Radiation Effects in Spacecraft and Aircraftlws.gsfc.nasa.gov › documents › mission_requirements › normand...Many satellites use very thin (few mils) thermal coatings, such as

BBoeing oeing RRadiation adiation EEffects ffects LLabab

13/7/05

Living With a Star WorkshopLiving With a Star Workshop

Radiation Effects in Spacecraft andAircraft

Dr. Eugene NormandChief Scientist, Boeing Radiation Effects Laboratory

NASA-Goddard Space Flight Center

February 9, 2000


23/7/05

Overview for Assessing Impact of SpaceOverview for Assessing Impact of SpaceEnvironment on Radiation EffectsEnvironment on Radiation Effects

Ionizing radiation is diverse, comprised of 3 main sources: Trapped belts [electrons (10 keV-5 MeV) & protons (100 keV-

500 MeV)], inner belt: e & p, outer belt-mainly electrons

Galactic Cosmic Rays (GCR) ~85% energy protons, ~13%alphas and 2% HZE, all at high energies (0.01-100 GeV/amu)

Solar energetic particle (SEP) events, mainly protons, alphasand HZE, but at much lower energies than GCR

4th source, Solar wind, very low energy protons (~1-5 keV)

Ionizing radiation can effect great variety of equipmenttypes, i.e, devices: electronics, optics, electro-optics,photovoltaics, thermal & optical coatings, MEMs, etc.

It can also effect biological systems, especially astronauts,but that won’t be dealt with in this presentation


33/7/05

Overview for Assessing Impact of SpaceOverview for Assessing Impact of SpaceEnvironment on Radiation Effects-ContEnvironment on Radiation Effects-Cont’’dd

There are orders of magnitude variations in: energy of theradiation, thickness of the devices, rad capability to penetratematerials, effects that can be induced, etc.

Thus, clear need to characterize the ionizing radiation indetail at both high and low energies

accurately describe energy spectra of each rad source

better describe variation of radiation sources over time

SEP events (“solar flares”) & creation of new “belts”

Enhancements in relativistic outer belt electrons

improve existing models (NASA, NRL, USAF)

predict lifetime, operability and reliability of devices beingselected for space missions

understand human threats (Shuttle, ISS & further missions)

understand/correlate different effects by different typesradiation in various components


43/7/05

Description of Three Main Types ofDescription of Three Main Types ofRadiation Effects in MicroelectronicsRadiation Effects in Microelectronics

Total Integrated Dose [TID] Cumulative effect of ionization (charge buildup) in IC leading

to a gradual degradation of electrical parameters

Single Event Effects [SEE] Disturbance of an active electronic device caused by a

single energetic particle; 4 main categories Upset (SEU) --change in logic state, e.g., bit flip in RAM

Latchup (SEL) --increase in current resulting from turningon parasitic pnpn (in CMOS devices)

Damage or burnout (SEGR & SEB) of power transistor

Functional interrupt (SEFI)- malfunctions in more complexparts sometimes as lockup, hard error, etc.

Displacement Damage Cumulative effect of displacing atoms out of their lattice


53/7/05

Overview in Assessing MagnitudeOverview in Assessing Magnitudeof Radiation Effects on ICsof Radiation Effects on ICs

TID

3 main environment parameters: daily dose rate (depends on orbit altitude and inclination)

mission time (number days); also effects flare probability

shielding (by structures, reduces dose rate)

TID = daily dose rate (rad/day) _ number days

Combine with measured response of ICs (passing doselevel at which degradation is measured)

SEE

GCR Heavy Ions Composite differential particle spectrum (ion/cm_day >E)

as function of E, then transformed from E→ LET

Trapped Protons Integral or differential daily flux, p/cm_day>E

Combine with measured response of ICs (SEE vs. LET)


63/7/05

Upsets in Shuttle Orbiter GPCUpsets in Shuttle Orbiter GPCComputers on Ground (1)Computers on Ground (1)

STS-37 (4/91) 1st flight with GPCs (general purpose computers) Use IMS1601 64K SRAMs (~13Mbits/GPC)

Protected by EDAC (records errors) on ground and in space

First upset in GPC memory during ground testing, 4/92

Since then, total of 14 SEUs have been recorded in the GPCsduring ground testing (13 in Orbiters, 1 in spare)

Average ground upset rate [based on total time (ETI, elapsedtime indicator) -flight time] is ~8E-12 Upset/Bit-hr Higher ground rate than for other SRAMs by factor of 4-8

Agrees w/WNR SEU measurement

Factor 1.5-2 high compared to IBM measm’t, Manassas, VA

GPC data fromTami Mitchell and Kathy Milon of KSC

Ground upsets in Shuttle Orbiter GPCs on the ground arerandom, therefore they are SEUs


73/7/05

Upsets in Shuttle Orbiter GPCUpsets in Shuttle Orbiter GPCComputers on Ground (2)Computers on Ground (2)

Ground upsets in Shuttle Orbiter GPCs on the ground arerandom, therefore they are SEUs

0

0.2

0.4

0.6

0.8

1

0 1 2 3 4 5 6

Upsets/Orbiter

Cu

mu

lati

ve

Pro

ba

bil

ity

Poisson Distribution

Shuttle Orbiter GPCs

Poisson based on 3.25 Upsets per Orbiter


83/7/05

SEU Observed in Autopilot in BoeingSEU Observed in Autopilot in BoeingCommercial AircraftCommercial Aircraft

Data obtained by Autopilot Vendor; original design had “No Bus Outputs”

Autopilot design modified to include triple-voted RAM to allow neutron SEUto be detected and corrected; occurrence of “No Bus Outputs” eliminated

Latitude vs. Altitude Autopilot SEUs

-60

-40

-20

0

20

40

60

80

0 10000 20000 30000 40000 50000

Altitude (Feet)

Lati

tud

e (

Deg

rees)


93/7/05

SEL Observed inSEL Observed in ERS ERS Satellite Led Satellite Ledto Failed Instrument After 6 Daysto Failed Instrument After 6 Days

PRARE instrument on ERS-1 Satellite (784 km, polar orbit), launched in 1991

Failed after 6 days, problem traced to SEL in one of 22 64Kbit SRAMs

No pre-flight testing; post-flight test indicated SRAM prone to proton-induced SEL

SEL test (60 MeV protons) gave X-Section of ~3E-9 cm_/dev, leading to meanfluence for single SEL of ~1.5 E7 p/cm_, agrees with 6-day orbit fluence

0.0E+0

5.0E+6

1.0E+7

1.5E+7

2.0E+7

2.5E+7

0 20 40 60 80 100 120

Time in Orbit, Hours

Inte

gral

Flu

ence

, p/c

m≤

E> 60 MeV

E>100 MeV


103/7/05

Single Even Burnout (SEB) in PowerSingle Even Burnout (SEB) in PowerMOSFETs Observed in SpacecraftMOSFETs Observed in Spacecraft

Single event burnout (SEB) caused by GCR ions, as well as protons, has beenconcern; designers avoided problem by operating MOSFETs at highly reduced Vds

CRUX experiment on APEX satellite (360_2540 km, 70° orbit) allowed 100 & 200VMOSFETs to be cycled through high voltage range, resulting SEBs were recorded

200V 2N6798 (flight lot) was tested by Boeing at HCL, yielding proton SEB crosssections; when combined w/ orbit environment, obtain good agreement w/flight data

1E-3

1E-2

1E-1

1E+0

1E+1

170 180 190 200 210 220

Vds (V)

# S

EB

/dev

ice-

day

Calculated, Avg Lab DataObserved SEBs on APEXRates Based on Lab Data Variations


113/7/05

Change in Solar Change in Solar Absorbtance Absorbtance of of AgAg/FEP/FEPThermal Coating due to Electron DoseThermal Coating due to Electron Dose

Many satellites use very thin (few mils) thermal coatings, such as silver/teflon(Ag/FEP), to control the UV absorbed and hence the temperature of satellite

As low energy electrons deposit energy in the coatings, absorptance increases

Result is higher temperature; examples of data from GEO and half-GEO satellites

0

0.05

0.1

0.15

0.2

0.25

1E+6 1E+7 1E+8 1E+9

Electron Dose, Rads

Incr

ease

in

So

lar

Ab

sorp

tan

ce CRETC: e/p,UV/VUV; e Fluence OnlyP-78 Data, Fit by Hall/FoteNavstar 5, Therm Expt DataNavstar 1, Battery DataNavstar 1, 1.5◊ Nom. Flux

CRETC-Lab data

P78 - GEO orbit

Navstar - 20,000 km, 63° orbit


123/7/05

ConclusionsConclusions

We have shown diverse effects measured in satellites, as well as airplanes andon ground, examples of impact ionizing radiation can have on materials

Most effects have been in electronics, but have also shown effect in very thinmaterials such as thermal coating (silver/teflon, Ag/FEP)

Many other speakers will be providing other examples of the effects ofionizing radiation and our attempts to measure it in space, and incorporatethat information into useful models of the space radiation environment

As we improve our understand the space radiation environment, the better wewill be able to understand and plan for its effect on the equipment that wewill be sending into space

The Living With A Star spacecraft constellation represents a uniqueopportunity for basic science experts to join forces with applied scienceresearchers to make measurements that will be useful and meaningful to bothconstituencies

Documents

Radiation Effects in Spacecraft and Aircraftlws.gsfc.nasa.gov › documents › mission_requirements › normand...Many satellites use very thin (few mils) thermal coatings, such as