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Radiation In Space

Radiation In Space. Patrícia Gonçalves LIP Laboratório de Instrumentação e Física Experimental de Partículas Lisboa, Portugal. sources of radiation in space. Three sources of radiation. Galactic Cosmic Rays Protons and ions low flux very energetic penetrating Solar Events (SEP)

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Radiation In Space

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  1. Radiation In Space Patrícia Gonçalves LIP Laboratório de Instrumentação e Física Experimental de Partículas Lisboa, Portugal

  2. sources of radiation in space

  3. 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

  4. Cosmic Radiation

  5. Cosmic Radiation Flux x E2.3 ( part/m2/s/sr/GeV-2.3) E/nucl (GeV)

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

  7. GCR spectra

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

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

  10. Solar cycle 24 6 December 2010 blast See movie in: http://spaceweather.com/images2010/06dec10/epicblast2.gif?PHPSESSID=q5k5l5jnes94g0kdqr6enjs0t3

  11. 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. 

  12. 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.

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

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

  15. SEP and the Apollo programme 1 1

  16. Magnetospheric Storms See movie in: http://www.youtube.com/watch?v=BDZj1CmsJ64&feature=related

  17. Aurora Charged particles captured in the radiation belts excite N2 and O2 molecules that emit visible light while returning to the fundamental state.

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

  19. Particles in the magnetosphere

  20. 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

  21. Example of Electron Data

  22. South Atlantic Anomally

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

  24. Aurora seen from the ISS

  25. Radiation Effects

  26. Space Weather Lucent Technologies’ Louis Lanzerotti

  27. Space Weather and radiation

  28. 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 wRDT,R • DT,R : average absorbed dose from radiation R, in tissue or organ T • wR :radiation weighting factor of radiation R ( depends of particle type and energy)

  29. 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 wTHT • 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. D=30cm  =1g/cm3 76,2% O 11,1%C 10.1%H 2.6%N ICRU Sphere

  30. Tackling the problema of radiation in space

  31. 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

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

  33. Mars

  34. Mars Case Atmosphere density ~1/100 Earth’s Atmosphere composition > 95% CO2 Mars magnetic field, unlike Earth’s, is not a dinamo, although in some regions there is a localized crustal field.

  35. MarsREM:the Mars Energetic Radiation Environment Models dMEREM : detailed Mars Energetic Radiation Environment Model eMEREM : 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

  36. dMEREM LIP developed dMEREM, a Geant4 based model for the radiation environment on Mars, Phobos and Deimos, including local treatment of surface topology andcomposition, atmospheric composition and density (including diurnal + annual variations) and localmagnetic 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 MarsGRAM (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 CO2 ice. Magnetic Field Models , from PLANETOCOSMICS

  37. Gamma Ray Spectrometer data Concentration estimates of equivalent-weight water found at mid-latitudes (left) and in Mars North Pole region (right), from Mars Orbiter Gamma Ray Spectrometer (GRS) data. Concentration estimates of equivalent-weight Si and Fe from from Mars Orbiter Gamma Ray Spectrometer data, in a 5o x 5o latitude-longitude grid

  38. dMEREM outputs Generation : 10 GCR protons 10 MeV < E(proton) < 10 GeV 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 H2O Effective dose Ambient Dose Equivalent

  39. dMEREM 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.

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

  41. Phoenix Viking 1 Mawrth Vallis

  42. Phoenix Viking 1 Mawrth Vallis

  43. The three sites Site 1: Viking 1 landing site (22.5N, 48W) Relatively smooth region in ChrysePlanitia (Plains of Gold) soil is Regolith low hydrated. Site 2: • Phoenix landing site (68.5N, 125.8W) • upper layer containing a small amount of water (5%) over an ice rich layer • CO2 ice layer in winter! • Site 3: • Mawrth Valley (23N, 19W) • 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

  45. GCR inputs GCR differential flux spectra (cm-2 s-1 sr-1 (MeV/nuc)-1) for H, He, Li and Fe. 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 minimum Solar maximum

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

  47. Results

  48. Results

  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.

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