ISO 12208:2015

Space systems — Space environment (natural and artificial) — Observed proton fluences over long duration at GEO and guidelines for selection of confidence level in statistical model of solar proton fluences

ISO 12208:2015 describes a method to estimate energetic proton fluences in geosynchronous earth orbit (GEO) over a long duration (beyond the 11-year solar cycle), and presents guidelines for the selection of a confidence level in a model of solar proton fluences to estimate solar cell degradation. Many of the proton data observed in GEO are archived, for example from GMS (Japan), METEOSAT (ESA) and GOES (USA). This method is a direct integration of these fluence data (or the observed data over 11 years is used periodically). As a result, the confidence level can be selected from a model of solar proton fluences. ISO 12208:2015 is an engineering-oriented method used for specific purposes such as estimating solar panel degradation.

Systèmes spatiaux — Environnement spatial (naturel et artificiel) — Fluences de protons observées sur une longue durée au GEO et lignes directrices pour la sélection du niveau de confiance dans le modèle statistique des fluences de protons solaires

General Information

• Status: Published
• Publication Date: 08-Oct-2015
• ICS: 49.140 - Space systems and operations
• Technical Committee: ISO/TC 20/SC 14 - Space systems and operations
• Drafting Committee: ISO/TC 20/SC 14/WG 4 - Space environment (natural and artificial)
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 09-Mar-2021

Relations

• Revises: ISO/TS 12208:2011 - Space systems — Space environment (natural and artificial) - Observed proton fluences over long duration at GEO and guideline for selection of confidence level in statistical model of solar proton fluences
• Effective Date: 05-Nov-2015

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 12208
First edition
2015-10-01
Space systems — Space environment
(natural and artificial) — Observed
proton fluences over long duration at
GEO and guidelines for selection of
confidence level in statistical model of
solar proton fluences
Systèmes spatiaux — Environnement spatial (naturel et artificiel) —
Fluences de protons observées sur une longue durée au GEO et lignes
directrices pour la sélection du niveau de confiance dans le modèle
statistique des fluences de protons solaires
Reference number
ISO 12208:2015(E)
ISO 2015
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ISO 12208:2015(E)
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© ISO 2015, Published in Switzerland

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ii © ISO 2015 – All rights reserved
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ISO 12208:2015(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Terms and definitions ..................................................................................................................................................................................... 1

3 Symbols and abbreviated terms ........................................................................................................................................................... 2

4 Principles of the method (see Reference [3]) ............................................................................................................................ 2

4.1 Cumulative fluence .............................................................................................................................................................................. 2

4.2 Confidence level ..................................................................................................................................................................................... 3

4.3 Archives of observed energetic protons in GEO ......................................................................................................... 3

4.4 Remarks ........................................................................................................................................................................................................ 3

5 Guidelines for selection of a confidence level in a statistical model of solar

proton fluences ...................................................................................................................................................................................................... 4

Annex A (informative) Example of estimation and selection ...................................................................................................... 5

Bibliography ................................................................................................................................................................................................................................ 9

© ISO 2015 – All rights reserved iii
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ISO 12208:2015(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 20, Aircraft and space vehicles, Subcommittee

SC 14, Space systems and operations.
This first edition of ISO 12208 cancels and replaces ISO/TS 12208:2011.
iv © ISO 2015 – All rights reserved
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ISO 12208:2015(E)
Introduction
This International Standard is intended for use in the engineering community.

It is well known that solar energetic protons (SEPs) damage spacecraft systems, i.e. electronics and

solar cells, through ionization and/or atomic displacement processes. This results in single-event

upsets and latch-ups in electronics, and output degradation of solar cells.

Solar cells of spacecraft are obviously one of the key components of spacecraft systems. Degradation of

solar cells by energetic protons is unavoidable and causes power loss in spacecraft systems. Estimation

of cell degradation is crucial to the spacecraft’s long mission life in geosynchronous earth orbit (GEO).

Therefore, an estimation of SEP fluences in GEO is needed when designing solar cell panels.

Solar cell engineers use a statistical model, the jet propulsion laboratory (JPL) fluence model for

example, for estimating solar cell degradation. However, with regard to solar cell degradation, a

statistical model predicts higher SEP fluences than the values actually experienced by spacecraft in

GEO, especially seven years after the launch. Nowadays, spacecraft manufacturers are very conscious

of minimum cost design of spacecraft because the lifetime of spacecraft is becoming longer (15 years

to 18 years) and the cost of manufacturing spacecraft is increasing. Therefore, the aerospace industry

requires a more accurate SEP fluence model for a more realistic design of solar cells.

© ISO 2015 – All rights reserved v
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INTERNATIONAL STANDARD ISO 12208:2015(E)
Space systems — Space environment (natural and
artificial) — Observed proton fluences over long duration
at GEO and guidelines for selection of confidence level in
statistical model of solar proton fluences
1 Scope

This International Standard describes a method to estimate energetic proton fluences in geosynchronous

earth orbit (GEO) over a long duration (beyond the 11-year solar cycle), and presents guidelines for the

selection of a confidence level in a model of solar proton fluences to estimate solar cell degradation.

Many of the proton data observed in GEO are archived, for example from GMS (Japan), METEOSAT (ESA)

and GOES (USA). This method is a direct integration of these fluence data (or the observed data over

11 years is used periodically).

As a result, the confidence level can be selected from a model of solar proton fluences.

This International Standard is an engineering-oriented method used for specific purposes such as

estimating solar panel degradation.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
confidence level
level used to indicate the reliability of a cumulative fluence estimation
2.2
extremely rare event

solar energetic proton (SEP) event that occurs about once in a solar cycle and whose fluence dominates

that for the entire cycle

Note 1 to entry: Examples are those which took place in August 1972, October 1989 and July 2000.

2.3
flux
number of particles passing through a specific unit area per unit time
2.4
fluence
time-integrated flux
2.5
n-year fluence
fluence during a mission of n years duration
© ISO 2015 – All rights reserved 1
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ISO 12208:2015(E)
3 Symbols and abbreviated terms
EOL end of life
ESA European Space Agency
JPL Jet Propulsion Laboratory
METEOSAT Meteorological Satellite
GEO Geosynchronous Earth Orbit
GMS Geosynchronous Meteorological Satellite
GOES Geostationary Operational Environmental Satellite
RDC relative damage coefficients
SEP solar energetic proton
SSN sun spot number
4 Principles of the method (see Reference [3])
4.1 Cumulative fluence

The n-year fluence for a given mission life of n-years is shown in Figure 1 and estimated as follows.

a) The n-year fluence is calculated by integrating observed daily fluences for n-years from archives.

The start day for integration is January 1 in the first year (defined as A). The integration windows

are shifted each day from January 2 in the first year to December 31 in n-years later (defined as

B, C ... Z). These are possible fluences that a spacecraft might experience during its mission life (see

A, B, C … Z in Figure 1).
b) The maximum of the n-year fluences, F (t), for the n-year mission life i
...