The ALTEA and ALTEA-Shield experiments onboard the

International Space Station

L. Di Fino, M. Larosa, L. Narici, V. ZaconteUniversity of Rome Tor Vergata

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)

Scientific goals

• Particle Detector (Silicon Detector System)6 Silicon Detector Units (SDU)

6 silicon planes – 8x16 cm2, 380 mm thickGeometrical factor

SDU 230 cm2srSDS 1180 cm2sr

Detectable LET range: 3 - 800 KeV/mm

ALTEA-Space facility

• EEG, VSU, Pushbutton• DAU

DOSI – CNSM configurations

Survey configuration

ALTEA facility onboard ISS

Onboard ISS since July 20062006-2007 ASI experiment2009-2010 NASA-SRAG experiment2010-2011 ESA experiment

> 800 days of acquisition time> 1 billion triggers

ALTEA facility onboard ISS

2006 2007 2008 2009 2010 2011 2012

DOSI (Dosimetry)Realtime measurement of radiation flux

Total acquisition time2006-2007: 224 days2009-2010: 320 days

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

ALTEA configurations

ALTEA-Shield SurveySame as DOSIDifferent 3D holderMeasurements in 4 different positions

Total acquisition time2006-2007: 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

• 6 SDUs, triggered particles• pole/equator and orbit precession modulations • increment during passages on the SAA

Particle Rate

• Filter fast particles (ΔE ~ Z2)• Fit with a sum of Landau functions

Particle flux and ion abundances

December 2006 Solar Particle Event

Integrated Particle Fluxes and LET rates

MEAN POLES EQUATOR SAA0.00E+00

2.00E-03

4.00E-03

6.00E-03

8.00E-03

1.00E-02

1.20E-02

1.40E-02

Particle Flux (LET > 3 KeV/mm)

XYZ

Parti

cle

Flux

(par

t s-1

cm

-2 sr

-1)

MEAN POLES EQUATOR SAA0.00E+00

2.00E-05

4.00E-05

6.00E-05

8.00E-05

1.00E-04

1.20E-04

Particle Flux (LET > 50 KeV/mm)

XYZ

Parti

cle

Flux

(par

t s-1

cm

-2 sr

-1)

MEAN POLES EQUATOR SAA0.00E+00

5.00E-03

1.00E-02

1.50E-02

2.00E-02

2.50E-02

3.00E-02

3.50E-02

4.00E-02

LET rate (LET > 3 KeV/mm)

XYZ

LET

rate

(keV

mm

-1 s-

1 cm

-2 sr

-1)

MEAN POLES EQUATOR SAA0.00E+00

1.00E-03

2.00E-03

3.00E-03

4.00E-03

5.00E-03

6.00E-03

7.00E-03

8.00E-03

LET rate (LET > 50 KeV/mm)

XYZ

LET

rate

(keV

mm

-1 s-

1 cm

-2 sr

-1)

Parti

cle

Flux

LET

rate

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

ConclusionsThe 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!

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.

METHOD: use ALTEA as single detector

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).

Parti

cle

Flux

LET

rate

Results: Poles SpectraZone B LPoles Any > 2Equator > 2.5*10-5 T < 2SAA < 2.5*10-5 T < 2

Parti

cle

Flux

LET

rate

Results: Equator SpectraZone B LPoles Any > 2Equator > 2.5*10-5 T < 2SAA < 2.5*10-5 T < 2

Parti

cle

Flux

LET

rate

Results: SAA SpectraZone B LPoles Any > 2Equator > 2.5*10-5 T < 2SAA < 2.5*10-5 T < 2

ALTEA - CNSM

7 sessioni eseguite, 3 Astronauti (1 sess + 2 sess + 4 sess)Astronaut LF Duration (min) Mean interval

(min)1 12 58 52 4 65 163 1 18 --2 0 63 --3 1 61 --2 1 62 --2 1 87 --

TOTAL 20 414 21

All E≤100 MeV/n E>100 MeV/nAll 18 2 16Z<6 16 2 14Z≥6 1.5 0.07 1.4

Numero di LF segnalati nelle sessioni CNSM

Rate di particelle passanti per l’occhio (part/min)

ALTEA - CNSM

Particella candidata (Z~3) alla generazione di un LF