ISO 17761:2015

INTERNATIONAL ISO
STANDARD 17761
First edition
2015-11-15
Space environment (natural and
artificial) — Model of high energy
radiation at low altitudes (300 km to
600 km)
Environnement spatial (naturel et artificiel) — Modèle de radiations
à énergie élevée à basses altitudes (300 km à 600 km)
Reference number
ISO 17761:2015(E)
©
ISO 2015

---------------------- Page: 1 ----------------------
ISO 17761:2015(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, Published in Switzerland
All 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. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 17761:2015(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2  Terms and definitions . 1
3 General concepts and assumptions . 2
Annex A (informative) Tables for proton and electron fluxes . 3
Bibliography . 6
© ISO 2015 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO 17761:2015(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.
iv © ISO 2015 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 17761:2015(E)

Introduction
The International Standard is intended for the estimation of high energy charged particle fluxes at
low altitudes (300 km to 600 km) in the Earth’s magnetosphere. Detailed information on high energy
charged particle fluxes is essential for developing spacecrafts and spacecraft equipment.
[1]
High energy galactic cosmic rays approaching the Earth interact with the atmosphere resulting
in a production of secondary particles. The flux of secondary particles is composed mainly by
electrons, protons, neutrons and gamma-rays which execute their trajectories in the Earth’s magnetic
[2]
field. An appreciable fraction of charged secondary particles with rigidity less than geomagnetic cut-
[3]
off can travel backward in space along the Earth’s magnetic field lines and can reach the satellite
altitudes forming a high energy radiation halo in the Earth vicinity. The other fraction of secondary
protons is trapped by geomagnetic field for years forming the inner radiation belt. These protons with
kinetic energies greater than some tens of MeV mainly originated from the β-decay of albedo neutrons
[4]
according to the so-called “Cosmic Ray Albedo Neutron Decay” (CRAND) mechanism. According
to this mechanism, the Earth is surrounded in its equatorial region by shaped ring of high radiation.
Because of a shift of geomagnetic dipole with respect to the Earth centre, in South Atlantic Anomaly
(SAA) trapped particles are observed at low altitudes approximately 300 km.
On the basis of the data primarily taken from mid-sixties to early seventies of the last century, the model
[4]
of the Earth’s trapped proton radiation has been provided by the NASA AP-8 models. Significant
improvements of radiation environment modelling in low Earth orbit (LEO) was carried out thanks
[5][6][7]
to data from satellite experiments, such as CRRES, SAMPEX/PET and the TIROS/NOAA series.
These models can be used for estimations of radiation environment for energies below ~100 МeV with
some procedures taking into account secular variations of the geomagnetic filed and drift of SAA for
current epoch (e.g. Reference [8]).
Modern, more accurate measurements of the high energy (Ekin above ~100 MeV) cosmic ray radiation
[9]
in LEO have been reported by the PAMELA mission. These new measurements including trapped
component and charged albedo components are the basis of this International Standard.
© ISO 2015 – All rights reserved v

---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD  ISO 17761:2015(E)
Space environment (natural and artificial) — Model of high
energy radiation at low altitudes (300 km to 600 km)
1 Scope
This International Standard describes the fluxes of charged particles for near-Earth space on base of
the PAMELA experiment data. This International Standard can be used to calculate fluxes of protons
with energy more than 100 MeV up to geomagnetic cut-off rigidity at low altitudes (300 km to 600 km).
The main goal of this International Standard is determining the impact of energetic charged particle
flux upon spacecraft instrumentation and astronauts.
2  Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
International Geomagnetic Reference Field model
IGRF model
[10]
geomagnetic reference field in the form of a series of spherical harmonic functions
Note 1 to entry: The International Association of Geomagnetism and Aeronomy (IAGA) is responsible for IGRF
[10]
model development and modifications and approves its coefficients every five years.
2.2
particle magnetic rigidity
magnetic rigidity of particle, R, is related to particle momentum, p, and its charge, Z, by:
R = pc/Z
[3]
where c is the speed of light.
2.3
cut-off rigidity
location of a transition for primary charged cosmic ray particles, in rigidity space, from allowed to
[3]
forbidden trajectories as rigidity is decreased
2.4
geomagnetic coordinates L and B
used to map differential fluxes j of energetic geomagnetically trapped particles
Note 1 to entry: B is absolute value of geomagnetic field in the point of observation. In the dipole approximation
of the geomagnetic field, L-shell is distance to magnetic field line in equatorial plane.
[11]
Note 2 to entry: Geomagnetic coordinates L-shell and B are introduced by MacIlwain.
2.5
Albedo trapped particles
part of cosmic ray charged radiation with rigidity below geomagnetic cut-off produced in interactions
of high energy cosmic rays with residual atmosphere of the Earth which execute their trajectories in
the Earth magnetic field
© ISO 2015 – All rights reserved 1

---------------------- Page: 6 ----------------------
ISO 17761:2015(E)

3 General concepts and assumptions
This International
...