1、BSI Standards PublicationBS ISO 12208:2015Space systems Spaceenvironment (natural andartificial) Observed protonfluences over long durationat GEO and guidelines forselection of confidence levelin statistical model of solarproton fluencesBS ISO 12208:2015 BRITISH STANDARDNational forewordThis British
2、 Standard is the UK implementation of ISO 12208:2015. It supersedes DD ISO/TS 12208:2011 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee ACE/68, Space systems and operations.A list of organizations represented on this committee can be obtained on reque
3、st to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2015.Published by BSI Standards Limited 2015ISBN 978 0 580 89355 1 ICS 49.140 Compliance with a British St
4、andard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 December 2015.Amendments/issued since publicationDate T e x t a f f e c t e dBS ISO 12208:2015 ISO 2015Space systems Space environment (na
5、tural and artificial) Observed proton fluences over long duration at GEO and guidelines for selection of confidence level in statistical model of solar proton fluencesSystmes spatiaux Environnement spatial (naturel et artificiel) Fluences de protons observes sur une longue dure au GEO et lignes dire
6、ctrices pour la slection du niveau de confiance dans le modle statistique des fluences de protons solairesINTERNATIONAL STANDARDISO12208First edition2015-10-01Reference numberISO 12208:2015(E)BS ISO 12208:2015ISO 12208:2015(E)ii ISO 2015 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2015, Publ
7、ished in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permiss
8、ion can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 12208:2015ISO 12208:2015(E)Forewo
9、rd ivIntroduction v1 Scope . 12 Terms and definitions . 13 Symbols and abbreviated terms . 24 Principles of the method (see Reference 3) 24.1 Cumulative fluence 24.2 Confidence level . 34.3 Archives of observed energetic protons in GEO . 34.4 Remarks 35 Guidelines for selection of a confidence level
10、 in a statistical model of solar proton fluences 4Annex A (informative) Example of estimation and selection 5Bibliography 9 ISO 2015 All rights reserved iiiContents PageBS ISO 12208:2015ISO 12208:2015(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of nat
11、ional 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. Interna
12、tional 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 inten
13、ded 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.
14、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 w
15、ill 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 expr
16、essions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee responsible for this document is ISO/TC 20, Aircraft and space vehicles, Subco
17、mmittee SC 14, Space systems and operations.This first edition of ISO 12208 cancels and replaces ISO/TS 12208:2011.iv ISO 2015 All rights reservedBS ISO 12208:2015ISO 12208:2015(E)IntroductionThis International Standard is intended for use in the engineering community.It is well known that solar ene
18、rgetic 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 c
19、omponents 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 spacecrafts long mission life in geosynchronous earth orbit (GEO). Therefore, an estimation of SEP fluences in
20、 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 th
21、e 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 spacecraf
22、t 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 vBS ISO 12208:2015BS ISO 12208:2015Space systems Space environment (natural and artificial) Observed proton fluences over long durati
23、on at GEO and guidelines for selection of confidence level in statistical model of solar proton fluences1 ScopeThis 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
24、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 t
25、he 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 definitionsFor
26、the purposes of this document, the following terms and definitions apply.2.1confidence levellevel used to indicate the reliability of a cumulative fluence estimation2.2extremely rare eventsolar energetic proton (SEP) event that occurs about once in a solar cycle and whose fluence dominates that for
27、the entire cycleNote 1 to entry: Examples are those which took place in August 1972, October 1989 and July 2000.2.3fluxnumber of particles passing through a specific unit area per unit time2.4fluencetime-integrated flux2.5n-year fluencefluence during a mission of n years durationINTERNATIONAL STANDA
28、RD ISO 12208:2015(E) ISO 2015 All rights reserved 1BS ISO 12208:2015ISO 12208:2015(E)3 Symbols and abbreviated termsEOL end of lifeESA European Space AgencyJPL Jet Propulsion LaboratoryMETEOSAT Meteorological SatelliteGEO Geosynchronous Earth OrbitGMS Geosynchronous Meteorological SatelliteGOES Geos
29、tationary Operational Environmental SatelliteRDC relative damage coefficientsSEP solar energetic protonSSN sun spot number4 Principles of the method (see Reference 3)4.1 Cumulative fluenceThe n-year fluence for a given mission life of n-years is shown in Figure 1 and estimated as follows.a) The n-ye
30、ar fluence is calculated by integrating observed daily fluences for n-years from archives. The start day for integration is January 1stin the first year (defined as A). The integration windows are shifted each day from January 2ndin the first year to December 31 in n-years later (defined as B, C . Z
31、). 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, Fmax(t), for the n-year mission life is obtained. Maximum fluence of an n-year mission is calculated using Formula (1):Ft()=()maxA, B, C Z (1)d
32、ata periodBACZtFigure 1 Cumulative fluencies (the data period is larger than 1,2 solar cycle)2 ISO 2015 All rights reservedBS ISO 12208:2015ISO 12208:2015(E)4.2 Confidence levelThe confidence level for a given mission duration of n-years is shown in Figure 2 and estimated as follows.a) A set of n-ye
33、ar fluences is made by integrating proton flux data while shifting the integration window daily.b) Occurrence distribution, f(F), of the data set of fluences, F, is built. The occurrence distribution of fluences is defined as the histogram of fluences F.c) Distribution is normalized to have unity wh
34、en integrated over maximum fluence, Fmax.d) Distribution from 0 to F is integrated to obtain the confidence level, p, for an n-year mission life.NOTE The confidence level reaches 100 % because this method does not include extremely rare events that did not happen during the period.KeyX fluence, FY1
35、occurrenceY2 confidence level, pFigure 2 Confidence level4.3 Archives of observed energetic protons in GEOThe following are examples of archives and their longitudes in GEO:a) GMS (E140);b) METEOSAT (E63, E0); https:/www.spenvis.oma.be/intro.php (European Space Agency,SPENVIS);c) GOES (W75, W135); h
36、ttp:/spidr.ngdc.noaa.gov/spidr/ (National Ocean and Atmospheric Administration).4.4 RemarksIf it is necessary to adjust the magnitude and probability to exceeding the given estimates (the biggest event on September to October 1989 events which is included in this IS), the historical analyses results
37、 described in References 1 and 2 may be used. ISO 2015 All rights reserved 3BS ISO 12208:2015ISO 12208:2015(E)5 Guidelines for selection of a confidence level in a statistical model of solar proton fluencesSelect the confidence level as follows:a) predict solar proton fluences using the confidence l
38、evel of a statistical model;b) estimate cumulative fluence with the method in 4.1;c) select a confidence level in 4.2 a) that will not exceed 4.2 d).4 ISO 2015 All rights reservedBS ISO 12208:2015ISO 12208:2015(E)Annex A (informative) Example of estimation and selectionA.1 Background informationDesi
39、gn of a solar panel is mainly limited by the end-of-life (EOL) output power, i.e. an estimation of the predicted radiation environment during mission life. Therefore, the radiation environment itself and estimation of the radiation environment are essential.The radiation environment consists of elec
40、trons and protons that affect the solar panel. In GEO, trapped electrons and solar energetic protons are the main factors. Trapped electrons are generally in a steady state and are easy to estimate. However, solar energetic protons are very intense and occur randomly, making them hard to estimate.A
41、solar panel is comprised of a panel, solar cells and a cover glass that acts as a shield against the radiation environment and is generally about 100 microns thick. With this cover glass, cosmic rays, especially proton energy, are attenuated, and low-energy protons are stopped within the cover glass
42、, never reaching the solar cell. When degradation is estimated, attenuation by the cover glass is obviously included.A.2 Degradation of solar cells by radiationA.2.1 Mechanism of degradationHigh-energy charged particles (namely electrons or protons) penetrate solar cells while losing energy. They da
43、mage solar cells uniformly along a direction of thickness. At this time, cosmic rays cause an elastic/non-elastic collision with the atoms of single-crystal solar cells, which, in turn, causes a lattice defect. Due to this defect, the characteristics of solar cells, short-circuit currents (Isc), ope
44、n-circuit voltage (Voc), and maximum power (Pmax) are degraded. The mechanism of degradation is called displacement damage, which is the same as bulk damage in semiconductor devices such as bipolar semiconductors.A.2.2 Method of degradation estimation (relative damage coefficients method)The JPL han
45、dbook4adopts the relative damage coefficients method, i.e. accumulated electron and proton fluences during the mission period are converted into numbers of 1-MeV electrons that damage equivalently, then degradation of the solar cells with these numbers of 1-MeV electrons is estimated.Relative damage
46、 coefficients are obtained by measuring the degradation of solar cells caused by particles (electrons and protons) of various types of energy.The parameters needed to estimate degradation are (1) energy dependence of degradation by electrons and protons, and (2) ratio of electron and proton degradat
47、ion.The basis for degradation parameters is normalized fluence dependence of characteristics of solar cell parameters.First, the normalized fluence dependence of characteristics is obtained from ground experiments of various types of electron and proton energy. The experimental data are fitted to em
48、pirical curves. From the curve data, fluence that gives the same degradation is obtained for each type of energy and particles. These fluences are normalized to 10 MeV for protons and to 1 MeV for electrons. These normalized values are called relative damage coefficients and are used as an index for
49、 the degree of degradation of solar cells. ISO 2015 All rights reserved 5BS ISO 12208:2015ISO 12208:2015(E)Next, empirical curves of 10-MeV protons and 1-MeV electrons provide the ratio (conversion factor) of 10-MeV protons to 1-MeV electrons.A.3 Estimation of solar cell degradation in GEOA.3.1 Step 1: Radiation sources in GEO and prediction of their fluencesA multi-junction solar cell, which is commonly employed today with a cover glass of 100 microns, shown in Figure A.1, degrades mainly by 3-MeV to 10-MeV proto
