solar cell radiation environment analysis models …solar cell radiation environment analysis models...

Solar Cell Radiation

Environment Analysis

Models (SCREAM)

2017 Space Environment Engineering

& Science Applications Workshop

(SEESAW)

Scott R. Messenger, Ph.D.

Principal Space Survivability Physicist

[email protected]

410-993-3976

• Omnidirectional (directional?)

• Energy Spectra (electrons & protons & plasmas)

• Nuclear activation (secondary production)

• Prompt effects (EMP, gammas, neutrons)

p+

COVERGLASS

SUBSTRATE

ACTIVE CELL

PANEL

p+

e-

e-

e-

e-

e-

p+

p+

p+

p+

p+

p+

COVERGLASS

SUBSTRATE

ACTIVE CELL

PANEL

p+

e-

e-

e-

e-

e-

p+

p+

p+

p+

p+

COVERGLASS

SUBSTRATE

ACTIVE CELL

PANEL

p+

e-

e-

e-

e-

e-

p+

p+

p+

p+

p+

protons

electrons

Space Radiation Environment for Solar Arrays

Ionizing and nonionizing radiation

solar UV

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=imgres&cd=&cad=rja&uact=8&ved=0ahUKEwj0-97l5uPMAhXFgj4KHde-DtMQjRwIBw&url=http://es.vectorhq.com/search/atom-bomb&psig=AFQjCNErdeUjbsdvbgAZcrTQJ5TxNv8vTA&ust=1463667048796291

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=imgres&cd=&cad=rja&uact=8&ved=0ahUKEwj0-97l5uPMAhXFgj4KHde-DtMQjRwIBw&url=http://es.vectorhq.com/search/atom-bomb&psig=AFQjCNErdeUjbsdvbgAZcrTQJ5TxNv8vTA&ust=1463667048796291

Outline

• Space Solar Cell Modelling

• Displacement Damage Dose (DDD) Model

– SCREAM

• SCREAM Success Stories

– TacSat4

– GPS-IIR SV41

– Low Thrust Trajectories (DDD accumulation)

• Summary

3

Space Solar Cell Degradation Prediction:

The Problem

Electron & Proton Ground Irradiation Data (Single Junction GaAs/Ge, 1991)

Electron & Proton Spectra for TacSat4

• To generate ground irradiation data necessary to predict the effect of a space particle energy spectrum on a solar cell

• This is accomplished by reducing the ground data to a characteristic dataset

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Inte

gra

l Flu

en

ce

(cm

-2)

Particle Energy (MeV)

TACSAT4 Orbit (700 x 12050 km, 63.4o , 1 year)

Trappped Protons

Solar Event Protons

Trapped Electrons

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.0E+09 1.0E+10 1.0E+11 1.0E+12 1.0E+13 1.0E+14 1.0E+15 1.0E+16 1.0E+17

No

rmal

ize

d M

axim

um

Po

we

r

Particle Fluence (#/cm2)

50 keV100 keV200 keV300 keV500 keV1 MeV3 MeV9.5 MeV

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.0E+09 1.0E+10 1.0E+11 1.0E+12 1.0E+13 1.0E+14 1.0E+15 1.0E+16 1.0E+17

No

rmal

ize

d M

axim

um

Po

we

r


0.6 MeV1 MeV2.4 MeV12 MeV

Protons

Electrons

GaAs/Ge1 Sun, AM0

25oC

THIS FIGURE IS FOUOTHIS FIGURE IS FOUO


The Solution(s)

1. JPL method RDCs equivalent 1 MeV electron fluence & Cpe

JPL Model Data Collapse

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E+12 1.E+13 1.E+14 1.E+15 1.E+16 1.E+17

Rem

ain

ing

Maxim

um

Po

wer

Equivalent 1 MeV Electron Fluence (cm-2)

GaAs/Ge(1 sun, AM0

Electrons

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12

Ream

inin

g M

axim

um

Po

wer

Displacement Damage Dose (MeV/g)

200 keV

300 keV

500 keV

1 MeV

3 MeV

9.5 MeV

12 MeV

2.4 MeV

1 MeV

0.6 MeV

1 MeV Equiv. U235 neutrons

DDD Fit

GaAs/Ge(1 sun, AM0 25oC)

Protons

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12

Ream

inin

g M

axim

um

Po

wer


200 keV

300 keV

500 keV

1 MeV

3 MeV

9.5 MeV

12 MeV

2.4 MeV

1 MeV

0.6 MeV


DDD Fit


*The heritage JPL model is well documented (1970-2000):H.Y.Tada and J.R.Carter, Solar Cell Radiation Handbook, JPL Pub. 77-56 (1977) – Green Book (Si)

B.Anspaugh, GaAs Solar Cell Radiation Handbook, JPL Pub. 96-9 (1996) – Blue Book (GaAs)

D.C. Marvin , Assessment of Multijunction Solar Cell Performance in Radiation Environments, TOR-00(1210)-1

THIS FIGURE IS FOUO


The Solution(s)

1. JPL method RDCs equivalent 1 MeV electron fluence & Cpe

2. NRL method NIEL displacement damage dose (DDD)

JPL Model Data Collapse NRL/DDD Model Data Collapse

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12

Rem

ain

ing

Maxim

um

Po

wer


GaAs/Ge(1 sun, AM0

Electrons

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12

Ream

inin

g M

axim

um

Po

wer


200 keV

300 keV

500 keV

1 MeV

3 MeV

9.5 MeV

12 MeV

2.4 MeV

1 MeV

0.6 MeV


DDD Fit


Protons

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12

Re

am

inin

g M

ax

imu

m P

ow

er


200 keV

300 keV

500 keV

1 MeV

3 MeV

9.5 MeV

12 MeV

2.4 MeV

1 MeV

0.6 MeV


DDD Fit


1 MeV Eq. 235U Neutrons

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E+12 1.E+13 1.E+14 1.E+15 1.E+16 1.E+17

Rem

ain

ing

Maxim

um

Po

wer

Equivalent 1 MeV Electron Fluence (cm-2)

GaAs/Ge(1 sun, AM0

Electrons

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12

Ream

inin

g M

axim

um

Po

wer


200 keV

300 keV

500 keV

1 MeV

3 MeV

9.5 MeV

12 MeV

2.4 MeV

1 MeV

0.6 MeV


DDD Fit


Protons

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12

Ream

inin

g M

axim

um

Po

wer


200 keV

300 keV

500 keV

1 MeV

3 MeV

9.5 MeV

12 MeV

2.4 MeV

1 MeV

0.6 MeV


DDD Fit


*The advanced NRL/DDD model is well documented (1994-2012):S.R. Messenger, et al., "Modeling solar cell degradation in space: A comparison of the NRL displacement damage

dose and JPL equivalent fluence approaches", Prog. Photovolt.: Res. Appl. vol. 9, pp. 103-121, 2001.

S.R. Messenger, et al., "SCREAM: A new code for solar cell degradation prediction using the displacement damage

dose approach," 35th IEEE PVSC, 2010, p. 1106.

THIS FIGURE IS FOUOTHIS FIGURE IS FOUO

NRL DDD Method

• Data needed (*AIAA S-111)– Protons

• E > 1-4 MeV (need uniform DD)(f = 1010 to 1013 p+/cm2)

– Electrons• E = 1 & >2 MeV(f = 1013 to 1016 e-/cm2)

• Advantages– ~3-4X cost reduction in qualification

– Convenient for new tech quals, design tweaks, requals

• Disadvantages– Heritage Heritage Heritage

– Not applicable to protons on thick silicon

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.0E+09 1.0E+10 1.0E+11 1.0E+12 1.0E+13 1.0E+14 1.0E+15 1.0E+16 1.0E+17

No

rmal

ize

d M

axim

um

Po

we

rParticle Fluence (#/cm2)

3 MeV

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.0E+09 1.0E+10 1.0E+11 1.0E+12 1.0E+13 1.0E+14 1.0E+15 1.0E+16 1.0E+17

No

rmal

ize

d M

axim

um

Po

we

r


0.6 MeV1 MeV2.4 MeV12 MeV

Protons

Electrons

GaAs/Ge1 Sun, AM0

25oC

Electron and Proton Ground Data

“Qualification and Quality Requirements for Space Solar Cells” (AIAA S-111A-2014) – JPL and/or DDD models acceptable

THIS FIGURE IS FOUO

Space Solar Cell Modeling:

NRL Displacement Damage

Dose (DDD)

NRL Displacement Damage Dose Model for

Solar Cell EOL Calculations

Input Nonionizing Energy Loss (NIEL) Data

(Energy Dependence of Damage

Coefficients)

Determine Characteristic Degradation

Curve vs. DDD (NIEL x Fluence)

(2 e- and 1 p+ energy)

Read Off EOL Value

Determine Incident Particle

Spectrum (e.g. AP8, AE8)

Calculate Slowed-Down

Spectrum (SDS) (Shielding)

Calculate DDD for Mission

(Integrate SDS with NIEL)

*RED – Measurements *Blue – Calculation *Green – Data input

DDD EOL Prediction Method

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Dif

fere

ntia

l Flu

ence

(p+ /c

m2 /M

eV)

Proton Energy (MeV)

TrP/2

1 mil

3 mils

6 mils

12 mils

20 mils

30 mils

60 mils

Omnidirectional Spectra

THIS FIGURE IS UNCLASSIFIED


1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Dif

fere

ntia

l Flu

ence

(p+ /c

m2 /M

eV)

Proton Energy (MeV)

TrP/2

1 mil

3 mils

6 mils

12 mils

20 mils

30 mils

60 mils

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Non

ioni

zing

Ene

rgy

Loss

(MeV

cm2 /g

)

Proton Energy (MeV)

GaAs

Nonionizing Energy Loss (2006)Omnidirectional Spectra

THIS FIGURE IS UNCLASSIFIED THIS FIGURE IS UNCLASSIFIED


1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

0 10 20 30 40 50 60 70

Dis

plac

emen

t Dam

age

Dos

e (M

eV/g

)

SiO2 Coverglass Thickness (mils)

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Dif

fere

ntia

l Flu

ence

(p+ /c

m2 /M

eV)

Proton Energy (MeV)

TrP/2

1 mil

3 mils

6 mils

12 mils

20 mils

30 mils

60 mils

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Non

ioni

zing

Ene

rgy

Loss

(MeV

cm2 /g

)

Proton Energy (MeV)

GaAs

Nonionizing Energy Loss (2006)Omnidirectional Spectra

Total Mission DDD




0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12

Rem

ain

ing

Maxim

um

Po

wer

DDD(protron) and DDD(1 MeV electron) (MeV/g)

GaAs/Ge (AM0, 1 sun, 25oC)

electrons

protons

neutrons

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

0 10 20 30 40 50 60 70

Dis

plac

emen

t Dam

age

Dos

e (M

eV/g

)

SiO2 Coverglass Thickness (mils)

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Dif

fere

ntia

l Flu

ence

(p+ /c

m2 /M

eV)

Proton Energy (MeV)

TrP/2

1 mil

3 mils

6 mils

12 mils

20 mils

30 mils

60 mils

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Non

ioni

zing

Ene

rgy

Loss

(MeV

cm2 /g

)

Proton Energy (MeV)

GaAs

Total Mission DDD

Nonionizing Energy Loss (2006)

Pmax Degradation

Omnidirectional Spectra

x

dd

D

DCA

P

DP1log

)(

0

Data Fit (a, C, Dx)




SCREAM (Solar Cell Radiation Environment

Analysis Models)

– Excel file driven menus as inputs• Input integral radiation spectra

– Single & multi-spectra, electron and proton

• Shielding material• Nonionizing energy loss (NIEL)• Multilayer shielding• Parametric degradation coefficients(GaAs, ITJ, UTJ, ATJ, Si-electrons, user)

– Output• Slowed-down radiation spectra• End-of-life (EOL) predictions• DDD only options (“ShielDDDose”)• Trajectory capability through “Time

Series Spectra” input option

SCREAM is available by request in CD format

*Contact: Dr. Scott R. Messenger (NGC)

SCREAM Success Stories

• TacSat4 (HEO: 700 km x 12,050 km, 63.4o)

– Used onboard dosimetry (CEASE-II) and solar cell experiment to explain

anomalously large solar array degradation rates

– SCREAM used CEASE-II data to corroborate solar cell experiment (full IV)

data and re-project mission lifetime

• GPS-IIR SV41 (MEO: 20,200 km, 55o)

– GPS has been plagued with anomalous solar array degradation since

onset (many mitigation paths successful, but anomaly continues)

– SCREAM used LANL BDD Detector data to help understand damage

mechanisms and eliminate displacement damage as the anomaly

• Low-Thrust Trajectory Orbit to GEO (LT2GEO)

– Low-thrust trajectories are extreme mass & cost cutting measures

• Spacecraft subjected to extreme proton belts

– SCREAM can simply analyze accumulated DDD to optimize LT trajectory

TacSat4 (HEO: 700 km x 12,050 km, 63.4o)

* Graphic created using AFGEOSPACE (V2.5)

>1 MeV electrons

>10 MeV protons

• NRL satellite launched 27 Sept. 2011 (Kodiak, AK)

TacSat4 (HEO: 700 km x 12,050 km, 63.4o) –

Trapped Protons Dominant

• Maximum Power Degradation on Emcore ATJ Solar Cell

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

9/27/2011 10/27/2011 11/26/2011 12/26/2011 1/25/2012 2/24/2012 3/25/2012

Re

mai

nin

g M

axim

um

Po

we

r

Date of Mission

Measured power exceeds predictions using

AP9 95th worst case environment!

Shielding

6 mils CMG

2 mils DC 93-500

Emcore BTJM 3J

AP9-MC-95th

AP8MIN

AP9Mean

1 year spec



• Two additional payloads on-board– AFRL: CEASE-II dosimeter package

• Several dosimeters (particle fluence, TID, SEE, SC)

• 0.7-80 MeV protons & 0.05-3 MeV electrons

– NRL: Two solar cell experiments yielding full IV curves

• SCE#1: SolAero BTJM (3J w/ 6 mil CMG coverglass)

SCE #1CEASE-II

CEASE Proton Energy Comparisons

CEASE Proton Energy Comparisons

*For 6 mil coverglass, omnidirectionally incident

protons having energy from 1-10 MeV are the

most important in causing damage to the

underlying cell. For 12-20 mil covers -- NO

ANOMALY --- but definitely NO FUN.



• SCREAM: Environment data through 6 mil CMG & 2 mil adhesive

0.0E+00

1.0E+07

2.0E+07

3.0E+07

4.0E+07

5.0E+07

6.0E+07

7.0E+07

8.0E+07

9.0E+07

9/14/2011 12/23/2011 4/1/2012 7/10/2012 10/18/2012 1/26/2013 5/6/2013

Dis

pla

cem

en

t D

amag

e D

ose

(M

eV

/g)

Date of Mission

CEASEAP8MINAP9MeanAP9-MC-95th

SCREAM Shielding

6 mils CMG

2 mils DC 93-500

Emcore BTJM 3J

AP9-95th

AP8MIN

AP9Mean

CEASE

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

Sep-11 Nov-11 Jan-12 Mar-12 May-12 Jul-12 Sep-12 Nov-12 Jan-13 Mar-13

Re

mai

nin

g P

aram

ete

r

Date of Mission

SOLID: SCREAM calculations using CEASE environment data

DOTTED: Onboard data collected from solar cell experiment

1016 2x1016(Equiv. 1 MeV electron fluence)

Isc

Voc

Pmax



• SCREAM: DDD results applied to SolAero ATJ solar cell technology

Shielding

6 mils CMG

2 mils DC 93-500

Emcore ATJ

GPS-IIR (MEO: 20,200 km, 55o)

• SVN41 Launched 10 Nov 2000

*NIM A 482, 653 (2002)

GPS-IIR (MEO: 20,200 km, 55o) – Trapped

Electrons Dominant

• GPS spacecraft have shown anomalous silicon solar array degradation

throughout [>30] year existence (Marvin, 1988)

• Many possibilities posed (coatings, coverglass, contamination, ESD,

radiation environment related) but none confirmed

• GPS III plans on using oversized arrays to maintain necessary EOL levels

0.68

0.70

0.72

0.74

0.76

0.78

0.80

0.82

0.84

0.86

0.88

0.90

0.92

0.94

0.96

0.98

1.001

2/1

0/0

0

12

/10

/01

12

/10

/02

12

/10

/03

12

/10

/04

12

/10

/05

12

/10

/06

12

/10

/07

12

/10

/08

12

/10

/09

Re

mai

nin

g C

urr

en

t at

28

.28

V

~25% deviation

after 9 yrs!

GPS SVN 41 (Block IIR-6)

Solar array

telemetry data

AE8MAX AE8MAX+ESP(50%)


Electrons Dominant

• LANL Burst Dosimeter Detector (BDD) onboard SVN41

– Ion-implanted Si detectors behind varying shielding levels

– Gives electron fluences for E>0.04 to >10 MeV

– Gives proton fluences for E>0.05 to >6 MeV

– Daily fluence and energy spectra supplied by LANL

*LA-UR-10-04234, LA-UR-08-2816


Electrons Dominant

• SCREAM used BDD data to determine expected Si solar cell degradation

behind 12 mil CMX coverglass

• Displacement damage eliminated from secondary damage mechanism

• Other damage mechanism causing anomaly

0.68

0.70

0.72

0.74

0.76

0.78

0.80

0.82

0.84

0.86

0.88

0.90

0.92

0.94

0.96

0.98

1.00

12/1

0/20

00

12/1

0/20

01

12/1

0/20

02

12/1

0/20

03

12/1

0/20

04

12/1

0/20

05

12/1

0/20

06

12/1

0/20

07

12/1

0/20

08

12/1

0/20

09

Re

mai

nin

g C

urr

en

t @

28

.28

V

AE8MAXAE8MAX + ESP Total (50%)LANL Electrons (JPL Model)LANL Electrons (NRL Model)Solar Array Current @ 28.28 V

Other damage

mechanisms

On-orbit

correction

AE8 not so bad!

GPS-IIR (MEO: 20,200km, 55o) – Trapped

Electrons Dominant

• Analytical determination between expected (SCREAM) and measured

showed interesting trends (IEEE Trans. Nucl. Sci. 58, p.3188 (2011))

– Fast rate (4%/yr): contamination, UV, photo-fixing --- AR coating/conductive oxide?

– Slow rate (1.5%/yr): trapped electrons --- coverglass damage, ESD (Ferguson et al. 2015)?

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

12/

10

/20

00

12

/10

/20

01

12

/10

/20

02

12

/10

/20

03

12

/10

/20

04

12

/10

/20

05

12

/10

/20

06

12

/10

/20

07

12

/10

/20

08

12

/10

/20

09

Dif

fere

nce

Bet

we

en

Mo

de

l an

d D

ata

~4%/year

~1.5%/year

*Two accumulative mechanisms for

anomalous degradation suggested!

Low-Thrust Trajectory to GEO (LT2GEO)

Trade Off• Reduced Launch Costs

• Increased Payload

• Delayed GEO operations

• More Radiation Exposure

>1 MeV electrons

>10 MeV protons

Graphic created using AFGEOSPACE (V2.5)


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12/1/2017 12/31/2017 1/31/2018 3/2/2018 4/2/2018 5/2/2018

Alt

itu

de

(km

)

Date Along Trajectory

“Minimum-Time” Low-Thrust Trajectory

131 days to GEO

*Initial Orbit - GTO


Electron & Proton Fluxes Along Trajectory (AE8MAX/AP8MAX)

1.0E+00

1.0E+01

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1.0E+03

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Par

ticl

e F

lux

(#/c

m2/s

)

Days in Mission

AE8MAX (>1 MeV electrons)AP8MAX (>10 MeV protons)

Low-Thrust Trajectory to GEO (LT2GEO) –


DDD Along Trajectory (AE8MAX/AP8MAX)

* Trapped protons dominate the DDD for the LT2GEO transfer

1.0E-02

1.0E-01

1.0E+00

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DD

D (

Me

V/g

)

Days in Mission

AP8MAX

AE8MAX

4.83 mils CMG (4 mils CMG & 1 mils adhesive)

Low-Thrust Trajectory to GEO (LT2GEO) –


Solar Cell Degradation (AP8MAX/AE8MAX)

*The LT2GEO transfer significantly degrades both 1J and 3J solar cells

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Re

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g P

ma

x

Days in Mission

4.83 mils CMG (4 mils CMG & 1 mil adhesive, infinite back)

Triple Junction

Single Junction

After further

15 year GEO

parked

environment

Summary

• SCREAM employs the DDD model for solar cell

degradation

– Slab geometry (2p)

• Bonus Capabilities

– Multi-layered shielding

– Time series spectra (on-orbit data, trade studies)

– ShielDDDose (Depth-DDD curves)

• Applications

– Easy interpretation of dosimeter data onboard spacecraft for ORS

• TacSat4 – helped understand extra radiation to project mission lifetime

• GPS – eliminated DDD effects in solar cell to push efforts elsewhere

• LT2GEO – aids in better solar array designs in present low-cost needs

– Not only for solar cells (LEDs, laser diodes, CCDs, etc.)

• Any ground data for which a parametric vs. DDD curve can be created

solar cell radiation environment analysis models …solar cell radiation environment analysis models...

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