1. 1 - Paul Scherrer Institut, 2 – SpaceIT, 3 - European Space Agency
Observations of Forbush Decreases with Fleet of ESA SREM Radiation Monitors
W. Hajdas1, L. Desorgher2, P. Buehler1,3, E. Daly3, H. Evans3, P. Nieminen3
1 - Paul Scherrer Institut, 2 – SpaceIT, 3 - European Space Agency

2. SREM – Main Features 3 Silicon Detectors in 2 heads; 1 telescope D1+D2
SREM – Standard Radiation Environment Monitor
Manufactured by RUAG AG
in collaboration with ESA and PSI
3 Silicon Detectors in 2 heads;
1 telescope D1+D2
1 single detector D3
Opening angle ±20°.
15 output counters with discriminators
11 single and 4 coincidence channels
Count rates > 100 kiloevents/sec.
Energy ranges:
E > 8 MeV protons
E > 0.5 MeV electrons)
Mass: 2.5 kg;
Dimensions: 96x122x217 mm3;
Power consumption 2 W
TID – total ionizing dose
SEE – Single event effects 2

3. Missions with SREM onboard
10 SREMs manufactured
7 currently flying
Missions with SREM:
STRV1c †
INTEGRAL
PROBA1
ROSETTA
HERSCHEL
PLANCK
GIOVE B
TID – total ionizing dose
SEE – Single event effects
3 Near Earth: Proba1, Integral, Giove B
3 Interplanetary: Rosetta, Herschel and Plack – L1 3

4. SREM Calibration All SREMs were calibrated using PSI facilities
Responses for protons from 10 MeV to 300 MeV
measured at PIF – Proton Irradiation Facility at PSI
Electron responses determined using sources
and electron monochromator
Each unit was modeled with parameters values
adjusted based on calibration data
Every SREM has its own response matrix
For Proba1, Integral, Rosetta, Giove B with the satellite
TID – total ionizing dose
SEE – Single event effects 4

5. Excess to SREM data and repository
Database includes all available SREM data in CDF format.
Access and more information at
Registration required, data commonly available
Repository includes all relevant documentation
as well as analysis software
Accessible via SVN at
Registration required, soon service will move to ESA
TID – total ionizing dose
SEE – Single event effects 5

6. Examples of SREM Data Proba1 / Integral / Integral /
polar horns
equator
SAA
Proba1 /
South Atlantic Anomaly
Integral /
Electron Belts
TID – total ionizing dose
SEE – Single event effects
Integral /
Solar Energetic Particles 6

7. Forbush decreases – SREMs and neutron monitors
Following events selected:
17-19 Feb 2011
5- 6 Apr 2010
14-20 Dec 2006
SREM data summed over 1 hour
(PSI database)
Neutron monitor - NM64 on Jungfraujoch
(Uni Bern database)
TID – total ionizing dose
SEE – Single event effects 7

8. Data comparison – Herschel, Planck and Rosetta and NM64
TID – total ionizing dose
SEE – Single event effects 8

9. Data Comparison – NM64 Neutron Monitor vs. SREM
TID – total ionizing dose
SEE – Single event effects
Data scaled to the same pre-decrease intensity
SREM energy threshold 40 MeV
NM64 cutoff rigidity 4.49 GV 9

10. Rise and fall time – Herschel/Planck, IREM, GIOVE B
TID – total ionizing dose
SEE – Single event effects
Data for IREM and GIOVE B cleaned up of high counting
rate events during belt passages 10

11. Duration - NM64 Neutron Monitor vs. SREM
TID – total ionizing dose
SEE – Single event effects
Data normalized to maximum in the selected period 11

12. Delay – SREM Herschel and Planck
TID – total ionizing dose
SEE – Single event effects
Magnitude and shape for Herschel and Planck are consistent
Satellites were at the distance of ca. 1.5105 km
Limiting factor - statistics 12

13. Energy dependence
TID – total ionizing dose
SEE – Single event effects
Hourly rates normalized to average rate within the observed period
Energy thresholds: TC1 – 20 MeV, TC2 – 40 MeV, C MeV 13

14. Summary
ESA Standard Radiation Environment Monitor SREM can detect Forbush decreases
Database from six SREM flying on various ESA satellites extends from 2002 until now and is commonly available
Data from selected events were compared with NM64 neutron monitor on Jungfraujoch (CH)
Intensity, timing and energy dependence weere investigated with SREMs flying on various satellites
Further analyzes and characterization will be performed while community is also encouraged to use SREM database
TID – total ionizing dose
SEE – Single event effects 14

15. Acknowledgements
Jungfraujoch neutron monitor data were kindly provided by the Cosmic Ray Group, Physikalisches Institut, University of Bern, Switzerland
The study was supported by PSI LTP and by ESA-ESTEC project: RFQ/ /07/NL/JD - “Support for Calibration, Analysis and Documentation of Radiation Monitors”
TID – total ionizing dose
SEE – Single event effects 15

16. Thank You