts of this work were carried

out during his last visit (April–May, 2015) to the Centre.

C. Valladares (Boston College); C. Huang (AFRL); S. Saito

(ENRI, Japan). UNO/Organizers ICG Expert Meeting for the

sponsorship.



Wishing you all, a Merry Xmas and a

Prosperous New Year ahead

On the tenth day of Christmas

my true love sent to me:

63 ICG experts are meeting63 ICG experts are meeting

…………………………………..

and a Partridge in a Pear Tree



Thank You Thank You

for your rapt attention!!!for your rapt attention!!!

Dr. A. O. Akala(Communication and Navigation Scientist)

[email protected]

[email protected]



Simultaneous Observations of EGNOS and GPS Amplitude Scintillations over Equatorial Africa · 2015....

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