Radiation Requirements for the LRO
431-RQMT-000045
Revision DRAFT
DRAFT
Robotic Lunar Exploration Program
Lunar Reconnaissance orbiter (LRO)
Radiation Requirements for the LRO
(04/14/2005)
Goddard Space Flight Center
Greenbelt, Maryland
National Aeronautics and
Space Administration
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Radiation Requirements for the LRO
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CM FOREWORD
This document is a Robotic Lunar Exploration Program (RLEP) Configuration Management
(CM)-controlled document. Changes to this document require prior approval of the RLEP
Program (or specific project if document only applies at project level) Manager. Proposed
changes shall be submitted to the RLEP CM Office (CMO), along with supportive material
justifying the proposed change. Changes to this document will be made by complete revision.
Questions or comments concerning this document should be addressed to:
RLEP Configuration Manager (TBD)
RLEP Configuration Management Office
Mail Stop 430
Goddard Space Flight Center
Greenbelt, Maryland 20771
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Radiation Requirements for the LRO
431-RQMT-000045
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Signature Page
Prepared by:
<Michael Xapsos>
<LRO Radiation Lead>
<Code 561>
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<Christian Poivey>
<LRO Radiation>
<MEI/Code 561>
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Reviewed by:
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Radiation Requirements for the LRO
431-RQMT-000045
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ROBOTIC LUNAR EXPLORATION PROGRAM
DOCUMENT CHANGE RECORD
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Radiation Requirements for the LRO
431-RQMT-000045
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List of TBDs/TBRs
Item
No.
Location
Summary
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Radiation Requirements for the LRO
431-RQMT-000045
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TABLE OF CONTENTS
Page
1.0
2.0
3.0
4.0
Introduction .................................................................................................................... 1-1
Component Total Ionizing Dose (TID) Specification ................................................. 2-1
Component Displacement Damage Dose (DDD) Specification .................................. 3-1
Single Event Effects (SEE) specification ...................................................................... 4-1
4.1
Definitions............................................................................................................ 4-1
4.2
Component SEE Specification ............................................................................. 4-1
Appendix A. Abbreviations and Acronyms ................................................................................1
ii
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Radiation Requirements for the LRO
431-RQMT-000045
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LIST OF FIGURES
Figure
Page
LIST OF TABLES
Table
Page
Table 4-1: minimum ion range as a function of rated VDS .......................................................... 4-2
Table 4-2: Environment to be assessed based on SEE Device LET Threshold........................... 4-3
iii
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Radiation Requirements for the LRO
1.0
431-RQMT-000045
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INTRODUCTION
This document gives the Total Ionizing Dose (TID), non-ionizing Displacement Damage Dose
(DDD), and Single Event Effects (SEE) requirements for the Lunar Reconnaissance Orbiter
(LRO). The LRO radiation environment is defined in document ref. 431-SPEC-0020 hereafter
called ENVDOC. We have assumed in this document a top-level shielding requirement of at
least 100 mils equivalent aluminum shielding between all components and free space. That is,
there must be 100 mils equivalent aluminum shielding in all solid angles projected from the
device out towards free-space. The requirements below assume that shielding for each
component meets this minimum shielding requirement.
1-1
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COMPONENT TOTAL IONIZING DOSE (TID) SPECIFICATION
No effect due to TID may cause permanent damage to or degradation of a system or subsystem.
Components or circuits shall be designed to be immune to TID induced performance degradation
that would induce system or subsystem functional failures, anomalies, or outages which are
catastrophic or require ground intervention to correct. A component is immune to TID effects if
its electrical parameters and functionality remain unchanged after 300krad-Si, as demonstrated
by Co-60 testing as per MIL-STD-883 Method 1019.6.
If component test data does not exist, ground testing is required. For commercial components,
testing is required on the flight procurement lot. All testing must follow Co-60 testing as per
MIL-STD-883 Method 1019.6.
For any component that is estimated to have on-orbit performance degradation due to TID, an
analysis must be performed to show that this degradation does not cause damage to or inducedegradation of system or subsystem performance. Alternatively, protective circuitry must be
added to eliminate the possibility of damage to or degradation of system or subsystem
performance, and must be verified by analysis or test.
TID environment specifications:
The top-level TID requirement to be used for analysis for the 1-year mission is 4.8 krad-Si.
A radiation design margin of 7 will be used when considering its effects on any linear bipolar
and BiCMOS components, and radiation design margin of 2 will be used when considering its
effects on any other component.
From top-level TID requirement and the radiation design margins above, the TID requirement
for linear bipolar and BiCMOS components is 33.5 krad-Si. For all other components it is 9.6
krad-Si.
The radiation design margin for a specific linear bipolar component can be reduced if it can be
shown that the component does not experience Enhanced Low Dose Rate susceptibility
(ELDRS) and/or DDD effects.
If a device’s performance degradation due to TID is not acceptable using the top-level
requirement then the space radiation environments will be estimated using a 3 dimensional
Monte Carlo analysis or a ray trace analysis. This can significantly reduce the estimated TID
requirement.
A design's resistance to component performance degradation due to TID for the specified
radiation environment must be demonstrated.
2-1
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COMPONENT DISPLACEMENT DAMAGE DOSE (DDD) SPECIFICATION
No effect due to DDD may cause permanent damage to or degradation of a system or subsystem.
Components or circuits shall be designed to be immune to performance degradation due to DDD
such that if this degradation were to occur it would induce system or subsystem functional
failures, anomalies, or outages that are catastrophic or require ground intervention to be
corrected. A component shall be defined as immune if its electrical parameters and functionality
remain unchanged after 4x1012 protons/cm2 of 10 MeV protons, as demonstrated by proton
testing.
Each component must be assessed for potential sensitivity to DDD effects. For those
components deemed sensitive to DDD, if component test data does not exist, ground testing is
required. For commercial components, if testing is required it must be performed on the flight
procurement lot. All testing must be performed using protons to a mission equivalent fluence.
For any component that is estimated to have on-orbit performance degradation due to DDD, an
analysis must be performed to show that this degradation does not cause damage to or inducedegradation of system or subsystem performance. Alternatively, protective circuitry must be
added to eliminate the possibility of damage to or degradation of system or subsystem
performance, and verified by analysis or test.
DDD environment specifications:
The top-level DDD requirement to be used for for the 1-year mission is 1.2E10 protons/cm2 of
10 MeV protons.
A radiation design margin of 2 will be used when considering their effects on component
performance.
From top-level DDD mission equivalent proton fluence and the radiation design margin above,
the top level DDD requirement for components is 2.4E10 p/cm2 of 10 MeV protons.
If a device’s performance degradation due to DDD is not acceptable using the top-level
requirements, then the space radiation environment on this device will be estimated using a more
accurate method such as 3-dimensional Monte Carlo analysis or ray trace analysis. This can
significantly reduce the estimated DDD.
Alternative proton energies can be used for test and analysis. The requirement will be scaled
according to the Non Ionizing Energy Loss (NIEL)
A design's resistance to component performance degradation due to DDD for the specified
radiation environment must be demonstrated.
3-1
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Radiation Requirements for the LRO
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4.0
SINGLE EVENT EFFECTS (SEE) SPECIFICATION
4.1
DEFINITIONS
Single Event Upset (SEU) - a change of state or transient induced by an energetic particle such as
a cosmic ray or proton in a device. This may occur in digital, analog, and optical components or
may have effects in surrounding interface circuitry (a subset known as Single Event Transients
(SETs)). These are “soft” errors in that a reset or rewriting of the device causes normal device
behavior thereafter.
Single Hard Error (SHE) - a SEU that causes a permanent change to the operation of a device.
An example is a stuck bit in a memory device.
Single Event Latchup (SEL) - a condition that causes loss of device functionality due to a single
event induced high current state. A SEL may or may not cause permanent device damage, but
requires power strobing of the device to resume normal device operations.
Single Event Burnout (SEB) - a condition that can cause device destruction due to a high current
state in a power transistor.
Single Event Gate Rupture (SEGR) - a single ion induced condition in power MOSFETs that
may result in the formation of a conducting path in the gate oxide.
Single Event Effect (SEE) - any measurable effect to a circuit due to an ion strike. This include
(but is not limited to) SEUs, SETs, SHEs, SELs, SEBs, SEGRs, and Single Event Dielectric
Rupture (SEDR).
Multiple Bit Upset (MBU) - an event induced by a single energetic particle such as a cosmic ray
or proton that causes multiple upsets or transients during its path through a device or system.
Linear Energy Transfer (LET) - a measure of the energy deposited per unit length as a energetic
particle travels through a material. The common LET unit is MeV*cm2/mg of material (Si for
MOS devices, etc.).
Threshold LET (LETth) - the minimum LET to cause an effect at a particle fluence of 1E7
ions/cm2. Typically, a particle fluence of 1E5 ions/cm2 is used for SEB and SEGR testing.
4.2
COMPONENT SEE SPECIFICATION
No SEE may cause permanent damage to a system or subsystem.
Electronic components shall be designed to be immune to SEE induced performance anomalies,
or outages that require ground intervention to correct. Electronic component reliability shall be
met in the SEE environment. Immunity is defined as a LETth > 75 MeVcm2/mg, which must be
shown by heavy ion testing or analysis.
4-1
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Radiation Requirements for the LRO
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If component test data does not exist, ground testing is required. For commercial components,
testing is required on the flight procurement lot.
For any component that is not immune to SEL or other destructive condition an analysis shall
demonstrate that the SEL probability of occurrence is negligible in the LRO mission
environment.
All N channel power MOSFETs may be susceptible to SEB in the off mode. Their sensitivity
shall be evaluated at the worst-case application. The survival VDS voltage shall be established
from exposure to minimum fluence of 1E6 ions/cm2 with a minimum LET of 26 MeVcm2/mg
and a range that is sufficient to penetrate the depletion depth of the device at its maximum
voltage. The minimum ion range as a function of rated VDS is given in Table 4-1.The application
shall be derated to 75% of the established survival voltage. Alternatively a derating factor of
40% (of VDS rated) can be applied for up to 200V devices from International Rectifier and
Intersil when no data is available. For any other device type and or vendor, a derating factor of
25% can be applied when no data is available.
All power MOSFET may be susceptible to SEGR in the off mode. Their sensitivity shall be
evaluated at the worst-case application. The survival VDS voltage shall be established from
exposure to minimum fluence of 1E6 ions/cm2 with a minimum LET of 26 MeVcm2/mg and a
range that is sufficient to penetrate the depletion depth of the device at its maximum voltage. The
minimum ion range as a function of rated VDS is given in Table 4-1. The application shall be
derated to 75% of the established survival voltage. Alternatively a derating factor of 40% (of VDS
rated) can be applied for up to 200V devices from International Rectifier and Intersil when no
data is available. For any other device type and or vendor, a derating factor of 25% can be
applied when no data is available.
Table 4-1: minimum ion range as a function of rated VDS
Max rated VDS (V)
Up to 100
100 to 250
250 to 400
400 to 1000
Minimum ion range (m)
30
40
80
200
For single particle events like SEU, SET, and MBU the criticality of a component in its specific
application must be defined. Please refer to the Single Event Effect Criticality Analysis (SEECA)
document for details. A SEECA analysis or a FMEA should be performed at the system level.
Component heavy-ion and proton testing (and from these a rate calculation) must be preformed
on each application of each component.
SEE testing and analysis to determine SEE rates must take place based on LETth of the
candidate devices as described in Table 4-2.
4-2
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Table 4-2: Environment to be assessed based on SEE Device LET Threshold
Device Threshold
LETth < 12 MeVcm2/mg
LETth = 12-75 MeVcm2/mg
LETth > 75 MeVcm2/mg
Environment to be Assessed
Galactic Cosmic Rays,
Solar Events Heavy ions and protons
Galactic Cosmic Ray Heavy Ions,
Solar Events Heavy Ions
No analysis required
SEE environment specification (recall top level shielding is 100 mils equivalent Al):
For non-destructive events, a radiation design margin of 2 will be used on all environment
estimates when considering their effects on component performance.
The cosmic ray integral-flux LET spectrum to be used for analysis is given in Figure 10 and
Table A8 of ENVDOC.
The solar particle event integral-flux LET spectrum to be used for analysis is given in Figure 11
and Table A9 of ENVDOC.
The worst-case solar proton energy spectra to be used for analysis are given in Figure 12 and
Table A10 of ENVDOC.
The improper operation caused by single particle event like SEU, SET and MBU shall be
reduced to acceptable levels. Systems engineering analysis of circuit design, operating modes,
duty cycle, device criticality etc. shall be used to determine acceptable levels for that device.
Means of gaining acceptable levels include part selection, error detection and correction
schemes, redundancy and voting methods, error tolerant coding, or acceptance of errors in noncritical areas.
A design's resistance to SEE for the specified radiation environment must be demonstrated.
4-3
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Appendix A. Abbreviations and Acronyms
Abbreviation/
Acronym
LRO
RLEP
TID
DDD
SEE
ELDRS
NIEL
SEU
SET
SHE
SEL
SEB
SEGR
SEDR
MBU
LET
LETth
SEECA
FMEA
DEFINITION
Lunar Reconnaissance Orbiter
Robotic Lunar Explorer Program
Total Ionizing dose
Displacement Damage Dose
Single Event Effect
Enhanced Low Dose Rate Sensitivity
Non Ionizing Energy Loss
Single Event Upset
Single Event Transient
Single Hard Errors
Single Event Latchup
Single Event Burnout
Single Event Gate Rupture
Single Event Dielectric Rupture
Multiple Bit Upset
Linear Energy Transfer
Linear Energy Transfer threshold
Single Event Effect Criticality Analysis
Failure Mechanism Analysis
A-1
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