ong>Reliabilityong> ong>Concernsong> ong>ofong> ong>Radiationong> ong>Effectsong>
on Space Electronics
Abstract—There is no space system in which radiation effects
can be neglected. Trapped electrons and protons in the Earth’s
radiation belt can lead sudden failure, and total dose can reduce
lifetime ong>ofong> the mission without a proper shielding. ong>Reliabilityong>
engineers should concern not only thermal, dynamical and
atmospheric circumstances ong>ofong> space but also harsh radiation.
In this review, space radiation is introduced, possible effects are
discussed, modeling and testing methods are evaluated for the
application on space electronics.
Natural space environment is a difficult challenge for electronics.
Trapped particles in the Earth’s radiation belts, solar
flares and cosmic rays jeopardize the operation and causes to
critical performance gradually. Single event effect (SEE) can
flip the bits in digital element and lead spontaneous system
failure, and total induced dose (TID) can reduce the lifetime
ong>ofong> the system. The radiation level in space environment
depends on the altitude, latitude, longitude and the time. For
instance, The South Atlantic Anomaly (SAA) is the region
where Earth’s inner Van Allen radiation belt makes its closest
approach to the planet’s surface. The satellites passing through
SAA exposes significantly high total dose damage. Therefore,
the dose and characteristics ong>ofong> radiation that will affect a space
satellite are greatly dependent on the launch date, duration
and orbit altitude. The desire to increase performance and
lifetime ong>ofong> a space system requires critical simulations ong>ofong> the
environment, evaluations ong>ofong> the reactions ong>ofong> material within
the estimated space environment. This makes the radiation a
great concern for reliability engineers on space electronics.
Early evaluation ong>ofong> various radiation effects in the design ong>ofong>
systems is mandatory for orbit selection, mass budget, thermal
protection, and component selection policy.
II. RADIATION SOURCES
The particles associated with ionizing radiation are categorized
into three main groups relating to the source ong>ofong>
the radiation: solar flare particles, cosmic rays, and trapped
radiation belt particles.
A. Solar Flares
Solar flares are powerful explosions in the sun’s atmosphere,
which release enormous amounts ong>ofong> energy. Solar flare, which
is associated with coronal mass ejection, heats the plasma
and accelerates protons, neutrons and electrons to relativistic
speeds. The solar cycle, or the solar magnetic activity cycle,
˙Ilknur Baylako˘glu & Murat Hudaverdi
TUBITAK, Space Technologies Research Institute
ODTU, 06531, Ankara, Turkey
is ∼11 years. This is the main source ong>ofong> periodic solar
variation driving variations in space weather. A space mission
should be designed to survive at least one massive solar flare.
Although a cycle can be defined for solar activities, nobody
guaranties a precise prediction or solar particle events. NOAA-
Space Weather Prediction Center predicts The Solar Cycle 24
maximum will occur about October, 2011 for the large cycle
case and August, 2012 for the small cycle (see Figure 1).
Fig. 1. The ong>ofong>ficial Solar Cycle 24 prediction is for Sunspot Number (Credit:
NOAA/Space Weather Prediction Center).
B. Cosmic Rays
Cosmic rays are energetic quantum particles originating
from space that affect on Earth’s atmosphere. The majority
(about 90%) ong>ofong> all the incoming cosmic rays are protons,
about the rest (9%) are helium nuclei (alpha particles) and
about very few (1%) are electrons. The variety ong>ofong> particles
causes the wide variety ong>ofong> errors on space device, ICs or solar
C. Trapped ong>Radiationong> Belt
The turbulent motion ong>ofong> molten iron core, the Earth has
a strong magnetic field around. This field concentrates highenergy,
ionizing particles including electrons, protons, and
some heavier ions. The field mechanism traps these charged
particles within specific regions, called the Van Allen belts.
Fig. 2. Trapped particles spiral back and forth along magnetic field lines
The Figure 2 shows the field lines which the trapped particles
travels back and forth along. Since the Earth’s dipolar field
displaced from the center, the radiation belts get very close
over the eastern coast ong>ofong> South America. This high particle
density region is called as the South Atlantic Anomaly (SAA).
Satellites at LEO experience a considerable natural shielding
from cosmic rays due to the Earths magnetic field.
III. RADIATION EFFECTS
High-energy particle or photon lose its kinetic energy in
different mechanisms, thus creating various damages.
A. Total Ionizing Dose (TID)
The first failure ong>ofong> TID goes back to early 1970s. The
Starfish nuclear weapon test in 1962 was held in an Johnston
Island in the Pacific Ocean. The particles were injected to
earth’s atmosphere, which formed a radiation belt at an altitude
ong>ofong> ∼400 km. For instance, Telstar satellite experienced a TID
100 times larger than expected. Within 7 months, the Starfish
nuclear weapon test destroyed seven satellites.
TID is the energy deposited per unit mass ong>ofong> material as a
result ong>ofong> ionization. It is caused by mainly protons. Electrons
are important for some planetary missions. TID may cause
drift in parameters ong>ofong> active electronic parts. TID depends on
orbit altitude, location, and time. To compute TID we need to
know the integrated particle energy spectrum, that is the effect
ong>ofong> particle energy. As TID increases, materials performance
decreases. Long exposure can cause device threshold shifts,
increased leakage and power consumption, timing changes,
and decreased functionality. Energetic particles can be partially
mitigated with shielding. Figure 3 shows the total dose
calculations for LEO satellite RASAT (the Turkish word for
observation), which is the second remote-sensing satellite
after the launch Turkey’s first remote sensing satellite B˙ILSAT
ong>ofong> TÜB˙ITAK UZAY. As it is clearly seen from Fig. 3, electrons
are more effectively shielded than protons. Using radhard
devices and considering a proper shielding, TID effects can
B. Single Event Effect (SEE)
SEE is an instantaneous failure mechanism and expressed
in terms ong>ofong> failure rate. Its are an important issue for all
Fig. 3. Total Dose calculations for LEO satellite RASAT. The relation
between Al shielding thickness and total dose in rads. The total dose and the
contribution ong>ofong> electrons, bremsstrahlung, trapped protons and solar protons
are represented in black, red, green, blue and light-blue, respectively.
spacecraft. SEE results from, as the term suggests, a single,
energetic particle. Some ong>ofong> the early pioneering work was by
May and Woods, who investigated alpha-particle-induced song>ofong>t
errors . In their work the source ong>ofong> alpha particles was not
from space but rather from the natural decay from uranium
and thorium present in integrated circuit packaging materials.
Single event phenomena can be classified into three effects (in
order ong>ofong> permanency):
1) Single event upset (song>ofong>t error): Single event upset (SEU)
is defined as the error caused by a radiation belt or
cosmic ray oriented particle pass through microelectronic
circuits and leaving electron-hole pairs behind.
They are song>ofong>t errors and non-destructive but requires
external interaction. A reset or switch ong>ofong>f results the
normal device performance. SEU can be seen in analog,
digital or optical components, or surrounding interface
circuits. The worse ong>ofong> SEU is single-event functional
interrupt (SEFI) in which the device is set to test mode,
halt or undefined state. SEFI requires a power reset for
2) Single event latch up (song>ofong>t or hard error): SEL is
triggered by heavy ions, protons and neutrons. They
are potentially destructive and can be recoverable by
power ong>ofong>f-on reset. If power is not removed quickly,
fatal failure may happen due to excessive heat, metalization
ong>ofong> bond wire failure. SEL is strongly temperature
dependent: the threshold for latch up decreases
at high temperature, and the cross section increases as
well [2,3]. Characterization ong>ofong> latch-up is difficult for
complex circuits but modern devices may have different
SUMMARY OF SPACE RADIATION EFFECTS, IMPACTS AND MITIGATION TECHNIQUES.
EFFECT SOURCE IMPACT MITIGATION
TID dominated by protons, and threshold shifts, increased leakage and Shielding
electrons for planetary missions power consumption, timing changes (effective for electron)
DD neutrons, protons, alpha particles, gain degradation and (partly) shielding
heavy ions, and very high energy gamma photons leakage current in bipolar transistors
SEE heavy ions, protons, neutrons change state ong>ofong> memory element, latch-up, Redundancy, power cycling,
voltage spike signal, damage to gate oxide EDAC, latch-up protection circuit
3) Single event burnout (hard failure): Single event burnout
(SEB) is caused by high current state and device fails
permanently. It is triggered by heavy ions, partly by
protons and neutrons. SEBs occur at CMOS, power
BJTs and MOSFETs. The types ong>ofong> SEBs are burnout ong>ofong>
power MOSFETs, gate rupture, frozen bits, and noise in
CCDs. SEB are more likely to happen with increasing
temperature . If a single ionizing particle leads to a
conducting path in a power MOSFET, the event is called
single-event gate rupture (SEGR). The very fist SEGR
is reported by Fischer in 1987 .
Fig. 4. Displacement Cascade Damage in Silicon (Credit: NOAA/SEE).
C. Displacement Damage (DD)
DD is caused by neutrons, protons, alpha particles, heavy
ions, and very high energy gamma photons. They change the
arrangement ong>ofong> the atoms in the lattice. Figure 4 shows a
pictorial representation ong>ofong> collision cascade in e.g. Si semiconductor.
These collisions are produced by incident heavy
particles and secondary particles. DD can be created by proton
at all energies, electron with energies >150 keV. Compared to
TID and SEE, DD is less concerned. Only a fraction ong>ofong> 1%
ong>ofong> the energy loss goes into displacement process Dale et al.
1991 . A typical DD effect would be gain degradation and
leakage current in bipolar transistors.
A. Spenvis 1
IV. RADIATION ENVIRONMENT MODELS
Space Environment Information System (Spenvis) ong>ofong> ESA is
an interactive modeling interface for space environment and its
effects. It includes radiation belts, solar particles, cosmic rays,
plasmas, gases. After defining the orbital parameters, one can
calculate particle fluxes, radiation doses for simple geometries,
a sectoring analysis for dose calculations in more complex
geometries, damage equivalent fluences, Geant4 Monte Carlo
simulations, LET, flux and SEE rates. Geomagnetic field lines
are also included, as well as world map visualization ong>ofong> the
satellite data, panel plots ong>ofong> the measured parameters. Micrometeoroid
and space junk models are also implemented.
B. CREME96 2
The Cosmic Ray ong>Effectsong> on Micro-Electronics (1996 Revision)
CREME96, is a group ong>ofong> four subprograms (SPEC,
LET, BENDEL, and UPSET). They are used for creating
numerical models ong>ofong> radiation environment and evaluating the
effect. SPEC is suitable for spectral analysis ong>ofong> integral and
differential energy, while LET (Linear Energy Transfer) produces
integral and differential spectra for different elements.
BENDEL and UPSET is used at the impact evaluation steps.
C. AE/AP Trapped Particles
AE/AP calculates trapped electron and proton fluxes in
Earth’s radiation belt. These are omni-directional, electron (AE
maps) and proton (AP maps) fluxes in 0.04-7 MeV energy
range for electrons and 0.1-400 MeV for protons. The flux
values are stores as energy functions. The very fist version
ong>ofong> series (AE-1 and AP-1) goes back to 1966 by J. I. Vette
. The different updated electron models ong>ofong> AE can be
distinguished as inner or outer zone models and solar cycle
maximum or minimum conditions. AE-8 covers the whole L
range and both solar cycle extrema. The AP maps are different
in energy range and solar cycle phase. AP-8 includes the whole
energy range and both solar cycle extrema.
The radiation type and effects are depend on location, timing
and duration ong>ofong> the mission. There are possible mitigation
techniques for each harmful effect but no single solution exist
for all impacts. ong>Radiationong> related problems are complex to
model thus require case by case bases mitigations.
 T.C. May, M.H. Woods, ”Alpha-particle-induced song>ofong>t errors in dynamic
memories,” IEEE Trans. on Electron Devices, vol. ED-26, no. 1, pp. 2-9,
 I. Mouret, M. Allenspach, R.D. Schrimpf, J.R. Brews, K.F. Galloway, P.
Calvel, ”Temperature and angular dependence ong>ofong> substrate response in
SEGR,” IEEE Trans. on Nuclear Science, vol. 41, no. 6, pp. 2216-2221,
 I. Mouret, M.-C. Calvet, P. Calvel, P. Tastet, M. Allenspach, K.A. LaBel,
J.L. Titus, C.F. Wheatley, R.D. Schrimpf, K.F. Galloway, ”Experimental
evidence ong>ofong> the temperature and angular dependence in SEGR,” Proceedings
ong>ofong> the Third European Conference on ong>Radiationong> and its ong>Effectsong> on
Components and Systems (RADECS), Arcachon, France, Sept. 1995.
 G.H. Johnson, R.D. Schrimpf, K.F. Galloway, R. Koga, ”Temperature
dependence ong>ofong> single-event burnout in n-channel power MOSFETs,” IEEE
Trans. on Nuclear Science, vol. 39, pp. 1605-1612, 1992.
 T.A. Fischer, ”Heavy-ion-induced, gate-rupture in power MOSFETs,”
IEEE Trans. on Nuclear Science, vol. 34, no. 6, pp. 1786-1791, 1987.
 Dale C, Marshall P (1991) Displacement damage in SI imagers for space
applications. Proc. SPIE Charge-Coupled Devices and Solid State Optical
Sensors II, Vol. 1447, p. 70-86,
 J. I. Vette, A. B. Lucero, J. A. Wright, J. H. King, J. P. Lavine, W. L.
Imhong>ofong>, C. O. Bostrom, D. S. Beall, J. C. Armstrong, H. H. Heckman, P.
J. Lindstrom, G. H. Nakano, G. A. Paulikas and J. B. Blake, ”Models
ong>ofong> the Trapped ong>Radiationong> Environment”, NASA SP-3024 by NASA,
Washington, D.C., 1966