RADIATION IN SPACE Patrcia Gonalves LIP Laboratrio de

RADIATION IN SPACE Patrícia Gonçalves LIP Laboratório de Instrumentação e Física Experimental de Partículas Lisboa, Portugal

SOURCES OF RADIATION IN SPACE 2

Three sources of radiation • Galactic Cosmic Rays Protons and ions low flux very energetic penetrating • Solar Events (SEP) protons and electrons high flux low energy sporadic very dangerous • Planetary Radiation Belts protons and electrons high radiation dose 3

Cosmic Radiation 4

Cosmic Radiation Flux x E 2. 3 ( part/m 2/s/sr/Ge. V-2. 3) E/nucl (Ge. V) 5

Galactic Cosmic Rays (GCR) Supernova in Crab nebula seen in X-ray (Chandra mission) 6

GCR spectra 7

Low flux but highly penetrant GCR • Protons and nuclei: energy spectra peak at ~1 Ge. V/n • Solar cycle modulated flux : inversely proportional to the Sun’s activity • E < 1 Ge. V/n: highly affected by solar activity Collision between an energetic CR and an atom. Photographic emulsion on a microscope. 8

11 year solar cycle Solar cycle Maximum: solar storms and SEP Minimum: more GCR 9

Solar cycle 24 6 December 2010 blast See movie in: http: //spaceweather. com/images 2010/06 dec 10/epicblast 2. gif? PHPSESSID=q 5 k 5 l 5 jnes 94 g 0 kdqr 6 enjs 0 t 3 10

SEP Eventos solares Blasting CME (SOHO) This image taken 8 January 2002, shows a widely spreading coronal mass ejection (CME) as it blasts more than a billion tons of matter out into space at millions of kilometers per hour. 11

The Sun SOHO : Solar and Heliospheric Observatory SOHO is a project of international cooperation between ESA and NASA to study the Sun, from its deep core to the outer corona, and the solar wind. 12

Solar Energetic Particle Events October 1989 : example of a very large SPE 13

Long term record of SPEs • More in “maximum” solar activity years • Highly unpredictable • Design for by making statistical assessment 14

SEP and the Apollo programme 1 1 15

Magnetospheric Storms See movie in: http: //www. youtube. com/watch? v=BDZj 1 Cms. J 64&feature=related 16

Aurora Charged particles captured in the radiation belts excite N 2 and O 2 molecules that emit visible light while returning to the fundamental state. 17

Radiation Belt Regions High radiation dose, electrons (<10 Me. V) & protons (<250 Me. V), Low Earth Orbits (LEO) • Inner belt (700 -10000 km) dominated by protons CRAND = Cosmic Ray Albedo Neutron Decay ~static E~100’s Me. V • Outer belt ( ~20000 -70000 km) dominated by electrons Controlled by “storms” Very dynamic E~ Me. V • Slot Usually low intensities of Me. V electrons Occasional injections of more particles 18

Particles in the magnetosphere 19

Radiation Belt models • Based om data from 1960 -1970 • Long term averages ( but : outer belt is very stormy) • ongoing work to update models Protons Electrons 20

Example of Electron Data 21

South Atlantic Anomally 22

International Space Station: 400 km altitude. Below inner belt! 23

Aurora seen from the ISS 24

RADIATION EFFECTS 25

Space Weather Lucent Technologies’ Louis Lanzerotti 26

Space Weather and radiation 14 th April 2011 27

Biologic effects Radiation exposure damages living tissue and high doses may result in mutations, cancer and death. The practical measure of radiation exposure is the Equivalent Dose H. The equivalent dose, HT, in an individual tissue or organ, T, is given by: HT= R w. R DT, R • DT, R : average absorbed dose from radiation R, in tissue or organ T • w. R : radiation weighting factor of radiation R ( depends of particle type and energy) 14 th April 2011 28

Efective Dose and Ambient Dose Equivalent The Effective Dose (ED) is the sum of the equivalent doses in all tissues and organs of the body, weighted by an organ/tissue weighting factor such that: ED= T w. T HT The Ambient Dose Equivalent (ADE) is the dose equivalent which would be generated in an oriented and expanded radiation field at a depth of 10 mm on the radius of an ICRU Sphere, oriented so as to be opposite to the direction of the incident radiation. ICRU Sphere D=30 cm =1 g/cm 3 76, 2% O 11, 1%C 10. 1%H 2. 6%N 29

TACKLING THE PROBLEMA OF RADIATION IN SPACE 30

Radiation in Space Radiation hazards Galactic Cosmic rays upset electronics long-term hazards to crews interfere with sensors Solar Energetic Particle Events upset electronics serious prompt hazards to crews interfere massively with sensors Radiation belts upset electronics hazards to astronauts interfere with sensors electrostatic charging 7 July 2010 31 31

Some solutions SEP , GCR, Trapped particles Understanding of emission and propagation mechanisms towards forecasting models and tools Planet (atmosphere, surface, orbit), Spacecraft Radiation environment simulation: in space on the surface of planets in-orbit Radiation monitors: detector design and optimisation detector simulation data analysis Spacecraft systems, EEE components, Humans EEE component degradation: Simulation component testing (ground/space) degradation modelling Shielding: study and design spacesuits, shelters spacecrafts 32

Mars 33

Mars Case Atmosphere density ~1/100 Earth’s Atmosphere composition > 95% CO 2 Mars magnetic field, unlike Earth’s, is not a dinamo, although in some regions there is a localized crustal field. 34

Mars. REM: the Mars Energetic Radiation Environment Models d. MEREM : detailed Mars Energetic Radiation Environment Model e. MEREM : engeneering Mars Energetic Radiation Environment Model interfaced to SPEs , GCR (p, , ions) and X-rays input flux models to be used by mission designers and planners and by radiation experts web-based and interfaced with existing radiation shielding and effects simulation tools Work sponsored by the ESA Technology Research Programme (http: //reat. space. qinetiq. com/marsrem) concluded in 2009 35

d. MEREM LIP developed d. MEREM, a Geant 4 based model for the radiation environment on Mars, Phobos and Deimos, including local treatment of surface topology and composition, atmospheric composition and density (including diurnal + annual variations) and local magnetic fields. Inputs as a function of latitude, longitude, in a 5 x 5 degree grid, and season. Atmosphere composition from EMCD (Eurpean Mars Climate Database) or Mars. GRAM (NASA) Topography from Mars Laser Altimeter aboard Mars Global Surveyor. Soil Composition from analysis of data from Gamma Ray Spectrometer aboard Mars Odyssey, including water content and CO 2 ice. Magnetic Field Models , from PLANETOCOSMICS 36

Gamma Ray Spectrometer data 37

d. MEREM outputs Generation : 10 GCR protons 10 Me. V < E(proton) < 10 Ge. V Outputs for any location on Mars surface, atmosphere, underground or on Phobos and Deimos Particle spectra for primaries and secondaries Particle Flux LET spectra im Si and H 2 O Effective dose Ambient Dose Equivalent 38

d. MEREM results: the effect of water atmosphere soil Neutron spectra for a default soil composition (blue line) and corresponding albedo (dashed blue line) and neutron spectrum (red line) and corresponding albedo (dashed red line) for the same soil composition but from which the water contribution was withdrawn. 39

Location Radiation Enviroment Study with d. MEREM “Characterization of the Martian radiation environment on selected locations using the ESA Mars Energetic Radiation Environment Models”, Accepted for publication by Icarus Magazine S. Mc. Kenna-Lawlor, P. Gonçalves, A. Keating, B. Morgado, D. Heynderickx, P. Nieminen, G. Santin, P, P. Truscott, F. Lei, B. Foing , and J. Balaz Three Martian landing sites characterised by significantly different topological conditions were studied during two significant flares for solar minimum and solar maximum conditions. 40

Phoenix Viking 1 Mawrth Vallis 41

Phoenix Viking 1 Mawrth Vallis 42

43

The three sites Site 1: Viking 1 landing site (22. 5 N, 48 W) Relatively smooth region in Chryse Planitia (Plains of Gold) soil is Regolith low hydrated. Site 2: Phoenix landing site (68. 5 N, 125. 8 W) upper layer containing a small amount of water (5%) over an ice rich layer CO 2 ice layer in winter! Site 3: Mawrth Valley (23 N, 19 W) Astrobiological interest. Situated in an apparent flood channel near the edge of the Martian highlands. Characterized by different types of clearly layered clays. Candidate landing site for the Mars Science Laboratory 44

Soil composition COMPOUND Default Viking Phoenix Mawrth Vallis Percentage composition Si. O 2 Fe 2 O 3 51. 2 9. 3 48. 4 15. 7 27. 0 4. 0 55. 0 38. 0 by weight Bulk(Al 2 Mg. Ca. Na 2 K 2 O 7) 32. 1 19. 0 0. 0 7. 4 100. 0 1. 7 3. 8 100. 0 1. 8 50. 0 100. 0 1. 2 7. 0 100. 0 2. 2 H 2 O Total Density (g/cm 3) 45

GCR inputs GCR differential flux spectra (cm-2 s-1 sr-1 (Me. V/nuc)-1) for H, He, Li and Fe. Solar minimum The differences are due to the scattering and deceleration of lower energy cosmic rays by the magnetic field embedded in the solar wind at the time of solar maximum. Solar maximum 46

SEP input Five minute averaged differential proton fluxes for SEPs. December, 2006 aboard GOES -11 April, 2002 aboard GOES-8 Fluxes were normalized to Mars orbit. 47

Results Viking 1 Model GCR SEP Total Effective Dose (m. Sv) Apr-02 Dec-06 Solar Maximum Solar Minimum d. MEREM 11, 11 0, 17 11, 3 e. MEREM 8, 85 0, 64 9, 5 d. MEREM 20, 22 0, 33 20, 6 e. MEREM 15, 05 1, 12 16, 2 Effective Dose (m. Sv) Phoenix Model GCR SEP Total Mawrth Vallis Model GCR SEP Total Apr-02 Solar Maximum d. MEREM 10, 75 0, 22 11, 0 e. MEREM 8, 7 0, 55 9, 3 18, 89 0, 2 19, 1 d. MEREM 5, 71 0, 3 6, 0 e. MEREM 6, 54 2, 35 8, 9 d. MEREM 9, 88 0, 59 10, 5 e. MEREM 9, 87 3, 97 13, 8 Ambient Dose Equivalent (m. Sv) Dec-06 Solar Minimum d. MEREM Ambient Dose Equivalent (m. Sv) Apr-02 Dec-06 Solar Maximum Solar Minimum e. MEREM 14, 74 0, 96 15, 7 Effective Dose (m. Sv) Apr-02 Dec-06 Solar Maximum Solar Minimum Apr-02 Solar Maximum d. MEREM 5, 09 0, 4 5, 5 e. MEREM 6, 22 1, 97 8, 2 Dec-06 Solar Minimum d. MEREM 7, 47 0, 329 7, 8 e. MEREM 9, 41 3, 34 12, 8 Ambient Dose Equivalent (m. Sv) Apr-02 Dec-06 Solar Maximum Solar Minimum d. MEREM e. MEREM 10, 79 0, 21 11, 0 8, 98 0, 79 9, 8 20, 03 0, 32 20, 4 15, 31 1, 32 16, 6 4 0, 31 4, 3 6, 43 2, 92 9, 4 7, 22 0, 44 7, 7 9, 75 4, 71 14, 5 48

Results Apr-2002, “Solar maximum” d. MEREM Viking Phoenix Mawrth Dec-2006, “Solar minimum” Viking Phoenix Mawrth ED (m. Sv) 11. 30 11. 00 20. 6 19. 10 20. 4 ADE (m. Sv) 6. 02 5. 49 4. 30 10. 5 7. 8 7. 67 ADE(i) / ADE (Viking) 1. 00 0. 91 0. 71 1. 00 0. 74 0. 73 H 2 O 3. 0 % 50. 0 % 9. 4 % 3. 0 % 50. 0 % 9. 4% Dry Ice No Yes No No Atmospheric depth (g/cm 2) 17. 8 19. 2 16. 5 17. 8 15. 1 Soil density (g/cm 3) 1. 8 1. 2 2. 2 49

Results GCR reach the surface of Mars and originate albedo neutrons increasing the ADE values. Most SEPs are degraded in the atmosphere and do not reach the surface. Both models agree on GCR but not on SEP prediction ( To be investigated) There is a resonable agreement between the MEREM and the HZTERN model used by NASA. Dose Equivalent (m. Sv) Regolith soil type “Solar minimum” “Solar maximum” HZETRN (De Angelis et al. , 2007) 11. 2 4. 5 e. MEREM – Viking 1* 13. 8 8. 0 d. MEREM – Viking 1* 10. 5 6. 0 50

Mission scenarios Mars Swingby Mars Short Surface Stay (sss) Mars Long Surface Stay (lss) __________________________ Scenario Duration Deep Space Surface Stay Days __________________________ Mars Swingby 600 0 Mars sss 430 400 30 Mars lss 1000 400 600 __________________________ These values are the mission parameters presently used by NASA in estimating mission risk and they may also be used for Mars mission radiation analysis. 51

30 days on Mars 30 Day Stay on Surface - solar minimum GCR induced dose Ionizing Radiation Exposure Limits for LEO (Simonsen et al. , 1993) e. MEREM Viking 1/Phoenix/Mawrth * d. MEREM Viking 1/Phoenix/ Mawrth * Dose Equivalent (m. Sv) Skin BFO 1500 250 21. 2/ 16. 0/21. 0/20. 3/14. 4 52

. . . it is possible ! It is possible to remain in Martian surface for some time with no serious risk for the astronauts! For longer permanences shelters are required. . . 53

The interplanetary travel The most dangerous phase in a triop to Mars , from the point of view of the radiation hazard, is the interplanetary travel ! The biggest danger is the possibility of a SEP reaching the mission. . Mitigation Strategies are under development: Shelters inside water compartments or other Faster propulsion system SEP Forecasting tools and alarms 54

Shielding from SEP Al : 1 g/cm 2 == 0. 37 cm H 2 O : 1 g/cm 2 == 1 cm Laurent Desorgher, Active Shielding study 55

Next steps SEP Forecasting models and tools are essential if we want to step beyond LEO. . . Need data from Mars to validate models! Radiation Monitors in Mars From Mars to the Moon: modeling the Lunar radiation environment for radiation environment assessment and model validation 56

57