ISO 21494:2019

INTERNATIONAL ISO
STANDARD 21494
First edition
2019-02
Space systems — Magnetic testing
Systèmes spatiaux — Essais magnétiques
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 3
5 Requirements . 3
5.1 EUT requirements . 3
5.2 Test requirements . 4
6 Test items . 4
7 Test room environments . 5
8 Magnetic field test methods . 5
8.1 Test purpose . 5
8.2 Test facilities. 5
8.3 Procedures for magnetic field test . 6
9 Magnetic moment test methods . 6
9.1 Test purpose . 6
9.2 Test facilities. 6
9.3 Procedures and calculating formulas for magnetic moment test . 7
9.4 Magnetic moment test in the geomagnetic field . 7
10 Magnetization and demagnetization test methods . 7
10.1 Test purpose . 7
10.2 Test facilities. 7
10.3 Procedures for magnetization and demagnetization test . 8
11 Magnetic compensation test method . 8
11.1 Test purpose . 8
11.2 Procedures for magnetic compensation test . 9
12 Test report . 9
Annex A (informative) Procedures for a magnetic field test .10
Annex B (informative) Procedures and calculating formulas for a magnetic moment test .13
Annex C (informative) Procedures for a magnetization and demagnetization test .24
Annex D (informative) Procedures for a magnetic compensation test .26
Bibliography .27
Foreword
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This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles,
Subcommittee SC 14, Space systems and operations.
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iv © ISO 2019 – All rights reserved

Introduction
The magnetic torque, which is created by the interaction between a geomagnetic field and the remnant
magnetic moment of the spacecraft, has considerable disturbance on the flight attitude of the spacecraft.
The magnetic field of the spacecraft itself will affect a magnetometer scientific payload sensitive to
spacecraft-induced magnetic fields. Thus, magnetic tests on Earth-orbiting or interplanetary spacecraft
missions with very stringent requirements on magnetic cleanliness are needed in order to ensure that
the spacecraft’s inherent magnetic properties meet the design goals.
This document provides magnetic test requirements and methods for measuring and evaluating
magnetic properties of the spacecraft. The magnetic test methods outlined in this requirements
document are effective enough to verify the compliance of magnetic requirements imposed on the
spacecraft and to ensure the success of spacecraft flight missions free of magnetic interference and
magnetic contamination due to magnetic materials and induced current-generated magnetic fields of
the spacecraft.
INTERNATIONAL STANDARD ISO 21494:2019(E)
Space systems — Magnetic testing
1 Scope
This document specifies magnetic test methods including magnetic field test methods, magnetic
moment test methods, magnetization and demagnetization test methods and magnetic compensation
test methods. This document is applicable to magnetic tests on several levels: spacecraft-level,
subsystem-level and unit-level.
This document gives guidelines for conducting magnetic tests both in zero-magnetic field environment
provided by magnetic test facilities and in the presence of the geomagnetic field environment.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 14644-1, Cleanrooms and associated controlled environments — Part 1: Classification of air cleanliness
by particle concentration
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
3.1
equipment under test
EUT
object under the magnetic test on system, subsystem or unit level generally
3.2
remnant magnetic moment
magnetic moment of the EUT in a zero-magnetic field environment when the EUT is not in a powered on
operational mode, that is mostly due to the residual magnetic fields from spacecraft materials
3.3
stray magnetic moment
magnetic moment of the EUT in zero-magnetic field environment when the EUT is in a powered on
operational mode
3.4
induced magnetic moment
additional magnetic moment of the EUT generated in an external magnetic field environment when the
EUT is not in a powered on operational mode, that is mostly due to soft magnetic materials that easily
magnetize in an external magnetic field
3.5
remnant magnetic field
magnetic field produced by the remnant magnetic moment of the EUT as measured at a distance from
the magnetic moment location and falls off as the inverse cube of the distance from the magnetic
moment location
3.6
stray magnetic field
magnetic field produced by the stray magnetic moment of the EUT in a powered on operational mode
3.7
induced magnetic field
magnetic field produced by the induced magnetic moment of the EUT and mostly due to soft magnetic
materials that easily magnetize in an external magnetic field
3.8
zero-magnetic field
magnetic field within a certain volume reduced to very low levels when the geomagnetic field is
compensated by a cancelling magnetic field provided by a typical main coil system such as a Helmholtz
coil or Braunbeck coil system
3.9
controllable magnetic field
magnitude of magnetic field within a certain volume that is controlled by adjusting electric current of a
typical main coil system such as a Helmholtz coil or Braunbeck coil system
3.10
magnetization field
magnetic field used for magnetization tests of the EUT when exposed to a uniform and steady magnetic
field for a certain period of time and provided by a magnetization and demagnetization coil system
3.11
demagnetization field
magnetic field used for demagnetization tests of the EUT by exposing them in an alternating sinusoidal
magnetic field with a continuously attenuated amplitude and provided by a magnetization and
demagnetization coil system
3.12
main coil system
coil system, usually composed of Helmholtz or Braunbeck coils and energized by power supplies, that
can provide a zero-magnetic field environment within
...