EN 16603-60-21:2018
(Main)Space engineering - Gyros terminology and performance specification
Space engineering - Gyros terminology and performance specification
This Standard specifies gyros functions and performances as part of a space project. This Standard covers aspects of functional and performance requirements, including nomenclature, definitions, functions and performance metrics for the performance specification of spaceborne gyros.
The Standard focuses on functional and performance specifications with the exclusion of mass and power, TM/TC interface and data structures.
When viewed from the perspective of a specific project context, the requirements defined in this Standard can be tailored to match the genuine requirements of a particular profile and circumstances of a project.
The requirements verification by test can be performed at qualification level only or also at acceptance level. It is up to the Supplier, in agreement with the customer, to define the relevant verification approach in the frame of a specific procurement, in accordance with clause 5.2 of ECSS-E-ST-10-02.
The present standard does not cover gyro use for launch vehicles.
This standard can be tailored for the specific characteristics and constraints of a space project in conformance with ECSS-S-ST-00.
Raumfahrttechnik - Kreiselinstrumente - Terminologie und Leistungsspezifikation
Ingénierie spatiale - Spécification des performances et terminologie des gyros
Vesoljska tehnika - Terminologija na področju žiroskopov in tehnična specifikacija
Ta standard določa funkcionalnost in zmogljivost žiroskopa v okviru vesoljskega projekta. Ta standard zajema vidike v zvezi z zahtevami glede funkcionalnosti in zmogljivosti, vključno z nomenklaturo, opredelitvami, funkcijami ter meritvami uspešnosti za specifikacijo zmogljivosti vesoljskih žiroskopov. Standard se osredotoča na specifikacije funkcionalnosti in zmogljivosti z izjemo mase in moči, vmesnika TM/TC ter podatkovnih struktur. Ko se obravnavajo v okviru posebnega dela projekta, je zahteve iz tega standarda mogoče prilagoditi tako, da se ujemajo z izvirnimi zahtevami posameznega profila in okoliščinami projekta. Preverjanje zahtev na podlagi preskušanja se lahko izvede samo na kvalifikacijski ravni ali tudi na ravni sprejemljivosti. Dobavitelj mora v dogovoru s stranko določiti ustrezen pristop preverjanja v okviru posebnega javnega naročila v skladu s točko 5.2 standarda ECSS-E-ST-10-02. Ta standard ne zajema uporabe žiroskopov za rakete. Ta standard se lahko prilagodi posameznim lastnostim in omejitvam vesoljskega projekta v skladu s standardom ECSS-S-ST-00.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-november-2018
9HVROMVNDWHKQLND7HUPLQRORJLMDQDSRGURþMXåLURVNRSRYLQWHKQLþQDVSHFLILNDFLMD
Space engineering - Gyros terminology and performance specification
Raumfahrttechnik - Kreiselinstrumente - Terminologie und Leistungsspezifikation
Ingénierie spatiale - Spécification des performances et terminologie des gyros
Ta slovenski standard je istoveten z: EN 16603-60-21:2018
ICS:
01.040.49 Letalska in vesoljska tehnika Aircraft and space vehicle
(Slovarji) engineering (Vocabularies)
49.140 Vesoljski sistemi in operacije Space systems and
operations
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD
EN 16603-60-21
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2018
ICS 01.040.49; 49.090; 49.140
English version
Space engineering - Gyros terminology and performance
specification
Ingénierie spatiale - Spécification des performances et Raumfahrttechnik - Kreiselinstrumente - Terminologie
terminologie des gyros und Leistungsspezifikation
This European Standard was approved by CEN on 11 July 2018.
CEN and CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for
giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical
references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to
any CEN and CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN and CENELEC member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN and CENELEC members are the national standards bodies and national electrotechnical committees of Austria, Belgium,
Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany,
Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,
Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
CEN-CENELEC Management Centre:
Rue de la Science 23, B-1040 Brussels
© 2018 CEN/CENELEC All rights of exploitation in any form and by any means Ref. No. EN 16603-60-21:2018 E
reserved worldwide for CEN national Members and for
CENELEC Members.
Table of contents
European Foreword . 5
Introduction . 6
1 Scope . 7
2 Normative references . 8
3 Terms, definitions and abbreviated terms . 9
3.1 Terms from other standards . 9
3.2 Terms specific to the present standard . 9
3.3 Abbreviated terms. 15
4 Functional requirements . 16
4.1 Overview . 16
4.2 Operating modes . 16
4.2.1 Operating modes Functional requirements . 16
4.2.2 Operating modes Verification requirement . 17
4.3 Start-up . 17
4.3.1 Start-up Functional requirements . 17
4.3.2 Start-up Verification requirements . 17
4.4 Warm-up . 18
4.4.1 Warm-up Functional requirements . 18
4.4.2 Warm-up Verification requirements . 18
4.5 Time and frequency, datation and synchronisation . 18
4.5.1 Time and frequency Functional requirements . 18
4.5.2 Time and frequency Verification requirements . 19
4.6 Alignment and scale factor . 19
4.6.1 Alignment and scale factor Functional requirements . 19
4.6.2 Alignment and scale factor Verification requirements . 20
4.7 Commandability and observability . 20
4.7.1 Commandability and observability Functional requirements . 20
4.7.2 Commandability and observability Verification requirements . 20
4.8 Failure diagnosis . 20
4.8.1 Failure diagnosis Functional requirements . 20
4.8.2 Failure diagnosis Verification requirements . 21
4.9 Measurement mode . 21
4.9.1 Measurement mode Functional requirements . 21
4.9.2 Measurement mode Verification requirements . 21
4.10 Auxiliary modes . 21
4.10.1 Auxiliary modes Functional requirements . 21
4.10.2 Auxiliary modes Verification requirements . 22
4.11 Anti-aliasing filter . 22
4.11.1 Anti-aliasing Functional requirements. 22
4.11.2 Anti-aliasing Verification requirements . 22
4.12 Stimulation . 22
4.12.1 Stimulation Functional requirements . 22
4.12.2 Stimulation Verification requirement . 22
4.13 Lifetime and duty cycle . 23
4.13.1 Lifetime and duty cycle Functional requirements . 23
4.13.2 Lifetime and duty cycle Verification requirement . 23
5 Performance requirements . 24
5.1 Use of the statistical ensemble . 24
5.1.1 Overview . 24
5.1.2 Provisions . 24
5.2 Performance Verification requirements . 25
5.3 General Performance requirements . 25
5.4 General performance metrics . 26
5.4.1 Overview and definition . 26
5.4.2 Bias . 27
5.4.3 Noise. 32
5.4.4 Scale factor error . 35
5.4.5 Misalignment . 38
5.4.6 Measurement datation and latency . 41
5.4.7 Start-up performances . 42
5.4.8 Warm-up phase performances . 43
5.4.9 Measured output bandwidth . 43
5.4.10 Anti-aliasing filter . 43
5.4.11 Data quantization . 44
5.4.12 Failure detection efficiency . 44
5.4.13 Stimulation . 45
5.5 Functional and performance mathematical model . 45
Annex A (normative) Functional and performance mathematical model
(FMM) description - DRD . 48
Annex B (informative) Example of data sheet . 50
Bibliography . 52
Figures
Figure 3-1: example alignment reference frame . 10
Figure 3-2: mechanical reference frame (MRF) . 14
Figure 4-1: Example of Start-up and Warm-up phases . 18
Figure 5-1: Examples of Bias evaluation from test or simulation data . 27
Figure 5-2: Switch-on bias repeatability computation . 31
Figure 5-3: Bias stability computation . 32
Figure 5-4: Monolateral PSD and Allan Variance. 34
Figure 5-5: Example of Functional Mathematical Model Architecture . 47
European Foreword
This document (EN 16603-60-21:2018) has been prepared by Technical
Committee CEN-CENELEC/TC 5 “Space”, the secretariat of which is held by
DIN.
This standard (EN 16603-60-21:2018) originates from ECSS-E-ST-60-21C.
This European Standard shall be given the status of a national standard, either
by publication of an identical text or by endorsement, at the latest by March
2019, and conflicting national standards shall be withdrawn at the latest by
March 2019.
Attention is drawn to the possibility that some of the elements of this document
may be the subject of patent rights. CEN shall not be held responsible for
identifying any or all such patent rights.
This document has been prepared under a standardization request given to
CEN by the European Commission and the European Free Trade Association.
This document has been developed to cover specifically space systems and has
therefore precedence over any EN covering the same scope but with a wider
domain of applicability (e.g. : aerospace).
According to the CEN-CENELEC Internal Regulations, the national standards
organizations of the following countries are bound to implement this European
Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia,
Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United
Kingdom.
Introduction
This Standard is intended to support the variety of space borne gyros either
available or under development, with the exception of the gyros used for the
launch vehicles.
This standard defines the terminology and specifications for the functions and
performance of gyros used on spacecraft. It focuses on the specific topics to be
found in the gyros procurement specification documents and is intended to be
used as a structured set of systematic provisions.
This standard is split in three main clauses:
• Terminology (clause 3)
• Functional requirements (clause 4)
• Performance requirements (clause 5)
NOTE This standard does not contain textbook material
on gyro technology. The readers and the users are
assumed to possess general knowledge of gyro
technology and its applications to space missions.
Scope
This Standard specifies gyros functions and performances as part of a space
project. This Standard covers aspects of functional and performance
requirements, including nomenclature, definitions, functions and performance
metrics for the performance specification of spaceborne gyros.
The Standard focuses on functional and performance specifications with the
exclusion of mass and power, TM/TC interface and data structures.
When viewed from the perspective of a specific project context, the
requirements defined in this Standard can be tailored to match the genuine
requirements of a particular profile and circumstances of a project.
The requirements verification by test can be performed at qualification level
only or also at acceptance level. It is up to the Supplier, in agreement with the
customer, to define the relevant verification approach in the frame of a specific
procurement, in accordance with clause 5.2 of ECSS-E-ST-10-02.
The present standard does not cover gyro use for launch vehicles.
This standard can be tailored for the specific characteristics and constraints of a
space project in conformance with ECSS-S-ST-00.
Normative references
The following normative documents contain provisions which, through
reference in this text, constitute provisions of this ECSS Standard. For dated
references, subsequent amendments to, or revision of any of these publications,
do not apply. However, parties to agreements based on this ECSS Standard are
encouraged to investigate the possibility of applying the more recent editions of
the normative documents indicated below. For undated references, the latest
edition of the publication referred to applies.
EN reference Reference in text Title
EN 16601-00-01 ECSS-S-ST-00-01 ECSS system - Glossary of terms
Terms, definitions and abbreviated terms
3.1 Terms from other standards
a. For the purpose of this Standard, the terms and definitions from ECSS-S-
ST-00-01 apply, in particular the following terms:
1. acceptance
2. assembly
3. availability
4. configuration
5. failure
6. lifetime
7. performance
8. qualification
9. redundancy
3.2 Terms specific to the present standard
3.2.1 alignment reference frame (ARF)
frame that is fixed with respect to the gyro external optical cube where and
whose origin is defined unambiguously with reference to the gyro external
optical cube
NOTE 1 The X, Y and Z axes of the ARF are a right-handed
orthogonal set of axes which are defined
unambiguously with respect to the normal of the
faces of the external optical cube. Figure 3-1
schematically illustrates the definition of the ARF.
NOTE 2 If the optical cube’s faces are not perfectly
orthogonal, the X-axis can be defined as the
projection of the normal of the X-face in the plane
orthogonal to the Z-axis, and the Y-axis completes
the RHR.
NOTE 3 The ARF is the frame used to align the sensor
during integration.
NOTE 4 This definition does not attempt to prescribe a
definition of the ARF, other than it is a frame fixed
relative to the physical geometry of the sensor
optical cube.
NOTE 5 This term is defined in the present standard with a
different meaning than in ECSS-E-ST-60-20. The
term with the meaning defined herein is applicable
only to the present standard.
Z
ARF
Y
ARF
X
ARF
Sensor
Optical
Cube
Figure 3-1: example alignment reference frame
3.2.2 angular increment
angular rotation between two user requests
3.2.3 angular random walk (ARW)
white noise on the gyro rate output, corresponding to a -1 slope on the Allan
variance plot to a -1/2 slope on the Allan variance standard deviation plot and
to a flat slope on the PSD plot
NOTE The plots are measured in log/log scale.
3.2.4 angular white noise (AWN).
white angle noise which corresponds to a -2 slope on the Allan variance plot, to
a -1 slope on the Allan variance standard deviation plot and to a +2 slope on the
PSD plot.
NOTE The plots are measured in log/log scale.
3.2.5 anti-aliasing filter
filter implemented in the gyro in order to avoid the aliasing of the high
frequency motion of the spacecraft input signal
3.2.6 bias
gyro measurement errors that are non-stochastic and not input rate dependant,
computed as the average of the rate error value over a defined time period
NOTE This term is defined in the present standard with a
different meaning than in ECSS-E-ST-60-20. The
term with the meaning defined herein is applicable
only to the present standard.
3.2.7 bias instability
low frequency noise component corresponding to flat slope on the Allan
variance standard deviation plot and to a -1 slope on the PSD plot
NOTE The plots are measured in log/log scale.
3.2.8 calibration
set of activities based on a set of tests allowing to characterise the gyro non-
random performance and, when relevant, to define the compensation
parameters used to improve the performance
NOTE This term is defined in the present standard with a
different meaning than in ECSS-S-ST-00-01. The
term with the meaning defined herein is applicable
only to the present standard.
3.2.9 configuration status
telemetry word indicating the states of the gyro tuneable settings
NOTE The configuration status scope is typically defined
by the gyro supplier.
3.2.10 cumulated angular increments
summation of angular increments
NOTE cumulated increments data output do not
correspond to an angular rotation between two
requests but to a cumulated angular rotation. The
customer typically manages the overflow. The use
of cumulated angular increments is robust to
transient data transmission issue.
3.2.11 deadband
input rotation range inside which the gyro output variation is less than a
specified value of the movement applied variation
NOTE The specified valued is normally expressed as a
percentage of the movement applied variation.
3.2.12 frozen outputs
situation occurring when the gyro output is erroneously identical over several
measurement acquisitions despite variation of the input signal
3.2.13 health status
telemetry word which contains the gyro internal monitoring survey results
NOTE The internal monitoring survey parameters are
defined by the gyro supplier.
3.2.14 input axis misalignment
angular error between the real sensing axis and the gyro reference sensing axis
3.2.15 multiple-axis configuration
gyro configuration with several sensing axes on the same mechanical structure
and oriented along different directions, physically defined w.r.t. the mechanical
reference frame (MRF) or the alignment reference frame (ARF)
3.2.16 noise
high frequency or short duration errors
NOTE 1 Noise measurements and noise model
characterization can be done at various
temperatures. However, during noise
measurement, gyro channel environmental
temperature is assumed identical within a
specified temperature range.
NOTE 2 This term is defined in the present standard with a
different meaning than in ECSS-E-ST-32-11. The
term with the meaning defined herein is applicable
only to the present standard.
3.2.17 quantisation error
noise due to the digital nature of the gyro output
NOTE This component of noise has the same asymptotic
behaviour than the AWN on Allan variance and
PSD plots.
3.2.18 repeatability
degree of closeness of test results taken during different periods of operations
NOTE 1 For instance before and after thermal cycles and
other environmental exposures, between
shutdowns and according to time between runs.
Unless otherwise specified, measurements are
carried-out in the same environmental conditions
(in particular, gyro channel environmental
temperature being assumed identical within a
specified temperature range).
NOTE 2 This term is defined in the present standard with a
different meaning than in ECSS-E-ST-35 and ECSS-
Q-ST-20. The term with the meaning defined
herein is applicable only to the present standard.
3.2.19 rate random walk (RRW)
noise component which corresponds to a +1 slope on the Allan variance plot to
a +1/2 slope on the Allan variance standard deviation plot and to a -2 slope on
the PSD plot.
NOTE The plots are measured in log/log scale.
3.2.20 scale factor non linearity
deviation of the output from a reference scale factor, over a given dynamic
range
NOTE the scale factor non linearity can be determined,
for example, by a least square linear fit of the
input/output data
3.2.21 scale factor non linearity error
residual errors after compensation of the scale factor non linearity component
3.2.22 scale factor error
gyro measurement errors that are non-stochastic and dependant of the rate
applied on the input axis
3.2.23 sensitivity
variation induced by a given environmental change, all other environmental
conditions being assumed unchanged and gyro channel being in continuous
operation
NOTE An environmental change can be, for example, a
change in temperature.
3.2.24 single-axis configuration
gyro configuration with only one sensing axis
3.2.25 stability
variation over a defined time period during which the gyro channel is
continuously submitted to specific operating conditions
NOTE Unless otherwise specified, measurements are
carried-out in the same environmental conditions
(in particular, gyro channel environmental
temperature being assumed identical within a
specified temperature range).
3.2.26 start-up phase
time interval between the switch-on of the gyro unit and the presence of a valid
output of the gyro that is fulfilling the pertaining performance requirements
NOTE See also Figure 4-1.
3.2.27 stimulation
function that allows to inject a simulated dynamic angular profile to the gyro
for ground test purposes
3.2.28 validity flag
flag that indicates whether the gyro measurement output is valid for use
3.2.29 warm-up duration
time interval between the switch-on of the gyro unit and the time when the full
nominal performances are achieved
NOTE See also Figure 4-1.
3.2.30 mechanical reference frame (MRF)
frame where the origin is defined unambiguously with reference to the
mounting interface plane of the gyro
NOTE 1 For example the Z-axis of the MRF is defined to be
perpendicular to the mounting interface plane,
which is the recommended convention. The X and
Y axes of the MRF are defined to lie in the
mounting plane such as to form an orthogonal
right hand rule reference frame (RHR) with the
MRF Z-axis.
NOTE 2 Figure 3-2 schematically illustrates the definition
of the MRF.
NOTE 3 If the gyro consists of several units, each unit has
its own MRF.
NOTE 4 This term is defined in the present standard with a
different meaning than in ECSS-E-ST-60-20. The
term with the meaning defined herein is applicable
only to the present standard.
Z
MRF
Y
MRF
Mounting Interface
X
Spacecraft Body
MRF
Figure 3-2: mechanical reference frame (MRF)
3.2.31 sensing reference frame (SRF)
physical reference frame in which individual gyro axes outputs are provided
NOTE 1 in case of a single-axis configuration, the sensing
axis is the Z-axis of the SRF.
NOTE 2 The sensing axis alignment w.r.t. the reference
frame (either MRF or ARF) is defined either by the
unitary vector of the ZSRF expressed in the
reference frame or by the transfer matrix between
the SRF and the reference frame.
NOTE 3 The sensing axis misalignments are the angular
projections of the true Z sensing axis on the X_SRF
and Y_SRF. Misalignment errors are expressed as
half-cone errors, i.e. root-sum square of both
projections.
3.3 Abbreviated terms
For the purpose of this Standard, the abbreviated terms from ECSS-S-ST-00-01
and the following apply:
Abbreviation Meaning
alignment reference frame
ARF
angular white noise
AWN
beginning-of-life
BOL
document requirements definition
DRD
electrical ground support equipment
EGSE
end-of-life
EOL
functional mathematical model
FMM
housekeeping
HK
mechanical reference frame
MRF
part per million
PPM
power spectral density
PSD
right hand rule
RHR
rate random walk
RRW
single event effect
SEE
sensing reference frame
SRF
telemetry
TM
with respect to
w.r.t.
Functional requirements
4.1 Overview
The gyro functional requirements address the following features:
• Operating modes and transient behaviours
• Timing aspects
• Lifetime and duty cycle
• Alignment and scale factor
• Commandability and observability
• Anti-aliasing
• Stimulation
The list of unit functional requirements is not exhaustive and generic functional
requirements (such as redundancy and reliability) are also considered in the
frame of a gyro requirements specification.
NOTE The requirements listed in clause 4 can be
complemented, as needed, with requirements
found in ECSS-E-ST-10, ECSS-E-ST-10-03, ECSS-E-
ST-60-30 and ECSS-E-ST-70-11.
4.2 Operating modes
4.2.1 Operating modes Functional requirements
a. The Gyro shall provide a Measurement Mode.
b. The TM data provided by the unit shall unambiguously report when the
Gyro has switched from Start-Up Mode to Measurement Mode.
c. The gyro shall perform a health-check at the end of the initialization
phase.
d. The health check shall comprise, as a minimum:
1. communications
2. memories
3. processor function
4. detector function
NOTE The detector function is a support for failure
diagnosis.
e. The gyro shall be capable to autonomously enter the measurement mode
after power on.
f. It shall be possible to power off the gyro at any time and in any mode of
operation without causing any damage to it.
g. The customer shall specify the transitions between the gyro operational
modes and phases and the transient behaviours.
h. The transition from one operation mode to another one shall not be
automatic, except in case of safety and integrity conditions.
i. A mode status shall be present in the HK data.
j. A reset capacity shall be available and commonly defined by the supplier
and the customer.
4.2.2 Operating modes Verification requirement
a. The operating mode requirements shall be verified by test during
qualification and acceptance tests.
4.3 Start-up
4.3.1 Start-up Functional requirements
a. The gyro channels shall provide valid inertial data on the interface bus
after switch-on of the equipment within a maximum duration whatever
is the angular rate within its dynamic range.
b. The start-up performance specified in clause 5.4.7 are achieved within a
maximum duration.
NOTE 1 For some gyros, the start-up performance are
reached at the time the validity bit is set.
NOTE 2 An example of start-up is given in Figure 4-1.
4.3.2 Start-up Verification requirements
a. The start-up duration shall be measured by an external mean.
b. The start-up requirement shall be tested over the whole range of
operational temperatures and dynamics.
4.4 Warm-up
4.4.1 Warm-up Functional requirements
a. The warm-up performance shall be achieved within a maximum
duration after switch-on.
NOTE The warm-up performance is specified in clause
5.4.8.
4.4.2 Warm-up Verification requirements
a. The warm-up duration shall be measured by an external mean.
b. The warm-up requirements shall be tested over the whole range of
operational temperatures and dynamics.
Figure 4-1: Example of Start-up and Warm-up phases
4.5 Time and frequency, datation and synchronisation
4.5.1 Time and frequency Functional
requirements
a. The gyro shall be capable to perform measurements together with the
associated validity check and the sampling of housekeeping data at a
frequency to be specified by the customer.
NOTE The sampling frequency is of up to some Hz to
some tens of Hz depending on the application.
b. The data output of each Gyro channel shall have its own date
measurement related to a clock reference.
NOTE The clock reference can be either internal or
external.
c. If a time tag counter is used, it shall not be reset after each reading.
NOTE This implies that the counter overflows is managed
at platform element level.
d. The output data shall be time tagged during data collection by the means
of a frame counter or a time stamp.
e. The unit shall be able to work either in synchronous mode or in
continuous mode.
f. When working in synchronous mode, the angular inertial data
measurement acquisition shall be synchronized with the external
interrogation signal.
NOTE The angular inertial data measurement made
available by the equipment are frozen.
g. When the gyro is working in synchronous mode, the external
interrogation signal shall have an accuracy as specified in clause 5.4.6.
h. The equipment shall offer also the possibility to choose the
synchronisation signal amongst two options:
1. a synchronisation signal on the chosen data interface - broadcast or
unicast on the data Bus or dedicated command on serial link- or
2. a pulse on a synchro link interface.
4.5.2 Time and frequency Verification
requirements
a. These requirements are verified by test with an external clock reference.
4.6 Alignment and scale factor
4.6.1 Alignment and scale factor Functional
requirements
a. A transformation matrix shall be provided by the Supplier.
b. The transformation matrix shall transform the sensitive axis/axes of each
Gyro unit into the reference frame, or frames.
NOTE The reference frame can be either MRF or ARF.
c. Scale factor of the gyro channels shall be positive when a positive
rotation is applied around the sensing axis.
NOTE 1 Positive scale factor means that angular increment
is positive or cumulated angular increments
output increases.
NOTE 2 The positive rotation is intended in a trigonometric
sense.
4.6.2 Alignment and scale factor Verification
requirements
a. The method shall be proposed by the supplier for customer approval.
b. The transformation matrix w.r.t. the mechanical reference frame shall be
measured before and after all the environmental tests performed during
the qualification and acceptance phases.
c. The transformation matrix measured during the acceptance phase shall
be delivered to the customer.
d. The customer shall choose the transformation matrix reference frame.
NOTE The reference frame can be both a mechanical
reference frame or alignment reference frame.
4.7 Commandability and observability
4.7.1 Commandability and observability
Functional requirements
a. The gyro shall provide in its periodic housekeeping data all the data
required for the monitoring and execution of all nominal and foreseen
contingency operations throughout the entire mission lifetime.
b. The gyro shall allow for on-request housekeeping data acquisition.
4.7.2 Commandability and observability
Verification requirements
a. The verification test shall be performed with a customer-specified
interface.
4.8 Failure diagnosis
4.8.1 Failure diagnosis Functional requirements
a. The unit shall provide information in the housekeeping data allowing, in
real time:
1. detection of a single failure potentially degrading the
measurement performances, or
2. gyro loss of functionality.
b. An analysis of the possible failures covered by the health status shall be
provided.
4.8.2 Failure diagnosis Verification requirements
a. The verification method for failure diagnosis shall be proposed by the
supplier and agreed with the customer.
b. During the gyro test, the health status shall be continuously monitored
and it shall be verified that no false alarm occurs on failure detection.
4.9 Measurement mode
4.9.1 Measurement mode Functional
requirements
a. The measurement mode shall provide:
1. measurement data, including an angular rate, an angle increment
or a cumulated angle increment,
2. a health status, and
3. a data validity flag.
b. The Gyro shall output a temperature measurement.
c. If internal filtering or compensation is applied to the measurement, both
raw and filtered or compensated data shall be provided.
d. The measurement bandwidth shall be specified for each of the following
outputs:
1. angular rate, unfiltered or filtered, or
2. an angle increment, unfiltered or filtered, or
3. a cumulated angle increment, unfiltered.
NOTE For further details, see clause 5.4.9.
4.9.2 Measurement mode Verification
requirements
a. The measurement mode functional requirements shall be verified by test.
4.10 Auxiliary modes
4.10.1 Auxiliary modes Functional requirements
a. The gyro shall provide a Test mode.
b. The use of the Test mode for the unit in-flight shall be specified if
necessary.
c. The gyro shall provide a Programmable mode.
d. The in-flight protection against misuse of these Test and Programmable
modes shall be implemented in agreement with the user specification.
4.10.2 Auxiliary modes Verification requirements
a. The auxiliary mode functional requirements shall be verified by test.
4.11 Anti-aliasing filter
4.11.1 Anti-aliasing Functional requirements
a. The equipment shall implement an anti-aliasing filter.
b. The anti-aliasing filter frequency shall be defined by the customer.
NOTE Anti-aliasing filter performances are defined in
clause 5.4.10.
c. If using an anti-aliasing filter which can be disabled, performance shall
be evaluated with and without the filter so that both raw and filtered
outputs satisfy the performance requirements.
4.11.2 Anti-aliasing Verification requirements
a. The anti-aliasing functional requirements shall be verified by test using
the raw and filtered output data or stimuli data.
4.12 Stimulation
4.12.1 Stimulation Functional requirements
a. It shall be possible to stimulate by an electrical mean including a digital
link via a dedicated test connector the gyro output data.
NOTE Further details are in clause 5.4.13.
b. The stimulation capability shall be compatible with the customer real
time acquisition frequency
c. The real time acquisition shall be specified by the customer.
d. If required for test input, the Supplier shall provide an Electrical Ground
Support Equipment (EGSE).
e. The stimulation capability shall be inhibited in flight.
4.12.2 Stimulation Verification requirement
a. The stimulation requirements shall be verified during the qualification
and acceptance tests by comparing the gyro outputs with the stimuli.
4.13 Lifetime and duty cycle
4.13.1 Lifetime and duty cycle Functional
requirements
a. The customer shall specify the number of years for the unit on ground,
with separately specified the amount of time of operation.
b. The customer shall specify the number of years during transfer and
operational lifetime, with separately specified the amount of time of
operation.
c. The number of ON/OFF cycles (for each channel) shall be specified for
the ground storage period and for the transfer and operational lifetime
period.
d. If any maintenance is required during the ground storage and on-board,
it shall be defined by the supplier.
e. The on ground storage and transport conditions shall be specified by the
customer.
NOTE For example temperature and vibrations.
4.13.2 Lifetime and duty cycle Verification
requirement
a. The verification method shall be agreed between supplier and customer,
depending on the gyro technology.
NOTE Gyro technology includes, for example, limited life
items and wear-out parts.
Performance requirements
5.1 Use of the statistical ensemble
5.1.1 Overview
Performances have a statistical nature, because they vary with time and from
one realization of a sensor to another.
Only an envelope of the actual performances can be provided. Central to this is
the concept of a ‘statistical ensemble’, made of ‘statistical’ sensors (i.e. not
necessarily built, but representative of manufacturing process variations) and
observations (depending on time and measurement conditions).
Further details can be found in ESSB-HB-E-003, in particular on the statistical
approaches to handle the statistical set of configurations.
The confidence levels are specified by the customer.
The conditions elected to populate the statistical ensemble are defined on a
case-by-case basis for each performance parameter or for a group of
performance parameters.
NOTE 1 A performance confidence level of 95 % is
equivalent to a 2 sigma confidence level for a
Gaussian distribution.
NOTE 2 A performance confidence level of 99,7 % used is
equivalent to a 3 sigma confidence level for a
Gaussian distribution.
5.1.2 Provisions
a. The worst-case performances shall be assessed by using the worst-case
sensor of the statistical ensemble.
b. The statistical ensemble shall be characterized and agreed with the
customer.
c. The performances shall be assessed by using the gyro EOL conditions
agreed with the customer.
NOTE The EOL conditions include ageing effects and
environmental effects.
5.2 Performance Verification requirements
a. The test method to verify performance specification shall be justified by
the supplier.
b. The validation of test raw data post-processing shall be demonstrated by
the supplier.
c. The adequacy of test equipment accuracy shall be agreed with the
customer.
d. The test success criteria shall be derived from the customer requirements
taking into account the test setup error budget.
e. The test inputs shall be in accordance with the required observability in
terms of operational range and the test resolution.
f. The validation of the post processing tools shall be performed using a set
of reference or simulated data.
g. The Earth rotation rate shall be taken into account in the tests, as an input
rate, or as a contributor to the raw gyro measurement.
h. The performance requirements verification shall be done with individual
tests or by combined tests.
NOTE One test serves the verification of several
performance requirements.
i. The unit calibration shall be performed before and after the whole set of
environmental tests.
j. The stability of the initial and final compensation parameters shall be
adequate w.r.t. the performance requirements.
k. The user shall state if raw or compensated measurements are used.
l. For gyro errors the thermal sensitivity shall be verified in the specified
temperature range.
m. The testability limits shall be declared by the supplier and agreed by the
customer.
NOTE The verification requirements listed in this clause
can be complemented, as needed, with
requirements found in ECSS-E-ST-10, ECSS-E-ST-
10-02, ECSS-E-ST-10-03 and ECSS-E-ST-60-30.
5.3 General Performance requirements
a. Each requirement or group of requirements shall indicate the relevant
conditions to be considered, as follows:
1. the performance conditions of the ‘statistical ensemble’
encompassing for EOL:
(a) worst-case unit temperature within specified range;
(b) worst-case radiation flux within specified range;
2. the input rate limit and the measurement range(s)
3. the maximum linear acceleration
4. the deadband limit
5. the (other) environmental effects (such as microvibrations and,
shocks)
6. the launch loads
7. the 1 g to 0 g effects
8. the SEE
9. the gyro warm-up effect
10. the power line variation effect
11. the ageing effect.
NOTE As regards statement 5.3a.1, additional values for
BOL can be given.
b. It shall be specified by the customer whether the PSD is computed as
bilateral or as monolateral.
NOTE In the monolateral case, all the energy is on the
positive frequency range. The monolateral PSD is
the recommended specification.
5.4 General performance metrics
5.4.1 Overview and definition
Present Clause 5.4 presents the general performance metrics for the errors
contributing to the gyro performances. In Annex B, an example of data sheet
built on the performance metrics is given.
The following error equation for a one axis gyro, or for each axis of a multiple
axis gyro, introduces the performance metrics developed in Claus
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