ISO 16378:2022

Space systems - Measurements of thermo-optical properties of thermal control materials

This document specifies the multiple measurement methods, instruments, equipment, and samples used to calculate the thermo-optical properties of thermal control materials. This document compares their features, indicates their limitations and biases, and guides the applications. This document also defines requirements for calibration and reference materials to ensure data quality. This document specifies the following test methods, including the configuration of samples and calculations. a) Solar absorptance using a spectrophotometer (αs) - Annex A. b) Solar absorptance using the comparative test method (αp) - Annex B. c) Hemispherical infrared emittance using the thermal test method (εh-t) - Annex C. d) Normal infrared emittance using an IR spectrometer (εn-s) - Annex D. e) Normal infrared emittance using ellipsoid collector optics (εn-e) - Annex E. f) Normal infrared emittance using two rotating cavities (εn-c) - Annex F.

Systèmes spatiaux — Mesures des propriétés thermo-optiques des matériaux de thermorégulation

General Information

• Status: Published
• Publication Date: 20-Sep-2022
• 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 6 - Materials and processes
• Current Stage: 6060 - International Standard published
• Start Date: 21-Sep-2022
• Due Date: 11-Oct-2022
• Completion Date: 21-Sep-2022

Relations

• Revises: ISO 16378:2013 - Space systems - Measurements of thermo-optical properties of thermal control materials
• Effective Date: 23-Apr-2020

Overview

ISO 16378:2022 - Space systems - Measurements of thermo‑optical properties of thermal control materials - defines standardized methods for measuring the thermo‑optical properties (solar absorptance and infrared emittance) of materials used in spacecraft thermal control. The standard specifies multiple test methods, required sample configurations, instruments, calibration and reference material requirements, and guidance on limitations, biases and data quality to ensure reliable ground‑based material property data for thermal design and verification.

Key topics and requirements

• Measured properties
  • Solar absorptance (αs, αp) - two approaches: spectrophotometer method (Annex A) and comparative test method (Annex B).
  • Infrared emittance - hemispherical thermal method (εh‑t, Annex C) and normal emittance methods using an IR spectrometer (εn‑s, Annex D), ellipsoid collector optics (εn‑e, Annex E), and two rotating cavities (εn‑c, Annex F).
• Sample preparation and handling
  • Defined sample properties, thickness and configuration, cleaning, handling, storage and identification requirements to reduce measurement variability.
• Facilities and equipment
  • Environmental, cleanliness and equipment specifications for valid measurements.
• Calibration and reference materials
  • Requirements for reference standards and working standards to achieve traceability and data comparability.
• Data quality and reporting
  • Mandatory content for test reports (identification, measurement conditions, results), uncertainty evaluation, precision, and non‑conformance handling.
• Quality assurance and audit
  • Procedures for calibration, traceability, uncertainty estimation and periodic audits/acceptance tests of measurement systems.

Applications and who uses it

• Who uses ISO 16378
  • Spacecraft thermal engineers, materials scientists, test laboratories, quality assurance teams, suppliers of thermal control coatings and multi‑layer insulation (MLI), and certification bodies.
• Practical uses
  • Material selection and qualification for spacecraft thermal control.
  • Input properties for thermal models and on‑ground to on‑orbit performance comparisons.
  • Process control and production quality assurance of thermal coatings and surface finishes.
  • Establishing traceable datasets for beginning‑of‑life thermal performance assessments.

Related standards

• ISO 16378 complements other space and radiometric standards that cover terminology, blackbody radiation and uncertainty/traceability practices (see ISO Online Browsing Platform for linked references). For spectral and radiometric definitions refer to ISO 80000 series and ISO 9288 where applicable.

Keywords: ISO 16378:2022, thermo‑optical properties, thermal control materials, solar absorptance, infrared emittance, space systems, calibration, traceability, spectrophotometer, IR spectrometer.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 16378
Second edition
2022-09
Space systems — Measurements of
thermo-optical properties of thermal
control materials
Systèmes spatiaux — Mesures des propriétés thermo-optiques des
matériaux de thermorégulation
Reference number
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 5
5 Preparatory conditions .5
5.1 Hazards, health, and safety precautions . 5
5.2 Preparation of samples . 5
5.2.1 Sample property . 5
5.2.2 Configuration . 5
5.2.3 Cleaning . 6
5.2.4 Handling and storage . 6
5.2.5 Identification . 6
5.3 Facilities . 6
5.3.1 Cleanliness . 6
5.3.2 Environmental conditions . 6
5.3.3 Equipment . 6
5.4 Standard materials . 6
5.4.1 General . 6
5.4.2 Reference standard material . 7
5.4.3 Working standard material . 7
5.4.4 Solar absorptance . 7
5.4.5 Infrared emittance . 7
6 Solar absorptance (α ) test methods . 7
s
7 Hemispherical infrared emittance (ε ) test method . 8
h
8 Normal infrared emittance (ε ) test methods . 8
n
9 Test report . 9
9.1 Standard tests . 9
9.1.1 Complete identification of the material tested . 9
9.1.2 Complete identification of the measurement condition . 9
9.1.3 Measurement results . 10
9.2 Non-standard tests . 10
10 Quality assurance .10
10.1 Precision . . . 10
10.2 Non-conformance . . 11
10.3 Calibration . 11
10.4 Traceability . 11
10.5 Uncertainty . 11
11 Audit of measurement equipment .11
11.1 General . 11
11.2 Initial audit of the system (acceptance) . 11
11.3 Annual regular review (maintenance) of the system. 11
11.4 Special review . 12
Annex A (normative) Solar absorptance using a spectrophotometer (α ) .13
s
Annex B (normative) Solar absorptance using the comparative test method (α ) .18
p
Annex C (normative) Hemispherical infrared emittance using the thermal test method (ε ) .20
h-t
Annex D (normative) Normal infrared emittance using an IR spectrometer (ε ) .24
n-s
iii
Annex E (normative) Normal infrared emittance using ellipsoid collector optics (ε ) .27
n-e
Annex F (normative) Normal infrared emittance using two rotating cavities (ε ) .32
n-c
Annex G (informative) Key parameters for measurement.35
Annex H (informative) Theoretical directional emissivity .36
Bibliography .37
iv
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.
This second edition cancels and replaces the first edition (ISO 16378:2013), which has been technically
revised.
The main changes are as follows:
— updated terms and definitions according to the referenced document revision;
— revised description of sample thickness precision requirements;
— deleted solar absorptance measurement with central sample mounting sphere.
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.
v
Introduction
Solar absorptance and infrared emittance are the key parameters of materials for both active and
passive thermal design of space systems.
This document describes the methodology, instruments, equipment, and samples used to calculate the
key parameters of thermal-control materials, i.e. solar absorptance (α or α ) and the infrared emittance
s p
(ε or ε ). The measurements defined in this document are performed at ground test facilities with the
h n
purpose of obtaining material properties. The measured properties are used for material selection,
thermal design of spacecraft, process control, quality control, etc. Also, on-orbit temperature data in
the beginning of life can be assessed using the data obtained by ground measurement.
vi
INTERNATIONAL STANDARD ISO 16378:2022(E)
Space systems — Measurements of thermo-optical
properties of thermal control materials
1 Scope
This document specifies the multiple measurement methods, instruments, equipment, and samples
used to calculate the thermo-optical properties of thermal control materials. This document compares
their features, indicates their limitations and biases, and guides the applications. This document also
defines requirements for calibration and reference materials to ensure data quality.
This document specifies the following test methods, including the configuration of samples and
calculations.
a) Solar absorptance using a spectrophotometer (α ) — Annex A.
s
b) Solar absorptance using the comparative test method (α ) — Annex B.
p
c) Hemispherical infrared emittance using the thermal test method (ε ) — Annex C.
h-t
d) Normal infrared emittance using an IR spectrometer (ε ) — Annex D.
n-s
e) Normal infrared emittance using ellipsoid collector optics (ε ) — Annex E.
n-e
f) Normal infrared emittance using two rotating cavities (ε ) — Annex F.
n-c
2 Normative references
There are no normative references in this document.
3 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
absorptance
α
quotient of absorbed radiant flux (3.8) and incident radiant flux, expressed by
α = Φ /Φ
a m
where Φ is absorbed radiant flux and Φ is incident radiant flux
a m
[SOURCE: ISO 80000-7:2019, 7-31.1]
3.2
emittance
ε
quotient of the radiant exitance of a radiator and the radiant exitance of a Planckian radiator at the
same temperature, expressed by
ε = M/M
b
where M is the radiant exitance of a thermal radiator and M is the radiant exitance of a Planckian
b
radiator at the same temperature
EXAMPLE Total hemispherical emittance.
Note 1 to entry: Total hemispherical exitance M of the considered surface divided by the total hemispherical
exitance M of the blackbody at the same temperature (see ISO 9288).
Note 2 to entry: The following adjectives should be added to define the conditions.
— Total: If they are related to the entire spectrum of thermal radiation (this designation can be considered as
implicit) (see ISO 9288).
— Spectral or monochromatic: If they are related to a spectral interval centred on the wavelength λ (see
ISO 9288).
— Hemispherical: If they are related to all directions along which a surface element can emit or receive radiation
(see ISO 9288).
— Directional: If they are related to the directions of propagation defined by a solid angle around the defined
direction (see ISO 9288).
— Normal: If they are related to the normal direction of propagation or incidence to the surface.
Note 3 to entry: When there is a certain need to distinguish a property of a material from a property of a real
object, the word “emissivity” can be used. Emissivity is a property of a material defined in terms of the emittance
of an ideal material that is semi-infinite medium limited by optically smooth surface. Annex H provides further
information about theoretical emissivity and practical emittance.
Emissivity depends on the temperature at which it is determined and wavelength range.
Emittance is a property of a particular object. It is determined by material emissivity, surface roughness,
oxidation, the sample’s thermal and mechanical history, surface finish, and measured wavelength range.
Although emissivity is a major component in determining emittance, the emissivity determined under laboratory
conditions seldom agrees with actual emittance of a certain sample.
∞∞
ελ= LT,/ελ dLλλ,Tdλ
() () ()
bb
∫∫
where
−1
−5 CT/λ
L (λ,T)
b is the spectral Planck distribution of blackbody radiation, C λ e −1 ;
()
–16 2
C is 3,741 77 × 10 W·m ;
–2
C is 1,438 8 × 10 m·K;
T is the absolute temperature, K;
λ is the wavelength, m;
∞
–1 4
σπ T ;
LT()λλ, d
b
∫
–8 -2 -4
σ is the Stefan-Boltzmann constant, 5,670 400 (40) × 10 W·m ·K .
[SOURCE: ISO 80000-7:2019, 7-30.1, modified — The term has been changed to "emittance"; the
EXAMPLE and notes to entry have been added.]
3.3
diffuse
indicating that flux propagates in many directions, as opposed to direct beam, which refers to a
collimated flux
Note 1 to entry: When referring to reflectance (3.9), diffuse reflectance is the ratio of the diffusely reflected part
of the (whole) reflected flux to the incident flux.
3.4
infrared emittance
emittance (3.2) in the infrared range at least from 5 μm to 25 μm
3.5
integrating sphere
optical device, which is used to either get flux proportional to that reflected or transmitted from a
sample into a hemisphere or to provide uniform irradiation of a sample from the whole hemisphere
Note 1 to entry: It consists of a cavity with apertures for admitting and detecting flux and usually having
additional apertures over which sample and reference specimens are placed.
3.6
irradiance
E
e
density of incident radiant flux (3.8) with respect to area at a point on a real or imaginary surface,
expressed by
E = dΦ /dA
e e
where Φ is radiant flux and A is area (see ISO 80000-3) on which the radiant flux is incident
e
Note 1 to entry: It is expressed in W/m .
[SOURCE: ISO 80000-7:2019, 7-7.1, modified — Note 1 to entry has been added.]
3.7
near-normal-hemispherical
indicating irradiance (3.6) to be directional near-normal to the specimen surface and that the flux
leaving the surface or medium is collected over an entire hemisphere for detection
3.8
radiant flux
Φ
e
change in radiant energy with time, expressed by
Φ = dQ /dt
e e
where Q is the radiant energy emitted, transferred, or received and t is time(ISO 80000-3)
e
Note 1 to entry: It is expressed in W.
[SOURCE: ISO 80000-7:2019, 7-4.1, modified — The alternative term "radiant power" has been removed;
note 1 to entry has been added.]
3.9
reflectance
ρ
quotient of reflected radiant flux (3.8) and incident radiant flux, expressed by
ρ = Φ /Φ
r m
where Φ is reflected radiant flux and Φ is incident radiant flux
r m
[SOURCE: ISO 80000-7:2019, 7-31.3]
3.10
solar
indicating that the radiant flux involved has the Sun as its source or has the relative
spectral distribution of solar flux
Note 1 to entry: The adjective “solar” is used for optical field as indicating a weighted average of the spectral
property, with a standard solar spectral irradiance (3.6) distribution as the weighting function.
3.12
solar absorptance
α
s
ratio of the solar (3.10) radiant flux (3.8) absorbed by a material (or body) to the radiant flux of the
incident radiation
Note 1 to entry: Differentiation is made between two methods:
a) Method of spectral measurements using a spectrophotometer covering the range from 250 nm to 2 500 nm
for the determination of α . In this case a weighted mean value of spectral characteristics with standard
s
spectral distribution of solar irradiation as a weighting function is calculated.
b) Method of α measurements using the tools which measure integral reflection factor by using a comparison
p
method. In this case a portable equipment is used which has a source of irradiation with spectral distribution
near to solar spectral distribution or when the registration is performed by using spectral correcting
elements, which can simulate registration of solar irradiation flux.
3.13
solar irradiance
radiation of the Sun integrated over the full disk and expressed in SI units of power through a unit of
-2
area, W·m
[SOURCE: ISO 21348:2007, 7-4.1, modified — Note 1 to entry has been removed.]
3.14
spectral
indicating that the property was evaluated at a specific wavelength, λ, within a small wavelength
interval, Δλ about λ
Note 1 to entry: The parameters of frequency, ν, wave number, κ, or photon energy can be substituted for
wavelength, λ, in this definition.
Note 2 to entry: At a specific wavelength, the wavelength at which the spectral concentration was evaluated can
be indicated by the wavelength in parentheses following the symbol, such as α (350 nm), or as a function of the
s
wavelength, such as α (λ).
s
3.16
specular
indicating that the flux leaves a surface or medium at an angle that is numerically equal to the angle of
incidence, lies in the same plane as the incident ray and the perpendicular, but is on the opposite side of
the perpendicular to the surface
Note 1 to entry: Reversing the order of terms in an adjective reverses the geometry of the incident and collected
flux, respectively.
3.17
transmittance
τ
quotient of transmitted radiant flux (3.8) and incident radiant flux, expressed by
τ = Φ /Φ
t m
where Φ is transmitted radiant flux and Φ is incident radiant flux
t m
[SOURCE: ISO 80000-7:2019, 7-31.5]
4 Abbreviated terms
IR infra-red
RT room temperature
5 Preparatory conditions
5.1 Hazards, health, and safety precautions
Attention shall be given to health and safety precautions. Hazards to personnel, equipment, and
materials shall be controlled and minimized.
5.2 Preparation of samples
5.2.1 Sample property
This document is applicable to materials having both specular and diffuse optical properties.
5.2.2 Configuration
The material samples shall be prepared according to the relevant process specification or manufacturer’s
data and shall be representative of batch variance.
The samples shall represent the work piece as exactly as possible. Expected changes in thermo-optical
properties from the measured sample to the flight equipment shall be considered in thermal design.
For instance, the application procedure for paint can result in different thermo-optical properties
depending on the painter and the type of spray gun used; therefore, the samples should be coated or
made at the same time as the work piece.
The surface roughness strongly affects the measurement results. Bare (uncoated) samples shall be
finished to the same surface condition as the work piece.
5.2.3 Cleaning
The cleaning method and other treatment of the sample shall always be the same as for the flight
hardware. Further cleaning or treatment of the sample is not allowed.
In particular, solar absorptance properties are very sensitive to contamination and if the sample or the
flight hardware is contaminated (even by hand grease), the test results can be significantly in error.
5.2.4 Handling and storage
Samples shall only be handled with clean nylon or lint-free gloves and shall be stored in a cleanliness-
controlled area, with a room temperature of 15 °C to 30 °C and a relative humidity of 20 % to 65 %.
Care should be taken to prevent excessive change from storage condition to measurement condition.
a) Coated surfaces shall be shielded from contact by using soft and inert material such as polyethylene
or polypropylene bags or sheets.
b) Mechanical damage shall be avoided in the standard way by packing the wrapped samples in clean
and dust and lint-free material.
c) Limited-life materials shall be labelled with their relative shelf lives and dates of manufacture.
5.2.5 Identification
a) Samples submitted for testing shall be accompanied by a completed “Material identification card”.
b) Hazardous samples shall be accompanied by a completed “Safety data sheet”.
c) The surface of the samples which is to be measured shall be clearly indicated unless the samples
have completely even properties on both surfaces.
5.3 Facilities
5.3.1 Cleanliness
a) The work area shall be clean and free of dust.
b) Air used for ventilation should be filtered to prevent contamination of the sample.
5.3.2 Environmental conditions
The ambient conditions for the process and work areas shall be from 15 °C to 30 °C with a relative
humidity of 20 % to 65 % unless otherwise stated.
5.3.3 Equipment
The equipment is specific for each test and defined in the Annexes.
5.4 Standard materials
5.4.1 General
Both reference and working (comparison) standards are required. Highly durable materials are
preferred. Standard materials shall be handled and stored in accordance with the associated
specification. Avoid touching the optical surfaces even with gloves.
5.4.2 Reference standard material
Reference standards are the primary standard material for the calibration of instruments and working
standards. Reference standards shall be traceable to a national or an international authority having
jurisdiction.
5.4.3 Working standard material
Working standards are used in the daily operation of the instrument to provide comparison curves
for data reduction. A working standard shall be calibrated annually by measuring its thermo-optical
properties relative to the properties of the appropriate reference standard. If degradation is noticeable,
the working standard shall be cleaned, renewed or replaced.
5.4.4 Solar absorptance
For transmitting samples, incident radiation shall be used as the standard relative to which the
transmitted light is evaluated. For some applications, calibrated transmittance standards are available.
For diffuse high-reflectance samples, a working standard that has high reflectance and is highly
diffusing over the range of the solar spectrum is required.
NOTE 1 White diffuser is commonly used as a diffuse high-reflectance standard material. Various white
1)
diffusers are provided by a national or an international authority such as NIST. Spectralon® is a commercially
available material that provides high-diffuse reflectance for 250 nm to 2 500 nm. BaSO and magnesium oxide
have been widely utilized but are no longer recommended for use as a standard since they are not stable for
longer periods.
For specularly reflecting samples, a working standard that is highly specular is required. Identified
suitable working standards are vacuum-deposited thin opaque films of metals. All front surface
metalized working standards shall be calibrated frequently with an absolute reflectometer or relative
to a national or an international standard reference material before being acceptable in this test
method.
NOTE 2 Aluminium-coated glass mirror is widely used because of its high reflectance and ease of deposition.
Although bare aluminium surface is highly vulnerable, protective coating can maintain the optical property.
For absorber materials, a working standard that has low reflectance over the range of the solar
spectrum is required in order to obtain an accurate zero line correction.
5.4.5 Infrared emittance
A set of high- and low-emittance materials are often provided by the instrument manufacturer as
standard materials. Typical high- and low-emittance standards can consist of black paint (or preferably
a blackbody cavity) and polished high-purity aluminium, respectively.
6 Solar absorptance (α ) test methods
s
Two test methods are described in this clause.
Though α has slightly bigger standard deviations than α , both methods provide well-repeatable data to
p s
use in thermal design. Solar absorptance obtained by these two methods shall be clearly distinguished
by the terms α and α .
s p
a) Solar absorptance using a spectrophotometer (α )
s
1) Spectralon® is the trademark of a product supplied by Labsphere. This information is given for the convenience
of users of this document and does not constitute an endorsement by ISO of the product named. Equivalent products
may be used if they can be shown to lead to the same results.
This method covers the measurement of spectral absorptance (α ), reflectance and transmittance of
s
materials using spectrophotometers equipped with integrating spheres.
α shall be measured in accordance with the procedure defined in Annex A.
s
b) Solar absorptance using the comparative test method (α )
p
The comparative method (α ) compares the reflection of a Xenon flash by a known reference material
p
to the reflection of an unknown sample. This method has limitations due to the difference between a
Xenon flash spectrum and the solar spectrum.
α shall be measured in accordance with the procedure defined in Annex B.
p
7 Hemispherical infrared emittance (ε ) test method
h
A test method is described in this clause.
Hemispherical infrared emittance obtained by the thermal test method shall be clearly defined by the
term ε .
h-t
Only the thermal test method enables direct measurement. Although the thermal method requires
more time and effort, it is the fundamentally correct method to obtain total hemispherical infrared
emittance. ε of wider temperature samples are obtained solely by the thermal method.
h
ε shall be measured in accordance with the procedure defined in Annex C.
h-t
NOTE The method that measures total hemispherical reflectance as absorptance of materials using infrared
spectrophotometers equipped with integrating spheres is still under study. ASTM E1392–96 can be referred to
for the measurement method development.
8 Normal infrared emittance (ε ) test methods
n
Three test methods are described in this clause.
a) Normal infrared emittance using an IR spectrometer (ε )
n-s
The IR spectrometer method measures the normal reflectance as residue from unity minus emittance
of materials using infrared spectrophotometers equipped with integrating spheres. Normal infrared
emittance obtained using an IR spectrometer shall be identified by the term ε .
n-s
ε shall be measured in accordance with the procedure defined in Annex D.
n-s
b) Normal infrared emittance using ellipsoid collector optics (ε )
n-e
The test method using ellipsoid collector enables direct measurement without knowing the exact
sample temperature. The source beam is provided to the sample with a near-normal incident angle. The
ellipsoid collector focuses over 99 % of the hemispherical reflected energy onto the detector. Normal
infrared emittance obtained using an ellipsoid collector shall be identified by the term ε .
n-e
ε shall be measured in accordance with the procedure defined in Annex E.
n-e
c) Normal infrared emittance using two rotating cavities (ε )
n-c
This method measures reflected energy of the sample using two rotating cavities that are maintained
at different temperatures. Sample temperature is not necessarily measured. Suitable calibration
with known reflectance standards is required to obtain reflectance values on samples. Total normal
emittance is calculated by subtracting the calibrated reflectance from unity.
Measured data with two rotating cavities is limited in accuracy by the degree to which the emittance
properties of calibrating standards are known and by the angular emittance characteristics of the
[12]
surfaces being measured. At the interlaboratory test performed in 2007 , the two rotating cavities
provided relatively low emittance compared to the direct measurements. The maximum difference of
ε measured by the two method was greater than 0,1. Normal infrared emittance obtained using two
n
rotating cavities shall be identified by the term ε . Although many historical data have been obtained
n-c
by this method, it is recommended to use the other two methods instead.
ε shall be measured in accordance with the procedure defined in Annex F.
n-c
9 Test report
9.1 Standard tests
9.1.1 Complete identification of the material tested
The test report shall contain as a minimum the following:
a) trade names and batch numbers of the materials under test;
b) name of the manufacturer or supplier through whom the purchase was made;
c) summary of the preparation and conditioning schedule (e.g. mixing proportions, coating thickness,
cure time and temperature, post-cure, cleaning procedure);
d) sample size and thickness, coating thickness of layers if available, surface contour if any, description
of optical properties such as diffuse or specularly reflecting, clear or translucent transmitting;
e) properties of the substrate when the material is applied on (e.g. trade name, material, thickness).
9.1.2 Complete identification of the measurement condition
The test report shall contain as a minimum the following:
a) utilized measurement method;
b) date and time the measurements were taken;
c) identification of the instrument used (manufacturer’s name and model number including
modifications and accessories is sufficient for a commercial instrument; other instruments shall be
described in detail including wavelength range and estimations of their accuracy; key accessories
information such as integrating sphere coating material and diameter, filter’s path band, shall be
included);
d) identification of the working standard materials used for calibration;
e) thermo-optical properties assumed for the working standard materials;
f) ambient temperature and related humidity;
g) sample temperature (RT or controlled certain temperature);
h) locations on the surface area at which measurements were performed (not applicable for small
individual test samples);
i) estimate precision (repeatability) and estimated accuracy reported as uncertainty due to bias; the
accuracy and precision shall be reported in the same units as the optical property itself;
j) any noticeable incident observed during the measurement shall be recorded;
k) the quality records (e.g. log sheets) shall be retained for at least 10 years or in accordance with
project contract requirements.
9.1.3 Measurement results
9.1.3.1 Solar optical properties
The test report shall contain as a minimum the following:
a) solar transmittance, absorptance, or reflectance, or all three, determined to the mean value of
minimum 3 repeated measurements up to 0,01 associated with their variation;
b) solar spectral irradiance source document or source data and weighting method used for
computation of the solar optical property.
9.1.3.2 Infrared optical properties
The test report shall contain as a minimum the following:
a) infrared emittance, absorptance, or transmittance, or all three, determined to the mean value of
minimum 3 repeated measurements up to 0,01 associated with their variation;
b) indicated meter reading (reflectance) for three successive measurements with their standard
deviation (not applicable for ε );
h-t
c) infrared emittance determined to the nearest 0,01 unit or 1 % obtained by subtracting an average
of the three reflectance values from one (not applicable for ε );
h-t
d) for samples with rough surface and/or inhomogeneous property, appropriate number of tests shall
be performed on multiple samples considering the sample condition (an average of the measured
values shall be reported with its standard deviation).
9.2 Non-standard tests
Measurement performed with any deviation from standard test conditions is considered as a
non-standard test. The test report shall clearly indicate all the deviation. Measured data shall be
distinguished from standard test data. It is recommended to note the assumed bias on the measurement
results caused by the deviations.
10 Quality assurance
10.1 Precision
The measurement precision for the key parameters shall be as follows:
a) solar absorptance measurement repeatability on the same point of a sample ±0,01 (non-dimension)
in repeated measurement data or 5 % of the mean measured value;
NOTE 1 0,1 % for spectrophotometer without integrating sphere; 0,5 % for spectrophotometer with
integrating sphere.
b) infrared emittance measurement repeatability on the same point of a sample ±0,01 (non-dimension)
in repeated measurement data or 5 % of the mean measured value;
NOTE 2 Random uncertainty of reflectance measurements performed by Labsphere, Inc. is 0,005 for the
spectral range (300 nm to 2 200 nm) and is equal to 0,02 over the spectral range (250 nm to 2 500 nm). (See
calibration certificate for Spectralon® reference.)
c) sample thickness: ±5 μm (sample thickness >10 μm);
d) sample thickness: ±0,5 μm (sample thickness <10 μm);
e) temperature: ±5 K.
10.2 Non-conformance
Any non-conformance that is observed in respect of the measurement procedure shall be resolved in
accordance with the quality assurance requirements.
10.3 Calibration
a) Each reference standard and piece of measuring equipment shall be calibrated according to the
equipment specific procedure.
b) Any suspected or actual equipment failure shall be recorded as a project non-conformance report
so that previous results can be examined to ascertain whether or not reinspection and retesting is
required.
c) The customer shall be notified of the non-conformance details.
10.4 Traceability
Traceability shall be maintained throughout the process from incoming inspection to final
measurements and calculations, including details of the test equipment and personnel employed in
performing the task.
10.5 Uncertainty
The measurement result contains uncertainties caused by multiple elements. The parameters which
affect the combined uncertainty are shown in Annex G.
11 Audit of measurement equipment
11.1 General
The thermo-optical property data from testing laboratories for the customer, obtained in the manner
laid down in this document, are only accepted for the customer if the testing laboratory is managed to
perform the relevant procedure in this document.
11.2 Initial audit of the system (acceptance)
a) Once a system has been built or purchased, it shall be audited by the customer’s product assurance
department before it can be accepted for running qualification or quality control tests on materials
for use in customer projects.
b) This initial audit shall, at least, consist of (but not necessarily be restricted to) an inspection of the
apparatus and associated equipment, the performance of a test on a defined set of materials, the
reporting of the non-conformance, and the audit findings.
11.3 Annual regular review (maintenance) of the system
a) Inspection of apparatus and associated equipment
b) Mutual comparability evaluation (testing)
c) Non-conformance
If the inspection of the system or the interlaboratory test shows a non-conformance with the applicable
audit specification of the customer or the acceptable limits of the test results, actions shall be
undertaken by the test house in order to determine the reasons for the non-conformance and a further
test shall be performed in accordance with 10.2 before a certificate of conformance is renewed.
d) Reporting of findings
1) A detailed written report of the result of the regular review shall be delivered to all participants
within six weeks after the end of the regular review or evaluation testing.
2) The certificate of conformance shall be renewed annually after a successful review.
11.4 Special review
a) All modifications of the apparatus or associated equipment shall be reported and, if deemed
necessary, be audited by the customer before utilization of the modified system for the customer’s
project.
b) Major modifications shall result in the retesting of apparatus as described in 10.2.
Annex A
(normative)
Solar absorptance using a spectrophotometer (α )
s
A.1 General
Solar absorptance is calculated using the absorption spectrum of the material over the region from
250 nm to 2 500 nm and this spectrum is then multiplied with the solar spectrum.
a) The absorption spectrum shall be measured using an integrating sphere.
b) Opaque samples shall be mounted on the wall of the integrating sphere.
c) Two measurements are required for transparent samples. Transmittance shall be measured
mounting the sample on the wall of the integrating sphere. Reflectance shall be measured with
central sample mounting.
d) For transmitting samples, incident radiation shall be used as the standard relative to which the
transmitted light is evaluated. For some applications, calibrated transmittance standards are
available.
NOTE A sphere with a sample holder on the sidewall can also be used. In this case, the reflectivity is
compared to a known standard (e.g. calibrated Al-mirror or calibrated Spectralon® standard).
Measurements of spectral near-normal-hemispherical transmittance (or reflectance) are made over the
spectral range from approximately 250 nm to 2 500 nm with an integrating sphere spectrophotometer.
The solar transmittance, reflectance, or absorptance is obtained by calculating a weighted average
with a standard solar spectral irradiance as the weighting function by either the weighted or selected
ordinate method.
A.2 Configuration of samples
The size of test specimens required depends on the dimensions of the integrating sphere. For wall-
mounted spheres, the specimen shall be large enough to fully cover the aperture of the sphere. If large
enough sample is not available, the test requester shall coordinate with test facility.
For example, when the aperture of the sphere was 15 mm × 15 mm, the sample shall be larger than
the 15 mm square regardless of its shape. Depending on the method and equipment used, these
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