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

ISO/TS 12208:2011 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 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/TS 12208:2011 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 ligne directrice pour la sélection du niveau de confiance dans le modèle statistique des fluences de protons solaires

General Information

• Status: Withdrawn
• Publication Date: 20-Sep-2011
• Withdrawal Date: 20-Sep-2011
• 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: 9599 - Withdrawal of International Standard
• Completion Date: 09-Oct-2015

Relations

• Revised: 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
• Effective Date: 05-Nov-2015

Standards Content (Sample)

TECHNICAL ISO/TS
SPECIFICATION 12208
First edition
2011-09-15
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
Systèmes spatiaux — Environnement spatial (naturel et artificiel) —
Fluences de protons observées sur une longue durée au GEO et ligne
directrice pour la sélection du niveau de confiance dans le modèle
statistique des fluences de protons solaires
Reference number
ISO/TS 12208:2011(E)
©
ISO 2011

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ISO/TS 12208:2011(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2011
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Published in Switzerland
ii © ISO 2011 – All rights reserved

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ISO/TS 12208:2011(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Symbols and abbreviated terms . 1
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 . 4
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 .10
© ISO 2011 – All rights reserved iii

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ISO/TS 12208:2011(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a technical
committee may decide to publish other types of document:
— an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
— an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee
casting a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a further
three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is confirmed,
it is reviewed again after a further three years, at which time it must either be transformed into an International
Standard or be withdrawn.
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.
ISO/TS 12208 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 14, Space systems and operations.
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ISO/TS 12208:2011(E)
Introduction
This Technical Specification 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 (15-18 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.
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TECHNICAL SPECIFICATION ISO/TS 12208:2011(E)
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
1 Scope
This Technical Specification 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 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 Technical Specification 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
a solar energetic proton (SEP) event that occurs about once in a solar cycle and whose fluence dominates that
for the entire cycle
NOTE Examples are those which took place in August 1972, October 1989 and July 2000.
2.3
flux
number of particles passing through a specific zone per unit time
2.4
fluence
time-integrated flux
2.5
n-year fluence
a given fluence during a mission of a selected duration, n years
3 Symbols and abbreviated terms
EOL end of life
ESA European Space Agency
JPL jet propulsion laboratory
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ISO/TS 12208:2011(E)
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 cumulative fluence for a given mission duration of n-years is shown in Figure 1 and estimated as follows:
a) N-year fluence is calculated by integrating observed daily fluences from archives while shifting the
integration windows each day. These are possible fluences that a spacecraft may experience during its
mission life (see A, B, C … Z in Figure 1).
b) The maximum of the integrated fluences, F(t), for the n-year mission duration is obtained. Maximum fluence of
an n-year mission — assuming a spacecraft is launched every day — is calculated using the following equation:
F(t) = max (A, B, C … Z)
SSN
t
data period
A
B
C
.....
Z
F(t) = max{A,B,C,., Z}
Figure 1 — Cumulative fluences
2 © ISO 2011 – All rights reserved

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