J. Barth/Code 562

The Radiation Environment

Solar Protons&

Heavier Ions

Galactic Cosmic Rays

Trapped Particles

Nikkei Science, Inc. of Japan, by K. Endo

J. Barth/Code 562

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

J. Barth/Code 562

Radiation & Effectsu Total Ionizing Dose

» Cumulative long termionizing damage due toprotons & electrons

u Displacement Damage» Cumulative long term non-

ionizing damage due toprotons, electrons, &neutrons

u Single Event Effects» Event caused by a single

charged particle - heavy ions& protons for some devices

E. Daly/ESA

J. Barth/Code 562

Sun

Yohkoh/SXT

SolarFlareu Dominates the

RadiationEnvironment» Source» Modulator

u Structure» Photosphere» Chromosphere» Corona

J. Barth/Code 562

Solar Windu Stream of Charged Particles from Sun’s

Corona» Electrons» Protons» Heavy Ions

u Magnetized Plasmau Detected Out to 10 billion km from Earth by

Pioneer 10u Velocity ~ 300 - 900 km/su Energy ~ .5 - 2.0 keV/nuc

Density ~ 1 - 30 / cm3}

J. Barth/Code 562

Solar Wind Density & Velocity

University of Maryland, SOHO/CELIAS

199723 Feb 25 Feb 27 Feb 29 Feb 1 Mar 3 Mar 5 Mar 7 Mar

300400

500

600

510152025

Den

sity

(#/c

m3 )

Velo

city

(km

/s)

J. Barth/Code 562

Magnetosphere

J. Barth/Code 562

Coronal Mass Ejections

Holloman AFB/SOON

u Bubble of Gas &Magnetic Field

u Ejects ~1017 gramsof Matter

u Shock WaveAcceleratesParticles toMillions of km/hr

u Associated withMagnetic Storms

u Proton Rich SolarEvents

J. Barth/Code 562

SOHO/LASCO During Solar Particle Event

J. Barth/Code 562

Solar Flares

u Sudden BrighteningNear Sunspots

u Solar System’sLargest ExplosiveEvents

u Particles AcceleratedDirectly by Event

u Heavy Ion Rich SolarEvents

J. Barth/Code 562

Magnetic Stormsu “Gusty” Solar Wind Disturbs the Current

Systems in the Magetosphereu Major Storms Probably the Result of CMEs

» Must Be Pointed Toward Earth» Strongest Arrive with Interplanetary Magnetic

Field Oriented Southu Cause Increase in Rate & Intensity of

Magnetic Sub-storms in the Geotail

J. Barth/Code 562

Electrical Currents

Discover Magazine - August 1995

u Normal Conditions» Currents Present on Quiet

Days

u Stormy Conditions» Intensified Currents

J. Barth/Code 562

Effects of Solar Stormsu Power Black-outs on Earthu Block Some Radio Communication

» Disturbs electrically charged gases in the ionosphereu Interfere with Cellular Phone Systems

» Ionospheric disturbances & satellite system failuresu Interfere with GPS Navigation (Ships & Airplanes)u Trigger Phantom Commands on Spacecraftu Increased Atmospheric Drag on Low Earth Orbit (LEO)

Satellitesu Increased Protons & Heavy Ion Particle Countsu “Pump Up” the Van Allen Belts

J. Barth/Code 562

1 6 11 16 21 25 311 6 11 16 21 25 31

Solar Wind Velocity (IMP-8 MIT) SAMPEX Electrons E > 1 MeV

Time of ANIK Failure

ANIK E1: Magnetic Storm

January 1994

Velo

city

(km

/s)

Coun

ts/s

(x10

)

8

1

23

4

5

6

7

0200

300

800

700

400

500

600

J. Barth/Code 562

Aurorau Particles stream down on

magnetic field lines from thegeomagnetic tail forming anauroral belt

u Electrons collide withatmospheric gases

u Electrons give energy to atomsand molecules which emitenergy as light

u Oxygen ---> Greenu Nitrogen ---> Red

J. Barth/Code 562

Aurora Borealis

u Northern lights ovalas measured byNOAA-14

u Centered on MagneticPole

J. Barth/Code 562

Early Warning: S-Curves

u Viewed with X-ray Imageryu Based on Two Years of

Observationsu Strong Correlation between

Sigmoid Regions and CMEsu Likely the Result of Twisted

Solar Magnetic Fieldsu May Provide Early Warning of

Particle Events

Montana State University

J. Barth/Code 562

Solar Activity: Cyclic Variationu Sunspot Cycle Discovered in mid 1800su Used as Indicator of Solar Activityu Increased Solar Activity Results in:

» Increased Rate of CMEs» Increased Rate of Solar Flares» Increased Rate of Magnetic Storms» Increased Levels of Electrons in Van Allen Belts» Decreased Levels of Protons in Van Allen Belts» Increased Incidence of New Belt Formation» Decreased Levels of Galactic Cosmic Rays» Increased Rate of Solar Particle Events

u Effects on Climate?

J. Barth/Code 562

Sunspot Cycle

1 7 5 0 1 8 0 0 1 8 5 0 1 9 0 0 1 9 5 0 2 0 0 00

5 0

1 0 0

1 5 0

2 0 0

2 5 0

Length Varies from 9 - 13 Years7 Years Solar Maximum, 4 Years Solar Minimum

Suns

pot N

umbe

rs

J. Barth/Code 562

1950 1960 1970 1980 1990 20000

50

100

150

200

250

Sunspot CycleSu

nspo

t Num

bers

Cycle 18

Cycle 22Cycle 21

Cycle 20

Cycle 19

J. Barth/Code 562

20

40

0

60

80

100

1930 19601940 1950 1970 1980 1990

150

0

100

200

50

Sunspot Cycle with Magnetic StormsA

nnua

l Num

ber o

f Day

s with

Ap>

4 Sunspots & Magnetic Storm Days

Ann

ual S

unsp

ot N

umbe

rSunspot Number# of Days with Ap > 4

J. Barth/Code 562

Solar Cycle - Aurora Days

From Way North Magazine

J. Barth/Code 562

Discovery of Galactic Cosmic Rays - 1913u Electroscope Experiments

» Dissipation of Charge on Leaves?» Emissions from Materials on Earth» “Clean” Instruments Did Not Eliminate Dissipation

u Hess» Balloon Experiments with Electroscopes» Hypothesis: Background Radiation Will Disappear with

Increasing Altitude» > 10,000 feet - Background Increased with Altitude» Named “Cosmic Rays” by Hess

J. Barth/Code 562

Galactic Cosmic Ray Ionsu All Elements in Periodic Table - 200 Million Years Oldu Energies in GeVu Found Everywhere in Interplanetary Spaceu Omnidirectionalu Mostly Fully Ionized - Protons & Bare Nuclei of Heavier

Elementsu Cyclic Variation in Fluence Levels

» Lowest Levels = Solar Maximum Peak» Highest Levels = Lowest Point in Solar Minimum

u Trajectories Bent by Magnetic Fieldu Single Event Effects Hazardu Model: CREME96

J. Barth/Code 562

1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 01 0 -2

1 0 -1

1 0 0

1 0 1

1 0 2

1 0 3

1 0 4

1 0 5

1 0 6

1 0 7

1 0 8

1 0 9

1 0 1 0

GCRs: Nuclear CompositionRe

lativ

e Flu

x (S

i = 1

06 )

C

Nuclear Charge (Z)

HHe

OSi Fe

ZrBa Pt

PbIndividual Elements Even-Z Elements Elemental Groups

Energy = 2 GeV/n, Normalized to Silicon = 106

J. Barth/Code 562

GCRs: Solar Modulation

1 9 7 5 1 9 7 7 1 9 7 9 1 9 8 1 1 9 8 3 1 9 8 5 1 9 8 7 1 9 8 9 1 9 9 1 1 9 9 3 1 9 9 51 0 -5

1 0 -4

1 0 -3

1 0 -2

1 0 -1

1 0 0

1 0 1

1 0 2

Date

CNO

(#/c

m2 /

ster

/s/M

eV/n

)CNO - 24 Hour Averaged Mean Exposure Flux

Energy = 25-250 MeV/n - IMP-8

J. Barth/Code 562

1 0 -1 1 0 0 1 0 1 1 0 2 1 0 3 1 0 4 1 0 51 0 -6

1 0 -5

1 0 -4

1 0 -3

1 0 -2

1 0 -1

1 0 0

1 0 1

S u rfa c e I n c i d e n t1 0 0 m ils ( 2 . 5 4 m m ) A l5 0 0 m ils ( 1 2 . 7 m m ) A l

GCRs: Shielded Fluences - FePa

rticle

s (#/

cm2 /

day/

MeV

/n)

Interplanetary, CREME 96, Solar Minimum

Energy (MeV/n)

J. Barth/Code 562

1 0 -1 1 0 0 1 0 1 1 0 2 1 0 3 1 0 4 1 0 51 0 -6

1 0 -5

1 0 -4

1 0 -3

1 0 -2

1 0 -1

G E OG T OM E OE O SL E O

GCRsGCRs: Shielded: Shielded Fluences Fluences - Fe - FeCREME 96, Solar Minimum, 100 mils (2.54 mm) Al

Energy (MeV/nuc)Parti

cles (

#/cm

2 /da

y/M

eV/n

uc)

J. Barth/Code 562

Solar Particle Eventsu Increased Levels of Protons & Heavier Ionsu Energies

» Protons - 100s of MeV» Heavier Ions - 100s of GeV

u Abundances Dependent on Radial Distance from Sunu Partially Ionized - Greater Ability to Penetrate

Magnetosphereu Number & Intensity of Events Increases Dramatically

During Solar Maximumu Models

» Dose - SOLPRO, JPL, Xapsos/NRL» Single Event Effects - CREME96 (Protons & Heavier Ions)

J. Barth/Code 562

Solar Particle Events

u Poor Correlation with Solar Flaresu Strong Correlation with Coronal Mass Ejections

» No Fundamental Association with Flares» Transient Shock Wave Disturbances in the Solar Wind» Large Geomagnetic Storms» Large Particle Events

“The Solar Flare Myth” - Gosling

J. Barth/Code 562

Solar Particle Events

u Gradual ~ 10 per Year» Coronal Mass Ejection Driven Shocks» Same Elemental Abundances & Ionization States

as Coronal & Solar Wind Plasmau Impulsive ~ 1000 per Year

» Flare Accelerated» Abundances Characteristic of Interactions in the

Flare Plasma

“A New Paradigm” - Reames2 Types of Events

J. Barth/Code 562

Sunspot Cycle with Solar Proton Events

1 9 6 5 1 9 7 0 1 9 7 5 1 9 8 0 1 9 8 5 1 9 9 0 1 9 9 51 0 7

1 0 8

1 0 9

1 0 1 0

1 0 1 1> 1 0 M e V ; Φ ≥ 1 0 8 p /c m 2

> 3 0 M e V ; Φ ≥ 1 0 7 p /c m 2

Z u r i c h S m o o t h e d S u n s p o t N u m b e r

C y c l e 2 0 C y c l e 2 1 C y c le 22

*

**

0

2 0

4 0

6 0

8 0

1 0 0

1 2 0

1 4 0

1 6 0

1 8 0

2 0 0

Prot

ons (

#/cm

2 )

Year

Proton Event Fluences

J. Barth/Code 562

Modeling Approach

u Statistical Engineering Model» Intensity as a Function of Mission Duration & Confidence Level» Does Not Predict When Events Occur

u Use Maximum Entropy Principle - Incomplete Data Set» Determines Frequency Distribution of Large Solar Proton Events» Frequency Distribution Consistent with Other Complex Physical

Phenomena such as Earthquakesu Use Extreme Value Theory

» Determines Upper Limit for Occurrence of Huge Events» New Upper Limit Consistent with Data Sets Dating Back to

Ancient Times - Lunar Rock Record

J. Barth/Code 562

Solar Protons: Orbits

1 0 -1 1 0 0 1 0 1 1 0 2 1 0 3 1 0 4 1 0 5

e 2

1 0 -1 41 0 -1 31 0 -1 21 0 -1 11 0 -1 0

1 0 -91 0 -81 0 -71 0 -61 0 -51 0 -41 0 -31 0 -21 0 -11 0 01 0 11 0 21 0 31 0 4

GE

O

G E OE O SI = 6 0 d e g / H = 8 0 0 k mL E O

Energy (MeV)

Prot

ons (

#/cm

2 /se

c/M

eV)

Proton Levels Predicted by CREME 96

Averaged Over Worst Day

J. Barth/Code 562

TIROS Measurement of ProtonsDay Before Coronal Mass Ejection

H= 870/870 km

J. Barth/Code 562

TIROS Measurement of ProtonsNovember 6, 1997 Coronal Mass Ejection

H= 870/870 km

J. Barth/Code 562

Trapped Radiation

Trapped ParticlesProtons, Electrons, Heavy Ions

Nikkei Science, Inc. of Japan, by K. Endo

J. Barth/Code 562

Charged Particle Motionu Birkeland - 1895

» Vacuum chamber experiments to study aurora» With Poincare showed that charged particles spiraled around field

lines and are repelled by strong fieldsu Stöermer -

» Continued work of Birkeland on aurora» Calculations led to theory that there was a belt-like area around the

earth in which particles were reflected back and forth between thepoles

u Singer (U. o f Md) - 1957» Proposed that ring current could be carried by lower energy

particles injected by into trapped orbits by magnetic stormsu Christofilos

» Study of particle motion in magnetic fields - Project Argus

J. Barth/Code 562

Discovery of the Radiation Beltsu James Van Allen

» First Observation of AuroralElectrons with a Rocket

» Cosmic Ray Detectoru Highlight of US Participation

in IGY

Explorer I31 Jan 1958

J. Barth/Code 562

Trapped - Van Allen Beltsu Omnidirectionalu Components

» Protons: E ~ .04 - 500 MeV» Electrons: E ~ .04 - 7(?) MeV» Heavier Ions: Low E - Non-problem for Electronics

u Location of Peak Levels Depends on Energyu Average Counts Vary Slowly with the Solar Cycleu Location of Populations Shifts with Timeu Counts Can Increase by Orders of Magnitude During

Magnetic Storms» March 1991 Storm - Increases Were Long Term

J. Barth/Code 562

Proton Drift

Magnetic Field LineElectron Drift

Flux Tube

Trapped Particle Trajectory

Mirror Point

Conjugate Mirror Point

Trapped Particle MotionsSpiral, Bounce, Drift

after Hess

J. Barth/Code 562

Van Allen Belts

Inner Belt

Outer Belt

High Latitude Horns

Slot Region

BIRA/IASB

J. Barth/Code 562

Proton & Electron Intensities

1 2 3 4 5 6 7 8 9 101234

L-Shell

AP-8 Model AE-8 ModelEp > 10 MeV Ee > 1 MeV

NASA/GSFC

#/cm2/sec #/cm2/sec

J. Barth/Code 562

TIROS/NOAA Trapped Protons

1976 1980 1984 1988 1992 1996

104

103

102

101 50

100

150

200

250

Prot

on F

lux

(#/c

m2 /s

)

Date

Solar Cycle Variation: 80-215 MeV Protons

L=1.20

L=1.18

L=1.16

L=1.14

B/Bmin=1.0

Rad

io F

lux

F 10

.7

Huston et al.

J. Barth/Code 562

CRRES - Measured Proton Belt

AF Phillips Laboratory, SPD/GD

J. Barth/Code 562

Activity in the Slot Region - SAMPEX

Day (1992)

L-Sh

ell

190 250 310 370 430 490 550

5

3

11

9

7

1

SAMPEX/P1ADC: Electrons E > 0.4 MeV

J. Barth/Code 562

Magnetic Storms - HipparcosL-

Shel

l

4-Day, 9-Orbit Averages

Star Mapper - Radiation Background

Daly, et al.

March1990 1991 1992

2

4

6

J. Barth/Code 562

SRAM Upset Rates on CRUX/APEX

- 1 8 0 - 1 5 0 - 1 2 0 -90 -60 -30 0 3 0 60 9 0 1 2 0 1 5 0 1 8 0

L o n g i t u d e

-90

-75

-60

-45

-30

-15

0

1 5

3 0

4 5

6 0

7 5

9 0

Latit

ude

H i t a c h i 1 M :A l t i t u d e : 1 2 5 0 k m - 1 3 5 0 k m

1 . 0 E - 7 t o 5 . 0 E - 75 . 0 E - 7 t o 1 . 0 E - 61 . 0 E - 6 t o 5 . 0 E - 65 . 0 E - 6 t o 1 . 0 E - 51 . 0 E - 5 t o 5 . 0 E - 55 . 0 E - 5 t o 1 . 0 E - 41 . 0 E - 4 t o 5 . 0 E - 45 . 0 E - 4 t o 1 . 0 E - 31 . 0 E - 3 t o 5 . 0 E - 3

U p s e t s / B i t / D a y

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180

Long i t ude

-90

-75

-60

-45

-30

-15

0

15

30

45

60

75

90

Latit

ude

Hi tach i 1M:A l t i t ude :650km - 750km

1 .0E-7 to 5 .0E-75 .0E-7 to 1 .0E-61 .0E-6 to 5 .0E-65 .0E-6 to 1 .0E-51 .0E-5 to 5 .0E-55 .0E-5 to 1 .0E-41 .0E-4 to 5 .0E-45 .0E-4 to 1 .0E-31 .0E-3 to 5 .0E-3

Upsets /B i t /Day

- 1 8 0 - 1 5 0 - 1 2 0 - 9 0 - 6 0 - 3 0 0 3 0 6 0 9 0 1 2 0 1 5 0 1 8 0

L o n g i t u d e

- 9 0

- 7 5

- 6 0

- 4 5

- 3 0

- 1 5

0

1 5

3 0

4 5

6 0

7 5

9 0

Latit

ude

H i t a c h i 1 M :A l t i t u d e : 1 7 5 0 k m - 1 8 5 0 k m

1 . 0 E - 7 t o 5 . 0 E - 75 . 0 E - 7 t o 1 . 0 E - 61 . 0 E - 6 t o 5 . 0 E - 65 . 0 E - 6 t o 1 . 0 E - 51 . 0 E - 5 t o 5 . 0 E - 55 . 0 E - 5 t o 1 . 0 E - 41 . 0 E - 4 t o 5 . 0 E - 45 . 0 E - 4 t o 1 . 0 E - 31 . 0 E - 3 t o 5 . 0 E - 3

U p s e t s / B i t / D a y

- 1 8 0 - 1 5 0 - 1 2 0 - 9 0 - 6 0 - 3 0 0 3 0 6 0 9 0 1 2 0 1 5 0 1 8 0

L o n g i t u d e

- 9 0

- 7 5

- 6 0

- 4 5

- 3 0

- 1 5

0

1 5

3 0

4 5

6 0

7 5

9 0

Latit

ude

H i t a c h i 1 M : A l t i t u d e : 2 4 5 0 k m - 2 5 5 0 k m

1 . 0 E - 7 t o 5 . 0 E - 75 . 0 E - 7 t o 1 . 0 E - 61 . 0 E - 6 t o 5 . 0 E - 65 . 0 E - 6 t o 1 . 0 E - 51 . 0 E - 5 t o 5 . 0 E - 55 . 0 E - 5 t o 1 . 0 E - 41 . 0 E - 4 t o 5 . 0 E - 45 . 0 E - 4 t o 1 . 0 E - 31 . 0 E - 3 t o 5 . 0 E - 3

U p s e t s / B i t / D a y

J. Barth/Code 562

Trapped Protons for E > 30 MeV(#/cm2/s) - Solar Minimum

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180

-80

-60

-40

-20

0

20

40

60

80

1 10 100

1000

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180

-80

-60

-40

-20

0

20

40

60

80

1

1

10

10

100

100

1000

1000

0

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180

-80

-60

-40

-20

0

20

40

60

80

1

1

10

10

100

100

1000

1000

10000

10000

-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180

-80

-60

-40

-20

0

20

40

60

80

1

1

10

10

100

100

1000

1000

10000

J. Barth/Code 562

Particle Cascades in Atmosphere

u Collisions betweencosmic rays &atmospheric O & N

u Important product isneutrons

» Single Event Upsets− Shuttle− Aircraft− Ground

» Passenger & crewexposure in aircraft

J. Barth/Code 562

Neutronsu Source - Secondary Products of Particle

Cascades» Spacecraft Materials» Galactic Comic Ray Collisions with

Atmospheric O & Nu Single Event Upset Hazard

» Ground Level in Large Memory Banks» Avionics» Low Earth Orbits - Shuttle

u First Recognized as Problem in 1980s

J. Barth/Code 562

Neutron Environmentγ γ γ γ γ γγ γ γ γ γ γγ γ γ η η η η γ γ γ η η η ηγ γ γ γ γ γ η η η η η η η ηγ γ γ γ γ γγ γ γ γ γ γ η η η η η η η η γ γ γ γ η η η η η η η ηπ µ π υγ π γ η η η η γ µ γ η η η η

η η η η η η η ηγ π µ η η η η γ π µ η η η η η η η η η η η η

π µ η η η η π µ η η η ηπ µ γ π υ γ η η η η η η η η η ηπ µ π µ π µ γ γ η η

60,000 feet20,000 m

1,000,000 feet330 km

Ground ~ 1/500 of Peak Flux

150,000 feet50,000 m

γ Primary Cosmic Rays

η Neutrons

π,µ Secondary Cosmic Rays

Shuttle

Top ofAtmosphere

PeakNeutron

Flux

Aircraft

γ

η π,µN,O ~ 35,000 feet

10,000 m

Normand et al.

J. Barth/Code 562

20,000 40,000 60,000 80,000 100,000 120,000 140,0000.0

1.0

0.8

0.6

0.4

0.2

Neutron Flux Measurements

1-10 MeV & 10-100 MeV Energy Ranges

Altitude (feet)

Nor

mal

ized

to P

eak

Mendell/Holt1-10 MeV

Ait/Ouamer10-100 MeV Preszler/Saxzena

10-100 MeV

J. Barth/Code 562

1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0A lt i tu d e

0 .0

0 .2

0 .4

0 .6

0 .8

1 .0

1 .2

1 .4

Flux

Neutron Models: Flux vs. Altitude

Altitude ( Thousands of feet)

1-10 MeV Atmospheric Neutron Flux

1-10

MeV

Neu

tron

Flux

(n/c

m2 /

s)

J. Barth/Code 562

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0La t i t ude

0.0

0 .2

0 .4

0 .6

0 .8

1 .0

1 .2

1 .4

Flux

Neutron Model: Flux vs. Latitude

Latitude (deg N)

1-10

MeV

Neu

tron

Flux

(n/c

m2 /

s)

1-10 MeV Atmospheric Neutron Flux

Averaged Over Longitude

J. Barth/Code 562

Terrestrial Radiation Sources

u Man-madeuNatural Emissions from Earth Materials

» Package Contaminationu Cosmic Rays - Particle Showers

J. Barth/Code 562

Terrestrial Cosmic Rays

u Particles That Hit the Earth from Outer Spaceu Need > 1 GeV to Penetrate to Sea Levelu Fewer Than 1% Are Primaryu Mostly 3rd to 7th Generation Cascade Particlesu Search for Cause of Interference on Laboratory

Instruments in Early 1900s» Led to Discovery of Cosmic Rays by Hess

u Induce SEUs: Neutrons + Protons + Pions

J. Barth/Code 562

Terrestrial Cosmic Rays

J. Barth/Code 562

1 2 3 4 5 60

102030405060708090

18,94011,500

803 250 126

137,445

Total Counts = 169,064

E.B. Hughes & P.L. Marsden, 1966

Perc

enta

ge C

ontri

butio

n

Protons Muons Muons Pions Showers Neutrons (Captured) (in Flight)

IGY Neutron Monitor ResponseCosmic Ray Contributions at Sea Level

J. Barth/Code 562

1 2 3 4 5 6 7 8 9 1010-13

10-12

10-11

10-10

10-9

10-8

Sea Level10 Km

AM9114 4K NMOS Error Rates

Protons Neutrons Muons Pions Pions >100 MeV >10 MeV (Stopping) >100 MeV (Stopping)

Pred

icted

Err

ors /

Dev

ice /

s

Predicted Error Rates at Two Altitudes

J.F. Dicello, et al.., 1989

J. Barth/Code 562

Radiation Issues -Three Prime Technical Drivers

u COTS & Emerging Technologies» More sensitive to radiation» Some devices have new effects

u COTS - greater uncertainty about radiation hardness» Limited control» Frequent process changes

u Devices exposed to more radiation on-orbit» Use of composite materials in spacecraft structures» Shrinkage in spacecraft size & weight

Result:We are using more radiation sensitive components with less

protection