The ALTEA and ALTEA-Shield
experiments onboard the
International Space Station
L. Di Fino, M. Larosa, L. Narici, V. Zaconte
University of Rome Tor Vergata
Scientific goals
ALTEA (Anomalous Long Term Effects on Astronauts) – PI: Prof. L. Narici
Exposure of crew to space radiation poses one of the most significant hazards
to space permanence.
A quest for understanding the risks for the Central Nervous System (CNS)
during long permanence in space due to cosmic rays exposure.
Rationale:
• anomalous Light Flash perceptions suggest that abnormal (though possibly
transient) CNS functional states may result
• Theoretically predicted by Tobias: Tobias C.A. 1952 J. Aviat. Med. 23 345
• First observed in 1969 by Aldrin during Apollo-11 mission
Scientific strategy:
• detailed measurement of radiation environment (DOSI)
• measurement of transient/long-term functional effects of space environment and
cosmic radiation on the CNS (CNSM)
• survey of the radiation environment in space habitats (Survey)
• test of shielding materials as countermeasures for CNS functional risks (Shield)
ALTEA-Space facility
• Particle Detector (Silicon Detector System)
6 Silicon Detector Units (SDU)
6 silicon planes – 8x16 cm2, 380 mm thick
Geometrical factor
SDU 230 cm2sr
SDS 1180 cm2sr
Detectable LET range: 3 - 800 KeV/mm
DOSI – CNSM configurations
Survey configuration
• EEG, VSU, Pushbutton
• DAU
ALTEA facility onboard ISS
Onboard ISS since July 2006
2006-2007 ASI experiment
2009-2010 NASA-SRAG experiment
2010-2011 ESA experiment
> 800 days of acquisition time
> 1 billion triggers
ALTEA facility onboard ISS
2006
2007
2008
2009
2010
2011
2012
ALTEA configurations
DOSI (Dosimetry)
Realtime measurement
of radiation flux
Total acquisition time
2006-2007: 224 days
2009-2010: 320 days
ALTEA-Shield Survey
CNSM (Central Nervous
System Monitoring)
During a 90-minute
session the astronaut
wears EEG cap, slides
under the SDS and
signals LF perceptions
2006-2007: 7 sessions
Same as DOSI
Different 3D holder
Measurements in 4
different positions
Total acquisition time
2006-2007: 281 days
Realtime data
ALTEA data are downloaded and analyzed in realtime at the ALTEA
User Home Base (UHB) at University of Rome Tor Vergata.
A subset of ALTEA realtime data
is publicly available through the
NASA
iNTEGRATED
SPACE
WEATHER ANALYSIS SYSTEM
(iSWA) web application.
http://iswa.ccmc.gsfc.nasa.gov
Particle Rate
• 6 SDUs, triggered particles
• pole/equator and orbit precession modulations
• increment during passages on the SAA
Particle flux and ion abundances
• Filter fast particles (ΔE ~ Z2)
• Fit with a sum of Landau functions
December 2006 Solar Particle Event
Integrated Particle Fluxes and LET rates
1.40E-02
1.20E-04
1.20E-02
1.00E-02
8.00E-03
X
Y
6.00E-03
Z
4.00E-03
2.00E-03
Particle Flux (part s-1 cm-2 sr-1)
Particle Flux (part s-1 cm-2 sr-1)
Particle Flux (LET > 3 KeV/mm)
MEAN
POLES
EQUATOR
8.00E-05
X
6.00E-05
Y
Z
4.00E-05
2.00E-05
MEAN
SAA
8.00E-03
LET rate (LET > 3 KeV/mm)
3.00E-02
2.50E-02
X
2.00E-02
Y
1.50E-02
Z
1.00E-02
5.00E-03
0.00E+00
LET rate (keV mm-1 s-1 cm-2 sr-1)
4.00E-02
LET rate (keV mm-1 s-1 cm-2 sr-1)
1.00E-04
0.00E+00
0.00E+00
3.50E-02
Particle Flux (LET > 50 KeV/mm)
7.00E-03
POLES
EQUATOR
SAA
LET rate (LET > 50 KeV/mm)
6.00E-03
5.00E-03
X
4.00E-03
Y
3.00E-03
Z
2.00E-03
1.00E-03
0.00E+00
MEAN
POLES
EQUATOR
SAA
MEAN
POLES
EQUATOR
SAA
LET rate
Particle Flux
Particle flux anisotropy
UsLab survey
ALTEA-Shield integral fluxes (Preliminary)
• Different positions and directions shows
similar fluxes except for Position1-Y
• For LET>50KeV/mm direction X shows a flux
attenuation as expected
any LET
LET > 50 keV/um
Conclusions
The ALTEA-Space facility onboard ISS is used since 2006 in
different experiments supported by all major space agencies.
• It delivered a detailed measurement of the radiation
environment inside the UsLab, several measurements on
astronauts and a survey of the radiation environment in
different positions.
• A strong anisotropy (up to a factor 3 in LET) was found
when considering high LET particles (LET > 50) coming from
different directions.
• The second step of ALTEA-Shield (Shield) experiment is
planned in 2012 to test the effectiveness of different
shielding materials and thicknesses
• A collaboration with Jaxa is under consideration for further
measurements on astronauts
At last… we are looking for students!
Thank you for your attention!
METHOD: use ALTEA as single
detector
Particle flux anisotropy in
raw angular flux
distribution is masked by
the SDUs’ angular
acceptance.
A Montecarlo simulation
(PHITS) of an isotropic
flux was used to obtain
each SDU angular
acceptance.
To use ALTEA as a single detector we sum all
the SDUs to obtain the angular acceptance of
the whole ALTEA detector - R(q,j).
LET rate
Particle Flux
Results: Poles Spectra
Zone
Poles
Equator
SAA
B
Any
> 2.5*10-5 T
< 2.5*10-5 T
L
>2
<2
<2
LET rate
Particle Flux
Results: Equator Spectra
Zone
Poles
Equator
SAA
B
Any
> 2.5*10-5 T
< 2.5*10-5 T
L
>2
<2
<2
LET rate
Particle Flux
Results: SAA Spectra
Zone
Poles
Equator
SAA
B
Any
> 2.5*10-5 T
< 2.5*10-5 T
L
>2
<2
<2
ALTEA - CNSM
7 sessioni eseguite, 3 Astronauti (1 sess + 2 sess + 4 sess)
Astronaut
LF
Duration (min)
1
2
3
2
3
2
2
TOTAL
12
4
1
0
1
1
1
20
58
65
18
63
61
62
87
414
Mean interval
(min)
5
16
-----21
Numero di LF segnalati nelle sessioni CNSM
All E≤100 MeV/n E>100 MeV/n
All 18
2
16
Z<6 16
2
14
Z≥6 1.5
0.07
1.4
Rate di particelle passanti per l’occhio (part/min)
ALTEA - CNSM
Particella candidata (Z~3) alla generazione di un LF