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Estimating the risk of SEPE: a service
dedicated to spacecraft operations
Feedback from ATV missions
Ph. Yaya, L. Hecker
CLS (Collecte Localisation Satellites)
Toulouse, FRANCE
ESWW13, Session 1, 14 Nov 2016
Summary
Page 2
-
Effect of particles on space vehicles
Flare characterization
Presentation of the service
Forecast validation for ATV-3/4/5
Improvements for ATV-4/5
Other possible improvements
ESWW13, Session 1, 14 Nov 2016
Summary
Page 3
-
Effect of particles on space vehicles
Flare characterization
Presentation of the service
Forecast validation for ATV-3/4/5
Improvements for ATV-4/5
Other possible improvements
ESWW13, Session 1, 14 Nov 2016
Effect of particles on space vehicles
Page 4
Charged particles are well known to be hazardous for on-board
electronics.
Miniaturization and digitization of electronics and logic circuits
have made space vehicles (launchers/satellites/…) more
vulnerable to radiation.
Origin of radiation :
- Van Allen radiation belts (mostly trapped p+/e-)  SAA
- Cosmic rays (very high energies but very low flux)
- Proton solar flares  « feed » radiation belts + direct impact if
intense enough
ESWW13, Session 1, 14 Nov 2016
Effect of particles on space vehicles
Page 5
Mean rate of daily SEU on all memories for SACC satellite (alt. 715 km)
(from C. Boatella-Polo, CNES)
Position of UOSAT-3 (alt. 785 km) when memory
errors were detected
(Fabien Faure, PhD thesis, INPG, 2005)
ESWW13, Session 1, 14 Nov 2016
Effect of particles on space vehicles
Page 6
Solar flares
Correlation between solar flares and number of SEU on SAC-C KM684000 memory
(Hubert et al, Multi-scale modeling to investigate the single event effects for space missions, Acta
Vol 69, Is. 7-8, pp 526-536, 2011)
Correlation between number of days :
- when >2 MeV electron fluence exceed 108cm-2sr-1
- when there was an ESD switch (internal discharge)
(G. Wrenn, R. Smith, Qinetiq)
ESWW13, Session 1, 14 Nov 2016
Effect of particles on space vehicles
Page 7
Effect of solar flares on SOHO solar panel
Effect of solar flares (inversed triangles)
on CLUSTER solar panel power
ADEOS-II failure :
Debris impacted the solar panel harness which
was charged due to auroras  electric arc !
Complete satellite failure on Oct 23rd 2003
(no direct link with a solar flare)
ESWW13, Session 1, 14 Nov 2016
Summary
Page 8
-
Effect of particles on space vehicles
Flare characterization
Presentation of the service
Forecast validation for ATV-3/4/5
Improvements for ATV-4/5
Other possible improvements
ESWW13, Session 1, 14 Nov 2016
Flare characterization
Page 9
SOHO/MDI
magnetogram,
oct 28, 2003
Mechanism :
 Complex loops of magnetic field near
active regions
 Energy
release
with
magnetic
reconfiguration
 Possible acceleration of energetic
particles
(e-,
p+,
ions),
with
electromagnetic signatures in many
wavelength
NB. Particles events represent only a few
percentage of the solar flares
ESWW13, Session 1, 14 Nov 2016
Propagation in the IMF
Page 10
E
W
The Sun rotates with a 27 days period,
creating a curved interplanetary magnetic
field (Parker spiral)
The charged particles ejected from a proton
solar flare follow the curved magnetic lines.
 Most of the flares that produce an SEPE
are located in the Western visible part of the
Sun.
J.P.Vallée, Observations of the Magnetic Fields Inside
and Outside the Solar System, "Fundamentals of
Cosmic Physics", Vol. 19, pp. 319-422, 1998.
ESWW13, Session 1, 14 Nov 2016
Measurements on Earth
Page 11
« Official » data provider for the Xray and proton flux : GOES satellite
(geostationary), which is an
operational satellite (redundancy)
Charged particles can reach Earth in
various delays, from a few minutes
(intense flare from well-connected
active region) to a few hours (max 2
days).
gradual
Depending on the
presence of a
impulsive
CME, or the
location of the flare
on the solar disk,
proton flux shape
may differ
ESWW13, Session 1, 14 Nov 2016
Summary
Page 12
-
Effect of particles on space vehicles
Flare characterization
Presentation of the service
Forecast validation for ATV-3/4/5
Improvements for ATV-4/5
Other possible improvements
ESWW13, Session 1, 14 Nov 2016
Customers of the service
Page 13
CLS forecast service was active for the 5 ESA/ATV missions (20082015)
Critical operations of ATV w.r.t. solar flares :
- ATV-ISS approach
- ISS refueling
- ISS propulsion support
- ATV-ISS undocking
- ATV re-entry
ESA/D. Ducros
In 2013-2014, service for
ESA/Gaia mission :
- post launch manoeuvers
- integration to L2 point
ESA/J. Huart
Since 2006, the service is
also active for SSO
launches
ESA
ESWW13, Session 1, 14 Nov 2016
Presentation of SFC service for ATV
Page 14
What : SEPE forecast service from CLS/SFC (Solar Forecast Center)
When :
Each day of the the ATV missions (from launch to re-entry).
- on working days: manual bulletin (with a previsionist)
- on week-ends: automatic bulletin, except in case of a critical operation ( human
analysis)
How :
CLS service to provide a level of risk of a SEPE within 48h, for which the criteria
were established in collaboration with the Paris Obs./LESIA, the CPTh/X, ONERA...
Every day, an operator analyses the sun looking for precursors or indicators of
SEPEs. They may be related to active regions morphology, position on the solar disk
(Earth connection), magnetic complexity, associated electromagnetic activities (radio
burst…), …
ESWW13, Session 1, 14 Nov 2016
Presentation of SFC service for ATV
Page 15
The level of risk depends on the sensitivity of the spacecraft instruments to
particles  important step = technical requirements.
Example for ATV: flux critical threshold define the event:
FEp+>50MeV > 10 p.f.u. (E)
4 levels of risk:
NO risk
LOW risk
MEDIUM risk
HIGH risk
Probability of (E) < 1%
Probability of (E) 1-10%
Probability of (E) 10-50%
Probability of (E) > 50%
ESWW13, Session 1, 14 Nov 2016
Time distribution of SEPEs
Page 16
SEPE may also occur
during cycle minimum !!
Eg. 1985, 2006.
ATV-1
ATV-2
ATV-3
ATV-5
ATV-4
Forecast & indicators analysis
Page 17
EXAMPLE OF A WEEKLY SYNOPTIC :
small
variations of
proton fluxes
Favorable
longitude for the
first SEPE.
Effect of flare
“chain reaction”
for the 2nd one ?
Type II or IV
radio bursts
every day
ESWW13, Session 1, 14 Nov 2016
Far side informations
Page 18
Far side
STEREO
Helioseismology
(NSO/GONG)
This region which
was Earth directed
(#11236) on June 21
2011, was detected
when it was on the
far side
Example of forecast bulletin
Page 19
January 23rd 2012 event
Page 20
ESWW13, Session 1, 14 Nov 2016
June 7th 2011 event
Page 21
The >50 MeV
proton flux
reached 12 pfu
(only 34 events
exceeded10 pfu
on the last cycle)
BUT : no
signs of a >
50 MeV
SEPE risk
ESWW13, Session 1, 14 Nov 2016
July 17th 2012: 10 MeV event
NASA/SRAG : no risk
CLS : high level risk
Page 22
ESWW13, Session 1, 14 Nov 2016
Summary
Page 23
-
Effect of particles on space vehicles
Flare characterization
Presentation of the service
Forecast validation for ATV-3/4/5
Improvements for ATV-4/5
Other possible improvements
ESWW13, Session 1, 14 Nov 2016
Forecast statistics & validation
Page 24
•
•
639 daily bulletins emitted between January 2012 and February 2015
17 events (50 MeV proton flux > 10 pfu in the 48 following hours)
Distribution of forecasted
levels
Distribution of events per
forecasted level
0%
4%
19%
18%
None
23%
None
Low
Low
Medium
53%
High
54%
Medium
29%
High
Rate (%)
Event rate per forecasted level
Forecasted
probability (%)
A posteriori
event rate (%)
40.0
Level
30.0
None
[0; 1 [
0.0
20.0
Low
[1; 10 [
0.9
10.0
Medium
[10; 50 [
4.1
High
[50; 100]
32.1
0.0
None
Low
Medium
High
ESWW13, Session 1, 14 Nov 2016
Summary
Page 25
-
Effect of particles on space vehicles
Flare characterization
Presentation of the service
Forecast validation for ATV-3/4/5
Improvements for ATV-4/5
Other possible improvements
ESWW13, Session 1, 14 Nov 2016
Prediction of ATV exposition to particles
Page 26
•
Goal : identify the hour of passes of the ISS in the zones exposed to particles.
• How ?
1/ Estimation of a worst case energy (Halloween event) corresponding to a 10 pfu
flux.
risk !
10 pfu@>75MeV = ATV threshold of sensitivity to particles
ESWW13, Session 1, 14 Nov 2016
Prediction of ATV exposition to particles
Page 27
2/ Identify the geographical zone on a energy cutoff* map. We used the equations from
« Adams, J., Letaw, J. & Smart, D., 1983. Cosmic ray effects on microelectronics part
II: The Geomagnetic cutoff effects »
Max lat
of ISS
Min lat
of ISS
3/ Compute the hours of passes in these zones thanks to the ISS ephemeris (from ATV-CC)
* Cutoff energy : minimum energy needed for a particle to reach a given point of the Earth environment (depends on the altitude)
ESWW13, Session 1, 14 Nov 2016
Prediction of ATV exposition to particles
Page 28
•
Risk of solar particles reaching ATV
when cutoff is low :
–
The visible part of the SEPE spectrum
includes > 50 MeV protons at fluxes > 10
pfu
•
No risk of solar particles reaching
ATV when cutoff is high :
–
The geomagnetic field blocks the
dangerous part of the SEPE spectrum
(proton flux > 10 pfu)
ESWW13, Session 1, 14 Nov 2016
Prediction of ATV exposition to particles
Page 29
• Low geomagnetic cutoff periods of the following 2 days :
–
–
Windows of a few minutes corresponding to passes over North America and South Indian Ocean
Windows groups over a few hours each day
• UT times of beginning and end of windows groups
• The color of windows is adaptating to the predicted risk level of SEPE
ESWW13, Session 1, 14 Nov 2016
Summary
Page 30
-
Effect of particles on space vehicles
Flare characterization
Presentation of the service
Forecast validation for ATV-3/4/5
Improvements for ATV-4/5
Other possible improvements
ESWW13, Session 1, 14 Nov 2016
Other possible improvements
Page 31
Inputs sources:
- Use of radio bursts information in real time (Nançay radioheliographs)
- Historical data (GOES protons flux up to cycle 21)
- Ions wrt protons (distribution, density)
Algorithm :
- Before SEPEs start
- After SEPEs start (SOLPENCO)
- Other indicator : confinement or SXR-SEP peak flux (Klein et al), CME conditions…
- Better understanding of some particular flare mechanism (ex: June 7th 2011 event)
ESWW13, Session 1, 14 Nov 2016