Spacecraft Radiation Protection

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ATI Course Schedule:
ATI's Spacecraft Radiation:
Professional Development Short Course On:
Spacecraft Radiation Protection
Instructor:
Dr. Alan C. Tribble

Summary
This two-day course provides an in-depth overview of
risks posed by radiation to spacecraft and working
solutions minimizing those risks. Students will gain a
solid understanding of the radiation environment, its
measurement, its effects and effective mitigation
strategies.
Course Outline
1. Space Radiation Environment. Trapped
protons and electrons. Solar energetic particles.
Cosmic rays. Neutrons and gamma rays from
Radioactive Thermoelectric Generators (RTGs).
Secondary neutrons from large space structures.
Mars surface and high altitude Earth enironment.
2. Total Dose and Effects. Energy per unit mass.
Units--rads, REMs, Grey, Sieverts. Ionization
effects. Charge deposition, migration and collection.
Effects on digital and analog MOS and bipolar
devices including ELDRS. Annealing, recovery,
rebound.
3. Displacement Damage. Crystalline lattice
deformations. Damage thresholds in silicon and
gallium arsenide. Damage equivalence and NIEL.
Effects of protons and neutrons on solar cells and
detectors such as CCDs. Dark current, charge
transfer efficiency, maximum power degradation.
4. Single Event Effects. Ionization by primary
particles and secondaries from nuclear collisions.
Charge collection in small structures. Effects in
digital and analog devices. Transient and permanent
upsets, soft errors, latch-up, burn-out, SEFI. Volatile
and non-volatile memories, micro and signal
processors, DC/DC converters, optoelectronics.
5. Testing and Mitigation Techniques. Total
dose testing. SEE testing. Facilities. Shielding.
Derating. Conservative circuit design. Systems
mitigation. EDAC, latch-up protection circuitry, watch
dog timers, autonomy.
6. Human Effects. Long duration exposure in
low Earth orbit and interplanetary transport vehicles.
Threat of high-energy neutrons to astronauts.
Effects in tissue and organs. Dose Equivalent and
weighting factors. Risk of carcinogenesis, DNA
damage. CNS effects
Instructor
Dr. Alan C. Tribble has provided space environments
effects analysis to more than one dozen NASA, DoD,
and commercial programs, including the International
Space Station, the Global Positioning System (GPS)
satellites, and survival surveillance spacecraft. He
holds a Ph.D. in Physics from the University of Iowa
and has been twice a Principal Investigator for the
NASA Space Environments and Effects Program. He is
the author of four books, including the course text: The
Space Environment - Implications for Space Design,
and over 20 additional technical publications. He is an
Associate Editor of the Journal of Spacecraft and
Rockets, and Associate Fellow of the AIAA and a
Senior Member of the IEEE. Dr. Tribble recently won
the 2008 AIAA James A. Van Allen Space
Environments Award. He has taught a variety of
classes at the University of Southern California,
California State University Long Beach, the University
of Iowa, and has been teaching courses on space
environments and effects since 1992
What You Will Learn
• What the models are for space
environments, where to find them, how to
use them.
• What the common radiation units mean.
• How to equate damage from different
species of radiation.
• How to conduct total dose test.
• How to conduct SEE tests.
• How to use dose-depth curves in determining
shield thickness.
• How to shield neutrons.
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Copyright Dr. Alan Tribble.
Do Not Reproduce Without Permission.
www.atribble.com
COURSE OBJECTIVE
• The purpose of this course is to characterize
space (and atmospheric) radiation effects and
how they are mitigated
– By the end of class, you should be able to read
and follow most papers and presentations in
radiation effects and know where to look for
further expertise

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ABOUT THE INSTRUCTOR
• Dr. Alan Tribble
– Over Twenty Years Experience in Space Environments and
Effects
• Author of First Text on Space Environments & Effects
• Principal Investigator for the NASA Space Environments & Effects
Program
• Associate Editor for the AIAA Journal of Spacecraft and Rockets
• Instructor for Space Environments & Effects Courses Since 1992
– Winner of the 2008 AIAA James A. Van Allen Award
• Presented to recognize outstanding contributions to space and
planetary environment knowledge and interactions as applied to
the advancement of aeronautics and astronautics.

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2009
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THE ENVIRONMENTS OF SPACE
• Vacuum Environment Effects
– Phenomena Associated With the Absence of a Substantial
Atmosphere
• Neutral Environment Effects
– Phenomena Associated With the Presence of a Tenuous Neutral
Atmosphere
• Plasma Environment Effects
– Phenomena Associated With the Presence of Low Energy (KeV
Range) Charged Particles
• Radiation Environment Effects
– Phenomena Associated With the Presence of High Energy (MeV -
GeV Range) Particles / Photons
• Micrometeoroid / Orbital Debris Effects
– Phenomena Associated With the Presence of Hypervelocity
Particles

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2009
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RADIATION ANOMALIES

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IMPACT DURATION

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FUNDAMENTAL FORCES
• Four Forces
– Strong Nuclear
• Important Near the
Nucleus
– Weak Nuclear
• Important Near the
Nucleus
– Electrical
• Very Significant for
Particles That are
Charged
– Gravitational
• Only Important for Very
Large Masses Nuclear Forces Only
Dominates Near the
Nucleus
Electrical Force Always
Dominates Outside
the Nucleus

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2009
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STOPPING POWER
http://en.wikipedia.org/wiki/Stopping_power_(particle_radiation)

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BRAGG PEAK
http://en.wikipedia.org/wiki/Stopping_power_(particle_radiation)

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LET VS RANGE

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Photon Energy (MeV)
AbsorptionCoefficient(cm^2/g)
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0.1 1 10 100
Compton
Pair Production
Photoelectric
Total
10-1
100
101
102
Cross
Section
(cm2
/g)
PHOTON CROSS SECTION

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2009
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ATMOSPHERIC NEUTRONS
• The Neutron Flux is
a Function of Altitude
and Latitude
• The Worst Location
is a Polar Route at
About 55,000 Feet
Neutron Flux vs Altitude
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 20 40 60 80 100
Altitude (Thousand Feet)
Flux(n/cm^2s)
Neutron Flux vs Latitude
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 20 40 60 80 100
Latitude (Deg.)
Flux(n/cm^2s)
Normand, E., and Baker, T. J., “Altitude and Latitude Variations in
Avionics SEU and Atmospheric Neutron Flux,” IEEE Tns. Nuc.
Sci., Vol. 40, No. 6, pp. 1484 - 1490, December 1993.

Sampler
2009
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EFFECTS OF INTERACTIONS
• Main Effects
– Ionization (~ 99%)
• Ionizing Target Atoms Produces More Charge Carriers
– Displacement (~1%)
• Lattice Atoms are Rearranged
– Absorption / Capture (< 1%)
• Target Nucleus May Absorb Radiation and Re-Emit
Other Particles
• Result
– Electrical and Chemical Properties of the Target
are Altered

Sampler
2009
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MEASURES OF ENERGY DEPOSITION
• Total Ionizing Dose
(TID)
– A Measure of the Amount
of Energy Lost Due to
Ionizations
– TID is a Function of
• The Radiation
– Energy and Type
• The Target Material
• Displacement Damage
(DD)
– A Measure of the Amount
of Energy Lost Due to
Displacements
– DD is a Function of
• The Radiation
– Energy and Type
• The Target Material

Sampler
2009
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MEASURES OF ENERGY LOSS / PATH
• Linear Energy Transfer
(LET)
– Measures the Amount of
Energy Lost Per Unit
Path Length Due to
Ionizations
• Non-Ionizing Energy
Loss (NIEL)
– Measures the Amount of
Energy Loss Per Unit
Path Length Due to
Displacements

Sampler
2009
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AREA OF REFLECTION
GEOLEO
Particle Motion
Trapping Moves Particles North - South
Drifts Move Particles East-West
MAGNETIC TRAPPING OF THE RADIATION BELTS
GPS

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2009
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GOES SATELLITE ENVIRONMENT DATA

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2009
Slide #18
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• Magnetic Field Lines Entering the Atmosphere at
High Latitudes Allow Charged Particles to Reach
Lower Altitudes in Polar Regions
• Consequently, the Radiation Dose and Dose Rate
are Increased in Polar Orbits
– An Example of This is the Aurora Borealis and the Aurora
Australialis
POLAR VS EQUATORIAL

Sampler
2009
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• A Decrease in the Dipole Term of the Earth’s
Magnetic Field Results in a Westward and
Southward Drift of the Ground-Level Local
Minimum in the Magnetic Field Known as the
South Atlantic Anomaly (SAA)
• This Allows Higher Energy Particles to Reach
Lower Altitudes Over the South Atlantic
SOUTH ATLANTIC ANOMALY - 1

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2009
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SOUTH ATLANTIC ANOMALY - 2

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Single Event Effects Often Maximize Over The SAA
SEU FOR ALEXIS SPACECRAFT

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SPE COMPOSITION
Large Solar Proton Event Spectra at 1 AU
1.00E+07
1.00E+08
1.00E+09
1.00E+10
1.00E+11
1 10 100 1000
Kinetic Energy (MeV)
IntegralFluence,(protons/
cm^2)
Feb 1956
Nov 1960
Aug 1972
Aug 1989
Sep 1989
Oct 1989
Wilson, J. W., Cucinotta, F. A., Simonsen, L. C., Shinn, J. L., Thibeault, S. A., and Kim, M. Y.,
"Galactic and Cosmic Ray Shielding in Deep Space", NASA TP 3682, December 1997

Sampler
2009
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GCR COMPOSITION
Galactic Cosmic Ray Fluence, Solar Max (1981)
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E+05
1.00E+06
1.00E-01 1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06
Kinetic Energy (A MeV)
AnnualFluence,(particles/cm^2-AMeV)
Z = 1
Z = 2
Z: 3 - 10
Z: 11 - 20
Z: 21 - 28
Wilson, J. W., Cucinotta, F. A., Simonsen, L. C., Shinn, J. L., Thibeault, S. A., and Kim, M. Y.,
"Galactic and Cosmic Ray Shielding in Deep Space", NASA TP 3682, December 1997

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2009
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MITIGATION TECHNIQUES
• Shielding
– Prevent the Radiation Environment From Reaching the Crew
or Sensitive Electronics
• Not Effective on Very Energetic (GeV) Charged Particles
• Parts Selection
– Choose Parts or Materials That Can Withstand the Total
Dose Environment Anticipated
– Choose Parts That are Immune or Resistant to SEE
• Fault Tolerance
– Hardware
• Redundancy, Majority Voting, …
– Software
• Error Detection and Correction (EDAC), Hamming Codes, …

Sampler
2009
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GPS Trapped Radiation: 20,000 km - 55 Deg
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09 1.00E+10 1.00E+11 1.00E+12 1.00E+13
Fluence (# cm ^-2 day^-1)
Energy(MeV)
Protons
Electrons - Solar Min
Electrons - Solar Max
20,000 km @ 55 degrees
104 105 106 107 108 109 1010 1011 1012 1013
Fluence (cm-2 day -1)
101
Energy
(MeV)
100
10-1
10-2
Protons
Electrons - Solar Min.
Electrons - Solar Max.
GPS RADIATION ENVIRONMENT

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Altitude = 20,000 km
Inclination = 55 deg.
Shielding = Full-Sphere
Shie ld ing Thic kne ss (m ils - Al)
Dose(rad/day)
0.10
1.00
10.00
100.00
1000.00
10000.00
10 100 1000
To ta l
Pro to n
Ele c tro n
Bre m s.
GPS RADIATION DOSE

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2009
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DESIGN EXAMPLE: SOLAR ARRAY SIZING
• Solar Array Size is Driven by the Amount of Energy
That Must be Produced
– A = Solar Array Area (m2)
– P = Power Required (W)
–  = Efficiency
• Efficiency is Degraded by Radiation
– BOL Value is Greater Than the EOL Value
• Efficiency Loss is Minimized by Adding a Transparent Shield
– Coverslide
– S = Sun’s Power Output (1367 W/m2 at Earth Orbit)
S
P
A



Sampler
2009
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TOTAL IONIZING DOSE III
• Digital Devices
– Suffer threshold voltage shifts, supply current
increases and timing degradation
• Linear Devices
– Experience increased input bias currents, offset
voltages and offset currents as circuitry becomes
unbalanced
• In worst cases functionality ceases
– Particularly when the timing is affected in a VLSI
device and after many nodes information does not
reach the next gate in the correct time window.

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2009
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DISPLACEMENT DAMAGE SKETCH

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• An Energetic Particle Passes Through a
Semiconductor and Creates a Trail of Ionized
Particles in the Vicinity of a Reverse Biased
PN Junction
– The Sudden Flux in Ionized Particles Can Cause
a Swing in Bias Across the Junction
– The Change May Alter the State of the Device
• This is an Example of a Single Event Effect
(SEE)
SINGLE EVENT EFFECTS (SEE)

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2009
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TYPES OF EFFECTS
• Single Event Upset
– Change in state of a memory element
– System-level manifestations depend on application
• Single Event Latchup
– Low resistance path develops between power and ground
through the device, usually destructive
– Sometimes observe “mini-latch” behavior
• Single Event Functional Interrupt
– Upset which places a device in an ill-defined condition
– Causes system to lock up or jump into an unknown
configuration
• Single Event Transient
– Spurious voltage spike that can cause system-level effects
– Increased noise in the system

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2009
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TYPES OF EFFECTS
• Single Event Burnout
– Localized short through power MOSFET
– Permanently damages the part
• Single Event Gate Rupture
– Localized short through drain-to-oxide interface in
a power MOSFET
– Permanently increases gate leakage
• Single Event Dielectric Rupture
– Oxide damage in non-volatile elements or anti-
fuse type FPGAs

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2009
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ION STRIKE SCHEMATIC

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VIN
VOUT
p-type substrate
n+ n+
n-well
p+ p+p+ n+
VSSVDD
Source
Gate
Drain Source
SEE ILLUSTRATION
Radiation
(proton, ion, neutron, …)
Upset occurs if
channel current turned on
Latchup occurs if
parasitic current loop initiated

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2009
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SEU EXAMPLE: SAMSUNG DRAM

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TOTAL IONIZING DOSE (TID) TEST FLOW
• 25° C anneal
– For simulation of reduction in oxide trapped charge
• 100° C anneal
– For accelerated production of interface trapped charge
Irr. To Spec.
50-300 rad/s
Pass
Elec?
Irr. 50% Over
50-300 rad/s
Biased Anneal
168 hr @ 100C
Pass
Elec?
Parts OK
Reject Parts
Yes
Yes
No
Biased Anneal
@ 25 C
Pass
Elec?
No
No
Yes

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2009
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ELDRS TEST FLOW
• May require extensive evaluation
Start Review Data
ELDRS?
TM1019
or other
Accept Risk?
Initial Test
1) Baseline high rate
at room temp
2) Compare to low
rate or elev. temp
ELDRS?
No
No
??
Yes Yes
1) Test at 10 mrad/s
with margin of 2 or
2) test at 10 rad/s, 100C
with margin of 3
Yes
1) Determine max low
dose rate enhancement
2) Elevated temperature
irradiation and anneal
No
Acceptance
Test

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2009
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TEST FACILITY REQUIREMENTS

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TEST FACILITY REQUIREMENTS

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2009
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NASA INTERNET SITES
• Glenn Research Center
– Space Environments and
Experiments Branch
• http://www.grc.nasa.gov/WWW
/epbranch/
• Goddard Space Flight Center
– Radiation Effects and Analysis
• http://radhome.gsfc.nasa.gov
– National Space Science Data
Center (NSSDC)
• http://nssdc.gsfc.nasa.gov
– Community Coordinated
Modeling Center (CCMC)
• http://ccmc.gsfc.nasa.gov/mod
elweb/
• Jet Propulsion Laboratory
– Radiation Effects Group
• http://parts.jpl.nasa.gov
• Johnson Space Center
– Orbital Debris Program Office
• http://orbitaldebris.jsc.nasa.gov
• Langley Research Center
– Space Environments and
Technology Archive System
(SETAS)
• http://setas-www.larc.nasa.gov/
• Marshall Space Flight Center
– Space Environments and Effects
Program
• http://see.msfc.nasa.gov

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OTHER INTERNET SITES
• NOAA
– Space Weather Prediction
Center
• http://www.swpc.noaa.gov
• Space Weather
– Science News and Information
• http://www.spaceweather.com
– Space Science Institute
• http://www.spaceweathercente
r.org/
• Space Environment Information
System (SPENVIS)
– interface to models of the space
environment and its effects,
including the natural radiation
belts, solar energetic particles,
cosmic rays, plasmas, gases,
and "micro-particles".
• www.spenvis.oma.be
• Instructor’s Web Site
– Links to Site’s of Interest
• http://www.atribble.com

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