EIWAC 2013, Tokyo, Japan. February 19-21, 2013

Flight Trials to collect GPS data underEquatorial Ionospheric Plasma Bubbles

Toshiaki Tsujii, Takeshi Fujiwara, Tetsunari Kubota
Japan Aerospace Exploration Agency (JAXA)
S. Saito and T. Yoshihara
Electronic Navigation Research Institute (ENRI)

Contents
 Bubble Impact on GBAS
 GPS Signal characteristics on Aircraft Maneuver and Vibration Effects
 Scintillation Effect Flight Test Configurations
 Measurement Results
 SummaryPage 2

Ionospheric Anomaly• Storm Enhanced Density (SED)
Rare– Mid~High Latitude Region– Spatial Gradient： ＞400mm/km• Equatorial Plasma Bubble (EPB)
Frequent– Low~Mid Latitude Region– Scintillation
Plasma Bubble（Density Depletion）

Ionosphere

Move Eastward～100m/s
Page 3

EPB observed by GUVI/TIMED satellite（Christensen et al., 2003）
Green belt : Equatorial Ionospheric Anomaly
Black line : Equatorial Plasma Bubble

Bubble Impact on GBAS (1)Steep Change of Iono. Delay

Spatial gradient of TEC would resultin wrong correction data
Page 4

TEC without Bubble

Three successive bubbles

 Degrade DGPS Accuracy

Bubble Impact on GBAS (2)Scintillation

Scintillations
Signalfluctuation

Page 5

Scintillation would cause
temporal loss of satellite
lock→ re-initialization of PRsmoothing→ go around due tomultiple satellites
lossesReduced Number of Satellite
Decrease GBAS Availability

GPS Signal characteristics on Aircraft
Aircraft Vibration Effect（RTCA DO-160F）

Carrier Tracking Error
at GROUND Receiver

Aircraft Masneuvour（RTCA DO-253C）

Mainly affected byClock Jitter & Thermal Noise1010

位相誤差 (deg, 1σ)

位相誤差(deg, (deg)1σ)
PhaseError

TrackingLimit1ClockThermalTotal0100101Loop Noise BW (Hz)ループバンド幅 (Hz)Page 61010102

位相誤差 (deg, 1σ)

Tracking
Margin ( T-Y Chiou, Thesisより)

1ClockThermalVibration
Total

0100101

Loop Noise BW (Hz)ループバンド幅 (Hz)10101021Clock
ThermalVibration
Dynamics
Total

0100101

ループバンド幅 (Hz)Loop Noise BW (Hz)RTCA: Radio Technical Commission for Aeronautics

102

Scintillation Effect
Scintillations
Signalfluctuation

Clock
ThermalScin_Amp
Scin_Phase
Total

100

Page 7101

ループバンド幅 (Hz)45

Loop Noise BW (Hz)505560656065

Phase variation

0455055
time (min)AIR101010σφ(radians)

Phase
Phase
Error(度,(deg)
追尾誤差1σ)Phase
Error(deg,(deg)
位相誤差1σ)100-1(S4=0.7)

GROUND

1021

Phase Scintillation Amplitude Scintillation

10Normarized power

4Intensity

Amplitude

Amplitude and Phase variation
due to scintillation

1ClockThermalVibration
Dynamics
Scin_Amp
Scin_Phase
Total

02

100101ループバンド幅 (Hz)Loop Noise BW (Hz)102

Flight Trial Campaign
September 4 ～ 13th, 2012
Date
BubbleOccurrence

45678910111213－－－－－－○○○○Flight test－－－○－－○○○○

Ishigaki-Island, Okinawa, Japan.
(N24.3452668, E124.183674)
ChinaJapanIshigaki Airport

TaiwanIshigaki (Okinawa)
Page 8ENRI’s siteEquipments

Research aircraft(Cessna Citation Sovereign) and onboard equipments

Main Airborne Equipments:
 MMR, Rockwell Collins GNLU-930-redlabel
 Ionospheric Scintillation Monitor (ISM), Septentrio PolaRxS Pro
 Software-based ISM, JAXA Javad Delta GNSS receiver (50Hz)
Main Ground Equipments:
 Ionospheric Scintillation Monitor (ISM), Septentrio PolaRxS Pro
 Software-based ISM, JAXA Javad Delta GNSS receiver (50Hz)
Page 9

Flight Pattern・Straight Level flight (20 NM Legs）
・Horizontal Acceleration (0.58g, MOPS) induced by banking (～30 deg)
Flight Profile (Sept.10)

Bank angle and horizontal acceleration
Page 10Observation of Plasma Bubbles

S4 corrected

Airglow image (630nm)＠Yonaguni（by ENRI）

S4 vs. Elevation
No Bubble

S4 corrected

H24/9/13 20:53(JST)Elevation (Deg)
Page 11

H24/9/13 22:47(JST)Sept. 13 Bubble occurredExample of Analysis Results (Data of Sept. 12)

Airglow (777.4nm) image at 22:34 LT(by ENRI)
Page 12Satellite trajectories.
(PRN9, 15 and 27 are emphasized)

Loss of Lock
PRN=27 Loss of Lock
1.2Loss1Loss Flag

0.8

0.6

0.4

0.2

022

22.5
23Local time (hour)

23.5

Lock Loss of PRN 27, MMR

S4 from Airborne ISM, PRN 27

PRN=9 Loss of Lock
1.2

1Loss Flag

0.8

0.6

0.4

0.2

S4 from Airborne ISM, PRN 9Page 13

Tracked022

22.5
23Local time (hour)

23.5

Lock Loss of PRN 9, MMR

Amplitude Scintillation
Index: S4

H24/9/12
22:34(JST)S4 corrected

Airglow image (777.4nm)

PRN271

Take off

PRN4

0.8
0.6
0.4
0.20GPS Trajectory(21:15～23:15)

15
Page 142121.52222.5PRN15274GROUNDAIRPhase Scintillation
Index: σφ

PRN15

GROUND

AIRBORNE

0.6

200.5

Commercial 0.4
ISM
0.3

15

0.2

5

100.1

021

21.5

2222.5

0.2

0.15

0.15

0.1

0.05

Page 15210.2

σφ (radians)

JAXA
ISM

σφ (radians)

00
2121.52222.5

21.5
22Local Time (hour)

22.5

0.1

0.05

21.5
22Local Time (hour)

22.5

021Ionospheric delay
Iono. Delay Measured by GROUND and AIRBORNE Rx(output of PolaRxS Pro)
Time Delay

Lock LOSSPRN 27
Page 16PRN 9

CCD Monitor
CCD filter output of GROUND
receiver (Post-Processing)

CCD filter output of AIRBORNE
receiver (Post-Processing)

Excluded
Page 17

No. of Sats and Protection Level
Number of used satellites (blue), lostsatellites (red), excluded satellites(green) by CCD monitor

VPL with BUBBLEs(real data)

VPL Increment
Due to BUBBLEs

Predicted VPL(without BUBBLE)

Lost
Page 18

Excluded
By CCDSummary Four flight tests were conducted under plasma bubbles
 A few satellites became unavailable due to loss of lockand CCD monitor (Maximum three satellites wereunavailable on Sept. 12). VPL increased correspondingly.
 INS-aiding will be applied and airborne scintillation data

will be investigated further.
 More flight tests are planned (March, Sept., 2013, March,2014)
 Any Suggestions on flight pattern, data collection, etc. arewelcome!
Page 19