INTERNAL THALES ALENIA SPACE -...

INTERNAL THALES ALENIA SPACE

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All rights reserved, 2011, Thales Alenia Space

INTERNAL THALES ALENIA SPACE – COMMERCIAL IN CONFIDENCE

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CHANGE RECORDS Paragraphs Change Record (List of paragraphs modified, new or deleted)

Issue Date Change Record Description Author

01 25/02/2009 Initial issue with reference MTG-TAF-SA-RS-0166 MTG Team 02 07/08/2009 Modification of Mechanisms section according to SDR issue 1

Modification of Mechanical Loads Factors according to SRD issue 1 MTG Team

01 15/09/2010 New reference MTG-TAF-SA-SS-0166 Transfer of previous section 3, General Design and Interface Requirements, into AD-33C, General Design and Interface Specification. Introduction of the new section 3 on the tailoring of ECSS-E thermal and mechanical engineering standards. Transfer of previous section 4.5, Mechanisms, into AD-39C, Mechanisms Design and Performance Requirements Specification. Transfer of previous section 4.6, Pyrotechnics, into AD-41C, Satellite Electro-Explosive Device Requirements Specification, and into AD-34C, Electrical Design Requirements Specification. Suppression of requirements MTG-SAT-MTDRS-REQ-1530, MTG-SAT-MTDRS-REQ-1610 and MTG-SAT-MTDRS-REQ-3110 duplicating new section content. Suppression of section 6 related to applicability to old ECSS standards. Update of AD and ND numbering. New Requirements are identified by “xxxx” Modified Requirements are “blue-marked”

MTG Team

02 23/11/2010 Note : the change log refers to old requirement numbering of issue 1. (The requirement numbering has been changed due to the transfer of the document in Doors Database). Modifications in Thermal Chapter according to Kick off (of confer MTG-TAF-SA-MN-0120) • Modified requirements which contains “satellite” in order to specify what is included in this term (satellite, system, modules, or equipments) • Suppression of the requirement “ITAR Free…..” ($5.2.5) (Transferred in GDIS) • Addition of a requirement for external MLI ($5.2.5) • Addition of two requirements for Cryocoolers in a new paragraph $5.4 • Modification of title pf $5.3.3 and add of a requirement “…TCS… shall establish…. a complete and coherent verification plan” Other modifications in Thermal Chapter: • Addition of a requirement to define “isothermal equipments” in $5.1.3 • Suppression of requirements about accepted Softwares ($5.3.1), requirements covered by MTG-SAT-MTDRS-REQ-3730 (reference to AD-43C) • Modification of wording of MTG-SAT-MTDRS-REQ-3710 in $5.3.1 • “Typical” Replaced by “Nominal” in $5.3.2.1 • Suppression of the redundant requirement “Final flight temperature predictions shall be performed …” and reformulation of the conserved requirement “Final worst case and typical flight temperature predictions…” • Add The following requirements in 5.2.4.1 :”The Module contractor …. shall identify and specify the thermal interface design requirement at unit level” • Move of two requirements about Thermal balance from 5.3.2.1 to 5.3.3 Modification in general or structural design requirements according to KO meeting MTG-TAF-SA-MN-0120 • Modification of the document scope clarifiying applicability per S/C levels • Clarification of fracture control programme applicability in section 3 • Deletion of reference to ‘aerospace standarts’ for fasteners in section 4.8.2 • Added requirement in section 4.8.2 for mismounting avoidance of symetrical units

MTG Team


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• Typo 1.5 X MDP corrected in Requirement [MTG-SAT-MTDRS-REQ-1730] of section 4.6.2 • Duplicated requirement adressing fasteners for safe life applications removed in section 4.8.3 • Requirement 2370 modified + two requirements deleted in chapter 4.8.4 to remove limitation of M5 standard use • Requirement 2420 of section 4.8.4 clarified : 15 mounting / dismounting operations required • Wording of the requirement 2520 corrected • Wording of the requirement 2640 corrected • Wording of the requirement 2660 corrected • Wording of the requirement 2680 corrected • Applicability of req 0800 clarified • Applicability of req 0810 clarified • Req 0810 split in two requirements • Applicability of req 0820 clarified • Addition of SA-CON-210 and 220 in section 4.7.2

02 20/12/2010 Modifications according to OHB/TAS-F collocation on the 14th December 2010 : Thermal subjects : • $4.8.5.1 , MTG-SAT-MTDRS-REQ-2540, “2.5 mm” replaced by “2.5 micrometers” • $5.1.1 : "Beq" removed from the text • $5.1.2 : Suppression of the note of MTG-SAT-MTDRS-2790 according to TAS-F/OHB Agreement and modification of the wording of this requirement. Moreover the category TH1 is deleted from the whole document (description in $5.1.1, requirement 3710 in $5.3.1) • $5.1.2. Suppression of the MTG-SAT-MTDRS-REQ-2840 requirement according to TAS-F/OHB Agreement • $5.1.2 : Wording of the MTG-SAT-MTDRS-REQ-2830, 2850, 2860, xxxx requirements modified according to TAS-F/OHB Agreement • $5.1.3 Wording of The MTG-SAT-MTDRS-REQ-2890, 2900, 2910, 2930, 2960 requirements modified according to TAS-F/OHB Agreement • $5.1.3 Suppression of The MTG-SAT-MTDRS-REQ-2940 requirement according to TAS-F/OHB Agreement • $5.1.4.1 : Wording of the MTG-SAT-MTDRS-REQ-2970 requirement modified according to TAS-F/OHB Agreement • $5.1.4.4 : Wording of the MTG-SAT-MTDRS-REQ-3060&3090 requirements modified according to TAS-F/OHB Agreement • $5.2.1 : Wording of the MTG-SAT-MTDRS-REQ_xxxx, xxxx, xxxx, 3150 Modified (ground testing, sensors, suppression of “unacceptable” & “reasonnable”, …) according to TAS-F/OHB Agreement • $5.2.1 MTG-SAT-MTDRS-3230 deleted • $5.2.2 : Wording of MTG-SAT-MTDRS-REQ_3290 Modified according to TAS-F/OHB Agreement • $5.2.4.1 : Requirement 3560 : Adding a note to explain the intention of the scheme • $5.2.5 : Wording of MTG-SAT-MTDRS-REQ_3620, 3630,3670 Modified according to TAS-F/OHB Agreement • $5.3.2. Requirement 3800 and $5.2.5, Requirement 3620 Addition of a reference to AD-06C • $5.3.3 : Wording of MTG-SAT-MTDRS-REQ_xxxx, xxxx Modified according to TAS-F/OHB Agreement Modifications according to OHB comments 11-01-11. mechanical subjects • Section 4.4.2 : Table with CoG uncertainty requirement deleted • [MTG-SAT-MTDRS-REQ-0880] : wording changed, and 1 mm changed by 2 mm • [MTG-SAT-MTDRS-REQ-0930] : word ‘only’ added to clarifiy requirement • [MTG-SAT-MTDRS-REQ-0950] : deleted • [MTG-SAT-MTDRS-REQ-1650] : deleted

L.HONORE


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• [MTG-SAT-MTDRS-REQ-2230] : wording changed • [MTG-SAT-MTDRS-REQ-2260] : wording changed • [MTG-SAT-MTDRS-REQ-2340] : wording changed • [MTG-SAT-MTDRS-REQ-2440] : deleted • [MTG-SAT-MTDRS-REQ-2700] : mention of margin deleted Other modifications, precedence • Tailored ECSS superseede ECSS Other modifications in Thermal Chapter, not yet reviewed with OHB • $5.2.1 : Addition of two requirements from ECSS 70-11 "Space segment operability" • $5.2.1 : Adddition of two requirements from deleted in EDRS and transfered in MTDRS • Preparation of the Document for DOORS. • Suppression of 2 Requirements which are in AD-43C (TMM) ($5.3.1) • 3740 & 3820 : Suppression of heat soak and Plume aspects covered by URD-PF. • End of $5.3.1 . Add of requirement URD-871 transferred from URD-PF. • $5.2.2 Add of requirement MTDRS-3355 in provenance from MTG-PF-URD-REQ-876 • 3130 Split of this requirement and URD-REQ-873. • Modification of REQ-3150 to cover URD-PF-875 and itself. • Add a requirement in provenance of URD-882 in $5.1. • Split the requirement on ground testability into a requirement and a note. • Rewording of [MTG-SAT-MTDRS-REQ-3300] • Suppression of Requiment 3410. • Suppression of Requiment 3630 covered by 3240 Modification in Thermal Chapter organisation: Move of some requirements and creation of new paragraph in order to clarify and increase the lisibity of the document. Other modifications in mechanical chapter, not yet reviewed with OHB • Section 3 : split of ECSS tailoring in several requirements • Addition of handling points definition in section 4.3 • [MTG-SAT-MTDRS-REQ-820] : deleted, transfered in AD28C • [MTG-SAT-MTDRS-REQ-0830] : reference to max mass added • [MTG-SAT-MTDRS-REQ-0860] : reference to max mass added for CoG calculation • [MTG-SAT-MTDRS-REQ-890] : CoG measurement accuracy changed from 0.5 mm to 1mm. • [MTG-SAT-MTDRS-REQ-0900] : reference to max MOI added, reference to POI added • Section 4.6.1 : Two requirementds added regarding alignmnent / stability, moved from PF URD • MTG-SAT-MTDRS-REQ-1680], 1690 and 1700 mention of 5mm removed • [MTG-SAT-MTDRS-REQ-1810] : deleted, covered in section 4.9.3 • Section 4.6.5 : table with safety factors corrected (mistake in titles) + notes added • Section 4.6.5 : tables removed, replaces with reference to ECSS structural safety factors • Section 4.6.5 : two requirements added adressing safety factors for hoisting points • [MTG-SAT-MTDRS-REQ-1830] : mention of FOSY and FOSU added • [MTG-SAT-MTDRS-REQ-1850] : note added regarding recursive logic, Figure modified. • [MTG-SAT-MTDRS-REQ-1910] : spec removed. • [MTG-SAT-MTDRS-REQ-1940] : FOSD deleted, KLD added, Km and Kp definition changed, notes added for clarification, Ka changed, Kq added for transportation loads


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• [MTG-SAT-MTDRS-REQ-2230] second bullet deleted covered by 2260 • [MTG-SAT-MTDRS-REQ-2240] : reference to Req 2700 changed to 2390 • [MTG-SAT-MTDRS-REQ-2660] : deleted (dealt in AD42C) • Requirement added in section 4.9.3 to flow down requirement SA-STR-570 • Requirement modified in section 4.9.3 to flow down requirement SA-STR-580 and 590 to equipment level.

02 08/02/2011 Final modifications in thermal chapter ($5.1) before Issue 2, following to OHB thermal final comments Following Wording: “- Equipment Category TH: This category covers all external units and is split in two categories - Equipment Category TH1: Deleted - Equipment Category TH2: Equipment which requires more detailed environmental and boundary conditions to perform thermal analysis, qualification test and life test, as UPS thrusters, SADM, mechanism and the external appendages such as antennae, solar array wings…” Replaced by : “- Equipment Category TH: This category covers all external units which requires more detailed environmental and boundary conditions to perform thermal analysis, qualification test and life test, as UPS thrusters, SADM, mechanism and the external appendages such as antennae, solar array wings…” And in consequence : 2790 : "The internal thermal control of the category CC, RC, TH2 equipment" replaced by "The internal thermal control of the all units" 2830 : "For units of category CC, RC or TH2," replaced by " For all units ".

L.HONORE

02 10/02/2011 Modifications in mechanical chapters following agreement with OHB 09/02/11 Section 4.4 : Units physical characteristics [MTG-SAT-MTDRS-REQ-830] : ‘maximal’ deleted [MTG-SAT-MTDRS-REQ-860] : ‘maximal’ deleted [MTG-SAT-MTDRS-REQ-890] : verified instead of measured [MTG-SAT-MTDRS-REQ-900] : ‘nominal and maximal’ deleted [MTG-SAT-MTDRS-REQ-930] : MOI shall be ‘verified’ Section 4.6.2 : Fracture Control requirements [MTG-SAT-MTDRS-REQ-1660] : note added for clarification Section 4.6.5 : Mechanical Loads Factors [MTG-SAT-MTDRS-REQ-1950] : note added for clarification Section 4.8.2 : Lug general design characteristics (boxes) [MTG-SAT-MTDRS-REQ-2190] : note added for clarification Section 4.8.4 : Fixation hardware [MTG-SAT-MTDRS-REQ-2390] : Pt definition clarified [MTG-SAT-MTDRS-REQ-2420] : 15 M/D changed with 10 [MTG-SAT-MTDRS-REQ-2490] : note added for clarification Section 4.9.1 : Modelling [MTG-SAT-MTDRS-REQ-2650] : ‘Modal survey’ replaced with ‘results of tests’.

L.HONORE

Requirements Change Record (List of requirements modified, new or deleted, sorted by ascending document issue)


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TABLE OF CONTENTS

TABLE OF CONTENTS...........................................................................................................................6

LIST OF FIGURES ........................................................................................................................................9

LIST OF TABLES .................................................................................................................................................9

1. INTRODUCTION........................................................................................................................................10

1.1 SCOPE.....................................................................................................................................................10 1.2 REQUIREMENT NUMBERING SYSTEM............................................................................................................10

2. DOCUMENTS............................................................................................................................................11

2.1 APPLICABLE DOCUMENTS...........................................................................................................................11 2.2 APPLICABLE NORMS AND STANDARDS..........................................................................................................11 2.3 REFERENCE DOCUMENTS ..........................................................................................................................11 2.4 ORDER OF PRECEDENCE ...........................................................................................................................11

3. TAILORING OF ECSS-E ENGENINEERING STATUS ..............................................................................12

4. MECHANICAL DESIGN AND INTERFACE REQUIREMENTS ..................................................................15

4.1 MECHANICAL REFERENCE FRAMES..............................................................................................................15 4.2 GENERAL REQUIREMENTS..........................................................................................................................15 4.3 HANDLING PROVISIONS ..............................................................................................................................15 4.4 UNITS PHYSICAL CHARACTERISTICS ............................................................................................................16

4.4.1 Mass ...............................................................................................................................................16 4.4.2 Centre of mass ................................................................................................................................16 4.4.3 Moments of inertia ...........................................................................................................................17 4.4.4 Size .................................................................................................................................................18

4.5 UNIT LAYOUT AND INTERFACES ...................................................................................................................18 4.6 STRUCTURAL DESIGN ................................................................................................................................19

4.6.1 General ...........................................................................................................................................19 4.6.2 Fracture Control requirements .........................................................................................................22 4.6.3 Stiffness requirements .....................................................................................................................26 4.6.4 Strength requirements .....................................................................................................................26 4.6.5 Mechanical Loads Factors ...............................................................................................................27 4.6.6 Design loads....................................................................................................................................32

4.7 ALIGNMENT ..............................................................................................................................................32 4.7.1 Alignment provisions........................................................................................................................32


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4.7.2 Alignment with mirror .......................................................................................................................33 4.7.3 Optical reference cube alignments ...................................................................................................34

4.8 UNIT FIXATION ..........................................................................................................................................35 4.8.1 Functional requirements...................................................................................................................35 4.8.2 Lug general design characteristics (boxes).......................................................................................36 4.8.3 Lug interface....................................................................................................................................39 4.8.4 Fixation hardware ............................................................................................................................40 4.8.5 Baseplate/surface finish...................................................................................................................44

4.8.5.1 General ......................................................................................................................................................44 4.8.5.2 Surface finish treatment ..............................................................................................................................45

4.8.6 Electrical bonding ............................................................................................................................45 4.8.7 Grounding........................................................................................................................................46 4.8.8 Damping supports............................................................................................................................46

4.9 VERIFICATION OF THE MECHANICAL DESIGN .................................................................................................46 4.9.1 Modelling .........................................................................................................................................46 4.9.2 Analyses..........................................................................................................................................47 4.9.3 Testing ............................................................................................................................................48

5. THERMAL DESIGN AND INTERFACE REQUIREMENTS.........................................................................50

5.1 DEFINITIONS AND RULES ............................................................................................................................50 5.1.1 Equipment classification...................................................................................................................50 5.1.2 Interface temperatures definition and requirements..........................................................................50 5.1.3 Equipments temperature limits.........................................................................................................53

5.1.3.1 Calculated temperatures .............................................................................................................................54 5.1.3.2 Predicted temperatures...............................................................................................................................55 5.1.3.3 Design temperatures...................................................................................................................................55 5.1.3.4 Acceptance temperatures ...........................................................................................................................56 5.1.3.5 Qualification temperatures ..........................................................................................................................56

5.2 THERMAL DESIGN RESPONSIBILITY SHARE....................................................................................................57 5.3 THERMAL DESIGN REQUIREMENTS ..............................................................................................................58

5.3.1 General Requirements.....................................................................................................................58 5.3.2 Performances Requirements............................................................................................................59 5.3.3 Thermal Design simplicity and flexibility Requirements.....................................................................60 5.3.4 Unit supplier thermal design Requirements ......................................................................................61 5.3.5 Active Thermal Control Requirements..............................................................................................63 5.3.6 Passive Thermal Control Requirements ...........................................................................................65 5.3.7 Thermal interfaces Requirements ....................................................................................................66

5.3.7.1 Modularity and decoupling of modules Requirements...................................................................................66


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5.3.7.2 Interface design..........................................................................................................................................68 5.3.7.3 Heat fluxes at thermal interface...................................................................................................................69

5.4 REQUIREMENTS FOR THERMAL MODELS AND ANALYSES.................................................................................70 5.4.1 Thermal Modelling Requirements.....................................................................................................70 5.4.2 Thermal analysis Requirements.......................................................................................................72

5.4.2.1 General Analysis Requirements ..................................................................................................................72 5.4.2.2 Unit thermal analysis Requirements ............................................................................................................73 5.4.2.3 Thermal analyses and models description reports........................................................................................74

5.4.3 Thermal control subsystem testing and verification...........................................................................74 5.5 REQUIREMENTS FOR CRYCOOLER ...............................................................................................................76

5.5.1 Operating requirement .....................................................................................................................76 5.5.2 Performance requirement ................................................................................................................76


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LIST OF FIGURES

Equation 4-1 : No sliding/gapping criteria (using USF for sliding)........................................................... 37 Equation 4-2 : Design loads at attachment points criteria (using USF for joints)..................................... 37 Figure 5-1 Equipment categories CC & RC unit interface temperatures................................................ 53 Figure 5-2 : Temperature limits definition............................................................................................... 54 Figure 5-3 Thermal interface with thermal washer................................................................................. 68 Figure 5-4 Thermal interface with heat pipe .......................................................................................... 68

LIST OF TABLES

Table 3-1 Tailoring requirements for ECSS-E-ST-31C, Thermal Control General Requirements, [ND 14]....................................................................................................................................................... 12

Table 3-2 Tailoring requirements for ECSS-E-ST-32C, Structural General Requirements, [ND 15] ...... 12 Table 3-3 Tailoring requirements for ECSS-E-ST-32C, Structural General Requirements, [ND 15] ...... 13 Table 3-4 Tailoring requirements for ECSS-E-ST-32-02C, Structural Design and Verification of

Pressurized Hardware, [ND 17] ...................................................................................................... 13 Table 4-1: Relationship between loads and factors................................................................................ 28 Table 4-2: Unit Lug Interface Design...................................................................................................... 36 Table 4-3 Friction coefficient values...................................................................................................... 38 Table4-4 : Screw capability.................................................................................................................... 41 Table 4-5 Thread characteristics for single inserts at external interfaces (intended for unit inserts) ...... 41 Table 4-6 Thread characteristics for special inserts (e.g. face-to-face inserts) at external interfaces

(intended for internal structural inserts)........................................................................................... 42 Table 4-7 : Inserts position tolerances.................................................................................................... 42 Table 5-1 : Allowable base contact heat flux .......................................................................................... 69


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1. INTRODUCTION

1.1 Scope

This specification establishes the general mechanical and thermal design and interface requirements that are to be met to ensure the correct hardware performances during assembly, integration, testing, storage, transportation, launch and orbital operations.

These requirements are addressing all the levels within the satellite : Spacecraft, Payload, Platform, Subsystems, units. When the applicability is limited to a specific level, it is highlighted in the requirement wording.

Unit has to be understood as any electronic box, structural element, module (group of units or components eventually delivered with dedicated structures and thermal control hardware) which is assembled before delivery to the Prime Contractor.

Additional mechanical and thermal design and interface requirements specific to a subsystem are given in the relevant subsystem specification.

1.2 Requirement numbering system

Each requirement will be unambiguously identified by a requirement identifier that has the following structure:

• MTG-SAT-MTRDS-REQ-nnnn

where nnnn is a sequential number.

The text which is not identified as a requirement can be considered as a guideline or a clarification for the proper use of requirements.

However, figures or tables which are called by a requirement are part of the requirement.


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2. DOCUMENTS

2.1 Applicable documents

Refer to the list of applicable documents provided in the document “MTG AD System List, Applicability to the Main Building Blocks and to Products Managed by Prime” referenced MTG-TAF-SY-LI-0346.

2.2 Applicable norms and standards

Refer to the list of applicable norms and standards provided in the document “MTG AD System List, Applicability to the Main Building Blocks and to Products Managed by Prime” referenced MTG-TAF-SY-LI-0346.

2.3 Reference documents

NA

2.4 Order of precedence

In case of conflict between a subsystem/unit specification and this applicable document, any discrepancy shall be notified to the attention of the Prime Contractor for clarification, resolution and approval.

Tailored ECSS superseedes the ECSS.


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3. TAILORING OF ECSS-E ENGENINEERING STATUS

# Reference [MTG-SAT-MTDRS-REQ-001]

The thermal control design shall fulfil the requirements of the ECSS-E-ST-31C, Thermal Control General Requirements, [ND 14], together with the requirements amended, completed or newly raised as listed hereafter and tailored in Table 3-1.

Clauses removed 4.1.5 Interplanetary phases 4.1.7 Docking, docked and separation phases 4.1.8 Descent, re-entry and landing 4.1.9 Post-landing phases 4.2.2 High temperature range 4.3.9 ECLS

Annex H High temperature range Reason: Relates to events and environment not encountered by MTG

Table 3-1 Tailoring requirements for ECSS-E-ST-31C, Thermal Control General Requirements, [ND 14]

# Parents : [MTG-SYS-AD-AD18-REQ-008]*


The structural design shall fulfil the requirements of the ECSS-E-ST-32C, Structural General Requirements, [ND 15], together with the requirements amended, completed or newly raised as listed hereafter and tailored in Table 3-2.

Clauses removed 4.2.5 c. 4 Load events: refers to re-entry descent and landing

4.6.3.15 c.1 Thermal cycling test: refers to launchers and re -entry vehicles 4.6.3.23 to 25 Aerothermodynamics test: spacecraft inside fairing during flight in the

atmosphere 4.8.1 b Ground inspection: no in-orbit inspection for MTG 4.8.5 c Repair : TBC

Clauses modified 4.2.1c. 2 Lifetime: all phases of pre-launch, launch and operation

Table 3-2 Tailoring requirements for ECSS-E-ST-32C, Structural General Requirements, [ND 15]



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The structural design shall fulfil the requirements of the ECSS-E-ST-32C, Structural General Requirements, [ND 15], together with the requirements amended, completed or newly raised as listed hereafter and tailored in Table 3-2.

Clauses modified

4.2.5 c. 3 Load Events: new text In-orbit loads: (a) operational pressures, (b) static and dynamic loads induced by thrusters, (c) shocks due to pyrotechnical operation and deployment of appendages (d) thermo-elastic loads induced by temperature variations, (e) hygroscopic-induced load due to variations in moisture content (f) micro-vibrations induced by moving elements (e.g. momentum wheels) and thrusters, (g) micrometeoroids and debris

Table 3-3 Tailoring requirements for ECSS-E-ST-32C, Structural General Requirements, [ND 15]



A reduced fracture control programme shall be in conformance with all the requirements given in the ECSS-E-ST-32-01C, Fracture Control, [ND 16], section 11.2.2 with the additions specified within this MTDRS document.



The structural design and verification of pressurized hardware shall fulfil the requirements of the ECSS-E-ST-32-02C, Structural Design and Verification of Pressurized Hardware, [ND 17], together with the requirements amended, completed or newly raised as listed hereafter and tailored in Table 3-3.

Clauses deleted 4.4.1 f References to manned missions

Table 4-3 References to manned missions Table 4-4 References to manned missions

Clauses modified 3.2.27 MDP=MEOP

4.2.3.2 c.1. MDP = MEOP

Table 3-4 Tailoring requirements for ECSS-E-ST-32-02C, Structural Design and Verification of Pressurized Hardware, [ND 17]



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The structural design shall fulfil the requirements of the ECSS-E-ST-32-10C, Structural Factors of Safety for Spaceflight Hardware, [ND 20], together with the requirements amended, completed or newly raised as listed hereafter, with the exception of references to launch vehicles through out and specifically as detailed in Clause 4.1.4.2 a Note 3, Clause 4.1.5.3 , Clause 4.2.2 and Annex A.



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4. MECHANICAL DESIGN AND INTERFACE REQUIREMENTS

4.1 Mechanical reference frames

Spacecraft reference frame, local orbital reference frame, instruments reference frames and unit axes are defined in AD-29C and AD-36C.

4.2 General requirements


The satellite, PF, PL and equipment shall be designed to withstand all mechanical static and dynamic loads encountered during its entire life, including: manufacturing, assembly, handling, transportation, testing, launch and in-orbit operations.

# *

4.3 Handling provisions


Each unit weighing more than 10 kg shall be equipped with handling points (e.g. threaded bushes) that enable the connection to special handling MGSE for integration or dismounting.

# *


Lifting and transportation interfaces shall be arranged such that, except for the points themselves, ground handling loads will not be a design governing requirement for the satellite, PF, PL, or equipment.

# *


Positioning of the satellite, PF and PL handling points shall be approved by the Prime.

# *


Handling points shall be defined in the ICDR.

# *


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4.4 Units physical characteristics

For mass properties (mass, centre of mass, inertia), the term "nominal" refers to the current best estimate, either calculated or measured depending on the development progress.

4.4.1 Mass


The mass of each unit, with tolerances, shall be given in the unit ICDR.

# *


The actual mass of all units intended for Qualification, Flight and Flight Spare(s) shall not deviate from the nominal value by more than:

• 0.5 % for masses > 20 kg

• 0.1 kg for masses > 10 kg and < 20 kg

• 1 % for masses > 1 kg and < 10 kg

• 10 g for masses < 1 kg.

# *


The masses shall be measured with an accuracy of:

• ± 0.1 % for masses > 50 kg

• ± 0.05 % for masses > 10 kg and < 50 kg

• ± 1 g for masses > 0 kg and < 10 kg.

# *

4.4.2 Centre of mass


The location of the centre of mass of each unit, with tolerances, shall be given in the unit ICDR.

# *


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For deployable units (Solar Array, antenna,...), calculated location of the centre of mass shall be given for each in-orbit configuration in S/C coordinates system.

# *


The location of the center of mass of equipment intended for Qualification, Flight and Flight Spare(s) shall not deviate from the nominal location by more than 2.0 mm radius sphere.

# *


The centre of mass location shall be verified with an accuracy of 1 mm.

# *

4.4.3 Moments of inertia


The products of inertia of each unit, with tolerances, shall be recorded in the unit ICDR.

# *


For deployable units (Solar Array, antenna,...), calculated inertia values shall be given for each in-orbit configuration in S/C coordinates system.

# *


The value of the moments of inertia of equipment intended for Qualification, Flight and Flight Spare(s) shall not deviate from the nominal value by more than 10% except for equipment having a moment of inertia lower than 0.1 kg.m².

# *


Verified values of moment of inertia shall be supplied.

# *


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The moments of inertia shall be measured with an accuracy of ± 5%.

# *


Inertia and products of inertia shall be defined according to the following convention:

• Ixx = Σmi [(yi-yG)²+(zi-zG)²]

• Ixy = Σ [mi (xi-xG)(yi-yG)]

where mi is one elementary mass (which has xi, yi and zi as co-ordinates) of the unit which has xG, yG and zG as coordinates for its centre of gravity.

# *

4.4.4 Size


All interface dimensional properties shall be indicated in Interface Control Drawings.

# *


The overall dimensions and associated tolerances of unit including interface assembly, shall not differ from the values stated in the ICDR.

# *

4.5 Unit layout and interfaces


The layout of each unit shall take into account:

• Electrical requirements

• Thermal control requirements

• Alignment and centre of mass requirements

• Mechanical requirements

• Easy access to electrical connectors

• Easy access to fasteners

• Easy mounting and removal

• Provision to avoid mismating


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• Flatness etc...

# *


The mechanical configuration and its interface requirements and dimensions shall be fully detailed in one (or more) Interface Control Drawing by the unit subcontractor.

# *

4.6 Structural design

4.6.1 General


The structure shall meet the requirements of ND 15.

# *


The following failure modes, for the satellite and all equipment at all levels of integration, shall be prevented:

• Permanent deformation

• Rupture

• Instability and buckling

• Gapping of bolted joints

• Degradation of bonded joints

• Vibration induced mounting interface slip

• Loss of alignment of equipment and payloads subject to alignment stability requirements

• Excessive strains or stresses impairing mechanisms operation, release, or deployment

• Distortion violating any specified envelope

• Distortion causing functional failure or short circuit.

# Parents : [SA-STR-310]*


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Structure shall be designed with sufficient redundancy to ensure that the failure of one structural element does not cause general failure of the entire structure with catastrophic consequences (e.g. loss of launcher, endangerment of human life).


Note 1 : Failure may be considered as rupture, collapse, seizure, excessive wear or any other phenomenon resulting in an inability to sustain limit loads, pressures or environments.

Note 2 : Derived from ECSS-E-ST-32C Rev.1 [ND15], section 3.2.21 & Clause 3.2.22


Redundancy concepts (fail-safe) shall be considered whenever possible to minimize single-point failures.



Where a single-point failure mode is identified and redundancy cannot be provided, the required strength and lifetime shall be demonstrated (safe-life).



Corresponding structural elements shall be tracked as Potential Fracture Critical Items (PFCI’s). the following items are at least PFCI’s as defined in ECSS-E-ST-32_01C [ND-16], clause 11:

• Pressurised systems

• Rotating machinery

• Fasteners in safe life design implantations (focusing on primary structure and large/heavy equipment)

• Items fabricated using welding, forging or casting used at limit stress levels 25% of the ultimate tensile strength

• Non-metallic fracture sensitive items.

# *


The structural design of the MTG satellite, platform and payload, and associated selection of materials, shall be consistent with the stringent pointing and pointing stability requirements of the MTG mission.



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The structure shall guarantee the required alignment between spacecraft references, sensors, actuators, equipments and instruments.



Alignment/stability requirements shall be maintained during AIT phase, after launch and during all mission duration.



The flight grade fasteners shall meet the requirements of the NDP-40 or equivalent aerospace standards.

# *

Note : This will allow supplier to use an other aerospace standard (DIN, NA, NAS...) with which they are more familiar than with ECSS. The idea is to ensure that:

• The thread are rolled, as opposed to cut: CoC referring to, for example DIN, part number and/or micro sectioning test report

• The material has indeed the assumed mechanical properties: material CoC

• Samples, out of the batch, have been tested: test report

• Traceability: through the CoC, referring to the batch number from which the fasteners are coming from

• The re-vendor (if applicable) has indeed supply fasteners associated with the above mentioned report: incoming inspection report.


The structural design of the MTG satellite and all constitutive structural units shall minimise the impacts of thermo-elastic transients which occur during entry and exit of eclipse.



The structural interface between the platform and payload instruments shall minimise potential distortions during instrument integration and resulting from local structural/thermo-elastic distortion effects. (e.g. iso-static mounts to be implemented).



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The design of the structural path between the platform AOCS sensors (star trackers and gyros) and instrument interfaces shall be designed to minimise relative pointing errors during in-orbit operations, particularly with respect to indeterminate or transient effects.



No yielding is allowed at proof load/proof pressure.



Proto-flight hardware shall not yield during testing.

# *

4.6.2 Fracture Control requirements


Fracture control principles shall be applied where structural failure can result in a catastrophic or critical hazard.

# *


A fracture control plan shall be implemented according to chapter 11, Reduced Fracture Control Programme, of ND 16.


Note : Derived from sections 4 and 3.1 of ND 16.

Catastrophic hazard: A potential risk situation that can result in loss of life, in life-threatening or permanently disabling injury, in occupational illness, loss of an element of an interfacing manned flight system, loss of launch site facilities or long term detrimental environmental effects.

Critical hazard: A potential risk situation that can result in:

• Temporarily disabling but not life-threatening injury, or temporary occupational illness

• Loss of, or major damage to, flight systems, major flight system elements or ground facilities

Loss of, or major damage to, public or private property; or short-term detrimental environmental effects.


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The non fail-safe structural elements shall be Potential Fracture Critical Items (PFCIs).

# *


To be considered as fail-safe, a design implementation shall be such that the failure of one structural element in the load path does not affect the stiffness of the structure significantly.

# *

When comfortable margins are demonstrated in the structural analysis, engineering judgment can be used as criteria to simplify redundancy analysis for declaring a given item fail-safe. Multiple failures can be treated at once in order to further reduce the analysis effort.


Fasteners shall be classified and analyzed as any other structural item.

# *

Note : this mean that fasteners shall be classified regarding fractrure control and eventually a fracture analysis shall be performed if required.


Fasteners with diameter smaller than 5 mm shall not be used in safe life applications.

# *

Note: derived from section 8.8 of ND-16


Titanium alloy fasteners shall not be used in safe life applications.

# *



All potential fracture-critical fasteners shall be procured and tested according to aerospace standards or specifications with equivalent requirements.

# *



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All safe life fasteners shall be marked and stored separately following NDI or proof testing.

# *



Pressure vessels shall be Potential Fracture Critical Items (PFCIs).

# *

Note : A pressure vessel is a pressurized container which:

• Contains stored energy of 19310 Joules or more, the amount being based on the adiabatic expansion of a perfect gas; or

• Contains a gas or liquid which will create a hazard if released; or

• Will experience a Maximum Design Pressure (MDP) greater than 0.69 MPa.

Derived from section 8.2.2 of ND 16.


Sealed containers shall be potential fracture critical items (PFCIs) unless they meet the following criteria:

• The container is not part of a system with a pressure source and is individually sealed

• And leakage of the contained gas does not result in a catastrophic hazard

• And the container/housing is made from a conventional alloy of steel, aluminium, nickel, copper or titanium

• And the MDP does not exceed 0.15MPa

• And the free volume within the container does not exceed 0.051 m 3 (1.8 cubic feet) at 0.15MPa or 0.076 m 3 at 0.10MPa, or any pressure/ volume combination not exceeding a stored energy potential of 19310 Joules.

# *

Note : A sealed container is a pressurized container, compartment or housing that is individually sealed to maintain an internal gaseous environment, but does not classify as a pressure vessel.


For sealed containers with a MDP higher than 0.15MPa, but less than 0.69MPa, and a potential energy not exceeding 19310 Joules, additional fracture assessment need not be performed if the following apply:

• The minimum factor of safety is 2.5xMDP (verified by stress analysis or test)

• The container is proof-tested to a minimum safety factor of 1.5xMDP

# *


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Note : derived from 8.2.5. of ND 16


In addition to the criteria presented herein, all sealed containers shall be capable of sustaining 0.10MPa pressure with a minimum safety factor of 1.5.

# *

Derived from section 8.2.5. of ND 16.


Rotating machinery shall be Potential Fracture Critical Items (PFCIs).

# *

Note 1 :Rotating machinery: Any rotating mechanical assembly that has a kinetic energy of 19 300 Joules or more or an angular momentum of 136 Nms or more.

Note 2 : The amount being based on 0.5 I ω2 where I is the moment of inertia in kg.m2 and ω is the angular velocity in rad/s.

Derived from section 3.2.35 of ND 16.


Fasteners used in safe life applications, items fabricated using welding, forging or casting and which are used at limit stress levels exceeding 25 % of the ultimate tensile strength of the material, and non-metallic structural items shall be Potential Fracture Critical Items (PFCIs).

# *

Note 1 : Derived from section 11.2.2.1.a 3, 4 and 5 of ND 16.

Note 2 : Although laminated, honeycomb aluminium skins must not be considered as forged item in Note 3 : The sense of the fracture control standard.

Machined metallic parts issued from laminated blocks must not be considered as forged or casted items in the sense of the fracture control standard.


A NDI after manufacturing (forging, machining and thermal treatment) shall be performed by the launcher interface ring supplier.

# *


PFCIs shall comply with ND 16 in full.

# *


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4.6.3 Stiffness requirements


The eigen frequencies of compact equipment and boxes in hard-mounted condition shall be above 140 Hz with 10% margin for FEM uncertainties prior to FEM correlation.

# *

4.6.4 Strength requirements


The structure shall withstand at element, subassembly, or complete spacecraft level the following:

• The ultimate load without rupture, collapse or permanent deformations that impact the integrity of other parts or the system performance

• The yield load, where applicable, without permanent deformation or any elastic or plastic deformation resulting in performance degradation

• The buckling load without elastic buckling or collapse taking into account a non perfection of the failing element, e.g. by knock-down factor.

# *


A strength analysis shall be performed and demonstrate a positive margin of safety and include, if applicable, yield load analysis, ultimate load analysis and buckling load analysis.



Load multipliers specified by the launcher design authority (e.g. development factor, uncertainty factor, acceptance factor, qualification factor, test factor) apply in addition to the design safety factors.



Satellite, subassembly and unit design shall ensure the survival of the structure under the worst feasible combination of mechanical and thermal loads for the complete lifetime of the satellite.


Note : The lifetime shall include: manufacturing, assembly, testing, transport, launch and in-orbit operations.


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4.6.5 Mechanical Loads Factors


Margins of Safety (MOS) shall be calculated by the following formula:

( )( ) 1

it_loaddesign_lim_

−×

=FOS

loadallowableMOS

where :

• Allowable load: allowable load under specified functional conditions (e.g. yield, buckling, ultimate)

• Design limit load: computed or measured load under defined load condition (design loads)

• FOS: Factor of Safety applicable to the specified functional conditions including the specified load conditions (e.g. yield, ultimate, buckling) = FOSY x KLD or FOSU x KLD


Note 1: Margins of safety express the margin of the applied load multiplied by a factor of safety against the allowed load.

Note 2 : Loads can be replaced by stresses if the load-stress relationship is linear.

Note 3 : derived from ECSS-E-ST-32C Rev. 1 [ND 15], section 4.5.16


All margins of safety (MOS) shall be positive.


Note 1 : derived from ECSS-E-ST-32C Rev. 1 [ND 15], section 4.5.16


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The relationship between loads and factors shall be the following:

SATELLITE TEST LOGIC

SATELLITE DESIGN LOGIC

SUB-SYSTEM DESIGN LOGIC

SUB-SYSTEMTEST LOGIC

SATELLITELIMIT LOAD

LL

QUALIFICATIONLOADS

ACCEPTANCELOADS

x KQ x KA

SATELLITEDESIGN LIMIT

LOADDLL

SUB-SYSTEMLIMIT LOAD

SS LL

SUB-SYSTEMDESIGN LIMIT

LOADSS DLL

x Coef A

x Coef A'

SUB-SYSTEMQUALIFICATION

LOADS

SUB-SYSTEMACCEPTANCE

LOADS

NEXT LEVEL SUB-SYSTEMDESIGN AND TEST LOGIC

x KA / KQ

COEFFICIENT A

COEFFICIENT A'

= KQ x KM x KP

= KM x KP

SATELLITE DESIGN FACTOR

SUB-SYSTEM DESIGN FACTOR

Table 4-1: Relationship between loads and factors


Note 1 : derived from ECSS-E-ST-32-10C [ND 20], section 4.2.1

Note 2 :The application logic for design factors as given in the figure above shall apply in a ‘recursive’ manner from system level to lower level components

The following applies to this approach.


The mechanical part of the LL at system (i.e. spacecraft) level shall be derived from [AD 36C] (e.g. quasi-static loads, minimum requested test loads) either directly or indirectly (via adequate analysis, e.g. frequency response



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The project factor KP shall account for possible mass increase at the start of the satellite/subsystem/ unit design.


Note : derived from ECSS-E-ST-32-10C [ND 20], section 4.1.4.3.


The model factor KM shall account for the uncertainty at the start of the satellite/subsystem/unit design with respect to mathematical model used to establish the design.


Note : derived from ECSS-E-ST-32-10C [ND 20], section 4.1.4.2.


Qualification loads QL and acceptance loads AL shall be as a minimum:

• KQ× LL final for qualification

• KA× LL final for acceptance

• Where LL final is the best knowledge of the LL as resulting from the LCDA (or an envelope thereof) approved by the Launcher Authorities.


Note : derived from ECSS-E-ST-32-10C [ND 20], section 4.2.1.


The above loads or factors relationship applies to the quasi-static and dynamic loads for general design, dimensioning and testing.



The following factors shall be used:

• KM (model factor) = 1.25 prior to verification of the structural dynamic model of the satellite / subsystem / unit by dynamic testing

• KM (model factor) = 1.00 after verification of the structural dynamic model of the satellite / subsystem / unit by dynamic testing and associated FEM correlation

• KP (project factor) = 1.00 Maximum Predicted Mass shall be taken into account

• KQ =1.25 to 1.3 (1) for flight loads

• KQ = 2 for local transportation loads

• KQ = 1.4 for other transportation loads


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• KA = 1.0

• FOSY = 1.10

• FOSU = 1.25 (2)

• KLD (local design factor) = 1.2 typical value or lower if justified (3)


Note 1 : 1.3 is the qualification factor for Soyuz launcher, 1.25 for the other specified launchers. The mechanical loads provided in EDTRS are qualification loads. For subsystems, acceptance loads are qualification loads divided by 1.25

Note 2 : These factors assume the use of classical materials (metallic or composites) for which the coefficient of variation (COV) of the ultimate properties is lower or equal to 5 %. In case the COV of a material exceeds this value, new adequate factors of safety need to be defined according to approved standards.

Note 3 : Local design factor shall be applied when the sizing approach or the local modelling are complex, where significant stress gradients occur (e.g : geometric similarities, fitting, welding, rivetting, bonding, holes, inserts…etc..).


The satellite hoisting points shall be designed taking into account the maximum mass, including the mass of the satellite and of all external items fixed on satellite (LVA, clampband, MGSE if any ...), lifted during AIT sequence, with a safety factor of 2.

# ECSS Parents : ND54 :4.2.4.3, ND55 4.2.4.3, ND56 : 3.4.5.2, ND20 : 4.3.1*


Instruments and units hosting points shall be designed taking into account the maximum mass, all external items lifted during AIT sequence, with a safety factor of 2.

# ECSS Parents : ND20 : 4.3.1*


Instruments and units hosting points shall be designed taking into account the maximum mass, all external items lifted during AIT sequence, with a safety factor of 2.

# ECSS Parents : ND20 : 4.3.1*


Minimum Factors of Safety against ultimate shall be:

• Pressure Vessels 1.5

• Lines and Fittings smaller than 38 mm diameter 4.0

• Lines and Fittings of 38 mm diameter or greater 2.0

• Valves, Filters, Regulators, Other Pressurised Components 2.5


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The overall safety factors as defined in ND20 (ECSS-E-ST-31-10) section 4.3.2 shall be used.

# ECSS Parents : ND20 section 4.3.2*


Limit stress of materials (yield stress or failure stress) and limit loads of structural elements (inserts,...) used in the computation shall be A-Basis values unless a technical justification can be provided for using B-Basis.

# *

Note : the requirement does not prohibit B-Basis values but this should be justified (e.g. : redundant concept, large margin..). Deviation to be adressed case by case.


The structure shall be testable at the Design Limit Load (DLL).

# *


For combined loads where L(P) is the load due to maximum expected operating pressure and L(M) is the non-pressure limit load, the factored, ultimate load case shall be: 1.5 L(M) + 1.5 L(P).



For load cases involving thermal and/or moisture de-sorption loads, the thermal/moisture de-sorption stress at the applicable temperature shall be factored by 1.5 to determine the equivalent ultimate thermal/ moisture de-sorption load and this shall be added to 1.5 times the non-pressure load and/or the pressure load.



Where pressure and/or temperature and/or moisture de-sorption relieves the non-pressure load, a Factor of Safety of 1.0 shall be used for the pressure and/or thermal and/or moisture de-sorption loads. In this case, the pressure load shall be based on the minimum operating pressure.



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4.6.6 Design loads

The loads defined in AD-36C are specified at qualification level for the spacecraft, the instruments and the units.

The Design Limit Load may be computed from these levels following the approach illustrated in requirement [MTG-SAT-MTDRS-REQ-068].

4.7 Alignment

4.7.1 Alignment provisions


For any equipment requiring positioning accuracy on the structure, 2 positioning points at least, when necessary, shims shall be provided with location and tolerance consistent with positioning requirements.

# *


For any equipment requiring positioning accuracy on the structure, the Contractor of the equipment shall specify the alignment tolerances between the mating and the sensitive axis, as well as between the dowel line and the sensitive axis (e.g. thrust axis).

# *


For any equipment requiring positioning accuracy on the structure, the Contractor of the equipment shall provide the Contractor of the structure with a drilled template in accordance with the dowel positioning.

# *


In case some accurate items require in situ alignment adjustment, the relevant Contractor shall formulate a request to the Prime Contractor with proper justification.

# *


For any equipment requiring positioning accuracy on the structure, the adjustment process shall be defined in each case by common agreement between the Contractor and the Prime Contractor.

# *


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4.7.2 Alignment with mirror


Optical alignment master reference cubes shall be placed on non-dismountable primary structure elements.

# Parents : [SA-CON-210]*


Optical alignment cubes shall be placed on all satellite alignment sensitive elements such as to derive accurate alignment vectors and transfer matrices to the master satellite reference frame



Any unit that requires an alignment accuracy of ± 0.15° or better shall have optical reflectors.

# *


The location of the mirror shall be identified in assembly drawings and in Interface Control Drawings.

# *


Each unit requiring alignment about 2 axes shall carry a reflecting mirror parallel to the plane containing those 2 axes or two reflecting mirrors, each one being perpendicular to the relevant axis ; details will be as specified in Interface Control Drawings. When two or more reflecting surfaces are provided, it is preferable to use an optical cube.

# *


Each unit requiring alignment about 3 axes shall carry two perpendicular reflecting mirrors. When two or more reflecting surfaces are provided, it is preferable to use an optical cube.

# *


The direction of the axes of the optical reference shall be known relatively to the direction of the unit axis with an accuracy as described in the unit specification.

# *


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The fixation of the alignment mirrors shall allow the alignment of the concerned unit on the integrated spacecraft.

# *


In case of only two or three reflecting mirrors are provided, the reflecting mirrors shall be positioned after agreement of the Prime Contractor in order to ensure they can be used when integrated on the satellite. This is not applicable in case four or five reflecting mirrors are provided.

# *


The reflecting surfaces shall be optically polished and flat to within Lambda/4 (Lambda: wavelength of the sodium yellow line).

# *


The optical references shall have a minimum diameter of 15 mm and a minimum thickness of 4 mm.

# *


The fixation of the alignment mirrors shall be compatible with mechanical and thermal vacuum testing environment, and with out gassing requirements.

# *


Reflecting surfaces shall be perpendicular with an accuracy of ± 10 arc sec.

# *

4.7.3 Optical reference cube alignments


Optical alignment cubes shall remain visible (in three orthogonal axes) throughout the AIT campaign.



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Optical reference shall withstand all the environments supported by the unit with stability better than ±15µrad with respect to each of the 3 unit axes.

# *


The alignment errors shall be included in pointing and localisation errors as established in the unit alignment and pointing error budget.

# *


The normals onto the surfaces of the alignment cubes shall form a rigid handed coordinate system within an accuracy of better than 25 µrad/5 arcsecs measured between any two directions.

# *


The cube supplier shall measure and provide the angle between the normals of all the cubes faces within an adequate accuracy.

# *

4.8 Unit fixation

4.8.1 Functional requirements


The attachment points shall provide a controlled surface contact between the units and the structure to allow control of thermal conditions on the unit as well as electrical bonding.

# *


This contact shall be maintained under all operating conditions, taking into account loading resulting from the different thermal coefficient expansion between dissimilar materials.

# *


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4.8.2 Lug general design characteristics (boxes)


The lugs shall be designed according to Figure below.

Table 4-2: Unit Lug Interface Design

# *

Note : this drawing is an exemple valid for M4 only.


One of the holes shall be identified as reference hole and marked with the capital letter R on the Interface Control Drawing.

# *


The box co-ordinates and the centre of mass co-ordinates shall be related to the reference hole.

# *


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The positive Z-axis shall be normal to the mounting surface, as defined in Figure 3-3 contained in AD-36C.

# *


Boxes with a mass < 1.5 kg shall not have more than 4 attachment points.

# *


The definition of the boxes attachment points shall comply with the following mechanical requirements, under application of the worst case of mechanical and thermal environments:

• No sliding/gapping at support structure interface, compatible with screws capabilities as defined in §4.8.4 according to the criteria of Equation 4-1.

1≤+

tP

QP

USF ρ

Equation 4-1 : No sliding/gapping criteria (using USF for sliding)

• Design loads at attachment points compatible with inserts loads capabilities according to the criteria of Equation 4-2.

1222

≤

+

+

mmm MM

QQ

PpUSF

Equation 4-2 : Design loads at attachment points criteria (using USF for joints)

where,

• USF are the Ultimate Safety Factors (= FOSU as previously defined)

• P and Q are the actual values of axial and lateral loads applied to the attachment bolt

• Pt is the minimum guaranteed screw tension given in [MTG-SAT-MTDRS-REQ-2390]. If the margin is < 0 with more than 3 bolts on one given joint, the nominal screw tension can be used

• ρ is the friction coefficient between the box and its support structure, as defined in Table below.


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support structure Aluminium box

material at box contact with alodine 1200S coating plated A5

aluminium with alodine 1200S coating

• max = 0.23 • max = 0.23

aluminium plated A5 • max = 0.23 • max = 0.23

CFRP • max = 0.2 • max = 0.2

Table 4-3 Friction coefficient values

• Pm, Qm and Mm are the insert strength capability specified by the satellite Contractor

• Pm in tension to be used to check no sliding criteria

• Pm in tension or compression to be used, depending of the equipment feet design, to check compatibility with inserts loads capabilities.

# *


The equipment design shall prevent single inserts loading in bending and torsion.

# *


The number and pattern of boxes attachment points shall be approved by the customer.

# *


For highly dissipative equipment, the number and location of attachment points shall be chosen according to thermal considerations.

# *


The box attachment points shall be contained inside the allocated box volume.

# *


The following cause of misalignment shall be analysed and quantified as a minimum:

• Setting due to mounting procedure

• Setting due to launch distortion


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• Misalignment due to gravity release

• Thermal deformation under in-orbit temperatures

• Ageing

• Composite structure deformation due to moisture release in-orbit.

# *


Sufficient clearance shall be allowed between mechanical parts of the units to cover design, manufacturing, assembly tolerances, alignment translation/rotation ranges and environmental displacements.

# *


Fasteners shall comply with the requirements of ECSS-Q-ST-70-46C.

# *


In case of symetrical packaging, a specific marking shall be implemented to prevent any mismounting.

# *

4.8.3 Lug interface


The distance between two adjacent lugs shall be smaller than 300 mm but not closer than 30 mm and in accordance with the ICDR.

# *


The location of each attachment hole centre w. r. t. the Reference Hole, shall be within a 0.2 mm diameter circle centred on the theoretical position.

# *


The lugs and clearance for mounting shall be dimensioned as shown in Figure of requirement [MTG-SAT-MTDRS-110].

# *


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No part of the box shall be in the volume above the lugs indicated as "free access required".

# *


The contact area shall be specified on the ICDR for each attachment point.

# *


For highly dissipative equipment, this area shall have to be agreed by customer according to thermal subsystem needs.

# *


The lug edge shall be rounded to minimum radius of 0.2 mm to avoid structural damage.

# *


The co-planarity of the lugs shall be within 0.1 mm/100 mm.

# *

4.8.4 Fixation hardware


When M4 standard bolts are used, the ratio "unit maximal mass / number of attachment points" shall be below 1.5 kg.

# *


Any deviation to this mass per attachment point shall be reported to the Prime.

Screws with a higher diameter of type M5, M6 or M8 will then have to be considered.

# *


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The units bolts type and number shall be defined to withstand the specified design loads and worst case environmental conditions.

# *


The screws used for unit mounting shall guarantee a minimum type B and nominal screw tension above the values given in Table below. Pt is the bolt preload without external load applied.

Screw type M4 M5 M6 M8

Minimum guaranteed screw tension Pt(N) type B

3200 5000 6800 14000

Nominal guaranteed screw tension Pt(N) 3500 6400 8800 18000

Table4-4 : Screw capability

# *


Compliance with these load requirements shall be shown in the ICDR. Any exception must be approved by the Prime Contractor.

# *


Spacecraft equipment fixation points shall provide threads characteristics as defined in the two Tables below.

Standard Usable thread length (mm)

Bolt penetration (mm)

M4 7.5 7.5 M5 9.5 9.5 M6 11.5 11.5

M8 x 1 15.9 15.9

Table 4-5 Thread characteristics for single inserts at external interfaces (intended for unit inserts)


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Standard Usable thread length Bolt penetration

M4 1.5 D 2 D M5 1.5 D 2 D M6 1.5 D 2 D

M8 x 1 1.5 D 2 D

Table 4-6 Thread characteristics for special inserts (e.g. face-to-face inserts) at external interfaces (intended for internal structural inserts)

# *


Threaded holes shall allow 10 mounting/dismounting operations with keeping the garanteed bolted joint properties.

# *


Insert design shall comply with ESA document “Insert design Book” - PSS-03-1202, last version.

# *


Spacecraft equipment fixation points shall be provided with the following position tolerances, as defined in Table below.

Shur-lok insert Face-to-face insert

Reference hole of the equipment in the platform drilling frame

* committing value 0.4 0.2

* committing value 0.3 0.2 Remaining holes with regard to the equipment reference hole

* target 0.25

Table 4-7 : Inserts position tolerances

# *


The use of blind rivets, minimum 3 mm diameter shall be allowed for the followed items:

• Harness and RF cabling brackets

• Pipe brackets.


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# *


The rivets shall be of the set head type.

# *


Tools used for riveting shall prevent any damage to structural parts.

# *


The responsible of structural connection of removable parts (e.g. brackets) shall define:

• Screws number

• Screws size to be between M4 and M8 (female bi-hexagonal screws)

• Torque's to be applied to the screws in accordance with type of inserts, washers and screws

• Inserts to be M4, M5, M6 or M8.

All these fixation hardware definitions have to be approved by the Prime Contractor.

# *

Note : the equipment supplier provides bolted joint justification, to be approved by the customer. The bolts are supplied by the PF.


Resistance to vibration will be ensured by effective locking provisions such as: locking helicoils, strapping compound, nylok...etc. Surface scratching locking means, such as split or star-washers, shall not be used.

These locking provisions must be capable of being subjected to a minimum of 5 tightening and slackening operations without any significant effect on its braking power.

# *

Note 1 : Onduflex washer can be used as secondary locking if a solid heritage is demonstrated.


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4.8.5 Baseplate/surface finish

4.8.5.1 General


The contact area between boxes and structure shall be at the area of the lugs.

# *


The contact area of the units shall be flat with no protrusion below the mounting plane.

# *


The contact area or spot faces area shall be unpainted.

# *


If for thermal reasons larger areas are requested, the contact area (complete bottom face) must meet the following requirements unless there are other mechanical or electrical constraints:

• Flatness of 0.1 mm/100 mm (for mounted box and structure in area of mounting plane)

• Overall mounting surface flatness < 0.2 mm

• Contact surface roughness < 3.2 micrometers (2.5 micrometers for contact surface w/o thermal interfiller).

Exceptions are subject to approval by the Prime Contractor.

# *


The flatness of the instrument interfaces on the platform Nadir panel shall be better than 0.1mm.

# *


The instruments shall take into account a platform flatness of 0.1mm for the overall instrument mounting plane.

# *


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Unit base plate thickness and dimensions shall be specified in ICDR.

# *


All mating surfaces between equipment and spacecraft structure shall be left bare.

# *

4.8.5.2 Surface finish treatment


No surface treatment is necessary for stainless steel (only passivation), beryllium, silver, fibreglass or carbon fibre, except for the needs of thermal control (if applied to external surfaces) or unless otherwise specified in AD-37C (EMC/ESD purpose).

Surfaces treatment shall be applied for:

• Aluminium alloys (except alloys of series 5000 with magnesium)

• Magnesium and its alloys (mandatory).

Surfaces treatment may be necessary for:

• Titanium and its alloys

• Copper.

Requirements for these treatments are defined in NDPA 32.

Surface treatment of other materials must be approved by the Prime Contractor.

Cadmium and Tin plating are not acceptable.

# *

4.8.6 Electrical bonding


Bonding of units and supports shall be performed according to section 4.2 of AD-34C.

# *


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4.8.7 Grounding


It is required to ground all units to the structure according to section 4.2 of AD-34C.

# *

4.8.8 Damping supports


At the exception of reaction wheels and instrument cryo-coolers, no damping supports external to the unit shall be used.

# *

4.9 Verification of the mechanical design

4.9.1 Modelling


Any structural Finite Element Model (FEM) shall be delivered compliant to AD-42C.

# *


A structural Finite Element Model shall be delivered for subsystem and units with a principal mode below 140 Hz. Principal modes are those modes with an effective modal mass > 10%.

# *


The FEM shall be detailed enough to ensure an appropriate derivation/verification of the design loads and the modal response for all important modes with an effective mass > 10 % of the total mass up to 140 Hz.

# *


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The FEM shall be supported by additional and more detailed models for the analysis and design of specific aspects (strength verification, thermal stress analysis, thermo-elastic analysis, interface stiffness analysis, optical analysis, as required).

# *


The FEM’s shall be correlated against the results of the qualification and acceptance tests carried out at component, subassembly and complete spacecraft level as specified in AD-42C.

# *

4.9.2 Analyses


All the design loads applicable to the various parts, subassemblies or complete spacecraft shall be substantiated by analyses of significant events during the complete lifetime.

# *


The design loads shall be reassessed after each test at subassembly or system level.

# *


The stiffness analysis shall demonstrate compliance with the requirements as indicated in section 4.9.1

# *


The analytically predicted frequencies shall be higher than the minimum requirement specifications.

# *


The stress analysis shall demonstrate positive MOS and cover loads originating from mechanical, thermal and moisture description effects combined adequately together.

# *


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In case of a proto-flight approach, the yield and ultimate MOS shall be greater than 0.2.

# *


Strength values for mechanical parts shall not be assumed higher than the values specified for the relevant qualification and acceptance tests.

# *


Fatigue analysis shall be carried out where relevant, and demonstrate a positive reserve after application of 4 times the most constraining life cycles.

# *


Fracture mechanics analysis shall be carried out on critical items (FCI), according to ND 16 (chapter 7).

# *

4.9.3 Testing


Verification of the mechanical performance shall be possible by test at element, subassembly or system level.

# *


A significant number (>7) of standard potted inserts with low margin of safety (MOS) shall be tested for workmanship.

# *


Any Structural / thermal model shall be able to survive 4 times all mechanical qualification tests.



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Where the model philosophy requires a protoflight model, the protoflight model shall be able to survive 4 times all mechanical qualification tests (at acceptance duration) plus one launch.



Any Flight Model shall be able to survive 4 times all mechanical acceptance tests plus one launch.



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5. THERMAL DESIGN AND INTERFACE REQUIREMENTS

5.1 Definitions and rules

5.1.1 Equipment classification

The equipments mounted on the satellite are submitted to different thermal environment according to their location on the spacecraft.

Five categories of equipments are defined according to their location (see Figure 5-1):

• Equipment Category CC: Equipment thermal control is mainly ensured by conductive exchanges. Three sub-categories are defined :

− Equipment Category CC1: Dissipative equipment mounted on external heat pipes

− Equipment Category CC2: Dissipative equipment mounted on Aluminium skin panels or non dissipative equipment mounted on Carbon skin panels

− Equipment Category CC3: Dissipative equipment mounted on Aluminium skin panels with embedded heat pipes

• Equipment Category RC: Equipment thermal control is mainly ensured by radiative exchanges. These equipment are mounted on carbon or aluminium skin panels. Very low conductive contact is taken into account

• Equipment Category TH: This category covers all external units which requires more detailed environmental and boundary conditions to perform thermal analysis, qualification test and life test, as UPS thrusters, SADM, mechanism and the external appendages such as antennae, solar array wings…

5.1.2 Interface temperatures definition and requirements

Three interface temperatures are defined:

• Reference Temperatures (RTi): These temperatures are defined at certain points of the unit housing

• Environmental Temperature (ET): The temperature to which the unit housing is coupled radiatively and conductively

• Nodal Temperature (NT): The equivalent temperature of a unit considered as being isotherm.


All temperature requirements of units shall refer to specific RTi points of these units.

# *


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The location of these reference points shall be defined by the unit Contractor such that their temperatures can be related to the general thermal status of the unit and the critical unit components.

# *


The location of these reference points shall be approved by the Module Contractor and the Prime Contractor.

# *


The number of TRPi shall be limited to one per unit, except for multiple unit TRPs previously discussed on case by case and approved by the module contractor and by the prime contractor.

# *


For Categories CC, the RTi point shall be on the unit base plate.

# *


When not indicated, the mechanical Reference Hole shall be considered as the Temperature Reference Point.

# *


For category RC units, the RTi point shall be defined on an unit point representative of the nodal temperature NT of the unit housing.

# *


For category TH units, the different RTi points shall have to be located in a sufficient number of unit points according to the temperature repartition.

# *


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The location of the Reference Temperature points shall be indicated in the ICD (Interface Control Document) and on the ICDR (Interface Control Drawings).

# ECSS Parents : ND14 : [Annex-D2.1.5]*


For isothermal units, the reference temperature point shall be associated to the temperature of the single thermal node used by the module supplier model.

# *


For non-isothermal units, the Unit Supplier shall define several isothermal nodes, and, in consequence, a local reference temperature point will be defined for each (isothermal) thermal node.

# *

Note 1: In this way, a local reference temperature point is defined for each (isothermal) thermal node.


For non-isothermal units, the Unit Supplier shall provide an associated Thermal Mathematical Model (TMM) as part of the Interface Control Document.

# *


A unit shall be considered as isothermal if the maximum temperature gradient of its housing (including its baseplate) is less than 3°C.

# *


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ET = RT0

HEAT PIPES

PANEL

UNIT A2

UNIT A1

REFERENCE TEMPERATURE RTO

OSR

SPACE

These areas are not contact areas

Contactarea

(ENVIRONMENT) ET

UNIT B NT

Beq PANEL

RT1

RT2

RT0

ET and NT are defined by the Module supplier RT are defined by the unit supplier

- Unit B:

Figure 5-1 Equipment categories CC & RC unit interface temperatures

5.1.3 Equipments temperature limits

Overall temperature limits and margin philosophy is described in Figure 5-2 and detailed in following sections.

The required values for operating, non-operating, switch-on qualification, acceptance, design and storage temperature limits are indicated in AD-36C.


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The switch-on temperature limit is the lowest temperature at which an equipment may have power applied to it, or be activated.

QU

ALI

FIC

ATI

ON

RA

NG

E

AC

CEP

TAN

CE

RA

NG

E

DES

IGN

RA

NG

E

WO

RST

CA

SE P

RED

ICTE

DFL

IGH

T R

AN

GE

WO

RST

CA

SEC

ALC

ULT

AED

FLIG

HT

RA

NG

E

UN

IT D

ESIG

N R

AN

GE

Qualification Maximal Limit

Acceptance Maximal Limit

Design Maximal Limit

Predicted Maximal Limit

Calculated Maximal Limit

Calculated Minimal Limit

Predicted Minimal Limit

Design Minimal Limit

Acceptance Minimal Limit

Qualification Minimal Limit

Unit Design Maximal Limit

Unit Design Minimal Limit

U.M.

U.M.

D.M.

D.M.

A.M.

A.M.

Q.M.

Q.M.

U.D.M.

U.D.M.

Sate

llit

e T

CS

Notes:

• U.M.= Calculation Uncertainty Margin

• D.M.= Thermal Control Design Margin / ABS (D.M.) > 0 °C

• A.M.= Acceptance Margin / A.M. = 5 °C

• Q.M.= Qualification Margin / Q.M. = 5 °C

• U.D.M.= Unit Design Margin / U.D.M > 0°C

Figure 5-2 : Temperature limits definition

5.1.3.1 Calculated temperatures


The calculated temperatures shall be obtained, by analysis, for the agreed TCS sizing mission phases.

# ECSS Parents : ND14 : [$3.2.1.2]*


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The computation of calculated temperatures shall include the effects of extreme case combination w. r. t. environmental and operating mode conditions (BOL/EOL conditions, unit dissipations, voltage of power available for heaters, external fluxes and radiation inputs…) but excluding failure cases.

# ECSS Parents : ND14 : [$3.2.1.3]*


The worst case conditions for computation of calculated temperatures shall be determined and justified by the thermal control responsible.

# *

5.1.3.2 Predicted temperatures


The uncertainties and the systematic errors (i.e modelling error, typically 3 [°C]) shall be added to the analytically calculated temperatures.

# Parents : [SA-TCR-310] ECSS Parents : ND14 : [$3.2.1.18] [$4.5.2.1.c]*


Uncertainties associated to the thermal parameters involved in the design shall be derived by means of sensitivity analysis.

# Parents : [SA-TCR-300]*


The predicted temperatures shall remain within the specified design temperature limits.

# ECSS Parents : ND14 : [$3.2.1.3]*

5.1.3.3 Design temperatures


The design temperature range, specified for the operating, non operating mode and switch-on condition of a unit, shall be obtained by subtracting suitable acceptance margin from the relevant acceptance temperature range.

# ECSS Parents : ND14 : [$3.2.1.7]*


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The acceptance margin shall be 5°C.


5.1.3.4 Acceptance temperatures


The acceptance temperature range, specified for the operating, non operating mode and switch-on condition of a unit, shall be obtained by subtracting suitable qualification margin from the relevant qualification temperature range.

# ECSS Parents : ND14 : [$3.2.1.2]*

Note : The acceptance temperature limits are the extreme temperatures that a unit can reach, but never exceed, during all envisaged mission phases (based on worst case assumptions), including failure cases.


During the acceptance tests, unit Temperature Reference Points (TRPs) shall be exposed to temperatures within but not exceeding the acceptance test temperature range.

# ECSS Parents : ND14 : [$3.2.1.2]*


The qualification margin shall be 5°C.


5.1.3.5 Qualification temperatures


The qualification temperature range, specified for the operating, non-operating and switch on conditions of a unit, shall be the temperature range for which this unit is guaranteed to function nominally fulfilling all required performances with the required reliability.

# ECSS Parents : ND14 : [$3.2.1.20]*


During qualification tests, unit Temperature Reference Points (RTs) shall be exposed to temperatures within but not exceeding the qualification test temperature range.

# ECSS Parents : ND14 : [$3.2.1.21]*


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5.2 Thermal design responsibility share


The satellite modules Thermal Control Subsystem (TCS) shall provide required thermal environment for all equipments over all mission lifetime, with the restrictions detailed hereafter.

# ECSS Parents : ND14 : [$4.1.1]*


The internal thermal control of all units shall be the responsibility of the unit supplier.

# *


However, in case of accommodation of some instrument units inside the platform, the thermal control of these units shall be under the responsibility of the platform Thermal Control Subsystem.

# *


For units of all units, the responsibility of the unit supplier shall be limited to the compliance of the specified unit design temperature limits (AD-36C) (EDRS) which are applicable at the agreed unit Temperature Reference Point TRPi (see § 5.1.2).

# *


The thermo-optical characteristics of the units shall be defined by the Module contractor responsible for the Thermal control and submitted to Prime approval.

# *


The external coating characteristics of the units shall be defined by the Module contractor responsible for the Thermal control and submitted to Prime approval.

# ECSS Parents : ND14 : [$3.2.1.42]*


The interface filler characteristics of the units shall be defined by the Module contractor responsible for the Thermal control and submitted to Prime approval.

# ECSS Parents : ND14 : [Annex-D2.1.5]*


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5.3 Thermal design requirements

5.3.1 General Requirements

The followings requirements are applicable at satellite and modules levels.


The thermal control shall withstand, operate and perform as specified, taking into account the natural and induced environmental conditions which they will experience throughout their ground and in orbit lifetime.



The thermal design shall ensure a stable and predictable thermal environment throughout the life of the mission.



The thermal design, in conjunction with the structural design, shall minimise the impacts of the in-orbit thermal transients (e.g entry and exit of eclips) on the satellite pointing and stability performances.



The thermal design shall not impose unaccepted constraints on other satellite sub-systems or on satellite operations.

# *


The TCS shall be protected against any single point of failure.

# ECSS Parents : ND14 : [$4.4.9.d]*


For each mission phase, as a minimum, the worst hot and cold case shall be identified, justified and analysed.



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For the main mission phases a “nominal” case taking into account “nominal” environmental conditions, dissipations shall be defined, justified and analysed.



At the start of the design and analysis process, design margins shall be established to cover modeling and hardware uncertainties and to indicate the sensitivity of the design to variations of various parameters.

# *


Geometrical, thermo-optical and thermal properties, contact area, dissipated power for various modes and qualification temperature range of each unit and Module thermal control hardware shall be defined in the ICD.

# ECSS Parents : ND14 : [$4.3.2.a]*


As a general requirement any thermo-optical and thermal properties defined in ICD shall be demonstrated by thermo-optical coating manufacturer data and process qualification report or measurement on sample or measurement on the equipment itself.

# ECSS Parents : ND14 : [$4.4.3], [$4.4.1.d], [$4.4.1.e]*


The thermal control responsible at module level shall ensure that its module (platform or payload) can be permanently operated during ground testing.


Note : If a dedicated cooling system is required, then it must be compatible with AIT constraints.

5.3.2 Performances Requirements


The thermal design shall ensure that all temperatures of equipments inside the Module remain within their design temperature limits defined during all phases of the mission, including ground testing.



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If applicable, the thermal design shall also ensure the required temperature stability for equipment.



The thermal design shall maintain the structural parts within the required temperatures and temperature stabilities such that the necessary alignments are met between units involved in the pointing or alignment required performances.

# *


Compliance to relevant performance requirements for the worst case observation conditions around midnight shall be demonstrated by analysis and testing


5.3.3 Thermal Design simplicity and flexibility Requirements


The thermal design shall be as simple as possible:

• MLI and radiators with thermal coatings control the Sun, Earth and albedo effects and the internal heat distribution and rejection

• Internally, thermal coatings and conductive paths will be used to control the temperature of critical units.

# *


The thermal design shall be made simple by using the inherent or designed-in thermal properties of structure and units.

# *


The thermal design shall be such that easy repair and minor changes in design are possible through simple removal and replacement of insulation blankets, foils, heaters and/or by in-place refurbishment of thermal control coatings and surface treatments.

# ECSS Parents : ND14 : [$4.4.7], [$4.4.8]*


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The thermal design shall minimize the need for ground operational testing and subsystem level thermal vacuum tests.

# *


The thermal control design shall include flexibility to accommodate changes in layout, power dissipation, mission requirements (e.g orbits) and required temperature ranges; margins in radiator area and heater power demand versus allocation have to be clearly identified.

# Parents : [SA-TCR-200] ECSS Parents : ND14 : [$4.4.7]*

5.3.4 Unit supplier thermal design Requirements


In order to ensure compatibility of equipment designs with the thermal control of the relevant Module, each equipment shall be designed according to the following requirements:

• To comply with operating, non-operating and minimum switch-on/off qualification level temperatures

• To comply with requirements specified in section 5.3

• To withstand the thermal environment as specified in AD-36C

• To withstand the unit qualification tests

• To comply with any special requirements identified in the applicable subsystem or equipment specifications.

# *


Any specific thermal requirement shall be identified by Equipment supplier in order to be taken into account by the responsible of thermal control design (temperature stability,…).

# *


The internal thermal control of equipment shall be fully passive and not use active devices (heating or cooling with thermo-electric effect) or special items as heat pipes.

# *

Note 1 : However, internal heaters are allowed as far as the total dissipation of the equipment is not exceeded.


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Each unit shall be designed so that all internal heat sources have the required insulation or heat flow to the thermal interfaces of the unit, when the interface temperature is within the applicable qualification temperature range defined in the relevant unit specification.

# *


In designing the unit and ascertaining the optimum heat flow paths, the equipment supplier shall take into account the mounting method and the exchanges with the environment by both conduction, convection and radiation.

# *


All units working in the 0°C-80°C temperature range with a skin radiated power larger than 65 W/m2 (or 50 W/m2 when the maximal operational temperature is inferior or equal to 45°C) shall be conductively controlled and designed to dissipate the heat through a flat base plate in contact with the support structure.

# *


To give maximum flexibility in location and application of each unit, the equipment shall be designed for the worst most general environments, i.e. for the environments specified in AD-36C.

# *


External housing coating of unit shall present an emissivity higher than 0.85, except the contact area with the satellite structure and electrical/RF parts, unless otherwise specified by relevant Module thermal control responsible.

# *


The unit supplier shall define, provide and install temperature sensors which are located inside the unit.

# *


The unit supplier shall provide a flat and coating free area for Module temperature sensor implementation on unit TRPs.

# ECSS Parents : ND14 : [$4.5.3.3.b]*


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This free area shall have a minimum dimension of 20 x 10 mm. If these dimensions are not allowable, the location shall be defined on a case by case basis with the Prime.

# *

5.3.5 Active Thermal Control Requirements


The thermal control responsible at module level shall define and justify sufficient temperature sensors acquired by the flight processors, including those at TRPs, to allow for temperature control, monitoring in orbit and on-ground, for nominal and non-nominal mission phases.

# Parents : [SA-TCR-170], [SA-TCR-180]*


The Module thermal control shall provide and install the temperature sensors, located on units TRPs.

# *


The thermal design shall use heaters when necessary.

# *


The active thermal control shall be based on thermistors and heaters controlled by a software algorithm.

# *


The Thermal Control shall allow manual override and inhibition/enabling of all automated functions individually from ground.


Note 1 : This requirement does not imply to be able to perform the thermal control manually from ground, but to be able to disable failed elements from ground.


Each heater circuit shall be sized with the minimum guaranteed value of orbital average voltage at heater ends considering voltage drop in the harness.

# ECSS Parents : ND14 : [4.3.3]*


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The maximum power density of each heating line shall be calculated by considering the maximum supply voltage : 50 Volts.

# *


Grouping of heaters circuit shall be implemented whenever feasible in order to minimize the total number of needed ON-OFF commands and power supply lines.

# *


For heater thermal control in the operational modes, three thermistors (majority voting) shall be used.



Each independently controlled heater shall have temperature sensors used for regulation and available as telemetry.

# *


Individual ON / OFF status of thermostatically controlled heater shall be monitored and available as telemetry.

# *


The capability shall be provided for the ground segment to enable and disable each individual thermal control loop.



The capability shall be provided to adjust the temperature control thresholds of each thermal control loop by ground command.

# ECSS Parents : ND40 : [$5.9.6.b]*


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The thermal control shall make use of fully qualified hardware and process.

# ECSS Parents : ND14: [$4.4.3]*

5.3.6 Passive Thermal Control Requirements


As far as possible, materials shall be chosen in order to limit stresses induced by thermal cycling i.e. with a low thermal expansion coefficient.

# *


Couple of materials shall be chosen to decrease differential thermal deformation i.e. with thermal expansion coefficients of the same order of magnitude.

# *


Use of OAC (Chromic Anodised Oxidation) or OAS (Sulphuric Anodised Oxidation) protective coatings on external surfaces shall be submitted to Prime approval.

# *


Paints and coatings must satisfy out gassing criteria, optical requirements and resistance to thermal cycling requirement and environment (UV...) described in AD-06C

# *


The outermost layer of external MLI’s shall be black coated (vacuum carbon deposit or black painted Kapton foil).

# *


Thermo physical properties of any interface filler material or of any adhesive tape or similar materials shall be or have been determined and/or verified experimentally.

# ECSS Parents : ND14 : [4.4.1.a], [4.4.3]*


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Thermal elements for which dismount ability is required during integration and verification shall be removable without degradation of their thermal characteristics.



The method of application of any thermal coating shall be such that, in event of damage occurring to any thermal surface, the rework/repair shall be capable of being performed outside equipment manufacturer premises (rework/repair carried out in Prime Contractor premises or on launch pad).

# *


The effects of material ageing, due to the thermal environmental [ AD-36C], satellite operational lifetime and satellite orientation, shall be considered when evaluating material thermo-optical properties.

# *


The emissivity value shall be guaranteed at ± 0.02 for emissivity <0.1 and at ± 0.03 for emissivity >0.1.

# *


The solar absorptivity value shall be defined for both BOL and EOL conditions and guaranteed at ± 0.03.

# ECSS Parents : ND14 : [$4.4.1]*


MLI efficiency and conductance values shall be justified and agreed by the Prime.

# *

5.3.7 Thermal interfaces Requirements

5.3.7.1 Modularity and decoupling of modules Requirements


The satellite thermal design shall achieve modularity between the various Modules thermal control.

# *


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The satellite individual module thermal concepts shall allow individual design and development, thermal hardware integration and in particular thermal testing with the minimum interaction between other module thermal concepts.

# *


In order to minimize mutual thermal interactions between modules, the module TCS responsible shall ensure radiative and conductive insulation.

# *


Therefore, in addition to radiative and conductive decoupling items (e.g. MLI's and insulating washers), the thermal control of the instruments shall include shielding for protecting their radiators from thermal interaction with other satellite parts.

# *


If the thermal control of the instruments do not include shielding for protecting their radiators from thermal interaction, a deviation shall be submitted to Prime approval.

# *


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5.3.7.2 Interface design


Equipment, mounted on the structural panels by interposition of thermal washers or thermal interface filer/heat pipes, shall comply with thermal interfaces, as described on Figure 5-3 and Figure 5-4.

Figure 5-3 Thermal interface with thermal washer

Figure 5-4 Thermal interface with heat pipe

# *

Note 1 : This scheme is not intended to show the mechanical mounting but only to show the need for the thermal washers below the screw head and between the insert and the unit.


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The contact surface of all equipment of categories CC1 and CC3 shall be compliant with the following interfillers:

• DC 93500

• Egraf or Sygraflex.

• Chotherm

• Any other kind of filler type that has been justified by the module responsible

# *


The Module contractor responsible of the definition of the unit mounting shall identify and specify the thermal interface design requirement at unit level.

# ECSS Parents : ND14 : [Annex-D2.1.5.d]*

5.3.7.3 Heat fluxes at thermal interface


Maximum allowable heat flux (or local hot spot) and average heat flux conducted through the base contact area shall not exceed the values listed in Table below.

Allowable Base Contact Heat Flux Thermal Element At Mounting Interface

Average Max Heat Pipes 1 W/cm2 4 W/cm2 Doubler 0.1 W/cm2 0.4 W/cm2

0.25 W/cm2 if contact area <100 cm2

0.15 W/cm2 if contact area >100 cm2

H/C Panel

0.05 W/cm2

0.5 W/cm2 if contact area <30 cm2

(hot spot for equipment mounted on feet only)

Table 5-1 : Allowable base contact heat flux

# *


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5.4 Requirements for thermal models and analyses

5.4.1 Thermal Modelling Requirements


Whenever simplified or reduced models are used, the correlation criteria between the detailed and simplified or reduced models shall be specified and agreed with the Agency.



The detailed thermal models shall be established in such a way that provided temperature maps for the structure thermo-elastic analysis take into account the requirements of the structural mathematical models.



Except for non dissipative internal units, Detailed Thermal Mathematical Models (DTMM) and Detailed Geometrical Mathematical Models (DGMM) of the satellite modules and units shall be created for analytical predictions representative of all the phases of the mission, including ground tests.

# *

Note 1 : Parametrical modelling approach is recommended to ease follow up of design definition.


The level of detail of detailed mathematical models shall be approved by the Prime.

# *


The level of detail of electronic box detailed mathematical models shall allow at least good modelling of each PCB.

# *


Reduced TMM and GMM shall be established for:

• All category CC internal units with unit dissipation higher than 5W

• All category RC units with unit dissipation higher than 10W

• All category TH2 equipments


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• All external units (Earth and Sun sensors…).

# *


Reduced unit models shall be incorporated in upper level detailed models (Module and/or Satellite level):

• To verify the thermal interfaces between units and module or between TCS and other modules

• To verify that units withstand the launch environment.

# ECSS Parents : ND14 : [Annex-A2.1.1.a]*


Detailed and/or reduced Geometrical Mathematical Models and Thermal Mathematical Models shall be established and delivered to the Prime and/or the Agency as specified in AD-43C.

# ECSS Parents : ND14 : [$4.9.4]*


Any deviation w. r. t. AD-43C requirements shall be submitted to Prime approval.

# *


The models shall cover the various unit operating status and unambiguously identify the model parameters which are changing depending on unit operating status as:

• Unit dissipations

• Dedicated cryo cooler control law in cooling down and nominal modes.

# ECSS Parents : ND14 : [$4.1.7], [$3.2.1.3]*


The models shall unambiguously identify the flight and the test monitoring points.

# *


The detailed DTMM and DGMM shall be correlated against the environmental test results.

# ECSS Parents : ND14 : [$4.2.1]*


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The thermal model complexity of satellite, modules (PF, PL), and equipments shall not prevent from being verified and used with confidence for cases for which testing on ground is not representative or affordable.

# *

5.4.2 Thermal analysis Requirements

5.4.2.1 General Analysis Requirements


The Prime and the Agency shall have access to all datas and information used for the thermal analyses; In case of proprietary data or methods, the Prime or the Agency could request a review of these data during a specific meeting.

# *


Early evidence that thermal design can meet requirements in all mission phase and modes shall be given by analysis, using detailed thermal mathematical models.



Final worst cases, nominal flight temperature predictions, and any other flight temperature predictions (transfert orbit, manoeuvers, safe mode, failures, redundancy, ect...) shall be performed by using detailed thermal mathematical models correlated with the thermal balance test temperatures within the agreed deviations.



Worst case flight temperature predictions shall be performed by considering at least :

• the min/max unit dissipation

• the worst case external fluxes

• the min/max interface temperature (boundary conditions).

# *


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Nominal flight temperature predictions shall be performed by considering at least :

• the nominal unit dissipation

• the worst case external fluxes

• the nominal interface temperature (boundary conditions).

# *

5.4.2.2 Unit thermal analysis Requirements


Thermal analyses shall be performed by the unit supplier for all dissipative units and all external units.

# *


For non dissipative internal units, no thermal analysis is required but the unit supplier shall verify and justify the compliance of its materials and processes with the specified qualification temperature range.

# *


For dissipative units including electronic components, the thermal analyses shall be performed with the objectives to predict all internal components temperatures for the worst equipment operating mode considering the specified thermal interfaces and environment and to verify the followings points:

• The temperatures of electronic parts are lower or equal to the limits allowed by the derating rules applicable to the project when submitted to acceptance environment (see AD-06C)

• The temperatures of electronic parts are lower or equal to the manufacturer guaranteed limits (max rating) when the environment reaches the qualification temperature. In order to demonstrate that in case of failure there is no propagation, the analyses can be performed showing that rating temperatures are not over passed

• The temperatures of material and processes are inside the qualified range

• The flux density at the interface with the platform is inside the specified values.

# ECSS Parents : ND 14 : [3.2.1.3]*


The compliance with the thermal performance requirements shall be demonstrated by analysis for the nominal operational and non-operational cases.

# ECSS Parents : ND14 : [Annex-C2.1.8.b]*


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5.4.2.3 Thermal analyses and models description reports


The following deliveries shall be provided:

• Analyses reports before each review

• Thermal models reports at each thermal model delivery.

# ECSS Parents : ND14 : [Annex-A], [Annex-B], [Annex-C]*

Note 1 : Design reviews and thermal models deliveries are defined in relevant TCS or equipment SOW.


The analysis reports shall include:

• The list of the analysis cases with the rationale for the selection of them

• A brief description of the model showing the main modelling assumptions (boundary conditions, dissipation etc...) and sketches of model if any

• A summary of the main results, including comparison with specified thermal performances

• Detailed results of all analysis cases, provided in report annexes.

# ECSS Parents : ND14 : [Annex-C]*


The thermal models description reports shall be established according to AD-43C requirements.

# *

5.4.3 Thermal control subsystem testing and verification


At satellite, modules and units levels, the Thermal Control Subsystem (TCS) shall establish, at an early stage, a complete and coherent verification plan and matrix clearly indicating for each item and level the intended verification approach.

# ECSS Parents : ND14 : [$4.9.3]*


Temperatures at the unit TRP shall be achieved, when possible, during acceptance and qualification thermal vacuum testing.



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The in flight thermal control design shall be verified by analysis using correlated thermal mathematical models.



The thermal design of all satellite modules shall be validated by thermal balance test.



The test cases shall cover, as far as practical, the extreme environmental conditions envisaged for the complete mission and the most critical predicted thermal situations.

# ECSS Parents : ND 14 : [$4.2.1.b]*


For all tests at satellite or module level, the correlation success criteria shall be agreed with the Prime contractor and the Agency.

# ECSS Parents : ND14 : [Annex-E] , [$4.5.3.2]*


For all tests at satellite or module level, all datas necessary for evaluation of test success criteria (temperature stabilization, test conditions) and for test correlation shall be continuously monitored during the test:

• Satellite temperatures, using satellite flight and test temperature sensors

• Test facility (temperature, pressure, external fluxes simulation) environmental data

• Satellite unit dissipation (unit current & voltage measurements)

• Heater power (heater current & voltage, ON/OFF status measurements).

# ECSS Parents : ND14 : [Annex-E], [$4.5.3.2]*


For all tests at satellite or module level, dedicated test temperature sensors shall be implemented close to satellite flight temperature sensors on critical units.

# ECSS Parents : ND14 : [Annex-E], [$4.5.3.2]*


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For all tests at satellite or module level, the type, location and number of test temperature sensors and test facility shall be approved by the Prime and the Agency.

# ECSS Parents : ND14 : [$4.5.3.1.d]*


The Thermal Balance test shall be representative of the (worst) cases environment, mission flight conditions and operating modes.



The Thermal Balance test(s) shall be based on a test approach and test success criteria unambiguously defined and approved by the Agency.


5.5 Requirements for crycooler

5.5.1 Operating requirement


The operation of the cryo-coolers shall be cold redundant.


5.5.2 Performance requirement


The thermal control of instruments shall ensure that the cryocooler(s) operate in a worst case at maximum 90% of their design capabilities without considering any contamination effect.


END OF DOCUMENT

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