Presentation on theme: "Variations in the Radiation Environment"— Presentation transcript:
1 Variations in the Radiation Environment C. D. GorskySGT, Inc.J. L. BarthNASA/GSFC
2 IntroductionA programmatic methodology for enabling COTS and emerging technology use in radiation environments requires an accurate definition of the environment with appropriate design margins.Variations in the environment are presented.Limitations of radiation environment models are presented with methods of extending their functionality.
3 The Radiation Environment Galactic Cosmic RaysSolar Protons&Heavier IonsTrapped ParticlesNikkei Science, Inc. of Japan, by K. Endo
5 Radiation Effects Total Ionizing Dose Single Event Effects Trapped Protons & ElectronsSolar ProtonsSingle Event EffectsProtonsTrappedSolarHeavier IonsGalactic Cosmic RaysSolar EventsNeutronsDisplacement DamageProtonsElectronsSpacecraft ChargingSurfacePlasmaDeep DielectricHigh Energy ElectronsBackground Interference on Instruments
6 Programmatic Methodology ref: LaBel et al. IEEE/NSREC 1998 Define the hazardEvaluate the hazard (e.g., dose-depth curves)Define requirementsEvaluate parts listsTest unknowns or perform radiation lot acceptance tests (RLATs) on non-RH guaranteed devicesEvaluate test data and predict performanceWork with designers on alternate device selection or mitigation options/validationRefine above as necessary3-D analysis of shielding rather than dose-depth curvesSelect harder part
7 Environment Definition for Programmatic Methodology Total Ionizing DoseDose-Depth Curves or Spacecraft Specific Dose LevelsTrapped Protons & ElectronsSolar ProtonsSecondary BremsstrahlungSingle Event Effects - Average & Peak ConditionsLET SpectraGalactic Cosmic Ray Heavy IonsSolar Heavy IonsEnergy SpectraTrapped ProtonsDisplacement DamageEnergy SpectraShielded Solar ProtonsShielded Trapped ProtonsCharging/DischargingSurface - Plasma ElectronsDeep-dielectric - High Energy ElectronsInstrument InterferencePrimary ParticlesSecondary Particles - Shielding Analysis
9 Solar Activity: Cyclic Variation Solar FlaresSunspot Cycle Discovered in mid 1800sCoronal Mass EjectionsIncrease in Solar Wind VelocitySolar Particle Events - Proton RichSolar FlaresIncrease in Solar Wind DensitySolar Particle Events - Heavy Ion RichSunspot CycleCoronal Mass Ejections50150200250100300Cycle 19Cycle 20Cycle 21Cycle 22Cycle 18Sunspot NumbersHolloman AFB/SOONYearsafter Lund Observatory
10 The Magnetosphere Defined by Interaction of: Earth’s Magnetic Field - Solar WindSolar Direction: Compressed to ~ 10 ERAnti-Solar Direction: Stretched into Long Magnetotail ~ 300 Earth RadiiOpen at the PolesBar Magnet Representation Accurate to Earth Radii
11 Magnetosphere Bow Shock Cusp Central Plasma Sheet Magnetopause Solar WindHeikkila (Color by University of Washington)
12 Particle Penetration of the Magnetosphere Most Solar Wind Particles Are Deflected (99.9%)Some Become Trapped & EnergizedGalactic Cosmic Ray & Solar Particle Penetration Depends on:Particle EnergyIonization StateGalactic Fully IonizedSolar & Anomalous Component of GCRs Have Lower Ionization StatesMeasured with Magnetic Rigidity in Units of GV
13 Magnetic Rigidity momentum charge H Z > 1 Total Energy Required to Penetrate the MagnetosphereH48 MeV87 MeV173 MeV284 MeV987 MeVMagnetic Equator2900 MeV2345671147 MeV/n313 MeV/n109 MeV/n46 MeV/n23 MeV/n12 MeV/nZ > 1after Stassinopoulos
14 Magnetic Storms / Space Weather “Gusty” Solar Wind Disturbs the Current SystemsMajor Storms Probably the Result of CMEsMust Be Pointed Toward EarthStrongest Arrive with Interplanetary Magnetic Field Oriented SouthCan Have Severe EffectsPower Blackouts on EarthDisruption of Communications SatellitesLoss of Satellites - ANIK-E1, Telstar 401
15 Sunspot Cycle with Magnetic Storms Sunspots & Magnetic Storm Days# of Days with Ap > 4Sunspot NumberAnnual Number of Days with Ap>4Annual Sunspot Number
16 ANIK E1: Magnetic Storm January 1994 Solar Wind Velocity (IMP-8 MIT) SAMPEX Electrons E > 1 MeV8200300800700400500600Time of ANIK Failure1234567Velocity (km/s)Counts/s (x10)161116212531161116212531January 1994
17 Trapped - Van Allen Belts OmnidirectionalComponentsProtons: E ~ MeVElectrons: E ~ (?) MeVHeavier Ions: Low E - Non-problem for ElectronicsLocation of Peak Levels Depends on EnergyAverage Counts Vary Slowly with the Solar CycleLocation of Populations Shifts with TimeCounts Can Increase by Orders of Magnitude During Magnetic StormsMarch 1991 Storm - Increases Were Long TermRadiation EffectsDose & DegradationSingle Event Effects - Protons onlyModels - AP8/NOAAPRO & AE8
18 Van Allen Belts High Latitude Horns Inner Belt Outer Belt Slot Region BIRA/IASB
19 Proton & Electron Average Models AP-8 ModelAE-8 Model12345678910Ep > 10 MeVEe > 1 MeV#/cm2/sec#/cm2/secL-ShellNASA/GSFC
20 Trapped Particle Variations ProtonsElectronsFairly StableCyclic Modulations Due to the Solar Cycle ~ 2Lowest Levels Are at Peak of Solar MaximumHighest Levels Are at Lowest Point in Solar MinimumRate of Change ~ 6%/yearGeomagnetic Field Shift Changes Location~ 6 ° westward / 20 yearsAnisotropy at Inner Edge ( km) 2 ~ 7Particle Increases at Outer Edge - New BeltsGeomagnetic StormsCyclic Modulation Due to the Solar Cycle ~ 2Highest Levels Are at Peak of Solar MaximumLowest Levels Are at Lowest Point in Solar MinimumInner Zone - Fairly StableOuter Zone - Dynamic 102 ~ 106Solar Cycle Variations Are MaskedLocal Time Variations Due to Magnetic Field Distortion27-Day Variation Due to Solar RotationMagnetic Storms & Sub-Storms
21 TIROS/NOAA Trapped Protons Solar Cycle Variation: MeV ProtonsB/Bmin=1.0L=1.20L=1.18L=1.16Proton Flux (#/cm2/s)Radio Flux F 10.7L=1.14197619801984198819921996DateHuston et al.
22 March 1991 Magnetic Storm New Proton Belt CRRES - AF Phillips Laboratory, SPD/GD
23 Activity in the Slot Region - SAMPEX SAMPEX/P1ADC: Electrons E > 0.4 MeV1902503103704304905505311971L-ShellDay (1992)
24 Magnetic Storms - Hipparcos Star Mapper - Radiation BackgroundMarch199019911992246L-Shell4-Day, 9-Orbit AveragesDaly, et al.
25 Proton Flux Contours Variations with Altitude Protons in SAA kmProton Flux ContoursVariations with AltitudeAt 800 km, SAA is an oval shapeAt 1300 km, the size of the oval shape increasesAt 3000 km, Van Allen “belt” structure of proton flux contoursLatitude (deg)Longitude (deg)Protons in SAA kmProtons in SAA kmLatitude (deg)Latitude (deg)Longitude (deg)Longitude (deg)
26 AP8 - MAX Spectra Integral Proton Fluences Energy Range Range in Al: MeVRange in Al:30 MeV ~ .17 inchEffects:Total DoseSingle Event EffectsSolar Cell DamageFluence (#/cm2/day)Energy (>MeV)
27 AE-8 - MAX Spectra Integral Electron Fluences Energy Range MeVRange in Al:Effects:Total DoseSurface ChargingDeep Dielectric ChargingSolar Cell DamageFluence (#/cm2/day)Energy (>MeV)
28 Single Event Effects - Proton Rates I=90 deg, H=1000/1000 km, Solar MinimumTrapped proton exposure in LEO depends on where satellite passes through the SAACalculate SEE rates forProton daily averageWorst case SAA passPeak proton counts in SAAImplications for memory scrub rates & other spacecraft operationsProtons (#/cm2/s)Energy (>MeV)
29 Particle Variations Protons and Photons Electrons extremely penetratingdifficult to shield againstElectronslower energies make them less penetrating
30 Dose Variation with Altitude 0 degree inclination
31 Dose Variation with Altitude 90 degree inclination
32 Dose-Depth Curves Dose Variation with Orbit Use “Dose-Depth Curves” to define top level dose requirements“Total Dose” includes contributions fromTrapped protonsTrapped electronsSolar protonsMinimum design margin of “x2” added to account for uncertainty in environment models and variation of device response within flight lots
33 Galactic Cosmic Ray Ions All Elements in Periodic TableEnergies in GeVFound Everywhere in Interplanetary SpaceOmnidirectionalMostly Fully IonizedCyclic Variation in Fluence LevelsLowest Levels = Solar Maximum PeakHighest Levels = Lowest Point in Solar MinimumSingle Event Effects HazardModel: CREME96
34 GCRs: Solar Modulation Galactic Cosmic RaysCNO - 24 Hour Averaged Mean Exposure FluxSolar eventsLong term cyclic variationPeak at solar minimumShielding ineffective for high energy ionsAttenuation by magnetosphere effective for low inclination, low altitude orbitsCNO (#/cm2/ster/s/MeV/n)YearsGCRs: Shielded Fluences - FeGCRs: Integral LET SpectraInterplanetary, CREME 96, Solar MinimumCREME 96, Solar Minimum, 100 mils (2.54 mm) AlParticles (#/cm2/day/MeV/n)LET Fluence (#/cm2/day)Energy (MeV/n)LET (MeV-cm2/mg)
35 Solar Particle Events Increased Levels of Protons & Heavier Ions EnergiesProtons - 100s of MeVHeavier Ions - 100s of GeVAbundances Dependent on Radial Distance from SunPartially Ionized - Greater Ability to Penetrate MagnetosphereNumber & Intensity of Events Increases Dramatically During Solar MaximumProblem for Total Ionizing Dose, Displacement Damage, & Single Event EffectsModelsDose & Displacement Damage - SOLPRO, JPL, ESPSingle Event Effects - CREME96 (Protons & Heavier Ions)
36 Sunspot Cycle with Solar Proton Events Proton Event FluencesSolar Proton EventsSolar proton events correlate with the sunspot cycleOnly low inclination, low altitude orbits are protected from solar proton eventsA problem for degradation & single event effectsESP model by NRL/NASAProtons (#/cm2)YearSolar Protons: OrbitsESP Model of Solar Proton Cumulative FluencesProton Levels Predicted by CREME 96Protons (#/cm2/s/MeV)Energy (MeV)
37 Integral LET Spectra , 100 mils AL Solar Heavy IonsFrequency & intensity increase during solar active phase of the solar cycleAttenuation by magnetosphere effective for low inclination, low altitude orbitsSolar heavy ion levels are orders of magnitude higher than galactic cosmic ray levelsShielding more effective than for galactic cosmic ray heavy ionsLET Fluence (#/cm2/sec)LET (MeV-cm2/mg)Differences in Energy SpectraGalactic Cosmic Ray & Solar Heavy Ion SpectraEffect of Shielding on Heavy Ions Galactic Cosmic Ray & Solar Heavy Ion SpectraCarbon, 100 mil ShieldInterplametaryAll Elements, 100 mil ShieldInterplametaryFluence (#/cm2/s)Fluence (#/cm2/s)Energy (MeV)LET (MeV-cm2/mg)
38 SummaryRequirements for the definition of the radiation environment for a programmatic methodology were defined.The variations in the radiation environment which must be considered in the definition were described.Appropriate models for defining the radiation environment were presented.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 1998.“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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