Space engineering - Star sensor terminology and performance specification

This Standard specifies star sensor performances as part of a space project. The Standard covers all aspects of performances, including nomenclature, definitions, and performance requirements for the performance specification of star sensors.
The Standard focuses on:
- performance specifications (including the impact of temperature, radiation and straylight environments);
- robustness (ability to maintain functionalities under non nominal environmental conditions).
Other specification types, for example mass and power, housekeeping data and data structures, are outside the scope of this Standard.
This Standard also proposes a standard core of functional interfaces defined by unit suppliers and avionics primes in the context of Space AVionics Open Interface aRchitecture (SAVOIR) initiative.
When viewed from the perspective of a specific project context, the requirements defined in this Standard should be tailored to match the genuine requirements of a particular profile and circumstances of a project.
This standard may be tailored for the specific characteristics and constraints of a space project in conformance with ECSS-S-ST-00.

Raumfahrttechnik - Terminologie und Leistungsspezifikation für Sternensensoren

Ingénierie spatiale - Specification des performances et terminologie des senseurs stellaires

This activity will be the update of EN16603-60-20 (published 2014).
This activity was started in ECSS to implement as urgent classified Change Requests.
TABLE
For details of the Scope and justification of the update see the ECSS NWIP in
attachment.

Vesoljska tehnika - Terminologija v zvezi s senzorji za zaznavanje zvezd in specifikacija lastnosti

General Information

Status
Published
Public Enquiry End Date
27-Nov-2019
Publication Date
02-Sep-2020
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
27-Aug-2020
Due Date
01-Nov-2020
Completion Date
03-Sep-2020

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SLOVENSKI STANDARD
SIST EN 16603-60-20:2020
01-november-2020
Nadomešča:
SIST EN 16603-60-20:2014
Vesoljska tehnika - Terminologija v zvezi s senzorji za zaznavanje zvezd in
specifikacija lastnosti
Space engineering - Star sensor terminology and performance specification
Raumfahrttechnik - Terminologie und Leistungsspezifikation für Sternensensoren

Ingénierie spatiale - Specification des performances et terminologie des senseurs

stellaires
Ta slovenski standard je istoveten z: EN 16603-60-20:2020
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
SIST EN 16603-60-20:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 16603-60-20:2020
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SIST EN 16603-60-20:2020
EUROPEAN STANDARD
EN 16603-60-20
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2020
ICS 01.040.49; 49.140
Supersedes EN 16603-60-20:2014
English version
Space engineering - Star sensor terminology and
performance specification

Ingénierie spatiale - Terminologie et spécification des Raumfahrttechnik - Terminologie und

performances des capteurs stellaires Leistungsspezifikation für Sternensensoren
This European Standard was approved by CEN on 20 May 2020.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,

Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia,

Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
CEN-CENELEC Management Centre:
Rue de la Science 23, B-1040 Brussels

© 2020 CEN/CENELEC All rights of exploitation in any form and by any means Ref. No. EN 16603-60-20:2020 E

reserved worldwide for CEN national Members and for
CENELEC Members.
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SIST EN 16603-60-20:2020
EN 16603-60-20:2020 (E)
Table of contents

European Foreword ................................................................................................... 5

Introduction ................................................................................................................ 7

1 Scope ....................................................................................................................... 8

2 Normative references ............................................................................................. 9

3 Terms, definitions and abbreviated terms .......................................................... 10

3.1 Terms from other standards .................................................................................... 10

3.2 Terms specific to the present standard ................................................................... 10

3.3 Abbreviated terms................................................................................................... 29

3.4 Nomenclature ......................................................................................................... 30

4 Functional requirements ...................................................................................... 31

4.1 Star sensor capabilities ........................................................................................... 31

4.1.1 Overview ................................................................................................... 31

4.1.2 Cartography .............................................................................................. 32

4.1.3 Star tracking .............................................................................................. 33

4.1.4 Autonomous star tracking .......................................................................... 33

4.1.5 Autonomous attitude determination ........................................................... 34

4.1.6 Autonomous attitude tracking .................................................................... 35

4.1.7 Angular rate measurement ........................................................................ 35

4.1.8 (Partial) image download........................................................................... 36

4.1.9 Sun survivability ........................................................................................ 37

4.2 Types of star sensors ............................................................................................. 37

4.2.1 Overview ................................................................................................... 37

4.2.2 Star camera .............................................................................................. 37

4.2.3 Star tracker ............................................................................................... 37

4.2.4 Autonomous star tracker ........................................................................... 38

4.3 Reference frames ................................................................................................... 38

4.3.1 Overview ................................................................................................... 38

4.3.2 Provisions ................................................................................................. 38

4.4 On-board star catalogue ......................................................................................... 38

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5 Performance requirements .................................................................................. 40

5.1 Use of the statistical ensemble ............................................................................... 40

5.1.1 Overview ................................................................................................... 40

5.1.2 Provisions ................................................................................................. 41

5.2 Verification methods ............................................................................................... 42

5.2.1 Overview ................................................................................................... 42

5.2.2 Provisions for single star performances ..................................................... 42

5.2.3 Provisions for attitude performances ......................................................... 42

5.2.4 Provision for tests ..................................................................................... 42

5.3 <> ........................................................................................................... 43

5.4 General performance requirements ........................................................................ 43

5.5 General performance metrics ................................................................................. 45

5.5.1 Overview ................................................................................................... 45

5.5.2 Bias ........................................................................................................... 45

5.5.3 Thermo elastic error .................................................................................. 46

5.5.4 FOV spatial error ....................................................................................... 46

5.5.5 Pixel spatial error ...................................................................................... 47

5.5.6 Temporal noise ......................................................................................... 48

5.5.7 Aberration of light ...................................................................................... 49

5.5.8 Measurement date error ............................................................................ 50

5.5.9 Measured output bandwidth ...................................................................... 50

5.6 Cartography ............................................................................................................ 50

5.7 Star tracking ........................................................................................................... 51

5.7.1 Additional performance conditions ............................................................ 51

5.7.2 Single star tracking maintenance probability ............................................. 51

5.8 Autonomous star tracking ....................................................................................... 51

5.8.1 Additional performance conditions ............................................................ 51

5.8.2 Multiple star tracking maintenance level .................................................... 52

5.9 Autonomous attitude determination ........................................................................ 52

5.9.1 General ..................................................................................................... 52

5.9.2 Additional performance conditions ............................................................ 52

5.9.3 Verification methods .................................................................................. 53

5.9.4 Attitude determination probability .............................................................. 53

5.10 Autonomous attitude tracking ................................................................................. 54

5.10.1 Additional performance conditions ............................................................ 54

5.10.2 Maintenance level of attitude tracking ....................................................... 55

5.10.3 Sensor settling time ................................................................................... 56

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5.11 Angular rate measurement ..................................................................................... 56

5.11.1 Additional performance conditions ............................................................ 56

5.11.2 Verification methods .................................................................................. 56

5.12 Mathematical model ................................................................................................ 57

5.13 Robustness to solar events ..................................................................................... 57

5.13.1 Additional robustness conditions ............................................................... 57

5.13.2 Continuity of tracking during a solar event ................................................. 58

5.13.3 Ability to solve the lost in space problem during a solar event ................... 59

5.13.4 Flux levels ................................................................................................. 59

Bibliography ............................................................................................................. 88

Figures

Figure 3-1: Star sensor elements – schematic ...................................................................... 13

Figure 3-2: Example alignment reference frame ................................................................... 15

Figure 3-3: Boresight reference frame .................................................................................. 16

Figure 3-4: Example of Inertial reference frame .................................................................... 16

Figure 3-5: Mechanical reference frame ............................................................................... 17

Figure 3-6: Stellar reference frame ....................................................................................... 18

Figure 3-7: Schematic illustration of reference frames .......................................................... 18

Figure 3-8: Schematic timing diagram .................................................................................. 20

Figure 3-9: Field of View ....................................................................................................... 22

Figure 3-10: Aspect angle to planetary body or sun .............................................................. 23

Figure 4-1: Schematic generalized Star Sensor model ......................................................... 32

Figure B-1 : Rotational and directional Error Geometry ........................................................ 65

Figure F-1 : Angle rotation sequence .................................................................................... 76

Figure H-1 : Example of detailed data sheet ......................................................................... 82

Tables

Table C-1 : Minimum and optional capabilities for star sensors ............................................ 69

Table G-1 : Contributing error sources ................................................................................. 78

Table I-1 : Command table ................................................................................................... 84

Table I-2 : Telemetry table .................................................................................................... 86

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SIST EN 16603-60-20:2020
EN 16603-60-20:2020 (E)
European Foreword
This document (EN 16603-60-20:2020) has been prepared by Technical
Committee CEN-CENELEC/TC 5 “Space”, the secretariat of which is held by
DIN.
This standard (EN 16603-60-20:2020) originates from ECSS-E-ST-60-20C Rev. 2.
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 February
2021, and conflicting national standards shall be withdrawn at the latest by
February 2021.
Attention is drawn to the possibility that some of the elements of this document
may be the subject of patent rights. CEN [and/or CENELEC] shall not be held
responsible for identifying any or all such patent rights.
This document supersedes EN 16603-60-20:2014.
The main changes with respect to EN 16603-60-20:2014 are:
• Update of several definitions in clause 3.2 including update of some of
the Figures.
• Update of list of Abbreviated term in clause 3.3.
• Addition of the Nomenclature in clause 3.4
• Addition of a standard set of core commands and telemetry (or
functional interfaces) prepared in the context of SAVOIR initiative in
clauses 4.1.5, 4.1.6, 4.1.7 and Annex I.
• Clause 5.1.1 rewritten.
• Addition of new clause 5.13 “Robustness to solar events” addressing
robustness and performance in presence of solar events.
• Heading of clauses 5.2, 5.2.3, 5.4 updated.
• Addition of new clauses
• 5.2.4 “Provision for tests”;
• 5.9.4.1 “Probability of correct attitude determination”;
• 5.9.4.2 “Probability of false attitude determination”;
• 5.9.4.3 “Probability of invalid attitude solution”
• Update of Clause 5 and Annex B and Annex G to be fully consistent with
the Control Performance Standard ECSS-E-ST-60-10 and to remove
irrelevant duplications.
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SIST EN 16603-60-20:2020
EN 16603-60-20:2020 (E)
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.
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SIST EN 16603-60-20:2020
EN 16603-60-20:2020 (E)
Introduction
In recent years there have been rapid developments in star sensor technology,
in particular with a great increase in sensor autonomy and capabilities. This
Standard is intended to support the variety of star sensors either available or
under development.
This Standard defines the terminology and specification definitions for the
performance of star sensors (in particular, star trackers and autonomous star
trackers). It focuses on the specific issues involved in the specification of
performances of star sensors and is intended to be used as a structured set of
systematic provisions.
This Standard is not intended to replace textbook material on star sensor
technology, and such material is intentionally avoided. The readers and users of
this Standard are assumed to possess general knowledge of star sensor
technology and its application to space missions.
This document defines and normalizes terms used in star sensor performance
specifications, as well as some performance assessment conditions:
• sensor components
• sensor capabilities
• sensor types
• sensor reference frames
• general performance conditions including temperature, radiation,
dynamic and stray light
• sensor performance metrics
This document also defines a standard core of functional interfaces which help
to harmonize the majority of commands and telemetry necessary to operate star
sensors.
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SIST EN 16603-60-20:2020
EN 16603-60-20:2020 (E)
Scope
This Standard specifies star sensor performances as part of a space project. The
Standard covers all aspects of performances, including nomenclature,
definitions, and performance requirements for the performance specification of
star sensors.
The Standard focuses on:
• performance specifications (including the impact of temperature,
radiation and straylight environments);
• robustness (ability to maintain functionalities under non nominal
environmental conditions).
Other specification types, for example mass and power, housekeeping data and
data structures, are outside the scope of this Standard.
This Standard also proposes a standard core of functional interfaces defined by
unit suppliers and avionics primes in the context of Space AVionics Open
Interface aRchitecture (SAVOIR) initiative.
When viewed from the perspective of a specific project context, the
requirements defined in this Standard should be tailored to match the genuine
requirements of a particular profile and circumstances of a project.

This standard may be tailored for the specific characteristics and constraints of a

space project in conformance with ECSS-S-ST-00.
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SIST EN 16603-60-20:2020
EN 16603-60-20:2020 (E)
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
EN 16603-60-10 ECSS-E-ST-60-10 Space engineering – Control performance
EN 16603-60-30 ECSS-E-ST-60-30 Space engineering – Satellite attitude and orbit
control system (AOCS) requirements
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EN 16603-60-20:2020 (E)
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, ECSS-E-ST-60-10 and ECSS-E-ST-60-30 apply.
NOTE Additional definitions are included in Annex B.
3.2 Terms specific to the present standard
3.2.1 Capabilities
3.2.1.1 aided tracking
capability to input information to the star sensor internal processing from an
external source
NOTE 1 This capability applies to star tracking,
autonomous star tracking and autonomous
attitude tracking.
NOTE 2 E.g. AOCS.
3.2.1.2 angular rate measurement
capability to determine, the instantaneous sensor reference frame inertial
angular rotational rates
NOTE Angular rate can be computed from successive star
positions obtained from the detector or successive
absolute attitude (derivation of successive
attitude).
3.2.1.3 autonomous attitude determination
capability to determine the absolute orientation of a defined sensor reference
frame with respect to a defined inertial reference frame and to do so without
the use of any a priori or externally supplied attitude, angular rate or angular
acceleration information
3.2.1.4 autonomous attitude tracking

capability to repeatedly re-assess and update the orientation of a sensor-defined

reference frame with respect to an inertially defined reference frame for an
extended period of time, using autonomously selected star images in the field
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EN 16603-60-20:2020 (E)
of view, following the changing orientation of the sensor reference frame as it
moves in space
NOTE 1 The Autonomous Attitude Tracking makes use of a
supplied a priori Attitude Quaternion, either
provided by an external source (e.g. AOCS) or as
the output of an Autonomous Attitude
Determination (‘Lost-in-Space’ solution).
NOTE 2 The autonomous attitude tracking functionality
can also be achieved by the repeated use of the
Autonomous Attitude Determination capability.
NOTE 3 The Autonomous Attitude Tracking capability
does not imply the solution of the ‘lost in space’
problem.
3.2.1.5 autonomous star tracking

capability to detect, locate, select and subsequently track star images within the

sensor field of view for an extended period of time with no assistance external
to the sensor
NOTE 1 Furthermore, the autonomous star tracking
capability is taken to include the ability to
determine when a tracked image leaves the sensor
field of view and select a replacement image to be
tracked without any user intervention.
NOTE 2 See also 3.2.1.9 (star tracking).
3.2.1.6 cartography
capability to scan the entire sensor field of view and to locate and output the
position of each star image within that field of view
3.2.1.7 image download

capability to capture the signals from the detector over the entire detector Field

of view, within a single integration, and output all of that information to the
user
NOTE See also 3.2.1.8 (partial image download).
3.2.1.8 partial image download

capability to capture the signals from the detector over the entire detector Field

of view, within a single integration, and output part of that information to the
user
NOTE 1 Partial image download is an image download (see
3.2.1.7) where only a part of the detector field of
view can be output for any given specific ‘instant’.
NOTE 2 Partial readout of the detector array (windowing)
and output of the corresponding pixel signals also
fulfil the functionality.
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EN 16603-60-20:2020 (E)
3.2.1.9 star tracking
capability to measure the location of selected star images on a detector, to
output the co-ordinates of those star images with respect to a sensor defined
reference frame and to repeatedly re-assess and update those co-ordinates for
an extended period of time, following the motion of each image across the
detector
3.2.1.10 sun survivability
capability to withstand direct sun illumination along the boresight axis for a
certain period of time without permanent damage or subsequent performance
degradation
NOTE This capability can be extended to flare capability
considering the potential effect of the earth or the
moon in the FOV.
3.2.2 Star sensor components
3.2.2.1 Overview
Figure 3-1 shows a scheme of the interface among the generalized components
specified in this Standard.
NOTE Used as a camera the sensor output can be located
directly after the pre-processing block.
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EN 16603-60-20:2020 (E)
BAFFLE
OPTICAL
HEAD
OPTICAL SYSTEM
DETECTOR
PRE-PROCESSING
MEMORY
PROCESSOR
CAMERA
OUTPUT
PROCESS OUPUT
Figure 3-1: Star sensor elements – schematic
3.2.2.2 baffle
passive structure used to prevent or reduce the entry into the sensor lens or
aperture of any signals originating from outside of the field of view of the
sensor
NOTE Baffle design is usually mission specific and
usually determines the effective exclusion angles
for the limb of the Earth, Moon and Sun. The Baffle
can be mounted directly on the sensor or can be a
totally separate element. In the latter case, a
positioning specification with respect to the sensor
is used.
3.2.2.3 detector
element of the star sensor that converts the incoming signal (photons) into an
electrical signal
NOTE Usual technologies in use are CCD (charge
coupled device) and APS (active pixel sensor)
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EN 16603-60-20:2020 (E)
arrays though photomultipliers and various other
technologies can also be used.
3.2.2.4 electronic processing unit
set of functions of the sensor not contained within the optical head
NOTE Specifically, the sensor electronics contains:
• sensor processor;
• power conditioning;
• software algorithms;
• onboard star catalogue (if present).
3.2.2.5 optical head
part of the sensor responsible for the capture and measurement of the incoming
signal
NOTE As such it consists of
• the optical system;
• the detector (including any cooling equipment);
• the proximity electronics (usually detector
control, readout and interface, and optionally
pixel pre-processing);
• the mechanical structure to support the above.
3.2.2.6 optical system
system that comprises the component parts to capture and focus the incoming
photons
NOTE Usually this consists of a number of lenses, or
mirrors and filters, and the supporting mechanical
structure, stops, pinholes and slits if used.
3.2.3 Reference frames
3.2.3.1 alignment reference frame (ARF)
reference frame fixed with respect to the sensor external optical cube where the
origin of the ARF is defined unambiguously with reference to the sensor
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 3-2
schematically illustrates the definition of the ARF.
NOTE 2 The ARF is the frame used to align the sensor
during integration.
NOTE 3 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.
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EN 16603-60-20:2020 (E)
NOTE 4 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 RHS.
ARF
ARF
ARF
Sensor
Optical
Cube
Figure 3-2: Example alignment reference frame
3.2.3.2 boresight reference frame (BRF)
reference frame where:
• the origin of the Boresight Reference Frame (BRF) is defined
unambiguously with reference to the mounting interface plane of the
sensor Optical Head;
NOTE In an ideally aligned opto-electrical system this
results in a measured position at the centre of the
detector.
• the Z-axis of the BRF is defined to be anti-parallel to the direction of an
incoming collimated light ray which is parallel to the optical axis;
• X-BRF-axis is in the plane spanned by Z-BRF-axis and the vector from
the detector centre pointing along the positively counted detector rows,
as the axis perpendicular to Z-BRF-axis. The Y-BRF-axis completes the
right handed orthogonal system.
NOTE 1 The X-axes and Y-axes of the BRF are defined to lie
(nominally) in the plane of the detector
perpendicular to the Z-axis, so as to form a right
handed set with one axis nominally along the
detector array row and the other nominally along
the detector array column.
...

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