ISO 23129:2021

INTERNATIONAL ISO
STANDARD 23129
First edition
2021-09
Space systems — Thermal control
coatings for spacecraft — Atomic
oxygen protective coatings on
polyimide film
Systèmes spatiaux — Revêtements de contrôle thermique pour engins
spatiaux — Revêtements de protection contre l’oxygène atomique sur
film polyimide
Reference number
ISO 23129:2021(E)
©
ISO 2021

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ISO 23129:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
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ISO 23129:2021(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 3
4 General requirements and recommendations . 3
4.1 General . 3
4.2 Visual characteristics . 4
4.3 Coating thickness . 4
4.4 Thermo-optical properties . 4
4.5 Thermal vacuum stability . 4
4.6 AO resistance . 4
4.7 UV resistance . 5
4.8 Radiation resistance . 5
4.9 Adhesion . 5
4.10 Volume resistance . 5
4.11 Surface resistance . 5
4.12 Secondary electron emission yield . 5
4.13 Photoelectron emission yield . 5
4.14 Thermal cycling . 5
4.15 Repair/Retouch . 5
4.16 Cleaning . 5
5 Test methods . 6
5.1 General . 6
5.2 Visual inspection . 6
5.3 Coating thickness . 6
5.4 Thermo-optical properties . 6
5.5 Thermal vacuum stability . 7
5.6 AO resistance . 7
5.6.1 Product qualification test . 7
5.6.2 Life estimation test . 7
5.7 UV resistance . 7
5.7.1 Product qualification test . 7
5.7.2 Life estimation test . 8
5.8 Radiation resistance . 8
5.8.1 Product qualification test . 8
5.8.2 Life estimation test . 8
5.9 Adhesion . 8
5.10 Volume resistance . 9
5.11 Surface resistance . 9
5.12 Secondary electron emission yield . 9
5.13 Photoelectron emission yield . 9
5.14 Thermal cycling (influence of temperatures) .10
5.15 Repair/Retouch .10
5.16 Cleaning .10
6 Requirements and recommendations for application .10
6.1 Consideration for usage .10
6.2 Identification .11
6.3 Protectors .11
6.4 Packing .11
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ISO 23129:2021(E)

7 Production program of quality assurance .11
7.1 General .11
7.2 Changes and revisions .12
7.3 Record of changes . .12
Annex A (informative) Types of coatings .13
Annex B (informative) General properties of atomic oxygen protective coatings .14
Annex C (informative) Coatings selection guideline .16
Annex D (informative) Visual characteristics guideline .18
Bibliography .19
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ISO 23129:2021(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 of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles,
Subcommittee SC 14, Space systems and operations.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 23129:2021(E)

Introduction
This document describes technical information for the selection and application of atomic oxygen
protective coatings as required to confirm conformity with the requirements for the protection of
polyimide film.
Satellites in low Earth orbit are bombarded by high-energy radiation particles and gas particles such
as atomic oxygen (AO). In particular, AO corrodes certain materials, thereby weakening a spacecraft’s
exterior and potentially damaging its instruments. Polymers are significantly eroded.
Polyimide films are widely used as multilayer insulation materials on a spacecraft’s exterior, which
is exposed directly to the space environment. Despite these interesting properties, polyimide shows
poor resistance to AO. Therefore, polyimide is often coated with an additional protective coating for
resistance to AO. Such films have unique characteristics that are relevant for different applications.
This document summarizes the coating properties, as well as a comparison or consideration of the pros
and cons for selection.
This document provides a property map of the types of AO protective coatings available to spacecraft
designers and thermal control film manufacturers. It enhances coating selection, indicates selection
guidelines, and improves the reliability of spacecraft.
Requirements for coating properties and quality control are also defined, so as to eliminate defective
products, improve the quality and function of films, accelerate the exchange and distribution of coating
techniques, invite new providers to the market, introduce competition, and enhance international
trade.
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INTERNATIONAL STANDARD ISO 23129:2021(E)
Space systems — Thermal control coatings for spacecraft
— Atomic oxygen protective coatings on polyimide film
1 Scope
This document defines the general requirements for atomic oxygen (AO) protective coatings that
are applied on polyimide thermal control films. It also describes the different properties of coated
polyimide films such as indium tin oxide (ITO), SiO , germanium, and silicone, property measurement
x
test methods, and selection guidelines.
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 16378, Space systems — Measurements of thermo-optical properties of thermal control materials
ISO 27025:2010, Space systems — Programme management — Quality assurance requirements
ASTM D257, Standard Test Methods for DC Resistance or Conductance of Insulating Materials
ASTM E595, Standard Test Method for Total Mass Loss and Collected Volatile Condensable Materials from
Outgassing in a Vacuum Environment
ASTM E1559, Standard Test Method for Contamination Outgassing Characteristics of Spacecraft Materials
ECSS-ST-Q70-02, Thermal vacuum outgassing test for the screening of space materials
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
atomic oxygen
oxygen molecules separated by ultraviolet light from the sun, which are main atmospheric constituents
in the range of about 200 km to 700 km
Note 1 to entry: As a spacecraft orbits the Earth at high speed, atomic oxygen can collide with the spacecraft's
surface at high speed and degrade the surface material.
3.1.2
coating
continuous layer formed from a single or multiple application of a coating material (3.1.3) to a substrate
(3.1.8)
[SOURCE: ISO 4618:2014, 2.50.1, modified — "continuous" has been added at the beginning.]
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ISO 23129:2021(E)

3.1.3
coating material
product, in liquid, paste or powder form, that, when applied to a substrate (3.1.8), forms a film possessing
protective and/or other specific properties
Note 1 to entry: Coating materials are often applied using a chemical or plasma vapour deposition process from
solid source materials. General types of AO protective coatings (3.1.2) are listed in Annex A.
[SOURCE: ISO 4618:2014, 2.51, modified — "layer" has been replaced by "film"; "decorative" after
"protective" has been removed; the original note 1 to entry has been removed and replaced by a new
one.]
3.1.4
coating process
process of applying a coating material (3.1.3) to a substrate (3.1.8), such as dipping, spraying, roller
coating (3.1.2), and brushing
Note 1 to entry: A chemical or plasma vapour deposition process is also commonly applied.
3.1.5
emittance
emissivity
ε
ε = M/M
b
where
M is the radiant exitance of a thermal radiator;
M is the radiant exitance of a blackbody at the same temperature
b
Note 1 to entry: The following adjectives should be added to define the conditions (see ISO 9288):
— total: when related to the entire spectrum of thermal radiation (this designation can be considered as
implicit);
— spectral or monochromatic: when related to a spectral interval centred on wavelength λ;
— hemispherical: when related to all directions along which a surface element can emit or receive radiation.
— directional: when related to the directions of propagation defined by a solid angle around the defined
direction;
— normal: when related to the normal direction of propagation or incidence to the surface.
Note 2 to entry: See ISO 80000-7: 2019, item 7-30.1.
3.1.6
polyimide
generic name of a polymer that contains imide monomers
3.1.7
solar absorptance
α
s
ratio of the solar radiant flux absorbed by a material (or body) to the radiant flux of the incident
radiation
[SOURCE: ISO 16378:2013, 3.12, modified — Note 1 to entry has been removed.]
3.1.8
substrate
surface to which a coating material (3.1.3) is applied or is to be applied
[SOURCE: ISO 16691:2014, 3.1.14]
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ISO 23129:2021(E)

3.1.9
witness sample
sample pieces that represent the coated product
Note 1 to entry: These samples are made in the form of flat plates using the same coating material (3.1.3) as used
with the product, and then coated simultaneously. They are used for destructive tests and testing that requires a
limited specimen size.
[SOURCE: ISO 16691:2014, 3.1.17, modified — Note 1 to entry has been updated editorially.]
3.2 Abbreviated terms
This document uses the following abbreviated terms:
AO atomic oxygen
CVCM collected volatile condensable materials
CVD chemical vapor deposition
EB electron beam
EMI electromagnetic interference
EOL end-of-life
ESH equivalent solar hours
ITO indium tin oxide
LEO low Earth orbit
MLI multi layer insulation
RF radio frequency
RML recovered mass loss
TML total mass loss
UV ultraviolet
VUV vacuum ultraviolet
4 General requirements and recommendations
4.1 General
This clause defines the requirements and recommendations regarding the fundamental properties
of coated film. The related data and test methods are provided to the customer for spacecraft design.
Table 1 lists the general test provisions.
Table 1 — Overview of general test provisions
Tests Requirement Recommendation
Visual characteristics X
Coating thickness X
Thermo-optical properties X
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ISO 23129:2021(E)

Table 1 (continued)
Tests Requirement Recommendation
Thermal vacuum stability X
AO resistance X
UV resistance X
Radiation resistance X
Adhesion X
Volume resistance X
Surface resistance X
Secondary electron emission X
yield
Photoelectron emission yield X
Thermal cycling X
4.2 Visual characteristics
The coated film as received by the customer shall be smooth, continuous, free from delamination
within the coating, uniform in appearance, and free from imperfections detrimental to usage of the
coated film. Coated film shall be visually free from scratches, cracks, separation and any unallowable
discoloration. Annex D provides the guideline to a visual inspection.
4.3 Coating thickness
The coating thickness range shall be provided. The thickness of AO protective coating shall be within
the allowable range defined in the product specifications. Excessive thickness would cause cracks and/
or separation.
Base film with perforations is more vulnerable due to coating failure around the holes. Coating shall be
applied on the section edge of a perforation to prevent AO erosion. Annex B lists the typical values of
the general coating thickness of AO protective coatings.
4.4 Thermo-optical properties
The thermo-optical properties of coated film shall be submitted. Annex B lists the typical values of the
general properties of AO protective coatings.
AO, UV, and energetic particles can cause changes in thermo-optical properties. Any changes in the
thermo-optical properties of coated film shall be measured when requested by project. AO protection
coating shall not increase the magnitude of a change in base film properties.
4.5 Thermal vacuum stability
Effused gas from coated film under a vacuum condition shall be low. Annex B lists the typical values of
the general properties of AO protective coatings.
4.6 AO resistance
AO protective coating shall guard its base film up to a spacecraft’s EOL without any openings penetrating
the coating layer. Erosion of the base film due to cracks, separation, degradation and erosion of AO
protective coating shall not occur. Annex B lists the typical mass loss values after AO irradiation.
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ISO 23129:2021(E)

4.7 UV resistance
Coated film applied to the outer surface of a spacecraft is subject to strong UV rays. Thermo-optical
properties are degraded by UV. The thermo-optical properties of AO protective coating should be
maintained within the allowable range. Annex B lists the typical thermo-optical properties after UV
irradiation.
4.8 Radiation resistance
Coated film is subject to protons and electrons. Thermo-optical properties are degraded by radiation.
The thermo-optical properties of AO protective coating should be maintained within the allowable
range. Annex B lists the typical thermo-optical properties after radiation exposure.
4.9 Adhesion
AO protection coating should have no peeling after the tape stripping test as defined in Clause 5.
4.10 Volume resistance
AO protective coating should not increase volume resistance of the base film.
Coated film that can have an adverse effect on spacecraft systems and hardware due to their electrical
characteristics and properties shall be reviewed by EMI engineering for conformity with program
specifications, and specifically approved for use on the program.
4.11 Surface resistance
Surface resistance data shall be provided to the customer. Annex B lists the surface resistance values of
typical coated films.
Coated film that can have an adverse effect on spacecraft systems and hardware due to their electrical
characteristics and properties shall be reviewed by EMI engineering for conformity with program
specifications, and specifically approved for use on the program.
4.12 Secondary electron emission yield
Secondary electron emission yield data should be provided to the customer when requested.
4.13 Photoelectron emission yield
Secondary electron emission yield data should be provided to the customer when requested.
4.14 Thermal cycling
Coated film should function in the temperature range of -190 °C to +200 °C, unless otherwise stated in
the standard for each coated film.
4.15 Repair/Retouch
When the coated film is repairable, the coating supplier shall provide the repair/retouch procedure.
4.16 Cleaning
Coated film shall be easy for cleaning. The coating supplier shall provide the cleaning procedure,
including compatible cleaning agent and prohibited chemicals.
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ISO 23129:2021(E)

5 Test methods
5.1 General
Both reliability and quality are confirmed by testing in the production of AO protective coatings to be
applied on polyimide thermal control films.
In addition, the effects of the space environment largely depend on the spacecraft service conditions,
which are defined by the orbits where spacecraft are intended to operate. Especially for LEO spacecraft,
AO attacks and erodes the surface material of spacecraft. And there are also general factors that affect
spacecraft serviceability and efficiency, such as a vacuum, electromagnetic solar radiation (including
UV and VUV radiation), ionizing radiation, temperature, and the effects of a contaminated environment.
Therefore, such undesirable effects as electrostatic charging, generating a spacecraft outer atmosphere,
and alternating thermal loads can occur during operation.
5.2 Visual inspection
Coated film shall be subject to visual inspection with the naked eye and/or electronic magnification.
Witness samples approved by the manufacturer shall be used for any required comparison. The samples
shall be prepared from the materials and processes that are used in spacecraft.
The product is considered acceptable when there are no harmful disadvantages in its use. Annex D
provides the guideline to a visual inspection.
5.3 Coating thickness
The thickness of coated film or the coating itself shall be controlled in the product process. Data on
coating thickness and its measurement method shall be provided to the customer when requested.
5.4 Thermo-optical properties
a) The thermo-optical properties shall be measured before and after space environment resistance
tests.
b) Measurements shall be performed on the samples according to ISO 16378. Another measureme
...