Hierarchical FDIR Concepts in SC Systems

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Hierarchical FDIR Concepts in S/C Systems

• SpaceOps 2004, Montreal May 20, 2004

Roland Gessner et al. EADS-Astrium
GmbH Friedrichshafen, Germany
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Agenda

• Rationale why hierarchical FDIR ?

• FDIR development within the Space Segment
  development

• Representation of FDIR hierarchies

• Typical FDIR resources and mechanisms

• Project examples

• Conclusions

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Rationale why hierarchical FDIR ?

• Increased autonomy needs in space missions (Deep
  Space missions and Earth Observation missions)
  and tightened schedules require tailored and
  systematic FDIR considerations in projects

• Hierarchical FDIR concept and description
  supports the project definition/specification
  phase

• Hierarchical FDIR helps to handle project
  interfaces

• Systematic approach for FDIR within projects is
  considered to have some room for improvement

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FDIR Development in Space Segment (1)

• Characteristics
• establish FDIR and Operational requirements to
  sufficient detail as early as possible
• Consequence early involvement of Operations
  people in projects and closely working with
  system engineering
• Set up FDIR related tasks according to project
  phases

• by
• description of FDIR process
• definition of interfaces to other disciplines /
  subcontractors

• Example

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FDIR Development in Space Segment (2)
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FDIR Concept

• Tasks
• Develop baseline hierarchical architecture for
  systems, subsystems and functions
• Define basic FDIR principles (system safing
  concept, system/subsystem reconfiguration
  approach, failure categories etc.)
• Include FDIR/Operational requirements into
  specifications

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FDIR Analysis (1)

• Method
• Develop functional architecture for system,
  subsystems and functions to a sufficient level of
  detail (functional decomposition)
• Describe failures on functional levels
• Complement by failures from FMECA (Failure Mode
  Effects and Criticality Analysis), usually
  developed somewhat later
• Refine FDIR principles and consolidate
  specifications

• Example

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FDIR Analysis (2)
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FDIR Functional Description Space Segment

• Use e.g. SADT (Structured Analysis and Design)
  Technique

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FDIR Model GOCE example
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FDIR Resources and Mechanisms (1)

• Redundancy Resources
• baseline for system safing concept
• very implementation specific could imply
  significant complexity

• System Safeguarding Mechanisms
• Definition of system alarms leading to system
  safing
• separation between HW and SW based failure
  handling

• Surveillance Techniques/Monitoring e.g.
  independent HW for nominal surveillance and for
  failure cases

• On Board Sequencing Functions (On-Board Control
  Procedures)

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FDIR Resources and Mechanisms (2)

• Services of the ECSS Packet Utilisation Standard
  (PUS)

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FDIR Specifics for Deep Space missions

• Fail operational approach during specific mission
  phases, e.g. Orbit Insertion phase

• Enhanced redundancy implementation scheme

• Configurability of onboard computers according to
  their functional needs

• Table-based configuration management allows
  avoidance of un-allowed configurations

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ADM-AEOLUS Mission

• Atmospheric Wind Speed Determination by LIDAR
  instrument (ALADIN)

• 7-day (nominal) autonomy

• Fail-operational approach to ensure high data
  availability

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ADM-AEOLUS Mission FDIR Specifics

• 7 day autonomy requirement plus single failure
  tolerance requirement drives FDIR

• Autonomous data downlink capabilities (orbit
  position schedule)

• Use of ECSS PUS functions (including OBCPs for
  FDIR)

• Safe Mode largely based on independent HW and SW

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Summary

• FDIR hierarchical approach is able to distinguish
  FDIR instances of different operational
  importance
• FDIR hierarchy can be set up to match project
  breakdown (organisational needs)
• Structured analysis and design techniques are
  useful to build an FDIR model and interfaces
  between different functions FDIR breakdown to
  detailed implementation levels is easily possible
  
• FDIR/Ops engineers to be included early in
  project phases

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Further Contacts

• EADS Astrium http//www.eads.net/
• Authors Roland.Gessner_at_astrium.eads.net
• Bernd.Koesters_at_astrium.eads.net
• Alfred.Hefler_at_astrium.eads.net
• Reinhard.Eilenberger_at_astrium.eads.net
• Joerg.Hartmann_at_astrium.eads.net
• Michael.Schmidt_at_esa.int