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P1 1 Barth Variations in the Radiation Environment J. L. Barth NASA/GSFC C. D. Gorsky SGT, Inc.

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Presentation on theme: "P1 1 Barth Variations in the Radiation Environment J. L. Barth NASA/GSFC C. D. Gorsky SGT, Inc."— Presentation transcript:

1 P1 1 Barth Variations in the Radiation Environment J. L. Barth NASA/GSFC C. D. Gorsky SGT, Inc.

2 P1 2 Barth Introduction u A programmatic methodology for enabling COTS and emerging technology use in radiation environments requires an accurate definition of the environment with appropriate design margins. u Variations in the environment are presented. u Limitations of radiation environment models are presented with methods of extending their functionality.

3 P1 3 Barth The Radiation Environment Solar Protons & Heavier Ions Galactic Cosmic Rays Trapped Particles Nikkei Science, Inc. of Japan, by K. Endo

4 P1 4 Barth Components of the Natural Environment u Transient »Galactic Cosmic Rays Protons & Heavier Ions »Solar Particle Events Protons & Heavier Ions u Trapped »Electrons, Protons, & Heavier Ions u Atmospheric & Terrestrial Secondaries »Neutrons

5 P1 5 Barth Radiation Effects u Total Ionizing Dose »Trapped Protons & Electrons »Solar Protons u Single Event Effects »Protons Trapped Solar »Heavier Ions Galactic Cosmic Rays Solar Events »Neutrons u Displacement Damage »Protons »Electrons u Spacecraft Charging »Surface Plasma »Deep Dielectric High Energy Electrons u Background Interference on Instruments

6 P1 6 Barth Programmatic Methodology ref: LaBel et al. IEEE/NSREC 1998 u Define the hazard u Evaluate the hazard (e.g., dose-depth curves) u Define requirements u Evaluate parts lists u Test unknowns or perform radiation lot acceptance tests (RLATs) on non-RH guaranteed devices u Evaluate test data and predict performance u Work with designers on alternate device selection or mitigation options/validation u Refine above as necessary »3-D analysis of shielding rather than dose-depth curves »Select harder part

7 P1 7 Barth Environment Definition for Programmatic Methodology u Total Ionizing Dose »Dose-Depth Curves or Spacecraft Specific Dose Levels Trapped Protons & Electrons Solar Protons Secondary Bremsstrahlung u Single Event Effects - Average & Peak Conditions »LET Spectra Galactic Cosmic Ray Heavy Ions Solar Heavy Ions »Energy Spectra Solar Protons Trapped Protons u Displacement Damage »Energy Spectra Shielded Solar Protons Shielded Trapped Protons u Charging/Discharging »Surface - Plasma Electrons »Deep-dielectric - High Energy Electrons u Instrument Interference »Primary Particles »Secondary Particles - Shielding Analysis

8 P1 8 Barth Sun: Dominates the Environment Trapped Particles Heavier Ions Protons Source Sun Modulator Galactic Cosmic Rays Atmospheric Neutrons Trapped Particles

9 P1 9 Barth Solar Flares Cycle 19Cycle 20Cycle 21Cycle 22 Cycle 18 Solar Activity : Cyclic Variation u Sunspot Cycle Discovered in mid 1800s u Coronal Mass Ejections »Increase in Solar Wind Velocity »Solar Particle Events - Proton Rich u Solar Flares »Increase in Solar Wind Density »Solar Particle Events - Heavy Ion Rich Holloman AFB/SOON Sunspot Numbers Years after Lund Observatory Sunspot Cycle Coronal Mass Ejections

10 P1 10 Barth The Magnetosphere u Defined by Interaction of: Earths Magnetic Field - Solar Wind u Solar Direction: Compressed to ~ 10 ER u Anti-Solar Direction: Stretched into Long Magnetotail ~ 300 Earth Radii u Open at the Poles u Bar Magnet Representation Accurate to Earth Radii

11 P1 11 Barth Magnetosphere Cusp Bow Shock Solar Wind Central Plasma Sheet Magnetopause Heikkila (Color by University of Washington)

12 P1 12 Barth Particle Penetration of the Magnetosphere u Most Solar Wind Particles Are Deflected (99.9%) »Some Become Trapped & Energized u Galactic Cosmic Ray & Solar Particle Penetration Depends on: » Particle Energy »Ionization State Galactic Fully Ionized Solar & Anomalous Component of GCRs Have Lower Ionization States u Measured with Magnetic Rigidity in Units of GV

13 P1 13 Barth Magnetic Rigidity Total Energy Required to Penetrate the Magnetosphere H Z > 1 Magnetic Equator 2900 MeV 12 MeV/n 23 MeV/n 46 MeV/n 109 MeV/n 313 MeV/n 1147 MeV/n 87 MeV 173 MeV 284 MeV 987 MeV 48 MeV momentum charge after Stassinopoulos

14 P1 14 Barth Magnetic Storms / Space Weather u Gusty Solar Wind Disturbs the Current Systems u Major Storms Probably the Result of CMEs »Must Be Pointed Toward Earth »Strongest Arrive with Interplanetary Magnetic Field Oriented South u Can Have Severe Effects »Power Blackouts on Earth »Disruption of Communications Satellites »Loss of Satellites - ANIK-E1, Telstar 401

15 P1 15 Barth Sunspot Cycle with Magnetic Storms Annual Number of Days with Ap>4 Sunspots & Magnetic Storm Days Annual Sunspot Number Sunspot Number# of Days with Ap > 4

16 P1 16 Barth Solar Wind Velocity (IMP-8 MIT)SAMPEX Electrons E > 1 MeV Time of ANIK Failure ANIK E1: Magnetic Storm January 1994 Velocity (km/s) Counts/s (x10)

17 P1 17 Barth Trapped - Van Allen Belts u Omnidirectional u Components »Protons:E ~ MeV »Electrons:E ~ (?) MeV »Heavier Ions: Low E - Non-problem for Electronics u Location of Peak Levels Depends on Energy u Average Counts Vary Slowly with the Solar Cycle u Location of Populations Shifts with Time u Counts Can Increase by Orders of Magnitude During Magnetic Storms »March 1991 Storm - Increases Were Long Term u Radiation Effects »Dose & Degradation »Single Event Effects - Protons only u Models - AP8/NOAAPRO & AE8

18 P1 18 Barth Van Allen Belts Inner Belt Outer Belt High Latitude Horns Slot Region BIRA/IASB

19 P1 19 Barth Proton & Electron Average Models L-Shell AP-8 ModelAE-8 Model E p > 10 MeVE e > 1 MeV NASA/GSFC #/cm 2 /sec

20 P1 20 Barth Protons u Fairly Stable u Cyclic Modulations Due to the Solar Cycle ~ 2 »Lowest Levels Are at Peak of Solar Maximum »Highest Levels Are at Lowest Point in Solar Minimum »Rate of Change ~ 6%/year u Geomagnetic Field Shift Changes Location » ~ 6 ° westward / 20 years u Anisotropy at Inner Edge ( km) 2 ~ 7 u Particle Increases at Outer Edge - New Belts »Geomagnetic Storms u Cyclic Modulation Due to the Solar Cycle ~ 2 »Highest Levels Are at Peak of Solar Maximum »Lowest Levels Are at Lowest Point in Solar Minimum u Inner Zone - Fairly Stable u Outer Zone - Dynamic 10 2 ~ 10 6 »Solar Cycle Variations Are Masked »Local Time Variations Due to Magnetic Field Distortion »27-Day Variation Due to Solar Rotation »Magnetic Storms & Sub-Storms Electrons Trapped Particle Variations

21 P1 21 Barth TIROS/NOAA Trapped Protons Proton Flux (#/cm 2 /s) Date Solar Cycle Variation: MeV Protons L=1.20 L=1.18 L=1.16 L=1.14 B/B min =1.0 Radio Flux F 10.7 Huston et al

22 P1 22 Barth March 1991 Magnetic Storm New Proton Belt CRRES - AF Phillips Laboratory, SPD/GD

23 P1 23 Barth Activity in the Slot Region - SAMPEX Day (1992) L-Shell SAMPEX/P1ADC: Electrons E > 0.4 MeV

24 P1 24 Barth Magnetic Storms - Hipparcos L-Shell 4-Day, 9-Orbit Averages Star Mapper - Radiation Background Daly, et al. March

25 P1 25 Barth Protons in SAA km Longitude (deg) Latitude (deg) Longitude (deg) Latitude (deg) Longitude (deg) Latitude (deg) Protons in SAA kmProtons in SAA km Proton Flux Contours uVariations with Altitude »At 800 km, SAA is an oval shape »At 1300 km, the size of the oval shape increases »At 3000 km, Van Allen belt structure of proton flux contours

26 P1 26 Barth AP8 - MAX Spectra u Energy Range » MeV u Range in Al: »30 MeV ~.17 inch u Effects: »Total Dose »Single Event Effects »Solar Cell Damage Energy (>MeV) Fluence (#/cm 2 /day) Integral Proton Fluences

27 P1 27 Barth AE-8 - MAX Spectra u Energy Range » MeV u Range in Al: u Effects: »Total Dose »Surface Charging »Deep Dielectric Charging »Solar Cell Damage Energy (>MeV) Fluence (#/cm 2 /day) Integral Electron Fluences

28 P1 28 Barth Single Event Effects - Proton Rates u Trapped proton exposure in LEO depends on where satellite passes through the SAA u Calculate SEE rates for »Proton daily average »Worst case SAA pass »Peak proton counts in SAA u Implications for memory scrub rates & other spacecraft operations Energy (>MeV) I=90 deg, H=1000/1000 km, Solar Minimum Protons (#/cm 2 /s)

29 P1 29 Barth Particle Variations uProtons and Photons »extremely penetrating »difficult to shield against uElectrons »lower energies make them less penetrating

30 P1 30 Barth Dose Variation with Altitude 0 degree inclination

31 P1 31 Barth Dose Variation with Altitude 90 degree inclination

32 P1 32 Barth u Use Dose-Depth Curves to define top level dose requirements u Total Dose includes contributions from »Trapped protons »Trapped electrons »Solar protons u Minimum design margin of x2 added to account for uncertainty in environment models and variation of device response within flight lots Dose-Depth Curves Dose Variation with Orbit

33 P1 33 Barth Galactic Cosmic Ray Ions u All Elements in Periodic Table u Energies in GeV u Found Everywhere in Interplanetary Space u Omnidirectional u Mostly Fully Ionized u Cyclic Variation in Fluence Levels »Lowest Levels = Solar Maximum Peak »Highest Levels = Lowest Point in Solar Minimum u Single Event Effects Hazard u Model: CREME96

34 P1 34 Barth GCRs: Solar Modulation Years CNO (#/cm 2 /ster/s/MeV/n) CNO - 24 Hour Averaged Mean Exposure Flux GCRs: Shielded Fluences - Fe Interplanetary, CREME 96, Solar Minimum Energy (MeV/n) Particles (#/cm 2 /day/MeV/n) GCRs: Integral LET Spectra LET Fluence (#/cm 2 /day) LET (MeV-cm 2 /mg) CREME 96, Solar Minimum, 100 mils (2.54 mm) Al Galactic Cosmic Rays »Long term cyclic variation »Peak at solar minimum »Shielding ineffective for high energy ions »Attenuation by magnetosphere effective for low inclination, low altitude orbits Solar events

35 P1 35 Barth Solar Particle Events u Increased Levels of Protons & Heavier Ions u Energies »Protons - 100s of MeV »Heavier Ions - 100s of GeV u Abundances Dependent on Radial Distance from Sun u Partially Ionized - Greater Ability to Penetrate Magnetosphere u Number & Intensity of Events Increases Dramatically During Solar Maximum u Problem for Total Ionizing Dose, Displacement Damage, & Single Event Effects u Models »Dose & Displacement Damage - SOLPRO, JPL, ESP »Single Event Effects - CREME96 (Protons & Heavier Ions)

36 P1 36 Barth Sunspot Cycle with Solar Proton Events Protons (#/cm 2 ) Year Proton Event Fluences Solar Protons: Orbits Proton Levels Predicted by CREME 96 Energy (MeV) Protons (#/cm 2 /s/MeV) Solar Proton Events »Solar proton events correlate with the sunspot cycle »Only low inclination, low altitude orbits are protected from solar proton events »A problem for degradation & single event effects »ESP model by NRL/NASA ESP Model of Solar Proton Cumulative Fluences

37 P1 37 Barth Effect of Shielding on Heavy Ions Galactic Cosmic Ray & Solar Heavy Ion Spectra Fluence (#/cm 2 /s) LET (MeV-cm 2 /mg) Solar Heavy Ions Integral LET Spectra, 100 mils AL LET (MeV-cm 2 /mg) LET Fluence (#/cm 2 /sec) »Frequency & intensity increase during solar active phase of the solar cycle »Attenuation by magnetosphere effective for low inclination, low altitude orbits »Solar heavy ion levels are orders of magnitude higher than galactic cosmic ray levels »Shielding more effective than for galactic cosmic ray heavy ions Differences in Energy Spectra Galactic Cosmic Ray & Solar Heavy Ion Spectra Fluence (#/cm 2 /s) Energy (MeV) Carbon, 100 mil Shield Interplametary All Elements, 100 mil Shield Interplametary

38 P1 38 Barth Summary u Requirements for the definition of the radiation environment for a programmatic methodology were defined. u The variations in the radiation environment which must be considered in the definition were described. u Appropriate models for defining the radiation environment were presented. u References: »Emerging Radiation Hardness Assurance (RHA) Issues: A NASA Approach for Spaceflight Programs, K. A. LaBel, J. L. Barth, R. A. Reed, and A. H. Johnston, IEEE Trans. on N.S., December »Applying Computer Simulation Tools to Radiation Effects Problems, Part I: Modeling Space Radiation Environments, J. L. Barth, Published in 1997 IEEE NSREC Short Course Notes, July 1997.

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