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Near-real time detection of solar radio bursts

impacting the GNSS signal reception

J.-M. Chevalier, N. Bergeot, C. Marqué and C. Bruyninx

Solar Radio Bursts

• The Sun emits in radio over a wide frequency range (from few kHz to GHz)

• Solar Radio Bursts (SRB) are intense radio emissions (durations from 10s to few hours)

The SRB power is measured in solar flux units (1 SFU = 10-22 W.m-2.Hz-1) at different frequencies [250 MHz; 34 GHz]

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

GNSS signals (e.g. GPS, GLONASS )

Solar Radio Bursts

• The Sun emits in radio over a wide frequency range (from few kHz to GHz)

• Solar Radio Bursts (SRB) are intense radio emissions (durations from 10s to few hours)

The SRB power is measured in solar flux units (1 SFU = 10-22 W.m-2.Hz-1) at different frequencies [250 MHz; 34 GHz]

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

Impact on GNSS signal reception

• GNSS signals:

– L1 [ 1550 ; 1610 ] MHz

– L2 [ 1170 ; 1300 ] MHz

– Right Hand Circular Polarized (RHCP)

– Low power (~-160dBW)

→ vulnerable to Radio Frequency Interferences

• SRBs increase the noise level of GNSS ground stations

• Carrier-to-Noise density (C/N0) [35; 55] dB-Hz

Cerruti et al. 2006

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

Impact on GNSS applications

Sreeja et al. 2013

Muhammad et al. 2015

SRB of the 24/09/2011

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

Motivation

Real-Time Index detecting fades of GNSS signal reception due to SRB over a regional area

(e.g. EU, AF, SAm)

Implementation into ROB-IONO software (Bergeot, et al. 2014) already

delivering European ionospheric maps in near-real time (www.gnss.be)

Developed and tested on 11 past SRB events occurring during the sunlit of Europe from 1999 until 2015 based on the solar radio observatory data from NOAA and with GNSS data (GPS and GLONASS) from the dense EUREF Permanent Network

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

EUREF Permanent Network (EPN)

• ~290 stations (Bruyninx et al. 2012)

• ~115 provide C/N0 in real-time

C/N0 extracted from RINEX files (S1

and S2 observations at respectively L1

and L2 frequencies)

But : no standardized unit

- C/N0 in dB-Hz

- Signal to Noise Ratio (SNR) in dB

SNR must be converted into C/N0 using

the manufacturer technical notes (Trimble,

Ashtech and Allen Osburn Associates)

Data input

www.epncb.oma.be

Daily Station Real-Time Station Real-Time Station delivering C/N0

http://epncb.oma.be

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

• C/N0 (t, sat) depends on : receiver and antenna type satellite elevation multipath ε (unidentified noise)

• Repeatable patterns removed by subtracting the C/N0 quiet normal

behaviour, i.e. the median <C/N0(t, sat)> of the 7 previous Ground Track Repeat Cycles (GTRC) :

∆C/N0(t, sat) = C/N0(t, sat) - <C/N0(t, sat)>7 GTRC With GPS GTRC: 1 sidereal day and GLONASS GTRC: 8 sidereal days

Detect abnormal fades of GNSS signal reception

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

SRB of the 24th September 2011

Post-processing on a past event

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

Post-processing on a past event SRB of the 24th

September 2011

∆C/N0 (t, sat, rec) ∆C/N0 (rec, t, sat) Median StD

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

∆C/N0 (t, sat, rec) Median StD Solar Radio Flux

Post-processing on a past event SRB of the 24th

September 2011

∆C/N0 (rec, t, sat)

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

Post-processing on past events

5 dB.Hz

5 dB.Hz

Max. Solar Flux in SFU

1700

1800 3000

10000 10000 22000 34000

54000 110000

7300

DATE

15/04/2001

28/10/2003

18/11/2003 14/07/2005

01/08/2010

03/08/2011

24/09/2011

04/03/2012

11/04/2013

04/11/2015

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

1700

1800 3000

10000 10000 22000 34000

54000 110000

7300

GPS and GLONASS

• Good agreement: the ∆C/N0 median agrees at the 0.1±0.2dB.Hz level

GPS GLONASS

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

Near-real time

detection in Europe

In collaboration with the Humain Radioastronomy Station http://sidc.be/humain/index.php

Reported on www.gnss.be

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

Index Level

Level GNSS ∆C/N0

Fade Effect

Quiet >-1dB-Hz none

Moderate -1 dB-Hz SRB detected but should not impact GNSS applications

Strong -3 dB-Hz Potential impact on GNSS applications

Severe -10 dB-Hz Potential failure of the GNSS receivers

Klobuchar et al., 1999

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

Africa

South America

Daily IGS GNSS Station Real-Time IGS GNSS Station

Applicable in other regions

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

Summary - Perspectives • GNSS signal reception fades due to SRB are now routinely monitored in

near-real time using the EPN with an index for each GNSS frequency bands.

• Developed based on the investigation of 11 SRB affecting GNSS receivers over Europe from 1999 until 2015. GPS and GLONASS showed good agreement.

• The monitoring is also applicable in other regions (Africa/S. America) and was tested with IGS data.

• Next steps: – 1Hz – Index <∆C/N0>=f(∆C/N0 , elsun)

ESWW13 2016 - Near-real time detection of solar radio bursts impacting the GNSS signal reception - Chevalier et al.

SOLAR RADIO BURST EVENT 2015-11-04 IN EUROPE (1HZ)