observations of the galileo radiation environment from merlin and srem instruments
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Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
Observations of the GALILEO radiation environment from MERLIN and SREM
instrumentsDavid Rodgers, Hugh Evans, Eamonn Daly, Ali Mohammadzadeh,
ESA/ESTEC, Noordwijk, The Netherlands
Keith Ryden, Alex Hands, Clive Dyer
QinetiQ Ltd, Farnborough, Hampshire, UK
Craig Underwood, Ben Taylor
University of Surrey, Guildford, UK
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
GALILEOGalileo – Europe’s future Global Navigation
Satellite System• 23200km altitude circular orbit• 3 orbital planes at 56° inclination. • 9 equally-spaced operational satellites per
plane, plus 1 spare.
Radiation Environment• Main threat comes from relativistic electrons • Electrons are trapped in two belts around the Earth. • Galileo orbit lies at and above the outer belt peak. (higher than GPS)
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
GIOVEGiove-A and -B
• Secure the frequencies allocated by the International Telecommunications Union (ITU)
• Verify critical technologies e.g. atomic clocks and signal generator
• Provide a test signal for ground-based systems.
• Characterise the radiation environment of the Galileo orbit.
Giove-A
Giove-B
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
MERLIN•Developed by QinetiQ•Evolution of the SURF and CREDO instruments•Mass – 1kg (2kg including CAN bus and additional shielding)
•Launched on Giove-A 28th Dec 2005.
Electron monitor•3x70mm ø aluminium plates•2 sensitivity ranges
RadFETS•3mm Al and 6mm Al shielding•Unbiased
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
MERLIN
Two telescopes-Heavy Ion LET-Proton Flux
Each Telescope- Two large-area planar silicon diodes
Species discrimination through pulse-height analysis
Non-coincidence channels
Coincident channels
Protons: 40-100MeVLET: 16 channels100 – 20000 MeV/g/cm2
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
SREM
•Developed by Oerlikon/Contraves and PSI (Switzerland)•Evolution of REM•One of a set of near-identical instruments purchased by ESA.•Mass 2.5kg•Power <2W
•Launched on Giove-B on 26th April 2008•Previously launched on Integral, STRV-1C, Proba-1 and Rosetta •3 x Si surface barrier detectors
•>0.5MeV electrons•>10MeV protons•>150MeV ions
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
Giove-B SREM
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
06/05/08 19:12 07/05/08 00:00 07/05/08 04:48 07/05/08 09:36 07/05/08 14:24 07/05/08 19:12 08/05/08 00:00
Coun
trate
(#/s
)TC1 (#/s)
TC2 (#/s)
TC3 (#/s)06
/05/
08 2
1:59
07/0
5/08
20:
56
Giove-B SREM count-rate for 1 day (~ >0.8, >2.0 >2.8MeV)
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
Solar wind velocity
SREM (>0.8 MeV, >2 MeV and >2.8 MeV)
MERLIN (>0.8MeV, >1.0MeV and >1.6MeV)
13-17 June 2008
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
MERLIN currents [>0.8 (white), >1.0 (dark green) and >1.6MeV (red)]and doses [3mm (light green) and 6mm (pink) Al equivalent].
2007
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
>40MeV protons, >1.6MeV electrons and dose under 6mm Al
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
>0.8MeV electrons and “hardness index” plate1/plate3
1/8/06 – 1/1/07
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
SREM electron data (>2MeV) from GIOVE-B (red) and INTEGRAL (green)
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
Cumulative charge – AE8MAX and MERLIN
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
Cumulative charge – AE8MAX and MERLIN
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
Cumulative charge – AE8MAX and MERLIN
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
Plate 1 (>0.8MeV)
Plate 3 (>1.6MeV)
FLUMIC v2 comparison
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
ConclusionsA new radiation environment is being explored.Merlin and SREM are returning good-quality data.There is good agreement between the datasets.
Spacecraft in the Galileo orbit are subject to frequent space weather enhancements of the outer belt in response to changes in the solar wind.
Electron enhancements are the dominant source of dose.Hardening of electron spectra during enhancements is
typically seen.
These instruments can tell us about space weather and the long term environment.
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
ConclusionsFLUMIC2 model
– may be too conservative for >0.8MeV electrons– exceeded by CME-related enhancement – consider yearly maximum for FLUMIC, for this orbit
AE-8 model– conservative ~0.8 MeV– under-predicts at higher energy
Divergence from the AE-8 model is within model uncertainties (factor 2-3)
A small fraction of one solar has been monitored.– Further monitoring with IOV/FOC are planned– EMU - a Merlin-like instrument
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
END
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
Abstract
The GIOVE satellites (A, B) are test satellites for the European Galileo constellation. It is recognized that the Galileo orbital radiation environment is particularly severe and therefore these satellites carry environment monitoring equipment. This contribution will present some of the observations made and discuss what they teach us about the environment expected for the final Galileo constellation.
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
CEDEX and MERLIN for the first 5 months of 2006.
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
MERLIN currents [>0.8 (red), >1.0 (blue) and >1.6MeV (black)]and doses [3mm (orange) and 6mm (yellow) Al equivalent].
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
1.E+04
1.E+05
1.E+06
1.E+07
1 2 3 4 5 6 7 8 9L-shell
Flu
x cm
-2 s
-1
AE-8 MINGalileoGPSGEO
>1MeV electron flux according to AE-8.
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
ONERA MEOv2 and AE-8 model spectra for the GPS orbit.
GPS Electron Spectra
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
0.1 1 10Energy [MeV]
Flu
x [/
cm2/
s/sr
]
MEOv2 lower
MEOv2 mean
MEO v2 upper
AE-8 (7 years MAX, 4 years MIN)
Electromagnetics & Space Environment Division – TEC-EESElectromagnetics & Space Environment Division – TEC-EES
Data ProcessingMerlin data processed by SSTL/UoS in collaboration with QinetiQ
Data products provided to the Galileo Project
PSI access SREM data
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