ISO 24411:2022

Space systems — Micro-vibration testing

This document specifies requirements for the implementation of spacecraft level micro-vibration tests on space systems to be considered by test providers, including test designers and test engineers. It also gives guidance for spacecraft designers and interested parties. The spacecraft level micro-vibration test is applicable to space systems which contain payload equipment sensitive to the micro-vibration environment which only induced by the internal disturbance sources on-orbit, e.g. for the purpose of earth observation, space telescopes, optical experiments, telecommunication.

Systèmes spatiaux — Essais de microvibration

General Information

• Status: Published
• Publication Date: 09-Oct-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 2 - System requirements, verification and validation, interfaces, integration, and test
• Current Stage: 6060 - International Standard published
• Start Date: 10-Oct-2022
• Due Date: 10-Sep-2022
• Completion Date: 10-Oct-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 24411
First edition
2022-10
Space systems — Micro-vibration
testing
Systèmes spatiaux — Essais de microvibration
Reference number
ISO 24411:2022(E)
© ISO 2022
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ISO 24411:2022(E)
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© ISO 2022

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ISO 24411:2022(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction .............................................................................................................................................................................................................................. vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Symbols and abbreviated terms..........................................................................................................................................................2

5 Test purpose ............................................................................................................................................................................................................. 2

6 General test information ............................................................................................................................................................................. 3

6.1 Tailoring ....................................................................................................................................................................................................... 3

6.2 Disturbance sources .......................................................................................................................................................................... 3

6.3 Preliminary analysis ......................................................................................................................................................................... 3

7 Test equipment ......................................................................................................................................................................................................3

7.1 Test configuration for transfer function measurement and modal survey test .......................... 3

7.2 Test configuration for response measurement ......................................................................................................... 4

7.3 Test equipment functional requirements and recommendations ............................................................ 5

7.3.1 Boundary simulation ...................................................................................................................................................... 5

7.3.2 Excitation .................................................................................................................................................................................. 7

7.3.3 Measurement, data acquisition and processing ..................................................................................... 7

8 Test requirements and recommendations............................................................................................................................... 8

8.1 General test requirements and recommendations ................................................................................................ 8

8.1.1 General ........................................................................................................................................................................................ 8

8.1.2 Transfer function measurement........................................................................................................................... 9

8.1.3 Modal survey test .............................................................................................................................................................. 9

8.1.4 Micro-vibration response measurement ...................................................................................................... 9

8.2 Pre-conditions ...................................................................... ................................................................................................................... 9

8.3 Test article configuration.............................................................................................................................................................. 9

8.4 Test environment .............................................................................................................................................................................. 10

8.4.1 Laboratory environment requirements ..................................................................................................... 10

8.4.2 Background noise requirements ....................................................................................................................... 10

8.5 Measurement ........................................................................................................................................................................................ 10

8.6 Safety............................................................................................................................................................................................................ 10

9 Test flow and procedure ...........................................................................................................................................................................11

9.1 Test flow .................................................................................................................................................................................................... 11

9.2 Test procedure ..................................................................................................................................................................................... 11

9.2.1 General ..................................................................................................................................................................................... 11

9.2.2 Before the test .................................................................................................................................................................... 12

9.2.3 Test implementation ....................................................................................................................................................12

9.2.4 After the test ....................................................................................................................................................................... 14

10 Test interruption and handling ........................................................................................................................................................14

10.1 Test interruption ...................................................................... .......................................................................................................... 14

10.2 Interruption handling ................................................................................................................................................................... 14

11 Test data and result evaluation ........................................................................................................................................................14

11.1 Test data .................................................................................................................................................................................................... 14

11.2 Result evaluation ............................................................................................................................................................................... 15

12 Test report ...............................................................................................................................................................................................................15

Annex A (informative) Typical internal disturbance sources and characteristics ........................................16

Annex B (informative) Guideline of the necessity of spacecraft level micro-vibration test .................17

Annex C (informative) Suspension frequencies measurement ............................................................................................18

iii
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ISO 24411:2022(E)

Bibliography .............................................................................................................................................................................................................................22

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ISO 24411:2022(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.

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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 24411:2022(E)
Introduction

Spacecraft on-orbit experience a micro-vibration environment which can induce severe disturbances to

sensitive payload with high pointing stability and/or position stability. It can affect mission success of

payload equipment, e.g. earth observation, space telescopes, optical experiments, telecommunication.

For such applications, it is necessary to verify their resistance to the micro-vibration environment on-

orbit. This verification may be supported by spacecraft level micro-vibration tests on ground. In that

case:

— the vibration transmissibility from the disturbance sources to the sensitive payloads should be

investigated;

— the performance of these payloads under the influence of the relevant disturbance sources should

be identified by response measurements;

— the modal parameters of the spacecraft should be extracted to update the analysis model.

This document specifies contents to meet test requirements. It includes test purpose, general test

information, test equipment, test requirements and recommendations, test flow and procedure, test

interruption and handling, test data and result evaluation, and test reports for spacecraft level micro-

vibration tests.
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INTERNATIONAL STANDARD ISO 24411:2022(E)
Space systems — Micro-vibration testing
1 Scope

This document specifies requirements for the implementation of spacecraft level micro-vibration tests

on space systems to be considered by test providers, including test designers and test engineers. It also

gives guidance for spacecraft designers and interested parties.

The spacecraft level micro-vibration test is applicable to space systems which contain payload

equipment sensitive to the micro-vibration environment which only induced by the internal disturbance

sources on-orbit, e.g. for the purpose of earth observation, space telescopes, optical experiments,

telecommunication.
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 14620-1, Space systems — Safety requirements — Part 1: System safety

ISO 15864:2021, Space systems — General test methods for spacecraft, subsystems and units

ISO 17566:2011, Space systems — General test documentation
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
micro-vibration environment

dynamic environment on-orbit which is characterized by very low acceleration level compared with the

usual dynamic environment during launch

Note 1 to entry: Micro-vibration environment affects the normal performance or function of sensitive payload

equipment of the spacecraft on-orbit.

Note 2 to entry: Generally, the micro-vibration environment of the sensitive payload equipment on-orbit is in the

[1]

range of micro-g's to milli-g’s, and the frequency range is from a few hertz up to a few hundred hertz .

3.2
background noise
noise coming from sources other than the test signal
[SOURCE: ISO 13472-1:2022, 3.8]
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ISO 24411:2022(E)
3.3
signal-to-noise ratio
S/N

difference between the level of the nominal useful signal and the level of the background noise (3.2) at

the moment of detection of the useful event
Note 1 to entry: The signal-to-noise ratio is given in decibels.
[SOURCE: ISO 13472-1:2022, 3.9]
3.4
design safety factor

factor by which limit loads are multiplied in order to account for uncertainties and variations that

cannot be analysed or accounted for explicitly in a rational manner

Note 1 to entry: Design safety factor is sometimes referred to as design factor of safety, factor of safety or just

safety factor.
[SOURCE: ISO 10786:2011, 3.15]
4 Symbols and abbreviated terms
FFT fast Fourier transform
FM flight model
LoS line-of-sight
RMS root mean square
S/N signal-to-noise ratio
SADA solar array drive assembly
SM structural model
STM structural/thermal model
5 Test purpose

The main purpose of the spacecraft level micro-vibration test is to verify the dynamic characteristics in

micro-vibration environment. This is achieved by:

— obtaining transfer characteristics from disturbance source to the sensitive payload to verify the

transfer path design through transfer function measurements;

— obtaining modal parameters of the spacecraft through a modal survey test, in order to update the

analysis model;

— obtaining the micro-vibration response of sensitive payload equipment through response

measurements.

Usually, the verification of the dynamic characteristics in a micro-vibration environment is based on a

combination of analytical prediction and test.
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ISO 24411:2022(E)
6 General test information
6.1 Tailoring

Requirements of this document may be tailored to fulfil the objectives of the test.

6.2 Disturbance sources

Disturbance sources can be classified as external sources and internal sources. External sources can be

found in the space environment, e.g. eclipse entry and exit. Internal sources can be found from within

the spacecraft.
Annex A presents typical internal disturbance sources and their characteristics.
6.3 Preliminary analysis

A preliminary micro-vibration analysis shall be conducted before the spacecraft level micro-vibration

test. The objectives of the preliminary analysis are:
a) to identify the payloads sensitive to micro-vibration;
b) to identify the main disturbance sources on-orbit;

c) to decide whether a spacecraft level micro-vibration test for a specified spacecraft is necessary.

Annex B may be considered to decide whether spacecraft level micro-vibration tests are necessary

or not for the spacecraft with pointing stability as the sensitive index, depending on the nature and

characteristics of the mission.

In cases where spacecraft level micro-vibration testing is decided to be necessary, modelling and

analysis of spacecraft dynamics should be done before test for test planning and the following tasks

shall be executed:
— Obtain the prediction results to be used for test planning and specification.

— Define the configuration of the test article under the consideration that the test configuration can

differ from the flight configuration.

— Determine the dynamic characteristics of the disturbance sources to be replaced by analogue

exciters in the test configuration.

— Define the test frequency range according to the sensitive frequency range of the sensitive payloads.

— Evaluate the influence of boundary simulation equipment.
7 Test equipment
7.1 Test configuration for transfer function measurement and modal survey test

The test configuration for the transfer function measurement and modal survey test shall:

a) provide approximated “free-free” boundary conditions for the test article;

b) apply the excitation force to the pre-defined excitation points in the test article;

c) measure, acquire and process response signals;

d) obtain transfer functions from the response signals with the excitation signal as the reference;

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ISO 24411:2022(E)

e) obtain modal parameters based on the transfer functions, so as to update the analysis model if

needed or requested.

NOTE The “free-free” boundary conditions can be chosen and justified so that it remains representative of

the dynamic characteristics of the test article on orbit flight conditions.
An example of test configuration is shown in Figure 1.

Figure 1 — Test configuration for transfer function measurements and modal survey test

7.2 Test configuration for response measurement
The test configuration for response measurement shall:
a) provide approximated “free-free” boundary conditions for the test article;
b) excite the test article by disturbance sources or analogue exciters;

c) measure, acquire and process response signals (typical sensors are accelerometers, displacement

sensors, force sensors, angular sensors).

NOTE The “free-free” boundary conditions can be chosen and justified so that it remains representative of

the dynamic characteristics of the test article on orbit flight conditions.
An example of test configuration is shown in Figure 2.
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ISO 24411:2022(E)
Figure 2 — Test configuration for response measurement of micro-vibration
7.3 Test equipment functional requirements and recommendations
7.3.1 Boundary simulation

The test configuration shall simulate the on-orbit dynamic conditions as close as possible in order to

get reliable estimates for the expected on-orbit performances. In particular, the test article shall be in

a quasi “free-free” boundary condition and the gravity forces acting on the structure and surrounding

air effects shall be minimized.

The requirements and recommendations for the boundary simulation equipment are as follows:

a) The boundary simulation equipment shall provide the function of suspension and safety protection

for the test article.

b) Suspension frequencies, which are the first six rigid body frequencies of the system composed of

boundary simulation equipment and the test article, should be lower than 25 % of the first elastic

modal frequency of the test article under the free-free boundary condition.

c) The attached mass moving synchronously with the test article should be sufficiently less than the

mass of the test article (e.g. less than 5 % of the mass of the test article) to ensure that its dynamic

characteristics are unchanged as far as possible.

d) The influence of the boundary simulation equipment on the dynamic characteristics of the test

article shall be analysed.

e) The design safety factor of boundary simulation equipment under static load induced by the gravity

force of the test article shall meet the requirements of the customers.

f) One end of the boundary simulation equipment shall match the interface of the test article, and the

other end shall match the ground base or coping of the laboratory.

NOTE The “free-free” boundary conditions can be chosen and justified so that it remains representative of

the dynamic characteristics of the test article on orbit flight conditions.
Examples for typical boundary simulation equipment are shown in Figures 3 and 4.
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ISO 24411:2022(E)
Key
1 flexible suspension component
2 safety protection component
3 mechanical interface component
Coping of the testing laboratory or structural frame.
Test article.
Figure 3 — Suspending-fashion boundary simulation equipment
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ISO 24411:2022(E)
Key
1 flexible suspension component
2 safety protection component
3 mechanical interface component
Coping of the testing laboratory or structural frame.
Test article.
Ground base of the testing laboratory.
Figure 4 — Supporting-fashion boundary simulation equipment
7.3.2 Excitation

The test configuration shall be able to excite the test article at the defined excitation points as specified

in the test specification.
The following requirements apply for excitation:

a) The excitation force of excitation equipment shall meet the test requirements.

b) Excitation equipment should be as small as possible to minimize the noise.

c) Sensors and signal conditioners shall meet the requirements specified in 7.3.3.

7.3.3 Measurement, data acquisition and processing
7.3.3.1 General

The test configuration shall provide measurement and data acquisition means capable of meeting test

requirements.
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7.3.3.2 Measurement sensors
The following requirements apply for measurement sensors:

a) Sensor resolution shall be sufficient to distinguish between low amplitude signals and noise.

b) Sensor mass should be as small as possible to minimize the influence of additional mass.

c) Sensor frequency response range shall meet the test requirements.

d) Sensor wiring shall be fixed according to practices to reduce induced physical constraint and noise.

7.3.3.3 Signal conditioning
The following requirement and recommendation apply for signal conditioning:

a) Signal conditioners shall cover the overall frequency range and shall have flat frequency response

properties.

b) Signal conditioners should be capable of signal filtering, power supplying for sensors and signal

amplification.
7.3.3.4 Data acquisition and processing
The following requirements apply for data acquisition and processing:

a) The data acquisition and processing system shall have enough channels to meet the test

requirements.

b) The S/N of the data acquisition and processing system shall meet the test requirements.

c) The data acquisition and processing system shall be capable of measuring the overall frequency

range and shall have flat frequency response properties.

d) The sampling rate of the data acquisition system shall meet the test requirements.

e) The data acquisition and processing system shall be capable of recording time domain signals and

post processing the data according to the characteristics of the signal.

The measurement equipment used for tests shall be calibrated and used within the valid calibration

period.
8 Test requirements and recommendations
8.1 General test requirements and recommendations
8.1.1 General

Spacecraft level micro-vibration test is typically composed of the following activities:

a) transfer function measurement (see 8.1.2);
b) modal survey test (see 8.1.3);
c) micro-vibration response measurement (see 8.1.4).
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ISO 24411:2022(E)
8.1.2 Transfer function measurement
The following recommendations apply:

a) If not specified otherwise, the mechanical interface location of each disturbance source should be

excited one at a time.

b) The corresponding transfer functions between the disturbance sources and the sensitive payloads

should be extracted.

c) During the test, the test article should be excited with different levels of excitation force to verify

the linearity of the transfer function.

NOTE The transfer functions can be used in the design, optimization and verification of the micro-vibration

attenuation of the test article.
8.1.3 Modal survey test
The following requirements apply:

a) In the modal survey test, the test article shall be excited on specific and well-defined points.

b) The test article’s transfer functions shall be extracted from the excitation and response data.

c) The modal parameters of the test article shall be identified according to the transfer functions.

NOTE The modal parameters can be used to update the analysis model.
8.1.4 Micro-vibration response measurement

During the micro-vibration response measurement, the micro-vibration response of the key locations

shall be measured when different disturbance sources work separately or work together.

NOTE Typical key locations for micro-vibration response measurement are disturbance source locations,

sensitive payload locations and the transfer path.
8.2 Pre-conditions
The following items shall be specified before the test:
a) the frequency range for measurement;
b) the target modes;
c) the measurement point plan;
d) the applicable exciter positions and allowable force levels;
e) the test cases.
8.3 Test article configuration

The test article can be the SM, STM and/or FM. Layout and state of the units on-board should be

consistent with the flight state. If the real state of a unit is difficult to achieve, it may be simplified or

represented by an equivalent mass.

Payloads sensitive to disturbance and their interface state should be present in their actual flight

configuration. The main disturbance sources should participate in the micro-vibration test. Disturbance

sources may be replaced by analogue exciters if it is difficult to include the real disturbance source into

the test configuration.
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ISO 24411:2022(E)
8.4 Test environment
8.4.1 Laboratory environment requirements

The laboratory environment shall comply with the customer’s requirements including temperature,

relative humidity, atmospheric pressure, cleanliness and other requirements.
8.4.2 Background noise requirements
Background noise shall be minimized. The S/N should be h
...